Greenhouse needs more heat

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Old 01-24-14, 01:14 PM
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Greenhouse needs more heat

I have a 130 s.f. greenhouse with insulating glass on the roof and three sides. One side is against the house and has a double pane sliding door connecting into the house. The calculated heat loss for the space at 0 degree outside temperature and 65 degree inside temperature is 15,285 BtuH.

This is a working greenhouse (not an occupied space) and in winter is set for 65 degrees daytime, 55 degrees overnight to accommodate orchid grow cycles. On sunny days in winter the temperature will go up to 75 to 80 degrees from solar gain and there is little or no call for heat.

The heating is 90 feet of copper/aluminum fin tube without enclosure on a separate zone. The fin tube runs inside the glass perimeter in an 8 inch deep “ditch” below the finished floor level but open to the space above, and between the joists under the floor. The joist spaces are open to the ditch on one end so in addition to heating the floor the heat there can escape through the ditch to the greenhouse space.

The problem I am encountering is that the greenhouse is not able to maintain 65 on cloudy days or 55 at night when outdoor temps are in single digits. I do not recall this happening with my old boiler running at a supply temp of 180. I have had to keep the door into the house open overnight on cold nights to keep the greenhouse above 50 degrees.

Since I converted to gas heat and installed an ES-2 boiler I have been taking readings that show generally the greenhouse return temp is about 9 degrees less than supply. That delta is consistent for supply temps in the 140s to 160s. I think this is indicating that the fin tube is delivering anywhere from 24,000 to 44,000 BtuH. I have calculated the heat output two ways:

(90 ft. of fintube) x (310 BtuH/ft.) x (.85 factor for H2O @ 140) = 23,715 BtuH

and

(490 constant for H2O @ 140) x (10 gpm flow) x (9 degrees delta T) = 44,100 BtuH
assuming a 10 gpm flow since the greenhouse piping is only about 4 feet above the Taco 007 pump on the return line.

Obviously something is wrong since those results are significantly higher than the calculated need. Overall for the entire house the actual heat losses determined from gas usage are running about 85% of the calculations, so I am reasonably confident that there is no major error there.

Here are the questions:

Which calculation should I believe?
Is the water hot enough?
Is the water flowing too fast to allow the fin tube to release enough heat to the space?

Please also comment on whether the following are possible solutions or provide others:

Install floor vents at the closed ends of the joist cavities to allow more air flow over the fintube.
Reduce the flow by partially closing the supply or return valves.
Repipe to obtain supply water for this zone ahead of the bypass (average about 14 degrees higher.)

Thanks for y our help.
 
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Old 01-26-14, 09:56 AM
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Anybody...anybody??

Is this too hard or just not interesting enough?
 
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Old 01-26-14, 10:13 AM
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Neither...

but busy with others... trying to keep up is difficult this time of year!

I'll look at it a bit more later, but one thing to note is that when baseboard elements are removed from the cabinets and installed 'creatively', they will usually not put out the BTU that they are rated for. This is because the cabinets are designed to channel the air flow across the fins to maximize the heat output... let's call it the 'chimney effect'.

Mounting a baseboard element in alternate ways usually means not as much air flow across the fins.
 
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Old 01-26-14, 10:43 AM
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readings that show generally the greenhouse return temp is about 9 degrees less than supply
Indicates either too much flow, or not much heat being taken out of the fin-tube.

(10 gpm flow)
That's very optimistic for (I presume you are using) 3/4" elements? Flow should not be that fast. If it is, you are slowly eroding the interior of the pipes. FOUR GPM is 'design' for 3/4" heating circuits.

Which calculation should I believe?
I don't think either.

Is the water hot enough?
Hotter water will obviously increase heat output.

Is the water flowing too fast to allow the fin tube to release enough heat to the space?
This needs some explanation.

Water can't flow 'too fast' to release enough heat.

Yes, the water coming back from a faster flowing loop is going to be hotter, but this does NOT mean that it's releasing less heat. In fact, it's probably releasing MORE heat because the AVERAGE temperature across the loop is HIGHER than it would be if the water were moving more slowly and the return temperature was cooler (greater delta T).

The QUANTITY of the water through the loop being higher means that the SAME or GREATER BTU can be withdrawn from that water but still have a smaller delta T.

As example, let's say that you have a flow of 1 GPM of 190F ENTERING water through 10K BTUH worth of heat emitters.

Your delta T will be 20F.

