Hi,

I have a 30 by 100 foot greenhouse. I have two heaters, forced air heaters,
that burn oil. One heater alone is enough to heat the greenhouse (on all
but the coldest nights). They hang on opposite side of the long greenhouse
and the un-used one is a back up incase the primary one dies. Two
thermostats hang in the middle of the space, 50 feet from the heaters about
midway way from the floor to the roof. One thermostat controls one heater
each and they are independent of each other. There are four temperature
monitoring stations in the greenhouse that are independent of the on/off
thermostats that are situated to read the two coldest spots and the two
warmest spots. The four spots are gathered from plant level around the
bench levels, (not extremely close to heaters or tucked down in cold
corners)

I can run the south wall heater with its thermostat set at 65 (in the middle
of the greenhouse) and the north end of the greenhouse will register around
63 and the heated side will register around 68 but the air is circulated by
LOTS of fans and the center air mass where the thermostat is, is 65 degrees.
The four temperature sensors around the greenhouse average 65. The same
pattern emerges no matter which heater I use; the far side is cool and the
heater side is hotter but the middle is 65.

If I set *both* heaters to come on at about 64, both sides of the greenhouse
heat to around 68 and the middle of the air mass turns on and off both
heaters at 64. And they don't seem to cycle on and off as often, and it
seems there is probably more radiant heat available from two heaters but
that may be an illusion because the outside night temperature varies a lot
from night to night and this has to effect how the heaters cycle on and off.

.....anyway the average temperature based on the 4 monitoring stations now
comes to just under 66.... I have to set the thermostats just about 63.5 to
get an average air temperature of 65, so it matches the average air
temperature of the single heater number.

Here's my question, so by running two identical heaters at 63.5 instead of
one heater at 65 am I using more oil, less oil, or the same amount of oil to
heat the same space to the same average temperature? there has to be an
equation that will answer this question. Anybody know how to figure it?

ps. logically I come up with the same btu's must be needed to reach the
same average temperature, but is this the truth?

"Al" <nospam [at] all.ever> wrote in message
news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
> Hi,
>
> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
> heaters, that burn oil. One heater alone is enough to heat the greenhouse
> (on all but the coldest nights). They hang on opposite side of the long
> greenhouse and the un-used one is a back up incase the primary one dies.
> Two thermostats hang in the middle of the space, 50 feet from the heaters
> about midway way from the floor to the roof. One thermostat controls one
> heater each and they are independent of each other. There are four
> temperature monitoring stations in the greenhouse that are independent of
> the on/off thermostats that are situated to read the two coldest spots and
> the two warmest spots. The four spots are gathered from plant level
> around the bench levels, (not extremely close to heaters or tucked down in
> cold corners)
>
> I can run the south wall heater with its thermostat set at 65 (in the
> middle of the greenhouse) and the north end of the greenhouse will
> register around 63 and the heated side will register around 68 but the air
> is circulated by LOTS of fans and the center air mass where the thermostat
> is, is 65 degrees. The four temperature sensors around the greenhouse
> average 65. The same pattern emerges no matter which heater I use; the
> far side is cool and the heater side is hotter but the middle is 65.
>
> If I set *both* heaters to come on at about 64, both sides of the
> greenhouse heat to around 68 and the middle of the air mass turns on and
> off both heaters at 64. And they don't seem to cycle on and off as often,
> and it seems there is probably more radiant heat available from two
> heaters but that may be an illusion because the outside night temperature
> varies a lot from night to night and this has to effect how the heaters
> cycle on and off.
>
> ....anyway the average temperature based on the 4 monitoring stations now
> comes to just under 66.... I have to set the thermostats just about 63.5
> to get an average air temperature of 65, so it matches the average air
> temperature of the single heater number.
>
> Here's my question, so by running two identical heaters at 63.5 instead of
> one heater at 65 am I using more oil, less oil, or the same amount of oil
> to heat the same space to the same average temperature? there has to be
> an equation that will answer this question. Anybody know how to figure
> it?
>

First it depends on the heaters - if they have standing pilot lights and
you normally have the backup off, you burn more.
Second if you really had a cold spot at the far end, then you were not
heating all the air to the same temp, so you are using more fuel
Third you put some BTU's up the stack, depending on the efficiency of
the heaters - more square inches of stack in operation, means more btu's
lost.

On the other hand if everything is perfectly efficient, then you would
use the same.
Also if the heaters are away from the wall of the greenhouse, and run
less, then less heat is radiated directly to the wall and lost that way,
meaning that you probably used less.

Doug

In article <hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com>,
"Al" <nospam [at] all.ever> wrote:

> ps. logically I come up with the same btu's must be needed to reach the
> same average temperature, but is this the truth?
>
> "Al" <nospam [at] all.ever> wrote in message
> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
> > Hi,
> >
> > I have a 30 by 100 foot greenhouse. I have two heaters, forced air
> > heaters, that burn oil. One heater alone is enough to heat the greenhouse
> > (on all but the coldest nights). They hang on opposite side of the long
> > greenhouse and the un-used one is a back up incase the primary one dies.
> > Two thermostats hang in the middle of the space, 50 feet from the heaters
> > about midway way from the floor to the roof. One thermostat controls one
> > heater each and they are independent of each other. There are four
> > temperature monitoring stations in the greenhouse that are independent of
> > the on/off thermostats that are situated to read the two coldest spots and
> > the two warmest spots. The four spots are gathered from plant level
> > around the bench levels, (not extremely close to heaters or tucked down in
> > cold corners)
> >
> > I can run the south wall heater with its thermostat set at 65 (in the
> > middle of the greenhouse) and the north end of the greenhouse will
> > register around 63 and the heated side will register around 68 but the air
> > is circulated by LOTS of fans and the center air mass where the thermostat
> > is, is 65 degrees. The four temperature sensors around the greenhouse
> > average 65. The same pattern emerges no matter which heater I use; the
> > far side is cool and the heater side is hotter but the middle is 65.
> >
> > If I set *both* heaters to come on at about 64, both sides of the
> > greenhouse heat to around 68 and the middle of the air mass turns on and
> > off both heaters at 64. And they don't seem to cycle on and off as often,
> > and it seems there is probably more radiant heat available from two
> > heaters but that may be an illusion because the outside night temperature
> > varies a lot from night to night and this has to effect how the heaters
> > cycle on and off.
> >
> > ....anyway the average temperature based on the 4 monitoring stations now
> > comes to just under 66.... I have to set the thermostats just about 63.5
> > to get an average air temperature of 65, so it matches the average air
> > temperature of the single heater number.
> >
> > Here's my question, so by running two identical heaters at 63.5 instead of
> > one heater at 65 am I using more oil, less oil, or the same amount of oil
> > to heat the same space to the same average temperature? there has to be
> > an equation that will answer this question. Anybody know how to figure
> > it?
> >

no continuous flame. The back of the heaters have about 3 feet space from
the outer wall. And they are not very efficient, I think the number was
somewhere around 75 to 85% efficient when I bought them.

"Doug Houseman" <doug [at] msen.com> wrote in message
news:doug-F4E7C5.18212516122005 [at] comcast.dca.giganews.com...
> First it depends on the heaters - if they have standing pilot lights and
> you normally have the backup off, you burn more.
> Second if you really had a cold spot at the far end, then you were not
> heating all the air to the same temp, so you are using more fuel
> Third you put some BTU's up the stack, depending on the efficiency of
> the heaters - more square inches of stack in operation, means more btu's
> lost.
>
> On the other hand if everything is perfectly efficient, then you would
> use the same.
> Also if the heaters are away from the wall of the greenhouse, and run
> less, then less heat is radiated directly to the wall and lost that way,
> meaning that you probably used less.
>
> Doug
>
> In article <hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com>,
> "Al" <nospam [at] all.ever> wrote:
>
>> ps. logically I come up with the same btu's must be needed to reach the
>> same average temperature, but is this the truth?
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>> > Hi,
>> >
>> > I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>> > heaters, that burn oil. One heater alone is enough to heat the
>> > greenhouse
>> > (on all but the coldest nights). They hang on opposite side of the
>> > long
>> > greenhouse and the un-used one is a back up incase the primary one
>> > dies.
>> > Two thermostats hang in the middle of the space, 50 feet from the
>> > heaters
>> > about midway way from the floor to the roof. One thermostat controls
>> > one
>> > heater each and they are independent of each other. There are four
>> > temperature monitoring stations in the greenhouse that are independent
>> > of
>> > the on/off thermostats that are situated to read the two coldest spots
>> > and
>> > the two warmest spots. The four spots are gathered from plant level
>> > around the bench levels, (not extremely close to heaters or tucked down
>> > in
>> > cold corners)
>> >
>> > I can run the south wall heater with its thermostat set at 65 (in the
>> > middle of the greenhouse) and the north end of the greenhouse will
>> > register around 63 and the heated side will register around 68 but the
>> > air
>> > is circulated by LOTS of fans and the center air mass where the
>> > thermostat
>> > is, is 65 degrees. The four temperature sensors around the greenhouse
>> > average 65. The same pattern emerges no matter which heater I use; the
>> > far side is cool and the heater side is hotter but the middle is 65.
>> >
>> > If I set *both* heaters to come on at about 64, both sides of the
>> > greenhouse heat to around 68 and the middle of the air mass turns on
>> > and
>> > off both heaters at 64. And they don't seem to cycle on and off as
>> > often,
>> > and it seems there is probably more radiant heat available from two
>> > heaters but that may be an illusion because the outside night
>> > temperature
>> > varies a lot from night to night and this has to effect how the heaters
>> > cycle on and off.
>> >
>> > ....anyway the average temperature based on the 4 monitoring stations
>> > now
>> > comes to just under 66.... I have to set the thermostats just about
>> > 63.5
>> > to get an average air temperature of 65, so it matches the average air
>> > temperature of the single heater number.
>> >
>> > Here's my question, so by running two identical heaters at 63.5 instead
>> > of
>> > one heater at 65 am I using more oil, less oil, or the same amount of
>> > oil
>> > to heat the same space to the same average temperature? there has to
>> > be
>> > an equation that will answer this question. Anybody know how to figure
>> > it?
>> >

It is less-efficient to run two.

When a heater comes on, you pay to heat the heater in addition to heating
the air. If you plotted a curve of the percentage of energy spent heating
the hardware versus heating the air, it gets more efficient with longer
individual run times. The longer the burn time per start, the more
efficient it is. That's why it doesn't pay to buy a 100K BTU heater when
your need is for a 50K unit - it may heat the air really fast, but it has to
do so more often. The ideal would be a heater that generated heat
continuously at the exact rate the greenhouse lost it.

With two heaters, you are heating double the mass of steel and running each
for half the time for each burn cycle.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Artwork, Books and Lots of Free Info!


