Greenhouse heater problem - Modine PAE50


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Old 12-24-08, 07:50 AM
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Greenhouse heater problem - Modine PAE50

Help! I've had several different service firms try to solve this and we're getting nowhere. I have a Modine PAE50 in my greenhouse which has an intermittent but recurring start-up problem. Thankfully I also have a 220 electric heater as backup.

On start-up cycle, when the burner starts to fire, there is a loud POOF which blows the pilot out. This unit was just serviced (again) 5 days ago, the pilot assembly replaced (again), and it's already repeating this recurring problem. It appears to be increasing in frequency - initially sometme overnight, then twice during the day yesterday, again last night, and I just restarted the pilot (initial cycle was successful) and the 2nd draw for heat resulted in the dreaded POOF.

According to the service people, everything is functioning properly and tests OK. Obviously they're missing something, but what? This is an older unit by now, which I simply didn't try to use for several years. I decided to try again recently, hoping that the latest HVAC service company could solve the problem.
 
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Old 12-24-08, 08:04 AM
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Originally Posted by carol_okc
Help! I've had several different service firms try to solve this and we're getting nowhere. I have a Modine PAE50 in my greenhouse which has an intermittent but recurring start-up problem. Thankfully I also have a 220 electric heater as backup.

On start-up cycle, when the burner starts to fire, there is a loud POOF which blows the pilot out. This unit was just serviced (again) 5 days ago, the pilot assembly replaced (again), and it's already repeating this recurring problem. It appears to be increasing in frequency - initially sometme overnight, then twice during the day yesterday, again last night, and I just restarted the pilot (initial cycle was successful) and the 2nd draw for heat resulted in the dreaded POOF.

According to the service people, everything is functioning properly and tests OK. Obviously they're missing something, but what? This is an older unit by now, which I simply didn't try to use for several years. I decided to try again recently, hoping that the latest HVAC service company could solve the problem.

Did they check the gas pressure? Also, is it natural gas or LP? if LP did they use an LP conversion kit?
 
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Old 12-24-08, 08:30 AM
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Thanks for your quick response!

I don't know if the newest service tech checked the gas pressure, but it's been checked several times in the past whilst trying to solve this problem. This is a propane unit which was professionally installed. Considering the fact that this has been a problem from the beginning, I have to question the 'professional' part, but there are virtually no local firms interested in working on a greenhouse heater.

In reading the Modine service manual, it suggests that there may be too much primary air and to adjust the air shutter. The pilot appears to have the correct yellow tip. But if primary air is the problem, wouldn't this be consistent?
 
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Old 12-24-08, 09:02 AM
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Originally Posted by carol_okc
Thanks for your quick response!

I don't know if the newest service tech checked the gas pressure, but it's been checked several times in the past whilst trying to solve this problem. This is a propane unit which was professionally installed. Considering the fact that this has been a problem from the beginning, I have to question the 'professional' part, but there are virtually no local firms interested in working on a greenhouse heater.

In reading the Modine service manual, it suggests that there may be too much primary air and to adjust the air shutter. The pilot appears to have the correct yellow tip. But if primary air is the problem, wouldn't this be consistent?
It seems you have read the service manual, I was going to post it for you. However now that you tell me it is LP, your gas pressure into the gas valve should be 12-14" in water collum, and your outlet pressure should be 10" in water. AT SEA LEAVEL. adjustments may need to be made if you are over around 1500' above sea level (approx)
Combustion air could be a problem, is the green house a real tight structure or is there alot of leakage? You may need to provide a combustion air supply to the unit. They make some dampers tha will open and close on demand electrically.

Also the pilot fame should be mostly blue with orange tip.

Good Luck & happy Holidays.
 
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Old 12-24-08, 09:41 AM
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stupid question i have to ask.....the TAG on the furnace is stamped for LP gas not NG?verify if it is for LP maybe the orifices are NG from the factory.....don't take anything for granted here tech or no tech.can't see there being an air problem in a greenhouse toooo much oxygen from the plants anything yellow pilot or burner is going to produce carbon.
 
