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.