"Al" <nospam [at] all.ever> wrote in message
news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
> ps. logically I come up with the same btu's must be needed to reach the
> same average temperature, but is this the truth?
>
> "Al" <nospam [at] all.ever> wrote in message
> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>> Hi,
>>
>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>> heaters, that burn oil. One heater alone is enough to heat the
>> greenhouse (on all but the coldest nights). They hang on opposite side
>> of the long greenhouse and the un-used one is a back up incase the
>> primary one dies. Two thermostats hang in the middle of the space, 50
>> feet from the heaters about midway way from the floor to the roof. One
>> thermostat controls one heater each and they are independent of each
>> other. There are four temperature monitoring stations in the greenhouse
>> that are independent of the on/off thermostats that are situated to read
>> the two coldest spots and the two warmest spots. The four spots are
>> gathered from plant level around the bench levels, (not extremely close
>> to heaters or tucked down in cold corners)
>>
>> I can run the south wall heater with its thermostat set at 65 (in the
>> middle of the greenhouse) and the north end of the greenhouse will
>> register around 63 and the heated side will register around 68 but the
>> air is circulated by LOTS of fans and the center air mass where the
>> thermostat is, is 65 degrees. The four temperature sensors around the
>> greenhouse average 65. The same pattern emerges no matter which heater I
>> use; the far side is cool and the heater side is hotter but the middle is
>> 65.
>>
>> If I set *both* heaters to come on at about 64, both sides of the
>> greenhouse heat to around 68 and the middle of the air mass turns on and
>> off both heaters at 64. And they don't seem to cycle on and off as
>> often, and it seems there is probably more radiant heat available from
>> two heaters but that may be an illusion because the outside night
>> temperature varies a lot from night to night and this has to effect how
>> the heaters cycle on and off.
>>
>> ....anyway the average temperature based on the 4 monitoring stations now
>> comes to just under 66.... I have to set the thermostats just about 63.5
>> to get an average air temperature of 65, so it matches the average air
>> temperature of the single heater number.
>>
>> Here's my question, so by running two identical heaters at 63.5 instead
>> of one heater at 65 am I using more oil, less oil, or the same amount of
>> oil to heat the same space to the same average temperature? there has to
>> be an equation that will answer this question. Anybody know how to
>> figure it?
>>
>
>

> "Al" <nospam [at] all.ever> wrote in message
> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>> ps. logically I come up with the same btu's must be needed to reach the
>> same average temperature, but is this the truth?
>>

Nope. Nothing in this game is that easy. In determining BTUs, the temp
difference between the outside and the inside is critical. The BTUs required
to maintain a difference is not linear with this temp difference. If I
understand all of this right, it would take fewer BTUs to keep a greenhouse
at a uniform 65.5 then it would be to maintain a greenhouse that is 68 one
side linearly dropping to 63 on the other. The extra BTUs required to
maintain the part of the greenhouse 2.5 degrees above normal would not be
made up with the savings of only heating the other side to 2.5 degrees below
normal.

Pat

So you all are saying that I am burring more oil by what I am doing:
by running two identical heaters at 63.5 instead of one heater at 65 to
maintain an average of 65 in the space I will spend more money?

"heating double the mass of steel and running each for half the time"
uses more oil?

The extra BTUs required to
"maintain the part of the greenhouse 2.5 degrees above normal would not be
made up with the savings of only heating the other side to 2.5 degrees below
normal" so I will use more oil?

Lacking some calculus equation I could not understand anyway, I'll take your
word for it. :-) I do kind of see what you are saying. So the smartest
thing I can do (since I was dumb enough to buy these inefficient heaters
anyway) is to set one heater at 65 and one at 63 so the second unit would
only come on if the outside temps/winds stressed the first unit's ability to
maintain the temperature or failed to start at all. My goal is to use the
least amount of oil while knocking the fewest buds off the phals.

I do like the nice even heat distribution I get with both heaters. I kind
of think some of the bud loss I got last year was from marauding cold dry
drafts in the circulating pattern. I will have to look into a way to
distribute the heat from one unit more evenly. Those clear plastic tubes
that hook in front of some heater brands and run down the length of the
greenhouse dispensing heated air though little holes will not work because
they can not be attached to the front of my heaters. The manufactures told
me so last year. If these things would just hurry up and rust away, I would
invest in a better method of heating; probably a boiler with fin-tubes of
circulating water running under the benches.

"Ray" <raybark [at] firstrays.com> wrote in message
news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
> It is less-efficient to run two.
>
> When a heater comes on, you pay to heat the heater in addition to heating
> the air. If you plotted a curve of the percentage of energy spent heating
> the hardware versus heating the air, it gets more efficient with longer
> individual run times. The longer the burn time per start, the more
> efficient it is. That's why it doesn't pay to buy a 100K BTU heater when
> your need is for a 50K unit - it may heat the air really fast, but it has
> to do so more often. The ideal would be a heater that generated heat
> continuously at the exact rate the greenhouse lost it.
>
> With two heaters, you are heating double the mass of steel and running
> each for half the time for each burn cycle.
>
> --
>
> Ray Barkalow - First Rays Orchids - www.firstrays.com
> Plants, Supplies, Artwork, Books and Lots of Free Info!
>
>
> "Al" <nospam [at] all.ever> wrote in message
> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>> ps. logically I come up with the same btu's must be needed to reach the
>> same average temperature, but is this the truth?
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>> Hi,
>>>
>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>> heaters, that burn oil. One heater alone is enough to heat the
>>> greenhouse (on all but the coldest nights). They hang on opposite side
>>> of the long greenhouse and the un-used one is a back up incase the
>>> primary one dies. Two thermostats hang in the middle of the space, 50
>>> feet from the heaters about midway way from the floor to the roof. One
>>> thermostat controls one heater each and they are independent of each
>>> other. There are four temperature monitoring stations in the greenhouse
>>> that are independent of the on/off thermostats that are situated to read
>>> the two coldest spots and the two warmest spots. The four spots are
>>> gathered from plant level around the bench levels, (not extremely close
>>> to heaters or tucked down in cold corners)
>>>
>>> I can run the south wall heater with its thermostat set at 65 (in the
>>> middle of the greenhouse) and the north end of the greenhouse will
>>> register around 63 and the heated side will register around 68 but the
>>> air is circulated by LOTS of fans and the center air mass where the
>>> thermostat is, is 65 degrees. The four temperature sensors around the
>>> greenhouse average 65. The same pattern emerges no matter which heater
>>> I use; the far side is cool and the heater side is hotter but the middle
>>> is 65.
>>>
>>> If I set *both* heaters to come on at about 64, both sides of the
>>> greenhouse heat to around 68 and the middle of the air mass turns on and
>>> off both heaters at 64. And they don't seem to cycle on and off as
>>> often, and it seems there is probably more radiant heat available from
>>> two heaters but that may be an illusion because the outside night
>>> temperature varies a lot from night to night and this has to effect how
>>> the heaters cycle on and off.
>>>
>>> ....anyway the average temperature based on the 4 monitoring stations
>>> now comes to just under 66.... I have to set the thermostats just about
>>> 63.5 to get an average air temperature of 65, so it matches the average
>>> air temperature of the single heater number.
>>>
>>> Here's my question, so by running two identical heaters at 63.5 instead
>>> of one heater at 65 am I using more oil, less oil, or the same amount of
>>> oil to heat the same space to the same average temperature? there has
>>> to be an equation that will answer this question. Anybody know how to
>>> figure it?
>>>
>>
>>
>
>

Hey Al,

I did not say which option would use less oil. It is a hard question and I
do not have enough information or remember the calculus. There are two
factors at play, the heat generation and the heat loss. On the generation
side it is more efficient to run one heater due to start up efficiency and
the loss of heat up the stacks. Heating the mass of steel is no big deal
since that is in the greenhouse and losses are into the greenhouse.
Barometric dampers will reduce the losses up the stack, but they never work
right for me and have lead to soot problems. On the heat loss side it is
better to have uniform heat for a given average. As a greenhouse gets
longer, at some length it would be better to have heaters on both end than a
single heater and a wide range of temperatures. I have no idea what the
length is, but one furnace is not always the best answer.

If you opt for two heaters you might consider reducing the burner nozzle
size. Nozzles are measured in gals per hour and only cost a couple of
dollars. This will reduce the BTU output of the furnaces and they will not
cycle on and off as much. If you change the nozzle, remember to reset the
air intake. Also make sure your nozzles are large enough for the coldest
nights. (we use big nozzles that are not always stocked on repair
trucks--always keep an extra one on hand.)

I have seen the long plastic tubes used even when they are not connected to
the furnace directly. This would help level out the temps (saving oil) but
would add another fan to your electric bill. Watch out for HAF fans blowing
against the plastic as this leads to greater temp and humidity loss as the
warm air moves down the greenhouse I have reduced the size of my HAF fans
and been more careful adjusting where they blow. I assume it has lead to
oil savings, I know it has help in growing.

If you think your greenhouses grow better with two heaters; increased sales
from better plants or faster growing plants will most likely more than pay
for the additional oil. Humidity will be more uniform in a greenhouse that
has uniform temps. How many blasted buds does it take to cost more than the
oil savings?

I like the temp difference across the greenhouse; oncs, zygos, and dens go
in the cold side, seedlings in the warm section, and mature phals in the
'average' section.

Sorry I can not help, I have no idea what is best.

