ICE help, No temperature rise
On our site we have three ICE (industrial commercial equipment) air handlers in a high bay that is controlled with a HEPA exhaust that expels around 18000 CFMs out of the building. We are having problems with the ICE units heat. They are supposed to have around a 90 degree temperature rise and ours have about 20-30 degree rise. They are six stage gas units with a modulating gas valve and modulating inducer motor. They are controled by an Icecon II board. We hooked up the combustion analyzer on it and it was reading that the oxygen level was a little high... We adjusted it with the icecon program and it helped a little but we still are not getting the temperature rise that we need. We contacted ICE about our problem and they didn't understand it at first then said they would call us back... They never called back. So we decided to call a week later and the only thing they came up with was that the flue and intake duct work must be the problem and that the flue cannot have 90 degree elbows on it. We are just skeptical about their answer because we don't think that will make a big enough difference... If anyone has any ideas of what it could be why we are not getting a big temperature rise then please let me know. Or if anyone has had a lot of experience working with these units. It is greatly appreciated. Thanks.
If you guys are the equipment owners, this thread belongs in commercial AOP.
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
AOP Forum Rules:
We do not own the equipment. The company that owns the equipment sub-contracts all the maintenance work to the company that we work for. Should i still be putting it in the "Commercial AOP" or should it stay in this category? I'm new to this site so i do apologize if i put it in the thread.
Never had good luck with their service .
Stay on them .
Not enough info to help.
Does this have a modular heat section as in six heating modules or one heat module with six stages. I take it to be indirect fired.
Is your airside CFM higher than spec ?
Does the icecon monitor discharge air temp and base its control using that?
Are you reading the discharge air temp with your thermometer or the units display?
Just a thought ,I've seen improperly placed sensors that give a good reading but was to close to the heating or cooling source and wouldn't allow all stages to come into effect.
IE discharge air sensor that gives the control a reference so it can modulate to setpoint that is to close to the heat exchanger . Giving a reading to high as the air hasn't mixed well . Solution ,move sensor downstream to a point where air is mixed properly.
Just a thought.
The units (we have a total of three that are having the same problems and are located in the same building.) have one heating module with six stages. It is indirect fired. The model is HDTM 1500 of the units. And yes the airside CFM is higher than spec. When we did a combustion analyzer test it was right on the border of negative and positive draft. (i am not sure if that is because the building itself needs to be on a negative pressure or if the flue is constricted. I do believe they are not constricted though i never checked to be 100% sure.) It bounced back and fourth. The control is based off the room temperature in which is a sensor that is wired into a honeywell program that we have. And the honeywell program is where we are getting our discharge air temperature reading. We have also checked the discharge with a thermometer as well and it read the same as the honeywell program.
Thanks for the reply!!
Im wondering if the ice controller has a discharge sensor that is used in conjunction with the staging . If it improperly placed it may affect staging .
Does he ice controller have its own discharge air sensor ?
Is it in a hot spot?
I would assume it would ,I could be wrong ,buy something to look into
The ice controller does not have a discharge air sensor at all. The discharge air sensor was installed by honeywell and runs with their programming. The unit itself is calling for 100% heat and we know that because we got 10v on the icecon board (the unit's call for heat works with 2-10v) and the modulating gas valve is opened 100% as well... The flue stack temperature is a little over 500 degrees farenheit. Its like the heat exchanger is not getting hot and not allowing the heat to transfer to the air blowing across it but the flue is hot. It's very puzzling to us.
You say your over on air .
Did you have a test and balance ?
What's your cfm and actual temp rise .
Assuming cfm is 18000 and td is 25....
CFM * 1.08 * tRise = btuh
roughly 480,000 btuh output.
Im thinking you need about 1,800,000 output ,,,,2,000,000 input btuh at 80% efficient.
What the input rating of the unit and efficiency rating (if known)
Compare that to your input minus rated efficiency.
From what I read you won't get ninety degrees with the air your moving
You said the gas valve is open 100%, what is the manifold gas pressure and is it at the rated pressure? Since you are having the same problem with all three units, it sounds like the building is too negative. Try shuting down the exhaust fans and see if the temperature rise goes up.
The gas pressure is 3.5 "WC and that is the rated pressure for those units. We actually shut down the exhaust system last night into this morning to test that and we came in the and temperature of the building was at 54 degrees farenheit with all three units running and no exhaust leaving the building. the discharge temp of the units were anywhere from 82- 86 degrees farenheit on the units. The units ran for about 12 hours without the exhaust system running and it did not make a difference.
Seems like you are underfired as stated. may be due to many issues. check manifold pressure, entering gas pressure, operation of all stages, rotation of induced draft fan, cleanliness of heat exchanger. I would be looking at heat exchanger and fan motor rotation first.