The AVERAGE water temperature in the loop will be 180 ( 190 + 170 ) / 2.

If you DOUBLE the flow to 2 GPM, the DT may go to 10 (or thereabout, too lazy to do the math). Now your AVERAGE water temp in the same loop is increased to 185F and this means that the SAME heat emitters will output MORE heat.

The amount of heat emitted does not depend on flow per se, but rather on the temperature of the water inside the pipe.

My guess is that the output from that element without the cabinets is probably 200 BTUH / LF or so.

One thing you could try... put a fan blowing into the ditches to move more air across the fins.
 
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Old 01-26-14, 10:48 AM
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By the way, BARE copper 3/4" heat emission is around 50 BTUH / LF at about 100F difference between the pipe surface and ambient. Just for reference... this is 'radiated' emission only, no air flow.
 
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Old 01-26-14, 12:50 PM
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busy with others... trying to keep up is difficult this time of year!
I can appreciate that. Thanks for getting back.

Indicates either too much flow, or not much heat being taken out of the fin-tube.
I suspected that.

(10 gpm flow)
I did not calculate head pressure but the total length of the loop from boiler to greenhouse and back is 90 feet fin tube and about 40 feet of bare 3/4 inch copper with probably 30 elbows and a couple of valves rising about 4 feet. I WAGged the head at about 7.5 feet for 10gpm flow from the TACO 007 pump curve. I suspect if I do the actual calc the head will be lower indicating an even higher flow.

I knew when I installed it that air flow would be restricted especially in the joist spaces, but until this year the heating was acceptable even though marginal at really low temps. A fan in the ditch would help as would creating a path for air to flow by adding open grates to the joist spaces.

But I would like to try reducing the water flow first. Can I use the supply and return valves to throttle it back?

Also, 90 feet of fin tube @ 200 BTUH = 18000 which should be enough to offset the calculated loss of 15285 BTUH so I think air flow is the key to solving this puzzle.

BTW: the supply temp to the SYSTEM after the bypass seldom goes above 165 and the average is about 145.
 
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Old 01-26-14, 01:29 PM
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I WAGged the head at about 7.5 feet
That's pretty close... but that's at FOUR GPM. And head increases with flow on a logarithmic scale.

A 'rule of thumb' that Bell & Gossett teaches that will get one PDC to the head of a system at 4 FPM flow velocity (which is close to 4 GPM in 3/4" pipe) is to forget about counting elbows, etc...

Multiply the total length of the pipe by 1.5 and then again by 0.04 to come up with head.

This works because for the smaller size pipes ( 1/2, 3/4, 1 ) at the CORRECT VELOCITY of around 4 FPM in the loop, the pipe will exhibit appx 4' of head per 100 feet. The larger size pipes start to skew the results a bit, but it's still close.

Multiplying by 1.5 gives you what can be considered an 'average' padding for the elbows and other fittings on a typical loop.

So, by doing the ROT for 130' of pipe, we come up with 7.8' of head... AT 4 GPM ...

Now, take a look at the following example chart. Here is an arbitrary SYSTEM CURVE plotted on top of a PUMP CURVE. YOUR system curve would be shifted a bit to the right in this example, but it serves to illustrate that the OPERATING POINT of the pump is the point where the two curves intersect. One can not simply follow a HEAD line to the right and then down to read the GPM, it doesn't work that way.:



The shape of all system curves is very similar due to the mathematical 'function' involved, so if you mentally shift the slope of that curve and draw a dot at the 7.8' HEAD / 4 GPM point and draw a curve of similar shape through that point, you will see that AT MOST, the 007 will be pumping about FIVE GPM through your loop, and probably more like 4.5 GPM.

What this tells us then is that because you are only seeing a 9F delta T you are taking little heat out of that water.

STILL, it is looking like enough based on your heat loss figures.

How did you arrive at the 15K BTUH requirement?
 
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Old 01-26-14, 01:40 PM
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I should also bring up another point about delta T ...

As the temperature in the loop is decreased, the delta T ALSO decreases.

The 20F figure I mentioned above is only valid at 180F water temperature. At lower temps, it has to be less.

I suspect that the greenhouse heat loss is higher than calculated, and the baseboard output may in fact even be lower than 200 / LF ... that part is a guessing game because there is no data available for your application of bare elements in a trough and under a floor. Too many variables to consider.
 