Pat

"Al" <nospam [at] all.ever> wrote in message
news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
> So you all are saying that I am burring more oil by what I am doing:
> by running two identical heaters at 63.5 instead of one heater at 65 to
> maintain an average of 65 in the space I will spend more money?
>
> "heating double the mass of steel and running each for half the time"
> uses more oil?
>
> The extra BTUs required to
> "maintain the part of the greenhouse 2.5 degrees above normal would not be
> made up with the savings of only heating the other side to 2.5 degrees
> below
> normal" so I will use more oil?
>
> Lacking some calculus equation I could not understand anyway, I'll take
> your word for it. :-) I do kind of see what you are saying. So the
> smartest thing I can do (since I was dumb enough to buy these inefficient
> heaters anyway) is to set one heater at 65 and one at 63 so the second
> unit would only come on if the outside temps/winds stressed the first
> unit's ability to maintain the temperature or failed to start at all. My
> goal is to use the least amount of oil while knocking the fewest buds off
> the phals.
>
> I do like the nice even heat distribution I get with both heaters. I kind
> of think some of the bud loss I got last year was from marauding cold dry
> drafts in the circulating pattern. I will have to look into a way to
> distribute the heat from one unit more evenly. Those clear plastic tubes
> that hook in front of some heater brands and run down the length of the
> greenhouse dispensing heated air though little holes will not work because
> they can not be attached to the front of my heaters. The manufactures
> told me so last year. If these things would just hurry up and rust away,
> I would invest in a better method of heating; probably a boiler with
> fin-tubes of circulating water running under the benches.
>
> "Ray" <raybark [at] firstrays.com> wrote in message
> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>> It is less-efficient to run two.
>>
>> When a heater comes on, you pay to heat the heater in addition to heating
>> the air. If you plotted a curve of the percentage of energy spent
>> heating the hardware versus heating the air, it gets more efficient with
>> longer individual run times. The longer the burn time per start, the
>> more efficient it is. That's why it doesn't pay to buy a 100K BTU heater
>> when your need is for a 50K unit - it may heat the air really fast, but
>> it has to do so more often. The ideal would be a heater that generated
>> heat continuously at the exact rate the greenhouse lost it.
>>
>> With two heaters, you are heating double the mass of steel and running
>> each for half the time for each burn cycle.
>>
>> --
>>
>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>> ps. logically I come up with the same btu's must be needed to reach the
>>> same average temperature, but is this the truth?
>>>
>>> "Al" <nospam [at] all.ever> wrote in message
>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>> Hi,
>>>>
>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>> greenhouse (on all but the coldest nights). They hang on opposite side
>>>> of the long greenhouse and the un-used one is a back up incase the
>>>> primary one dies. Two thermostats hang in the middle of the space, 50
>>>> feet from the heaters about midway way from the floor to the roof. One
>>>> thermostat controls one heater each and they are independent of each
>>>> other. There are four temperature monitoring stations in the
>>>> greenhouse that are independent of the on/off thermostats that are
>>>> situated to read the two coldest spots and the two warmest spots. The
>>>> four spots are gathered from plant level around the bench levels, (not
>>>> extremely close to heaters or tucked down in cold corners)
>>>>
>>>> I can run the south wall heater with its thermostat set at 65 (in the
>>>> middle of the greenhouse) and the north end of the greenhouse will
>>>> register around 63 and the heated side will register around 68 but the
>>>> air is circulated by LOTS of fans and the center air mass where the
>>>> thermostat is, is 65 degrees. The four temperature sensors around the
>>>> greenhouse average 65. The same pattern emerges no matter which heater
>>>> I use; the far side is cool and the heater side is hotter but the
>>>> middle is 65.
>>>>
>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>> greenhouse heat to around 68 and the middle of the air mass turns on
>>>> and off both heaters at 64. And they don't seem to cycle on and off as
>>>> often, and it seems there is probably more radiant heat available from
>>>> two heaters but that may be an illusion because the outside night
>>>> temperature varies a lot from night to night and this has to effect how
>>>> the heaters cycle on and off.
>>>>
>>>> ....anyway the average temperature based on the 4 monitoring stations
>>>> now comes to just under 66.... I have to set the thermostats just
>>>> about 63.5 to get an average air temperature of 65, so it matches the
>>>> average air temperature of the single heater number.
>>>>
>>>> Here's my question, so by running two identical heaters at 63.5 instead
>>>> of one heater at 65 am I using more oil, less oil, or the same amount
>>>> of oil to heat the same space to the same average temperature? there
>>>> has to be an equation that will answer this question. Anybody know how
>>>> to figure it?
>>>>
>>>
>>>
>>
>>
>
>

Al -

At 85% the furnaces use about 4% more fuel to operate at 1.5 degrees
lower with both running, instead of one running at the higher temp.
(assuming 100L BTU and a hoop house design with a 2% per hour air loss
and double poly inflated plastic as the covering for the top and
assuming R-9 in the end walls). according to the model that I have and
ran. I made a lot of assumptions.

Doug

Hope this helps.

In article <11q8btvhli4v15e [at] corp.supernews.com>,
"Pat Brennan" <orchidsNOT [at] rica.net> wrote:

> Hey Al,
>
> I did not say which option would use less oil. It is a hard question and I
> do not have enough information or remember the calculus. There are two
> factors at play, the heat generation and the heat loss. On the generation
> side it is more efficient to run one heater due to start up efficiency and
> the loss of heat up the stacks. Heating the mass of steel is no big deal
> since that is in the greenhouse and losses are into the greenhouse.
> Barometric dampers will reduce the losses up the stack, but they never work
> right for me and have lead to soot problems. On the heat loss side it is
> better to have uniform heat for a given average. As a greenhouse gets
> longer, at some length it would be better to have heaters on both end than a
> single heater and a wide range of temperatures. I have no idea what the
> length is, but one furnace is not always the best answer.
>
> If you opt for two heaters you might consider reducing the burner nozzle
> size. Nozzles are measured in gals per hour and only cost a couple of
> dollars. This will reduce the BTU output of the furnaces and they will not
> cycle on and off as much. If you change the nozzle, remember to reset the
> air intake. Also make sure your nozzles are large enough for the coldest
> nights. (we use big nozzles that are not always stocked on repair
> trucks--always keep an extra one on hand.)
>
> I have seen the long plastic tubes used even when they are not connected to
> the furnace directly. This would help level out the temps (saving oil) but
> would add another fan to your electric bill. Watch out for HAF fans blowing
> against the plastic as this leads to greater temp and humidity loss as the
> warm air moves down the greenhouse I have reduced the size of my HAF fans
> and been more careful adjusting where they blow. I assume it has lead to
> oil savings, I know it has help in growing.
>
> If you think your greenhouses grow better with two heaters; increased sales
> from better plants or faster growing plants will most likely more than pay
> for the additional oil. Humidity will be more uniform in a greenhouse that
> has uniform temps. How many blasted buds does it take to cost more than the
> oil savings?
>
> I like the temp difference across the greenhouse; oncs, zygos, and dens go
> in the cold side, seedlings in the warm section, and mature phals in the
> 'average' section.
>
> Sorry I can not help, I have no idea what is best.
>
> Pat
>
> "Al" <nospam [at] all.ever> wrote in message
> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
> > So you all are saying that I am burring more oil by what I am doing:
> > by running two identical heaters at 63.5 instead of one heater at 65 to
> > maintain an average of 65 in the space I will spend more money?
> >
> > "heating double the mass of steel and running each for half the time"
> > uses more oil?
> >
> > The extra BTUs required to
> > "maintain the part of the greenhouse 2.5 degrees above normal would not be
> > made up with the savings of only heating the other side to 2.5 degrees
> > below
> > normal" so I will use more oil?
> >
> > Lacking some calculus equation I could not understand anyway, I'll take
> > your word for it. :-) I do kind of see what you are saying. So the
> > smartest thing I can do (since I was dumb enough to buy these inefficient
> > heaters anyway) is to set one heater at 65 and one at 63 so the second
> > unit would only come on if the outside temps/winds stressed the first
> > unit's ability to maintain the temperature or failed to start at all. My
> > goal is to use the least amount of oil while knocking the fewest buds off
> > the phals.
> >
> > I do like the nice even heat distribution I get with both heaters. I kind
> > of think some of the bud loss I got last year was from marauding cold dry
> > drafts in the circulating pattern. I will have to look into a way to
> > distribute the heat from one unit more evenly. Those clear plastic tubes
> > that hook in front of some heater brands and run down the length of the
> > greenhouse dispensing heated air though little holes will not work because
> > they can not be attached to the front of my heaters. The manufactures
> > told me so last year. If these things would just hurry up and rust away,
> > I would invest in a better method of heating; probably a boiler with
> > fin-tubes of circulating water running under the benches.
> >
> > "Ray" <raybark [at] firstrays.com> wrote in message
> > news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
> >> It is less-efficient to run two.
> >>
> >> When a heater comes on, you pay to heat the heater in addition to heating
> >> the air. If you plotted a curve of the percentage of energy spent
> >> heating the hardware versus heating the air, it gets more efficient with
> >> longer individual run times. The longer the burn time per start, the
> >> more efficient it is. That's why it doesn't pay to buy a 100K BTU heater
> >> when your need is for a 50K unit - it may heat the air really fast, but
> >> it has to do so more often. The ideal would be a heater that generated
> >> heat continuously at the exact rate the greenhouse lost it.
> >>
> >> With two heaters, you are heating double the mass of steel and running
> >> each for half the time for each burn cycle.
> >>
> >> --
> >>
> >> Ray Barkalow - First Rays Orchids - www.firstrays.com
> >> Plants, Supplies, Artwork, Books and Lots of Free Info!
> >>
> >>
> >> "Al" <nospam [at] all.ever> wrote in message
> >> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
> >>> ps. logically I come up with the same btu's must be needed to reach the
> >>> same average temperature, but is this the truth?
> >>>
> >>> "Al" <nospam [at] all.ever> wrote in message
> >>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
> >>>> Hi,
> >>>>
> >>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
> >>>> heaters, that burn oil. One heater alone is enough to heat the
> >>>> greenhouse (on all but the coldest nights). They hang on opposite side
> >>>> of the long greenhouse and the un-used one is a back up incase the
> >>>> primary one dies. Two thermostats hang in the middle of the space, 50
> >>>> feet from the heaters about midway way from the floor to the roof. One
> >>>> thermostat controls one heater each and they are independent of each
> >>>> other. There are four temperature monitoring stations in the
> >>>> greenhouse that are independent of the on/off thermostats that are
> >>>> situated to read the two coldest spots and the two warmest spots. The
> >>>> four spots are gathered from plant level around the bench levels, (not
> >>>> extremely close to heaters or tucked down in cold corners)
> >>>>
> >>>> I can run the south wall heater with its thermostat set at 65 (in the
> >>>> middle of the greenhouse) and the north end of the greenhouse will
> >>>> register around 63 and the heated side will register around 68 but the
> >>>> air is circulated by LOTS of fans and the center air mass where the
> >>>> thermostat is, is 65 degrees. The four temperature sensors around the
> >>>> greenhouse average 65. The same pattern emerges no matter which heater
> >>>> I use; the far side is cool and the heater side is hotter but the
> >>>> middle is 65.
> >>>>
> >>>> If I set *both* heaters to come on at about 64, both sides of the
> >>>> greenhouse heat to around 68 and the middle of the air mass turns on
> >>>> and off both heaters at 64. And they don't seem to cycle on and off as
> >>>> often, and it seems there is probably more radiant heat available from
> >>>> two heaters but that may be an illusion because the outside night
> >>>> temperature varies a lot from night to night and this has to effect how
> >>>> the heaters cycle on and off.
> >>>>
> >>>> ....anyway the average temperature based on the 4 monitoring stations
> >>>> now comes to just under 66.... I have to set the thermostats just
> >>>> about 63.5 to get an average air temperature of 65, so it matches the
> >>>> average air temperature of the single heater number.
> >>>>
> >>>> Here's my question, so by running two identical heaters at 63.5 instead
> >>>> of one heater at 65 am I using more oil, less oil, or the same amount
> >>>> of oil to heat the same space to the same average temperature? there
> >>>> has to be an equation that will answer this question. Anybody know how
> >>>> to figure it?
> >>>>
> >>>
> >>>
> >>
> >>
> >
> >

My heater eminence people were shocked at the size of the burner nozzles
that came with the heaters. They already reduced them and adjusted all the
other stuff to compensate. I only ran using the larger nozzles the first
year. One day I will learn to do this maintenance myself. One of the
heaters MELTS the burner nozzle about twice a year and nobody has been able
to figure out why yet. The other heater does not have the same gremlin
living in it and has never melted a nozzle or, for that matter, had any real
problems at all. Yet they are exactly the same make and model and are
configured the same way.

I appreciate the input. :-)

Actually what I want most is to find no bud blast at all every morning when
I check. It is down considerably this year (so far) as compared to last
year. When I grew indoors, at a much smaller scale, I don't remember any
bud blast and I attribute the difference to the environment in the basement
having more variables under my control, especially the light. There was
never a cloudy day in the basement. In the greenhouse I am lucky if I get
ten sunny days a month this time of year. I think this plays a role in bud
loss too.

