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Old 16-12-2005, 11:39 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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?


  #2   Report Post  
Old 16-12-2005, 11:51 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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?



  #3   Report Post  
Old 17-12-2005, 12:21 AM posted to rec.gardens.orchids
Doug Houseman
 
Posts: n/a
Default Greenhouse oil heat math question

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 ,
"Al" 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" wrote in message
...
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?

  #4   Report Post  
Old 17-12-2005, 12:50 AM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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 ,
"Al" 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" wrote in message
...
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?



  #5   Report Post  
Old 17-12-2005, 01:01 AM posted to rec.gardens.orchids
Ray
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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" wrote in message
...
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?







  #6   Report Post  
Old 17-12-2005, 05:44 AM posted to rec.gardens.orchids
Pat Brennan
 
Posts: n/a
Default Greenhouse oil heat math question



"Al" wrote in message
...
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



  #7   Report Post  
Old 17-12-2005, 03:12 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?







  #8   Report Post  
Old 17-12-2005, 04:45 PM posted to rec.gardens.orchids
Pat Brennan
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?









  #9   Report Post  
Old 17-12-2005, 04:47 PM posted to rec.gardens.orchids
Doug Houseman
 
Posts: n/a
Default Greenhouse oil heat math question

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 ,
"Pat Brennan" 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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?







  #10   Report Post  
Old 17-12-2005, 05:04 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?













  #11   Report Post  
Old 17-12-2005, 05:41 PM posted to rec.gardens.orchids
Pat Brennan
 
Posts: n/a
Default Greenhouse oil heat math question

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

"Al" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?













  #12   Report Post  
Old 17-12-2005, 05:56 PM posted to rec.gardens.orchids
Pat Brennan
 
Posts: n/a
Default Greenhouse oil heat math question


"Al" wrote in message
...
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.



  #13   Report Post  
Old 17-12-2005, 06:22 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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 ,
"Pat Brennan" 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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?









  #14   Report Post  
Old 17-12-2005, 06:32 PM posted to rec.gardens.orchids
Al
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
Al, Do you know about the fan limit controller and have YOU played with
it?

"Al" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?















  #15   Report Post  
Old 17-12-2005, 08:41 PM posted to rec.gardens.orchids
Pat Brennan
 
Posts: n/a
Default Greenhouse oil heat math question

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" wrote in message
...
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" wrote in message
...
Al, Do you know about the fan limit controller and have YOU played with
it?

"Al" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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" wrote in message
...
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?

















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