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Old 01-26-14, 02:42 PM
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I do not recall this happening with my old boiler running at a supply temp of 180.
BTW: the supply temp to the SYSTEM after the bypass seldom goes above 165 and the average is about 145.
I think these two statements say a lot towards where your problem lies. Why don't you run 180 degree water to the greenhouse first before you do anything else? If 180 degree water solves your problem, set the greenhouse up on it's own zone like it is a indirect hot water heater. You can then set it to have priority and demand 180 F water without affecting your ODR setup. It's been awhile since I fiddled with my ES2, but I believe there is also a timeout feature for the priority zone. That way you won't freeze the rest of the house if the greenhouse never meets temp.
 

Last edited by NJT; 01-26-14 at 03:06 PM.
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Old 01-26-14, 03:09 PM
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Thanks Droop, I meant to bring up the point about treating it as DHW but kept getting sidetracked with all that other mumbo-jumbo...

I'm too lazy to read back though... maybe John already has indirect?

On my MPO, which I believe is 'basically' the same controls, there is a DHW input and the boiler will ignore all other settings and fire to high limit if that input is closed. (I have a 'test switch' wired there so that I can bypass the ODR and fire to high limit when adjusting burner without having to pull the ODR module)

I'm pretty sure that the system pump can be configured to run, or not, when there is a DHW call.

That would be a very easy change to make if it's that simple!
 
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Old 01-26-14, 03:40 PM
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They are the same control. although I think yours has a couple new features than mine. Prepurge on the pump? Anyhow, I didn't see him mention having an indirect. I'm sure it wouldn't matter to have two zones set up as priority. Even though the controls have the DHW input, you still need a relay for the priority.
 
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Old 01-26-14, 03:42 PM
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still need a relay for the priority
Isn't the priority built into the boiler control also?
 
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Old 01-26-14, 04:46 PM
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I forget the details. Maybe it is because I have two heating zones that requires the relay. Perhaps if I had one heating zone and the DHW zone, I wouldn't need it.
 
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Old 01-26-14, 06:32 PM
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Thanks guys, you have given me some good information and things to think about.

I do not have indirect DHW. I have a separate gas water heater. A plugged tee was installed for future DHW and I was thinking I could take the supply from there for the greenhouse, including using the boiler DHW control with or without priority (built-in in the boiler control) for that zone. The water temp there averages about 15 degrees higher than the mixed supply temp after the bypass.

First I will try an experiment to get the water to 180 degrees and see the results.

How did you arrive at the 15K BTUH requirement?
130 square feet, 1300 cubic feet, 330 s.f window @ R3.2, 330 s.f [email protected] R4, 208 s.f roof @ R4.2,
Total BTUH loss = 235.149, Total loss at 65 degree delta = 15285.

I did not account for air changes or floor losses for this space independently. Air change losses were added to the total house loss.

Since the 330 s.f of wall is common to the house the delta for that loss will be 10 degrees when the house is set for 65 degree setback and the GH wants 55 overnite. I sort of traded that advantage off against not including a calculation for floor loss.

The floor below the heat is insulated with 1/2 inch plywood, 1 inch rigid foam, 3/4 inch plywood, and 8 inch fiberglass. I am certain that there is some floor loss, especially since raccoons ripped out most of the 8 inch fiberglass in the crawl space two years ago. I plan to have that replaced with spray foam next summer.
 
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Old 01-27-14, 08:54 AM
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Brain cramp:
delta for that loss will be 10 degrees when the house is set for 65 degree setback and the GH wants 55 overnite.
It ain't a loss it'a a GAIN. I'm glad I remembered that before you guys saw it.

Further on the floor loss: I looked again at the calks and realized that I took it into account in the
330 s.f [email protected] R4
. The wall common to the house is 200 s.f and the floor area is 130 s.f.. Since the calculator spreadsheet I was using did not have a category for floor I entered all that as wall. To be conservative I used R4 even though the floor assembly has a higher R value and in retrospect there is a gain through the house wall not a loss.

Fan in ditch test: Last night was not a good time to test because the outside temps rose constantly from 22 to 45 degrees overnight. However I put a small table top fan blowing in the ditch to see what might happen. At 11 PM the GH temp was 51 and calling for heat (set point 52). This morning at 8 AM the temp was 57 (set point 52). The sun was not bright yet but there might have been some solar gain. The minimum overnight in the GH was 51. Temps are going to reverse today and it will be back to the teens tomorrow and this week so I will continue to test (including water at 180 as droop suggested) but it looks like an air flow solution is possible.
 