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Old 12-24-08, 10:04 AM
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Originally Posted by sminker
stupid question i have to ask.....the TAG on the furnace is stamped for LP gas not NG?verify if it is for LP maybe the orifices are NG from the factory.....don't take anything for granted here tech or no tech.can't see there being an air problem in a greenhouse toooo much oxygen from the plants anything yellow pilot or burner is going to produce carbon.
The model #PAE should stand for LP.

DUH, I didn't think about the O2 in the place from plants; good call Sminker, check orfices and check data plate, however I do think it is LP from the factory.
 
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Old 12-24-08, 10:26 AM
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thanks again, both of you!

I'd originally ordered this for LPG, and it arrived set for NG but with the conversion kit (which the original installer did install, supposedly correctly). The primary air shutter is the one showing as LPG in the Modine manual. I was playing with the shutter adjustment a bit this morning, though I tend to be VERY nervous doing anything with gas - had an old gas oven with a bad pilot blow up in my face many years ago, so dealing with LPG is nerve-wracking.

I've changed the location of the 220 backup heater in case that's causing some difficulty if they both come on. There is a large Shaffer fan diagonally to the Modine, and I may try shutting that off to see if it has any impact on a draft-caused problem (though air circulation is critical to my orchids' health). The house itself is fairly air-tight during the winter, but oxygen definitely isn't a problem - the house is a 14x18, and there are about 500 orchids along with a number of other plants.

I don't have a pressure gauge, but may purchase one - I'm a sucker for tools of any kind (go figure - I'm a little old woman who relishes rebuilding engines, etc).
 
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Old 12-24-08, 10:40 AM
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just one more to throw out there.......how far away is the LP tank from the heater and is the pipe exposed to the outside cold......might need to heat the propane as it is delivered to the heater.merry christmas.....from NYC
 
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Old 12-24-08, 11:03 AM
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Gas line is buried from the big tank to the greenhouse - have the line split at the tank to drive the gas auxiliary and hot water in the house and to the greenhouse. The tank is about 50' from both.

I love redundancy - I even have a spare 220 electric heater in case the one in the greenhouse fails. And a generator with a 220 outlet in case of another sustained power failure. And a kerosene heater in case I run out of gas for the generator...
 
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Old 12-25-08, 02:54 AM
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how is the main tank standing pressure?if you break the union at the heater then with another union 1/2 and, brass adapter into it and,that pressure guage you should be reading the main tank pressure on the line....sounds like the LP is rolling into the burner section with that POOF your hearing.
 
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Old 12-25-08, 09:30 AM
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I think I fixed it!!!

After reading your comments and going back over the service manual, I decided to play around with the primary air shutter adjustment and restricted the input a bit more (since it was about the only thing I could do without tackling stuff not to be tackled on Christmas Eve). I went out this morning early and darned if it wasn't still running properly! I'm not counting on it yet, but so far, so good!

Hope you all are having a lovely holiday!
 
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Old 12-25-08, 10:06 AM
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Have the burners been pulled out and cleaned. Maybe a pilot relight needs to be installed on the pilot.
 
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Old 12-25-08, 10:55 AM
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Primary air shutters make sense, too much air is about as bad as not enough. Hope to hear more good news on this! Merry Christmas for GA
 
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Old 12-30-08, 09:33 AM
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Six days and counting! Modine is running like a champ! It's SO nice to go into the greenhouse in the morning (or any other time) and find that it's working properly.

And the HVAC people still haven't returned my calls for additional service. Guess it's time to find still another service company. I'm running out of options in case the heatpump/gas burner in the house needs more attention (yeah, that's another story. Anyone have access to a service manual for an Amana RHA48A2A?)
 
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Old 01-17-09, 08:25 AM
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I have had the similar problem

My pilot light goes out I have adjusted the airflow and turned it on and off at least 25 times all with positive results. all though when I checked it at 5 am it was not lit.
 
 

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