I am probably going to run on double heaters a few more weeks and just see
how things work.

I still have plenty of coolish spots in the greenhouse. I have a few
cymbidiums and zygos in bud and ten I have an entire bench of masd in
bloom too.

"Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
news:11q8btvhli4v15e [at] corp.supernews.com...
> Hey Al,
>
> I did not say which option would use less oil. It is a hard question and
> I do not have enough information or remember the calculus. There are two
> factors at play, the heat generation and the heat loss. On the generation
> side it is more efficient to run one heater due to start up efficiency and
> the loss of heat up the stacks. Heating the mass of steel is no big deal
> since that is in the greenhouse and losses are into the greenhouse.
> Barometric dampers will reduce the losses up the stack, but they never
> work right for me and have lead to soot problems. On the heat loss side
> it is better to have uniform heat for a given average. As a greenhouse
> gets longer, at some length it would be better to have heaters on both end
> than a single heater and a wide range of temperatures. I have no idea
> what the length is, but one furnace is not always the best answer.
>
> If you opt for two heaters you might consider reducing the burner nozzle
> size. Nozzles are measured in gals per hour and only cost a couple of
> dollars. This will reduce the BTU output of the furnaces and they will
> not cycle on and off as much. If you change the nozzle, remember to reset
> the air intake. Also make sure your nozzles are large enough for the
> coldest nights. (we use big nozzles that are not always stocked on repair
> trucks--always keep an extra one on hand.)
>
> I have seen the long plastic tubes used even when they are not connected
> to the furnace directly. This would help level out the temps (saving oil)
> but would add another fan to your electric bill. Watch out for HAF fans
> blowing against the plastic as this leads to greater temp and humidity
> loss as the warm air moves down the greenhouse I have reduced the size
> of my HAF fans and been more careful adjusting where they blow. I assume
> it has lead to oil savings, I know it has help in growing.
>
> If you think your greenhouses grow better with two heaters; increased
> sales from better plants or faster growing plants will most likely more
> than pay for the additional oil. Humidity will be more uniform in a
> greenhouse that has uniform temps. How many blasted buds does it take to
> cost more than the oil savings?
>
> I like the temp difference across the greenhouse; oncs, zygos, and dens go
> in the cold side, seedlings in the warm section, and mature phals in the
> 'average' section.
>
> Sorry I can not help, I have no idea what is best.
>
> Pat
>
> "Al" <nospam [at] all.ever> wrote in message
> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
>> So you all are saying that I am burring more oil by what I am doing:
>> by running two identical heaters at 63.5 instead of one heater at 65 to
>> maintain an average of 65 in the space I will spend more money?
>>
>> "heating double the mass of steel and running each for half the time"
>> uses more oil?
>>
>> The extra BTUs required to
>> "maintain the part of the greenhouse 2.5 degrees above normal would not
>> be
>> made up with the savings of only heating the other side to 2.5 degrees
>> below
>> normal" so I will use more oil?
>>
>> Lacking some calculus equation I could not understand anyway, I'll take
>> your word for it. :-) I do kind of see what you are saying. So the
>> smartest thing I can do (since I was dumb enough to buy these inefficient
>> heaters anyway) is to set one heater at 65 and one at 63 so the second
>> unit would only come on if the outside temps/winds stressed the first
>> unit's ability to maintain the temperature or failed to start at all. My
>> goal is to use the least amount of oil while knocking the fewest buds off
>> the phals.
>>
>> I do like the nice even heat distribution I get with both heaters. I
>> kind of think some of the bud loss I got last year was from marauding
>> cold dry drafts in the circulating pattern. I will have to look into a
>> way to distribute the heat from one unit more evenly. Those clear
>> plastic tubes that hook in front of some heater brands and run down the
>> length of the greenhouse dispensing heated air though little holes will
>> not work because they can not be attached to the front of my heaters.
>> The manufactures told me so last year. If these things would just hurry
>> up and rust away, I would invest in a better method of heating; probably
>> a boiler with fin-tubes of circulating water running under the benches.
>>
>> "Ray" <raybark [at] firstrays.com> wrote in message
>> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>>> It is less-efficient to run two.
>>>
>>> When a heater comes on, you pay to heat the heater in addition to
>>> heating the air. If you plotted a curve of the percentage of energy
>>> spent heating the hardware versus heating the air, it gets more
>>> efficient with longer individual run times. The longer the burn time
>>> per start, the more efficient it is. That's why it doesn't pay to buy a
>>> 100K BTU heater when your need is for a 50K unit - it may heat the air
>>> really fast, but it has to do so more often. The ideal would be a
>>> heater that generated heat continuously at the exact rate the greenhouse
>>> lost it.
>>>
>>> With two heaters, you are heating double the mass of steel and running
>>> each for half the time for each burn cycle.
>>>
>>> --
>>>
>>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>>
>>>
>>> "Al" <nospam [at] all.ever> wrote in message
>>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>>> ps. logically I come up with the same btu's must be needed to reach
>>>> the same average temperature, but is this the truth?
>>>>
>>>> "Al" <nospam [at] all.ever> wrote in message
>>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>>> Hi,
>>>>>
>>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>>> greenhouse (on all but the coldest nights). They hang on opposite
>>>>> side of the long greenhouse and the un-used one is a back up incase
>>>>> the primary one dies. Two thermostats hang in the middle of the space,
>>>>> 50 feet from the heaters about midway way from the floor to the roof.
>>>>> One thermostat controls one heater each and they are independent of
>>>>> each other. There are four temperature monitoring stations in the
>>>>> greenhouse that are independent of the on/off thermostats that are
>>>>> situated to read the two coldest spots and the two warmest spots. The
>>>>> four spots are gathered from plant level around the bench levels, (not
>>>>> extremely close to heaters or tucked down in cold corners)
>>>>>
>>>>> I can run the south wall heater with its thermostat set at 65 (in the
>>>>> middle of the greenhouse) and the north end of the greenhouse will
>>>>> register around 63 and the heated side will register around 68 but the
>>>>> air is circulated by LOTS of fans and the center air mass where the
>>>>> thermostat is, is 65 degrees. The four temperature sensors around the
>>>>> greenhouse average 65. The same pattern emerges no matter which
>>>>> heater I use; the far side is cool and the heater side is hotter but
>>>>> the middle is 65.
>>>>>
>>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>>> greenhouse heat to around 68 and the middle of the air mass turns on
>>>>> and off both heaters at 64. And they don't seem to cycle on and off
>>>>> as often, and it seems there is probably more radiant heat available
>>>>> from two heaters but that may be an illusion because the outside night
>>>>> temperature varies a lot from night to night and this has to effect
>>>>> how the heaters cycle on and off.
>>>>>
>>>>> ....anyway the average temperature based on the 4 monitoring stations
>>>>> now comes to just under 66.... I have to set the thermostats just
>>>>> about 63.5 to get an average air temperature of 65, so it matches the
>>>>> average air temperature of the single heater number.
>>>>>
>>>>> Here's my question, so by running two identical heaters at 63.5
>>>>> instead of one heater at 65 am I using more oil, less oil, or the same
>>>>> amount of oil to heat the same space to the same average temperature?
>>>>> there has to be an equation that will answer this question. Anybody
>>>>> know how to figure it?
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>

Al, Do you know about the fan limit controller and have YOU played with it?