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Old 01-27-14, 09:22 AM
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Just adding more heat may not be whole solution.

For the nights, the problem is the radiant heat loss to outer space. May of the greenhouses here use a sliding cloth material that can be drawn to cut the heat loss in cold weather in the winter. A clear dark night sky will just such out the radiant heat, but a light curtain (almost like a sheet) will cut the evening energy loss. It is not automatic usually, but it can easily be slid across and slid back to get the solar gain on a cold winter day.

R-values and insulation are effective when it comes to walls and floors. If your green house was here in MN, (-16F and clear and heading for -25F) the evening radiant heat loss from the slab also reduces the thermal storage of your area.

Dick
 
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Old 01-27-14, 09:26 AM
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Yes, the driving force for heat loss to outer space is tremendous... heat travels fastest from hot to cold and O.S. is COLD!

I puzzled for years why only the TOP of my car parked outdoors had frost in the mornng, and not the sides... same with the roof of the house and not the sidewalls...

And why the insulation in the attic is so darn important ...

Reflective curtain, great idea!
 
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Old 02-03-14, 11:55 AM
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Thumbs up Final update

The "fan in the ditch" is doing a good job of keeping the temperature at or above set point. We have not experienced any single digit outside temps since but I think the circulating air will deliver enough heat under those conditions as well since it is now extracting heat after the t'stat is satisfied and overrunning the set point by a couple of degrees. After the heating season I intend to relocate the supply for this zone to the DHW tap ahead of the bypass connection. That will provide hotter water to this zone and allow me to use lower supply temp to the other zones. If necessary I will connect the greenhouse zone pump and thermostat to the DHW controls in the IQ boiler control, but I will try with the existing controls first. And the insulation under the floor will be repaired next summer, too.

Thanks to all for your input, comments and suggestions.

John
 
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Old 02-03-14, 12:50 PM
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After the heating season I intend to relocate the supply for this zone to the DHW tap ahead of the bypass connection.
Why do you need to repipe? I think that's what you are saying?

I believe that all you need to do to get the full temperature water to that zone is to wire it's thermostat to the proper terminals of the boiler control and configure the controls to treat that call as DHW and over-ride the ODR settings...

Maybe I don't understand your piping scheme though?
 
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Old 02-03-14, 03:11 PM
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The problem is not the ODR but the volume of cold return/bypass. I think a piping change has to be made.

Because of the volume of the house zone (CI radiators, old large gravity piping) it is very difficult to get the supply mix temp after the bypass high enough for the greenhouse fin tube to be more effective. The supply mix averages in the high 140s and I have only seen it go above 170 about 6 times this season. The house actual heat loss is running about 15% below my calculation. The house calls for heat are not very often and the water cools down pretty close to ambient before the next call.

The supply temp before the bypass averages about 14 degrees hotter and usually is hotter than the IQ boiler temp reading by as much as 12 degrees. I think it will be a better source for the greenhouse.

I can probably keep the same control because the greenhouse "problem" does not occur within the ODR range but usually when the ODR is at max anyway.

I am not using the IQ ODR module but a separate Dayton wired in series between the TT terminals in my Taco control and the boiler. Since my water temp probe is in the supply piping after the bypass (not in the boiler) it is acting as a system ODR rather than as a boiler ODR. By taking the greenhouse supply ahead of the bypass the ODR should have little effect on it especially when the ODR is at max at or near OD design temp.

If I find that the ODR is limiting the temp to the greenhouse (or if I move it ahead of the bypass) then I will use the DHW zone features of the IQ for control since wiring the GH t'stat to the DHW zone will eliminate the ODR from its control circuit completely.
 
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Old 02-03-14, 04:00 PM
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I puzzled for years why only the TOP of my car parked outdoors had frost in the mornng, and not the sides... same with the roof of the house and not the sidewalls...
I know this is OT, but that happens because dew settles from top to bottom.
 
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Old 02-03-14, 04:06 PM
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I don't think so Droo... I don't believe that dew 'settles'. It's not 'fog'. It 'forms'.

The top of structures radiates heat faster because that's where the coldest area is, in outer space. The highest driving force for heat loss is UP.

I can't recall if I've ever seen frost on a cloudy morning or not, but now I'm going to have to pay attention.

Yes, OT, but interesting...
 