"Al" <nospam [at] all.ever> wrote in message
news:SICdnfryiuZzqzneRVn-qg [at] adelphia.com...
> My heater eminence people were shocked at the size of the burner nozzles
> that came with the heaters. They already reduced them and adjusted all
> the other stuff to compensate. I only ran using the larger nozzles the
> first year. One day I will learn to do this maintenance myself. One of
> the heaters MELTS the burner nozzle about twice a year and nobody has been
> able to figure out why yet. The other heater does not have the same
> gremlin living in it and has never melted a nozzle or, for that matter,
> had any real problems at all. Yet they are exactly the same make and
> model and are configured the same way.
>
> I appreciate the input. :-)
>
> Actually what I want most is to find no bud blast at all every morning
> when I check. It is down considerably this year (so far) as compared to
> last year. When I grew indoors, at a much smaller scale, I don't remember
> any bud blast and I attribute the difference to the environment in the
> basement having more variables under my control, especially the light.
> There was never a cloudy day in the basement. In the greenhouse I am
> lucky if I get ten sunny days a month this time of year. I think this
> plays a role in bud loss too.
>
> I am probably going to run on double heaters a few more weeks and just see
> how things work.
>
> I still have plenty of coolish spots in the greenhouse. I have a few
> cymbidiums and zygos in bud and ten I have an entire bench of masd in
> bloom too.
>
> "Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
> news:11q8btvhli4v15e [at] corp.supernews.com...
>> Hey Al,
>>
>> I did not say which option would use less oil. It is a hard question and
>> I do not have enough information or remember the calculus. There are two
>> factors at play, the heat generation and the heat loss. On the
>> generation side it is more efficient to run one heater due to start up
>> efficiency and the loss of heat up the stacks. Heating the mass of steel
>> is no big deal since that is in the greenhouse and losses are into the
>> greenhouse. Barometric dampers will reduce the losses up the stack, but
>> they never work right for me and have lead to soot problems. On the heat
>> loss side it is better to have uniform heat for a given average. As a
>> greenhouse gets longer, at some length it would be better to have heaters
>> on both end than a single heater and a wide range of temperatures. I
>> have no idea what the length is, but one furnace is not always the best
>> answer.
>>
>> If you opt for two heaters you might consider reducing the burner nozzle
>> size. Nozzles are measured in gals per hour and only cost a couple of
>> dollars. This will reduce the BTU output of the furnaces and they will
>> not cycle on and off as much. If you change the nozzle, remember to
>> reset the air intake. Also make sure your nozzles are large enough for
>> the coldest nights. (we use big nozzles that are not always stocked on
>> repair trucks--always keep an extra one on hand.)
>>
>> I have seen the long plastic tubes used even when they are not connected
>> to the furnace directly. This would help level out the temps (saving
>> oil) but would add another fan to your electric bill. Watch out for HAF
>> fans blowing against the plastic as this leads to greater temp and
>> humidity loss as the warm air moves down the greenhouse I have reduced
>> the size of my HAF fans and been more careful adjusting where they blow.
>> I assume it has lead to oil savings, I know it has help in growing.
>>
>> If you think your greenhouses grow better with two heaters; increased
>> sales from better plants or faster growing plants will most likely more
>> than pay for the additional oil. Humidity will be more uniform in a
>> greenhouse that has uniform temps. How many blasted buds does it take to
>> cost more than the oil savings?
>>
>> I like the temp difference across the greenhouse; oncs, zygos, and dens
>> go in the cold side, seedlings in the warm section, and mature phals in
>> the 'average' section.
>>
>> Sorry I can not help, I have no idea what is best.
>>
>> Pat
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
>>> So you all are saying that I am burring more oil by what I am doing:
>>> by running two identical heaters at 63.5 instead of one heater at 65 to
>>> maintain an average of 65 in the space I will spend more money?
>>>
>>> "heating double the mass of steel and running each for half the time"
>>> uses more oil?
>>>
>>> The extra BTUs required to
>>> "maintain the part of the greenhouse 2.5 degrees above normal would not
>>> be
>>> made up with the savings of only heating the other side to 2.5 degrees
>>> below
>>> normal" so I will use more oil?
>>>
>>> Lacking some calculus equation I could not understand anyway, I'll take
>>> your word for it. :-) I do kind of see what you are saying. So the
>>> smartest thing I can do (since I was dumb enough to buy these
>>> inefficient heaters anyway) is to set one heater at 65 and one at 63 so
>>> the second unit would only come on if the outside temps/winds stressed
>>> the first unit's ability to maintain the temperature or failed to start
>>> at all. My goal is to use the least amount of oil while knocking the
>>> fewest buds off the phals.
>>>
>>> I do like the nice even heat distribution I get with both heaters. I
>>> kind of think some of the bud loss I got last year was from marauding
>>> cold dry drafts in the circulating pattern. I will have to look into a
>>> way to distribute the heat from one unit more evenly. Those clear
>>> plastic tubes that hook in front of some heater brands and run down the
>>> length of the greenhouse dispensing heated air though little holes will
>>> not work because they can not be attached to the front of my heaters.
>>> The manufactures told me so last year. If these things would just hurry
>>> up and rust away, I would invest in a better method of heating; probably
>>> a boiler with fin-tubes of circulating water running under the benches.
>>>
>>> "Ray" <raybark [at] firstrays.com> wrote in message
>>> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>>>> It is less-efficient to run two.
>>>>
>>>> When a heater comes on, you pay to heat the heater in addition to
>>>> heating the air. If you plotted a curve of the percentage of energy
>>>> spent heating the hardware versus heating the air, it gets more
>>>> efficient with longer individual run times. The longer the burn time
>>>> per start, the more efficient it is. That's why it doesn't pay to buy
>>>> a 100K BTU heater when your need is for a 50K unit - it may heat the
>>>> air really fast, but it has to do so more often. The ideal would be a
>>>> heater that generated heat continuously at the exact rate the
>>>> greenhouse lost it.
>>>>
>>>> With two heaters, you are heating double the mass of steel and running
>>>> each for half the time for each burn cycle.
>>>>
>>>> --
>>>>
>>>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>>>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>>>
>>>>
>>>> "Al" <nospam [at] all.ever> wrote in message
>>>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>>>> ps. logically I come up with the same btu's must be needed to reach
>>>>> the same average temperature, but is this the truth?
>>>>>
>>>>> "Al" <nospam [at] all.ever> wrote in message
>>>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>>>> Hi,
>>>>>>
>>>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>>>> greenhouse (on all but the coldest nights). They hang on opposite
>>>>>> side of the long greenhouse and the un-used one is a back up incase
>>>>>> the primary one dies. Two thermostats hang in the middle of the
>>>>>> space, 50 feet from the heaters about midway way from the floor to
>>>>>> the roof. One thermostat controls one heater each and they are
>>>>>> independent of each other. There are four temperature monitoring
>>>>>> stations in the greenhouse that are independent of the on/off
>>>>>> thermostats that are situated to read the two coldest spots and the
>>>>>> two warmest spots. The four spots are gathered from plant level
>>>>>> around the bench levels, (not extremely close to heaters or tucked
>>>>>> down in cold corners)
>>>>>>
>>>>>> I can run the south wall heater with its thermostat set at 65 (in the
>>>>>> middle of the greenhouse) and the north end of the greenhouse will
>>>>>> register around 63 and the heated side will register around 68 but
>>>>>> the air is circulated by LOTS of fans and the center air mass where
>>>>>> the thermostat is, is 65 degrees. The four temperature sensors around
>>>>>> the greenhouse average 65. The same pattern emerges no matter which
>>>>>> heater I use; the far side is cool and the heater side is hotter but
>>>>>> the middle is 65.
>>>>>>
>>>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>>>> greenhouse heat to around 68 and the middle of the air mass turns on
>>>>>> and off both heaters at 64. And they don't seem to cycle on and off
>>>>>> as often, and it seems there is probably more radiant heat available
>>>>>> from two heaters but that may be an illusion because the outside
>>>>>> night temperature varies a lot from night to night and this has to
>>>>>> effect how the heaters cycle on and off.
>>>>>>
>>>>>> ....anyway the average temperature based on the 4 monitoring stations
>>>>>> now comes to just under 66.... I have to set the thermostats just
>>>>>> about 63.5 to get an average air temperature of 65, so it matches the
>>>>>> average air temperature of the single heater number.
>>>>>>
>>>>>> Here's my question, so by running two identical heaters at 63.5
>>>>>> instead of one heater at 65 am I using more oil, less oil, or the
>>>>>> same amount of oil to heat the same space to the same average
>>>>>> temperature? there has to be an equation that will answer this
>>>>>> question. Anybody know how to figure it?
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>

"Al" <nospam [at] all.ever> wrote in message
news:SICdnfryiuZzqzneRVn-qg [at] adelphia.com...
> One day I will learn to do this maintenance myself.

Yep, 2:30 AM, ice storm, greenhouse temp 44 and dropping. BTW, that guy you
can always count on is still on vacation in sunny FLA.

The endwalls are twinwall lexan. The design resembles a wide low pentagon
shape more than a hoop. The average wall height is 5 feet. The average
center ridge height is 14 feet. (The greenhouse is built on a slope.) The
roof area and wall area are covered in inflated double poly 6 mill plastic.

The heaters are rated at 210,000 BTU, (new, with original nozzles. I can't
find the efficiency rating but I think it is 85%.
http://www.aaagreenhouse.com/quantumoil.htm (Siebring Quantum 210), the
size of refrigerators. The pictures make them look tiny.

I am not sure I see what effect most of the variables like greenhouse
covering, outside night temps, etc, have on the question but I think you
answered it. I think changing the heater efficiency would effect the
answer.

I think you are telling me: Assuming all other variables remain equal I use
a bit more oil with the two heater method I described ...but you can't say
exactly how much more unless you know more specifics about my greenhouse,
and my local temps and wind patterns etc.

I have a calculation on a spread sheet that has pretty closely predicted how
much oil my greenhouse will use over the course of the last 5 winters. For
instance, last years gallons used were 3186 and the spread sheet, based on
average mean temps in my area came up with 3325. I was not able to look at
these calculations and see how to adjust them to answer my one heater or two
heater question.

"Doug Houseman" <doug [at] msen.com> wrote in message
news:doug-874F03.10472917122005 [at] comcast.dca.giganews.com...
> Al -
>
> At 85% the furnaces use about 4% more fuel to operate at 1.5 degrees
> lower with both running, instead of one running at the higher temp.
> (assuming 100L BTU and a hoop house design with a 2% per hour air loss
> and double poly inflated plastic as the covering for the top and
> assuming R-9 in the end walls). according to the model that I have and
> ran. I made a lot of assumptions.
>
> Doug
>
> Hope this helps.
>
> In article <11q8btvhli4v15e [at] corp.supernews.com>,
> "Pat Brennan" <orchidsNOT [at] rica.net> wrote:
>
>> Hey Al,
>>
>> I did not say which option would use less oil. It is a hard question and
>> I
>> do not have enough information or remember the calculus. There are two
>> factors at play, the heat generation and the heat loss. On the
>> generation
>> side it is more efficient to run one heater due to start up efficiency
>> and
>> the loss of heat up the stacks. Heating the mass of steel is no big deal
>> since that is in the greenhouse and losses are into the greenhouse.
>> Barometric dampers will reduce the losses up the stack, but they never
>> work
>> right for me and have lead to soot problems. On the heat loss side it is
>> better to have uniform heat for a given average. As a greenhouse gets
>> longer, at some length it would be better to have heaters on both end
>> than a
>> single heater and a wide range of temperatures. I have no idea what the
>> length is, but one furnace is not always the best answer.
>>
>> If you opt for two heaters you might consider reducing the burner nozzle
>> size. Nozzles are measured in gals per hour and only cost a couple of
>> dollars. This will reduce the BTU output of the furnaces and they will
>> not
>> cycle on and off as much. If you change the nozzle, remember to reset
>> the
>> air intake. Also make sure your nozzles are large enough for the coldest
>> nights. (we use big nozzles that are not always stocked on repair
>> trucks--always keep an extra one on hand.)
>>
>> I have seen the long plastic tubes used even when they are not connected
>> to
>> the furnace directly. This would help level out the temps (saving oil)
>> but
>> would add another fan to your electric bill. Watch out for HAF fans
>> blowing
>> against the plastic as this leads to greater temp and humidity loss as
>> the
>> warm air moves down the greenhouse I have reduced the size of my HAF
>> fans
>> and been more careful adjusting where they blow. I assume it has lead to
>> oil savings, I know it has help in growing.
>>
>> If you think your greenhouses grow better with two heaters; increased
>> sales
>> from better plants or faster growing plants will most likely more than
>> pay
>> for the additional oil. Humidity will be more uniform in a greenhouse
>> that
>> has uniform temps. How many blasted buds does it take to cost more than
>> the
>> oil savings?
>>
>> I like the temp difference across the greenhouse; oncs, zygos, and dens
>> go
>> in the cold side, seedlings in the warm section, and mature phals in the
>> 'average' section.
>>
>> Sorry I can not help, I have no idea what is best.
>>
>> Pat
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
>> > So you all are saying that I am burring more oil by what I am doing:
>> > by running two identical heaters at 63.5 instead of one heater at 65 to
>> > maintain an average of 65 in the space I will spend more money?
>> >
>> > "heating double the mass of steel and running each for half the time"
>> > uses more oil?
>> >
>> > The extra BTUs required to
>> > "maintain the part of the greenhouse 2.5 degrees above normal would not
>> > be
>> > made up with the savings of only heating the other side to 2.5 degrees
>> > below
>> > normal" so I will use more oil?
>> >
>> > Lacking some calculus equation I could not understand anyway, I'll take
>> > your word for it. :-) I do kind of see what you are saying. So the
>> > smartest thing I can do (since I was dumb enough to buy these
>> > inefficient
>> > heaters anyway) is to set one heater at 65 and one at 63 so the second
>> > unit would only come on if the outside temps/winds stressed the first
>> > unit's ability to maintain the temperature or failed to start at all.
>> > My
>> > goal is to use the least amount of oil while knocking the fewest buds
>> > off
>> > the phals.
>> >
>> > I do like the nice even heat distribution I get with both heaters. I
>> > kind
>> > of think some of the bud loss I got last year was from marauding cold
>> > dry
>> > drafts in the circulating pattern. I will have to look into a way to
>> > distribute the heat from one unit more evenly. Those clear plastic
>> > tubes
>> > that hook in front of some heater brands and run down the length of the
>> > greenhouse dispensing heated air though little holes will not work
>> > because
>> > they can not be attached to the front of my heaters. The manufactures
>> > told me so last year. If these things would just hurry up and rust
>> > away,
>> > I would invest in a better method of heating; probably a boiler with
>> > fin-tubes of circulating water running under the benches.
>> >
>> > "Ray" <raybark [at] firstrays.com> wrote in message
>> > news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>> >> It is less-efficient to run two.
>> >>
>> >> When a heater comes on, you pay to heat the heater in addition to
>> >> heating
>> >> the air. If you plotted a curve of the percentage of energy spent
>> >> heating the hardware versus heating the air, it gets more efficient
>> >> with
>> >> longer individual run times. The longer the burn time per start, the
>> >> more efficient it is. That's why it doesn't pay to buy a 100K BTU
>> >> heater
>> >> when your need is for a 50K unit - it may heat the air really fast,
>> >> but
>> >> it has to do so more often. The ideal would be a heater that
>> >> generated
>> >> heat continuously at the exact rate the greenhouse lost it.
>> >>
>> >> With two heaters, you are heating double the mass of steel and running
>> >> each for half the time for each burn cycle.
>> >>
>> >> --
>> >>
>> >> Ray Barkalow - First Rays Orchids - www.firstrays.com
>> >> Plants, Supplies, Artwork, Books and Lots of Free Info!
>> >>
>> >>
>> >> "Al" <nospam [at] all.ever> wrote in message
>> >> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>> >>> ps. logically I come up with the same btu's must be needed to reach
>> >>> the
>> >>> same average temperature, but is this the truth?
>> >>>
>> >>> "Al" <nospam [at] all.ever> wrote in message
>> >>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>> >>>> Hi,
>> >>>>
>> >>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>> >>>> heaters, that burn oil. One heater alone is enough to heat the
>> >>>> greenhouse (on all but the coldest nights). They hang on opposite
>> >>>> side
>> >>>> of the long greenhouse and the un-used one is a back up incase the
>> >>>> primary one dies. Two thermostats hang in the middle of the space,
>> >>>> 50
>> >>>> feet from the heaters about midway way from the floor to the roof.
>> >>>> One
>> >>>> thermostat controls one heater each and they are independent of each
>> >>>> other. There are four temperature monitoring stations in the
>> >>>> greenhouse that are independent of the on/off thermostats that are
>> >>>> situated to read the two coldest spots and the two warmest spots.
>> >>>> The
>> >>>> four spots are gathered from plant level around the bench levels,
>> >>>> (not
>> >>>> extremely close to heaters or tucked down in cold corners)
>> >>>>
>> >>>> I can run the south wall heater with its thermostat set at 65 (in
>> >>>> the
>> >>>> middle of the greenhouse) and the north end of the greenhouse will
>> >>>> register around 63 and the heated side will register around 68 but
>> >>>> the
>> >>>> air is circulated by LOTS of fans and the center air mass where the
>> >>>> thermostat is, is 65 degrees. The four temperature sensors around
>> >>>> the
>> >>>> greenhouse average 65. The same pattern emerges no matter which
>> >>>> heater
>> >>>> I use; the far side is cool and the heater side is hotter but the
>> >>>> middle is 65.
>> >>>>
>> >>>> If I set *both* heaters to come on at about 64, both sides of the
>> >>>> greenhouse heat to around 68 and the middle of the air mass turns on
>> >>>> and off both heaters at 64. And they don't seem to cycle on and off
>> >>>> as
>> >>>> often, and it seems there is probably more radiant heat available
>> >>>> from
>> >>>> two heaters but that may be an illusion because the outside night
>> >>>> temperature varies a lot from night to night and this has to effect
>> >>>> how
>> >>>> the heaters cycle on and off.
>> >>>>
>> >>>> ....anyway the average temperature based on the 4 monitoring
>> >>>> stations
>> >>>> now comes to just under 66.... I have to set the thermostats just
>> >>>> about 63.5 to get an average air temperature of 65, so it matches
>> >>>> the
>> >>>> average air temperature of the single heater number.
>> >>>>
>> >>>> Here's my question, so by running two identical heaters at 63.5
>> >>>> instead
>> >>>> of one heater at 65 am I using more oil, less oil, or the same
>> >>>> amount
>> >>>> of oil to heat the same space to the same average temperature?
>> >>>> there
>> >>>> has to be an equation that will answer this question. Anybody know
>> >>>> how
>> >>>> to figure it?
>> >>>>
>> >>>
>> >>>
>> >>
>> >>
>> >
>> >