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Old 02-14-14, 09:25 AM
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Update and question

Yesterday I installed a 48 inch long by 4 inch wide floor grate that allows air to flow from inside the heated joist space to the greenhouse. Now that some air can flow by convection across the fin tubes the situation at colder outside temps should improve.

Last night I turned off the "fan in the ditch" to see what effect the new grate would have. The t'stat is set for a nighttime temp of 52. At 8 PM when the setback from (65 to 52) goes into effect the t'stat read 64 and was calling for heat. This morning at 9 AM the t'stat read 55 and a separate low temp memory thermometer showed the overnight low to be 54. The outside temperature overnight was constant at about 32-33. It appears based on those readings (set point 52, low temp 54) that the greenhouse did not call for heat overnight. (Daylight gain and a 400W grow light that turns on at 8 AM probably account for the 1 degree difference between t'stat and low temp readings.)

How do I calculate the actual heat loss based on inside temperature change from 64 to 54 in a 13 hour period and constant outdoor average temp of 32?
 
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Old 02-14-14, 12:27 PM
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How do I calculate the actual heat loss based on inside temperature change from 64 to 54 in a 13 hour period and constant outdoor average temp of 32?
I'm not even sure Richard Fyneman could cipher that!

Really, that's an extremely difficult calculation. You would have to know how much mass is inside the envelope of the greenhouse, the specific heat of each of the different types of mass, the emissivity of each of those masses... and more.

Ummmm... fuggedaboudit... really.
 
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Old 02-14-14, 12:50 PM
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I thought it might be a good way to validate the heat loss calculation for that room. At 32 outside temp my calculation shows the loss to be 4708 BTUH for 52* inside and 7525 BTUH for 64* inside. Assuming the mass to be only the volume of air in the space (10 X 13 X 10 = 1300 cubic feet) could I work backwards to determine whether the R values used in the calculations are close to reality?

It may sound crazy but as Feynman said/wrote: "What do you care what other people think?
 
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Old 02-14-14, 01:27 PM
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"What do you care what other people think?"
HA! You're absolutely right! and I live by that, pink hair and all... j/k, it's not pink. And yes, my apologies to Richard's ghost... I spelt his name rong... FEYNMAN ... there, all is right with the universe now.

Assuming the mass to be only the volume of air in the space
There's probably not much heat stored in the air itself. It's the structure and furnishings, and potting soil, etc... that store the heat that is emitted into the room as it cools down. Without another heat source adding heat, everything else basically becomes a radiator.
 
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Old 12-18-14, 12:05 PM
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Update on Greenhouse heating

This is to provide an update of the greenhouse heating situation that was discussed last year.

Last summer the greenhouse floor was insulated in the crawl space underneath with 4 inches of closed cell spray foam insulation. That improved the heating performance at the beginning of this heating season BUT...

-- I realized when installing the blower described below that the amount of bare fin-tube is only 60 feet, not the 90 feet that I had thought was installed. That reduces my estimate of the potential heating output to a point where it barely exceeds the BTUH loss for a 0 degree design condition.

-- I started my boiler this season with a 140 degree high limit which works very well for the other zones but definitely does not provide water temp high enough to get more heat into the greenhouse. It struggles to get to 65 on cloudy days when outside temps are around 32. More on the overall system performance on my other thread

http://www.doityourself.com/forum/bo...s2-boiler.html

Since the "fan-in-the-ditch" worked so well last year I decided to make it permanent. I had an old kick-space heater that was removed from a bathroom. I removed the coil (just to allow maximum air flow) and I installed the blower in the joist space below the floor so that it sucks air through the floor vent and blows it over the fin tube and out through the ditch by the window wall. The unit has a thermal switch that turns the blower on whenever the adjacent pipe gets hot and it continues to run after the t'stat is satisfied until the pipe is cool. It's noisy (that's why it was removed from the master bath) but in the greenhouse it's OK. The overnight temps have been 52 or above. Daytime temps reach 65 but I am still concerned that lower outside temps may cause a continuous call for heat and run hotter water than needed to the other zones.

So...after reviewing the previous discussions about using the DWH controls I have resorted to the following:

--Purchased the IQ ODR module (not cheap at $420 with tax and shipping, but a $225 NationalGrid rebate brings it into the range of "why not?".)

--Connected the greenhouse zone (t'stat and pump) to run on the "TT" boiler input with settings: HL=180, dF=30, Hb=170 (for now), Lb=130, Ho=65, Lo=0, Lt=120.

--Connected the house and master bedroom/bath zones (via Taco control with Dayton ODR override) to the dWH input on the ODR module. The boiler control is set to recognize it as tt2. Dayton settings are: Hb=140, Lb=120, Ho=40, Lo=0.

My intent is to run the greenhouse on a higher temp curve to get higher temp water through the fin-tube. When the GH alone calls for heat (on TT) the boiler temps will be set by the IQ ODR to the higher temps. If another zone is also calling for heat at the same time it will circulate that higher temp water, too. If the GH is not calling for heat and another zone is (on TT2) then the Dayton ODR will hold the water temp lower than the IQ ODR setpoint. I suspect that the boiler will operate on the lower curve about 50% of the time based on solar gain both in the GH and in the main zone.

This arrangement has been in place for 10 days and the outside temps have been in the 40s so the full effect is not yet known.

This chart shows the ODR intent:
ODR.pdf
 

Last edited by NJT; 12-18-14 at 03:21 PM.
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Old 12-18-14, 03:28 PM
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I don't think you need the second Dayton ODR.

I would wire the home to the T T inputs of the boiler, and the greenhouse to the DHW inputs on the IQ control ODR.

This will allow the home to run on the reset curve, while running the greenhouse tstat to the DHW terminals of the ODR module will allow that to completely bypass the ODR curve.

I don't see the benefit of running two ODR curves simultaneously...

Is there a model number on that Dayton ODR? Is it a 'mechanical' model, like the White Rodgers?
 
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Old 12-19-14, 10:34 AM
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Is there a model number on that Dayton ODR? Is it a 'mechanical' model, like the White Rodgers?
Dayton 2E398. Left over from my old oil burner days. It is exactly the same as the White Rodgers Type 1050. Control Range:80-250 F, Switch Action: SPST Open on rise, Differential: Fixed 10 F. I have a PDF scan of the instructions but at 3.4Mb it is too large to load here. I could not find them on line but they look like the same ones (including the temp curves) that I found for the W-R. It is mechanical in that it has outdoor and boiler temp sensors connected by capillary tubes and uses mechanical dials for selecting and adjusting temperature ranges.

My intent when I decided to buy the IQ ODR module was to run the greenhouse on the ODR curve and run the house zones on the fixed DWH settings. However the DWH high limit setting does not allow below 150. I have had great success running the house zones at 140 so far this season (to be described in an update of another thread) so I first tried running the greenhouse on the DHW settings and the house on the ODR curve. I also activated the boost feature so that the water temp to the GH would increase if the demand was not satisfied within 15 minutes.

The result of that first connection was that the GH demand always required boost mode and the boiler was running closer to 160-170 more often than I wanted. I turned off boost mode but the GH was still driving the boiler temp higher than I wanted for long periods of time. Then I decided to reverse the connections so the GH would run on the ODR curve and the house would run on the DHW settings but tempered by the Dayton ODR which I already had in place. It's not perfect in that the curves are harder to calibrate and I think it might be reducing the burn times that I have been trying to extend as much as possible. Also since the Dayton does not have the ability to set a fixed low limit I am concerned about running the boiler too low and causing condensing. I thought the Low Boiler Limit (Lt) on the IQ ODR module would prevent that but I have discovered it does not. (More on that in another thread to be posted soon.)

I don't see the benefit of running two ODR curves simultaneously.
The benefit I am hoping for is that, whenever the house zones are calling for heat in the absence of a call from the GH, the boiler will be held to a lower temperature. This will apply most of the night when only the MBR bathroom radiant floor is calling for heat and in the early morning when the main house zone is heating up from a modest setback. Except for extremely cold outdoor temps the GH should be mostly "in charge" only during its late morning warm-up from a much larger (52 to 65 degree--dictated by the plants) setback or if there is no solar gain on a very cloudy cold day.

I got the idea to run two ODR curves partly from the settings available in the IQ ODR module. The new version includes settings for a second ODR curve to operate in conjunction with the IQ Zone Circulator Panel for a "Low Temperature" heat demand. From the description in the instructions (not yet on line): "The Heating Zone 2 demand allows the boiler to provide cooler water when the Heating Zone 1 and DHW demand are not calling for heat."

That describes my situation exactly if I consider the main house zones as the "Heating Zone 2" described. So since I do not have the IQ zone panel (and really don't think I need it in any case) I am trying to duplicate the control scheme using what I have.
 
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