You mean in relation to the burner nozzle melt downs? Yes I know about it
and yes *I* have messed with it. :-) Last spring after the second melt
down I asked the maintenance guy to look at it and see if he though the
settings were causing the problem. He said it could very well be the case,
checked it out, adjusted them *both* a bit but said the settings he had
found on the one i messed with were probably not causing the nozzle to melt.
Maybe he was just being tactful. So far this year, knock on wood, the
gremlinated heater is functioning without problem. I use the gremlinated
heater as the main heater. I would not be able to sleep at night if it were
the backup knowing that it was the more likely one to break down. Using it
as the primary gives me a very secure safety net should it fail with the
same frequency it did last year.

"Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
news:11q8f70l26fnfa1 [at] corp.supernews.com...
> Al, Do you know about the fan limit controller and have YOU played with
> it?
>
> "Al" <nospam [at] all.ever> wrote in message
> news:SICdnfryiuZzqzneRVn-qg [at] adelphia.com...
>> My heater eminence people were shocked at the size of the burner nozzles
>> that came with the heaters. They already reduced them and adjusted all
>> the other stuff to compensate. I only ran using the larger nozzles the
>> first year. One day I will learn to do this maintenance myself. One of
>> the heaters MELTS the burner nozzle about twice a year and nobody has
>> been able to figure out why yet. The other heater does not have the same
>> gremlin living in it and has never melted a nozzle or, for that matter,
>> had any real problems at all. Yet they are exactly the same make and
>> model and are configured the same way.
>>
>> I appreciate the input. :-)
>>
>> Actually what I want most is to find no bud blast at all every morning
>> when I check. It is down considerably this year (so far) as compared to
>> last year. When I grew indoors, at a much smaller scale, I don't
>> remember any bud blast and I attribute the difference to the environment
>> in the basement having more variables under my control, especially the
>> light. There was never a cloudy day in the basement. In the greenhouse I
>> am lucky if I get ten sunny days a month this time of year. I think this
>> plays a role in bud loss too.
>>
>> I am probably going to run on double heaters a few more weeks and just
>> see how things work.
>>
>> I still have plenty of coolish spots in the greenhouse. I have a few
>> cymbidiums and zygos in bud and ten I have an entire bench of masd in
>> bloom too.
>>
>> "Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
>> news:11q8btvhli4v15e [at] corp.supernews.com...
>>> Hey Al,
>>>
>>> I did not say which option would use less oil. It is a hard question
>>> and I do not have enough information or remember the calculus. There
>>> are two factors at play, the heat generation and the heat loss. On the
>>> generation side it is more efficient to run one heater due to start up
>>> efficiency and the loss of heat up the stacks. Heating the mass of
>>> steel is no big deal since that is in the greenhouse and losses are into
>>> the greenhouse. Barometric dampers will reduce the losses up the stack,
>>> but they never work right for me and have lead to soot problems. On the
>>> heat loss side it is better to have uniform heat for a given average.
>>> As a greenhouse gets longer, at some length it would be better to have
>>> heaters on both end than a single heater and a wide range of
>>> temperatures. I have no idea what the length is, but one furnace is not
>>> always the best answer.
>>>
>>> If you opt for two heaters you might consider reducing the burner nozzle
>>> size. Nozzles are measured in gals per hour and only cost a couple of
>>> dollars. This will reduce the BTU output of the furnaces and they will
>>> not cycle on and off as much. If you change the nozzle, remember to
>>> reset the air intake. Also make sure your nozzles are large enough for
>>> the coldest nights. (we use big nozzles that are not always stocked on
>>> repair trucks--always keep an extra one on hand.)
>>>
>>> I have seen the long plastic tubes used even when they are not connected
>>> to the furnace directly. This would help level out the temps (saving
>>> oil) but would add another fan to your electric bill. Watch out for HAF
>>> fans blowing against the plastic as this leads to greater temp and
>>> humidity loss as the warm air moves down the greenhouse I have reduced
>>> the size of my HAF fans and been more careful adjusting where they blow.
>>> I assume it has lead to oil savings, I know it has help in growing.
>>>
>>> If you think your greenhouses grow better with two heaters; increased
>>> sales from better plants or faster growing plants will most likely more
>>> than pay for the additional oil. Humidity will be more uniform in a
>>> greenhouse that has uniform temps. How many blasted buds does it take
>>> to cost more than the oil savings?
>>>
>>> I like the temp difference across the greenhouse; oncs, zygos, and dens
>>> go in the cold side, seedlings in the warm section, and mature phals in
>>> the 'average' section.
>>>
>>> Sorry I can not help, I have no idea what is best.
>>>
>>> Pat
>>>
>>> "Al" <nospam [at] all.ever> wrote in message
>>> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
>>>> So you all are saying that I am burring more oil by what I am doing:
>>>> by running two identical heaters at 63.5 instead of one heater at 65 to
>>>> maintain an average of 65 in the space I will spend more money?
>>>>
>>>> "heating double the mass of steel and running each for half the time"
>>>> uses more oil?
>>>>
>>>> The extra BTUs required to
>>>> "maintain the part of the greenhouse 2.5 degrees above normal would not
>>>> be
>>>> made up with the savings of only heating the other side to 2.5 degrees
>>>> below
>>>> normal" so I will use more oil?
>>>>
>>>> Lacking some calculus equation I could not understand anyway, I'll take
>>>> your word for it. :-) I do kind of see what you are saying. So the
>>>> smartest thing I can do (since I was dumb enough to buy these
>>>> inefficient heaters anyway) is to set one heater at 65 and one at 63
>>>> so the second unit would only come on if the outside temps/winds
>>>> stressed the first unit's ability to maintain the temperature or failed
>>>> to start at all. My goal is to use the least amount of oil while
>>>> knocking the fewest buds off the phals.
>>>>
>>>> I do like the nice even heat distribution I get with both heaters. I
>>>> kind of think some of the bud loss I got last year was from marauding
>>>> cold dry drafts in the circulating pattern. I will have to look into a
>>>> way to distribute the heat from one unit more evenly. Those clear
>>>> plastic tubes that hook in front of some heater brands and run down the
>>>> length of the greenhouse dispensing heated air though little holes will
>>>> not work because they can not be attached to the front of my heaters.
>>>> The manufactures told me so last year. If these things would just
>>>> hurry up and rust away, I would invest in a better method of heating;
>>>> probably a boiler with fin-tubes of circulating water running under the
>>>> benches.
>>>>
>>>> "Ray" <raybark [at] firstrays.com> wrote in message
>>>> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>>>>> It is less-efficient to run two.
>>>>>
>>>>> When a heater comes on, you pay to heat the heater in addition to
>>>>> heating the air. If you plotted a curve of the percentage of energy
>>>>> spent heating the hardware versus heating the air, it gets more
>>>>> efficient with longer individual run times. The longer the burn time
>>>>> per start, the more efficient it is. That's why it doesn't pay to buy
>>>>> a 100K BTU heater when your need is for a 50K unit - it may heat the
>>>>> air really fast, but it has to do so more often. The ideal would be a
>>>>> heater that generated heat continuously at the exact rate the
>>>>> greenhouse lost it.
>>>>>
>>>>> With two heaters, you are heating double the mass of steel and running
>>>>> each for half the time for each burn cycle.
>>>>>
>>>>> --
>>>>>
>>>>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>>>>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>>>>
>>>>>
>>>>> "Al" <nospam [at] all.ever> wrote in message
>>>>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>>>>> ps. logically I come up with the same btu's must be needed to reach
>>>>>> the same average temperature, but is this the truth?
>>>>>>
>>>>>> "Al" <nospam [at] all.ever> wrote in message
>>>>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>>>>> Hi,
>>>>>>>
>>>>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>>>>> greenhouse (on all but the coldest nights). They hang on opposite
>>>>>>> side of the long greenhouse and the un-used one is a back up incase
>>>>>>> the primary one dies. Two thermostats hang in the middle of the
>>>>>>> space, 50 feet from the heaters about midway way from the floor to
>>>>>>> the roof. One thermostat controls one heater each and they are
>>>>>>> independent of each other. There are four temperature monitoring
>>>>>>> stations in the greenhouse that are independent of the on/off
>>>>>>> thermostats that are situated to read the two coldest spots and the
>>>>>>> two warmest spots. The four spots are gathered from plant level
>>>>>>> around the bench levels, (not extremely close to heaters or tucked
>>>>>>> down in cold corners)
>>>>>>>
>>>>>>> I can run the south wall heater with its thermostat set at 65 (in
>>>>>>> the middle of the greenhouse) and the north end of the greenhouse
>>>>>>> will register around 63 and the heated side will register around 68
>>>>>>> but the air is circulated by LOTS of fans and the center air mass
>>>>>>> where the thermostat is, is 65 degrees. The four temperature sensors
>>>>>>> around the greenhouse average 65. The same pattern emerges no
>>>>>>> matter which heater I use; the far side is cool and the heater side
>>>>>>> is hotter but the middle is 65.
>>>>>>>
>>>>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>>>>> greenhouse heat to around 68 and the middle of the air mass turns on
>>>>>>> and off both heaters at 64. And they don't seem to cycle on and off
>>>>>>> as often, and it seems there is probably more radiant heat available
>>>>>>> from two heaters but that may be an illusion because the outside
>>>>>>> night temperature varies a lot from night to night and this has to
>>>>>>> effect how the heaters cycle on and off.
>>>>>>>
>>>>>>> ....anyway the average temperature based on the 4 monitoring
>>>>>>> stations now comes to just under 66.... I have to set the
>>>>>>> thermostats just about 63.5 to get an average air temperature of 65,
>>>>>>> so it matches the average air temperature of the single heater
>>>>>>> number.
>>>>>>>
>>>>>>> Here's my question, so by running two identical heaters at 63.5
>>>>>>> instead of one heater at 65 am I using more oil, less oil, or the
>>>>>>> same amount of oil to heat the same space to the same average
>>>>>>> temperature? there has to be an equation that will answer this
>>>>>>> question. Anybody know how to figure it?
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>

The meltdowns was not why I was asking, but that would be the first thing I
checked. May meltdowns be something I never know about. I was wondering if
you set back the blower kick in (the middle set point) if you might not get
more uniform temps across the greenhouse. My little greenhouse works best
with the blower always on (controller set to manual). I have run it that
way a couple of years now. Watch the guys that set these, they are used to
setting them for humans in houses. There may be some oil savings in
dropping the low temp fan shutoff.

Pat

"Al" <nospam [at] all.ever> wrote in message
news:edCdnSXAjshK1jneRVn-rA [at] adelphia.com...
> You mean in relation to the burner nozzle melt downs? Yes I know about it
> and yes *I* have messed with it. :-) Last spring after the second melt
> down I asked the maintenance guy to look at it and see if he though the
> settings were causing the problem. He said it could very well be the
> case, checked it out, adjusted them *both* a bit but said the settings he
> had found on the one i messed with were probably not causing the nozzle to
> melt. Maybe he was just being tactful. So far this year, knock on wood,
> the gremlinated heater is functioning without problem. I use the
> gremlinated heater as the main heater. I would not be able to sleep at
> night if it were the backup knowing that it was the more likely one to
> break down. Using it as the primary gives me a very secure safety net
> should it fail with the same frequency it did last year.
>
> "Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
> news:11q8f70l26fnfa1 [at] corp.supernews.com...
>> Al, Do you know about the fan limit controller and have YOU played with
>> it?
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:SICdnfryiuZzqzneRVn-qg [at] adelphia.com...
>>> My heater eminence people were shocked at the size of the burner nozzles
>>> that came with the heaters. They already reduced them and adjusted all
>>> the other stuff to compensate. I only ran using the larger nozzles the
>>> first year. One day I will learn to do this maintenance myself. One of
>>> the heaters MELTS the burner nozzle about twice a year and nobody has
>>> been able to figure out why yet. The other heater does not have the
>>> same gremlin living in it and has never melted a nozzle or, for that
>>> matter, had any real problems at all. Yet they are exactly the same
>>> make and model and are configured the same way.
>>>
>>> I appreciate the input. :-)
>>>
>>> Actually what I want most is to find no bud blast at all every morning
>>> when I check. It is down considerably this year (so far) as compared to
>>> last year. When I grew indoors, at a much smaller scale, I don't
>>> remember any bud blast and I attribute the difference to the environment
>>> in the basement having more variables under my control, especially the
>>> light. There was never a cloudy day in the basement. In the greenhouse
>>> I am lucky if I get ten sunny days a month this time of year. I think
>>> this plays a role in bud loss too.
>>>
>>> I am probably going to run on double heaters a few more weeks and just
>>> see how things work.
>>>
>>> I still have plenty of coolish spots in the greenhouse. I have a few
>>> cymbidiums and zygos in bud and ten I have an entire bench of masd in
>>> bloom too.
>>>
>>> "Pat Brennan" <orchidsNOT [at] rica.net> wrote in message
>>> news:11q8btvhli4v15e [at] corp.supernews.com...
>>>> Hey Al,
>>>>
>>>> I did not say which option would use less oil. It is a hard question
>>>> and I do not have enough information or remember the calculus. There
>>>> are two factors at play, the heat generation and the heat loss. On the
>>>> generation side it is more efficient to run one heater due to start up
>>>> efficiency and the loss of heat up the stacks. Heating the mass of
>>>> steel is no big deal since that is in the greenhouse and losses are
>>>> into the greenhouse. Barometric dampers will reduce the losses up the
>>>> stack, but they never work right for me and have lead to soot problems.
>>>> On the heat loss side it is better to have uniform heat for a given
>>>> average. As a greenhouse gets longer, at some length it would be better
>>>> to have heaters on both end than a single heater and a wide range of
>>>> temperatures. I have no idea what the length is, but one furnace is
>>>> not always the best answer.
>>>>
>>>> If you opt for two heaters you might consider reducing the burner
>>>> nozzle size. Nozzles are measured in gals per hour and only cost a
>>>> couple of dollars. This will reduce the BTU output of the furnaces and
>>>> they will not cycle on and off as much. If you change the nozzle,
>>>> remember to reset the air intake. Also make sure your nozzles are
>>>> large enough for the coldest nights. (we use big nozzles that are not
>>>> always stocked on repair trucks--always keep an extra one on hand.)
>>>>
>>>> I have seen the long plastic tubes used even when they are not
>>>> connected to the furnace directly. This would help level out the temps
>>>> (saving oil) but would add another fan to your electric bill. Watch
>>>> out for HAF fans blowing against the plastic as this leads to greater
>>>> temp and humidity loss as the warm air moves down the greenhouse I
>>>> have reduced the size of my HAF fans and been more careful adjusting
>>>> where they blow. I assume it has lead to oil savings, I know it has
>>>> help in growing.
>>>>
>>>> If you think your greenhouses grow better with two heaters; increased
>>>> sales from better plants or faster growing plants will most likely more
>>>> than pay for the additional oil. Humidity will be more uniform in a
>>>> greenhouse that has uniform temps. How many blasted buds does it take
>>>> to cost more than the oil savings?
>>>>
>>>> I like the temp difference across the greenhouse; oncs, zygos, and dens
>>>> go in the cold side, seedlings in the warm section, and mature phals in
>>>> the 'average' section.
>>>>
>>>> Sorry I can not help, I have no idea what is best.
>>>>
>>>> Pat
>>>>
>>>> "Al" <nospam [at] all.ever> wrote in message
>>>> news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
>>>>> So you all are saying that I am burring more oil by what I am doing:
>>>>> by running two identical heaters at 63.5 instead of one heater at 65
>>>>> to maintain an average of 65 in the space I will spend more money?
>>>>>
>>>>> "heating double the mass of steel and running each for half the time"
>>>>> uses more oil?
>>>>>
>>>>> The extra BTUs required to
>>>>> "maintain the part of the greenhouse 2.5 degrees above normal would
>>>>> not be
>>>>> made up with the savings of only heating the other side to 2.5 degrees
>>>>> below
>>>>> normal" so I will use more oil?
>>>>>
>>>>> Lacking some calculus equation I could not understand anyway, I'll
>>>>> take your word for it. :-) I do kind of see what you are saying. So
>>>>> the smartest thing I can do (since I was dumb enough to buy these
>>>>> inefficient heaters anyway) is to set one heater at 65 and one at 63
>>>>> so the second unit would only come on if the outside temps/winds
>>>>> stressed the first unit's ability to maintain the temperature or
>>>>> failed to start at all. My goal is to use the least amount of oil
>>>>> while knocking the fewest buds off the phals.
>>>>>
>>>>> I do like the nice even heat distribution I get with both heaters. I
>>>>> kind of think some of the bud loss I got last year was from marauding
>>>>> cold dry drafts in the circulating pattern. I will have to look into
>>>>> a way to distribute the heat from one unit more evenly. Those clear
>>>>> plastic tubes that hook in front of some heater brands and run down
>>>>> the length of the greenhouse dispensing heated air though little holes
>>>>> will not work because they can not be attached to the front of my
>>>>> heaters. The manufactures told me so last year. If these things would
>>>>> just hurry up and rust away, I would invest in a better method of
>>>>> heating; probably a boiler with fin-tubes of circulating water running
>>>>> under the benches.
>>>>>
>>>>> "Ray" <raybark [at] firstrays.com> wrote in message
>>>>> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>>>>>> It is less-efficient to run two.
>>>>>>
>>>>>> When a heater comes on, you pay to heat the heater in addition to
>>>>>> heating the air. If you plotted a curve of the percentage of energy
>>>>>> spent heating the hardware versus heating the air, it gets more
>>>>>> efficient with longer individual run times. The longer the burn time
>>>>>> per start, the more efficient it is. That's why it doesn't pay to
>>>>>> buy a 100K BTU heater when your need is for a 50K unit - it may heat
>>>>>> the air really fast, but it has to do so more often. The ideal would
>>>>>> be a heater that generated heat continuously at the exact rate the
>>>>>> greenhouse lost it.
>>>>>>
>>>>>> With two heaters, you are heating double the mass of steel and
>>>>>> running each for half the time for each burn cycle.
>>>>>>
>>>>>> --
>>>>>>
>>>>>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>>>>>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>>>>>
>>>>>>
>>>>>> "Al" <nospam [at] all.ever> wrote in message
>>>>>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>>>>>> ps. logically I come up with the same btu's must be needed to reach
>>>>>>> the same average temperature, but is this the truth?
>>>>>>>
>>>>>>> "Al" <nospam [at] all.ever> wrote in message
>>>>>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>>>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>>>>>> greenhouse (on all but the coldest nights). They hang on opposite
>>>>>>>> side of the long greenhouse and the un-used one is a back up incase
>>>>>>>> the primary one dies. Two thermostats hang in the middle of the
>>>>>>>> space, 50 feet from the heaters about midway way from the floor to
>>>>>>>> the roof. One thermostat controls one heater each and they are
>>>>>>>> independent of each other. There are four temperature monitoring
>>>>>>>> stations in the greenhouse that are independent of the on/off
>>>>>>>> thermostats that are situated to read the two coldest spots and the
>>>>>>>> two warmest spots. The four spots are gathered from plant level
>>>>>>>> around the bench levels, (not extremely close to heaters or tucked
>>>>>>>> down in cold corners)
>>>>>>>>
>>>>>>>> I can run the south wall heater with its thermostat set at 65 (in
>>>>>>>> the middle of the greenhouse) and the north end of the greenhouse
>>>>>>>> will register around 63 and the heated side will register around 68
>>>>>>>> but the air is circulated by LOTS of fans and the center air mass
>>>>>>>> where the thermostat is, is 65 degrees. The four temperature
>>>>>>>> sensors around the greenhouse average 65. The same pattern emerges
>>>>>>>> no matter which heater I use; the far side is cool and the heater
>>>>>>>> side is hotter but the middle is 65.
>>>>>>>>
>>>>>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>>>>>> greenhouse heat to around 68 and the middle of the air mass turns
>>>>>>>> on and off both heaters at 64. And they don't seem to cycle on and
>>>>>>>> off as often, and it seems there is probably more radiant heat
>>>>>>>> available from two heaters but that may be an illusion because the
>>>>>>>> outside night temperature varies a lot from night to night and this
>>>>>>>> has to effect how the heaters cycle on and off.
>>>>>>>>
>>>>>>>> ....anyway the average temperature based on the 4 monitoring
>>>>>>>> stations now comes to just under 66.... I have to set the
>>>>>>>> thermostats just about 63.5 to get an average air temperature of
>>>>>>>> 65, so it matches the average air temperature of the single heater
>>>>>>>> number.
>>>>>>>>
>>>>>>>> Here's my question, so by running two identical heaters at 63.5
>>>>>>>> instead of one heater at 65 am I using more oil, less oil, or the
>>>>>>>> same amount of oil to heat the same space to the same average
>>>>>>>> temperature? there has to be an equation that will answer this
>>>>>>>> question. Anybody know how to figure it?
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>

I second this one from Pat. I'm pretty sure I use far less than heat than
you do, although I do still wince everytime we have to fill up the LP tank
.... but I suspect I spend way more for summer cooling, even without cool
pads. Cutting corners on either expense hasn't worked out well for us --
keeping the plants at their best, we've found, is more cost-effective. And
for us, at least, it's more than bud-blast on Phals. E.g., an extra 3
degrees F of heat greatly reduced our leaf-loss on the vandaceous plants.

That said, 65F is warmer than we try to stay. We haven't found that 58F
hurts anything, including budded Phals* -- except ME, when I have to be out
at dawn. I'm not set up for anything under 75F! Fortunately, the plants
are tougher than I am. Kenni

The other factor that affects us probably more than you is the likelihood of
really BIG diurnal shifts, esp. if we don't get the place opened back up
early after a cold night. Despite an overnight low in the low 40s
[outdoors], the high can get into the 80s the next day. THAT will blast
some buds.


> If you think your greenhouses grow better with two heaters; increased
> sales from better plants or faster growing plants will most likely more
> than pay for the additional oil. Humidity will be more uniform in a
> greenhouse that has uniform temps. How many blasted buds does it take to
> cost more than the oil savings?

Al,

If temperature distribution is your primary concern, why not just run more
fans> They're probably less expensive to operate than the heaters.

The key to efficiency is to match the heating capacity to the greenhouse
demand. The ideal is a heater that puts out the exact amount of energy that
the greenhouse loses, such that it is on constantly. Obviously it's
impossible to have such a device, as outside temperature changes and
sunlight affect the balance.

As there is no way to actually meet that ideal, one tries to size the heater
to be able to keep up with the demand under your worst case scenario - in my
case with an "even worse than that" built in safety factor - knowing that it
will operate less efficiently under "better-than-worst-case" conditions.

If one of your heaters has the capacity to heat your greenhouse, it is more
efficient to heat exclusively with one, and have the second as a backup with
the thermostat for it set lower than the primary. If each your heaters has
half of the necessary capacity, using them both with be immeasurably less
efficient than running a single unit with twice the capacity, the difference
being the amount of oil that has to be burned in order to heat the extra
mass of metal.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Artwork, Books and Lots of Free Info!


"Al" <nospam [at] all.ever> wrote in message
news:C5CdnUE3785ZgTnenZ2dnUVZ_v-dnZ2d [at] adelphia.com...
> So you all are saying that I am burring more oil by what I am doing:
> by running two identical heaters at 63.5 instead of one heater at 65 to
> maintain an average of 65 in the space I will spend more money?
>
> "heating double the mass of steel and running each for half the time"
> uses more oil?
>
> The extra BTUs required to
> "maintain the part of the greenhouse 2.5 degrees above normal would not be
> made up with the savings of only heating the other side to 2.5 degrees
> below
> normal" so I will use more oil?
>
> Lacking some calculus equation I could not understand anyway, I'll take
> your word for it. :-) I do kind of see what you are saying. So the
> smartest thing I can do (since I was dumb enough to buy these inefficient
> heaters anyway) is to set one heater at 65 and one at 63 so the second
> unit would only come on if the outside temps/winds stressed the first
> unit's ability to maintain the temperature or failed to start at all. My
> goal is to use the least amount of oil while knocking the fewest buds off
> the phals.
>
> I do like the nice even heat distribution I get with both heaters. I kind
> of think some of the bud loss I got last year was from marauding cold dry
> drafts in the circulating pattern. I will have to look into a way to
> distribute the heat from one unit more evenly. Those clear plastic tubes
> that hook in front of some heater brands and run down the length of the
> greenhouse dispensing heated air though little holes will not work because
> they can not be attached to the front of my heaters. The manufactures
> told me so last year. If these things would just hurry up and rust away,
> I would invest in a better method of heating; probably a boiler with
> fin-tubes of circulating water running under the benches.
>
> "Ray" <raybark [at] firstrays.com> wrote in message
> news:O7KdnUS6cL3syD7eRVn-rw [at] comcast.com...
>> It is less-efficient to run two.
>>
>> When a heater comes on, you pay to heat the heater in addition to heating
>> the air. If you plotted a curve of the percentage of energy spent
>> heating the hardware versus heating the air, it gets more efficient with
>> longer individual run times. The longer the burn time per start, the
>> more efficient it is. That's why it doesn't pay to buy a 100K BTU heater
>> when your need is for a 50K unit - it may heat the air really fast, but
>> it has to do so more often. The ideal would be a heater that generated
>> heat continuously at the exact rate the greenhouse lost it.
>>
>> With two heaters, you are heating double the mass of steel and running
>> each for half the time for each burn cycle.
>>
>> --
>>
>> Ray Barkalow - First Rays Orchids - www.firstrays.com
>> Plants, Supplies, Artwork, Books and Lots of Free Info!
>>
>>
>> "Al" <nospam [at] all.ever> wrote in message
>> news:hfWdnaWMFK1s2T7e4p2dnA [at] adelphia.com...
>>> ps. logically I come up with the same btu's must be needed to reach the
>>> same average temperature, but is this the truth?
>>>
>>> "Al" <nospam [at] all.ever> wrote in message
>>> news:94qdnUb-l6uR3z7eRVn-gg [at] adelphia.com...
>>>> Hi,
>>>>
>>>> I have a 30 by 100 foot greenhouse. I have two heaters, forced air
>>>> heaters, that burn oil. One heater alone is enough to heat the
>>>> greenhouse (on all but the coldest nights). They hang on opposite side
>>>> of the long greenhouse and the un-used one is a back up incase the
>>>> primary one dies. Two thermostats hang in the middle of the space, 50
>>>> feet from the heaters about midway way from the floor to the roof. One
>>>> thermostat controls one heater each and they are independent of each
>>>> other. There are four temperature monitoring stations in the
>>>> greenhouse that are independent of the on/off thermostats that are
>>>> situated to read the two coldest spots and the two warmest spots. The
>>>> four spots are gathered from plant level around the bench levels, (not
>>>> extremely close to heaters or tucked down in cold corners)
>>>>
>>>> I can run the south wall heater with its thermostat set at 65 (in the
>>>> middle of the greenhouse) and the north end of the greenhouse will
>>>> register around 63 and the heated side will register around 68 but the
>>>> air is circulated by LOTS of fans and the center air mass where the
>>>> thermostat is, is 65 degrees. The four temperature sensors around the
>>>> greenhouse average 65. The same pattern emerges no matter which heater
>>>> I use; the far side is cool and the heater side is hotter but the
>>>> middle is 65.
>>>>
>>>> If I set *both* heaters to come on at about 64, both sides of the
>>>> greenhouse heat to around 68 and the middle of the air mass turns on
>>>> and off both heaters at 64. And they don't seem to cycle on and off as
>>>> often, and it seems there is probably more radiant heat available from
>>>> two heaters but that may be an illusion because the outside night
>>>> temperature varies a lot from night to night and this has to effect how
>>>> the heaters cycle on and off.
>>>>
>>>> ....anyway the average temperature based on the 4 monitoring stations
>>>> now comes to just under 66.... I have to set the thermostats just
>>>> about 63.5 to get an average air temperature of 65, so it matches the
>>>> average air temperature of the single heater number.
>>>>
>>>> Here's my question, so by running two identical heaters at 63.5 instead
>>>> of one heater at 65 am I using more oil, less oil, or the same amount
>>>> of oil to heat the same space to the same average temperature? there
>>>> has to be an equation that will answer this question. Anybody know how
>>>> to figure it?
>>>>
>>>
>>>
>>
>>
>
>

Reading this thread makes me glad I went through the extra trouble and
expense of putting in hot water perimeter heating. With only one small fan
to keep the air moving the GH stays at 58 to 61 F except when the sun
shines then I have to vent on days above 25 F.