ICE help, No temperature rise

[breegle1313]

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.

[timebuilder]

If you guys are the equipment owners, this thread belongs in commercial AOP.

[breegle1313]

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.

[mikeacman]

ICE

Ahem ....

Sorry...

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 ?

[mikeacman]

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.

[breegle1313]

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!!

[mikeacman]

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

[breegle1313]

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.

[mikeacman]

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.

[mikeacman]

http://www.ice-ww.com/HTDM%20performance.pdf


From what I read you won't get ninety degrees with the air your moving

[hands]

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.

[breegle1313]

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.

[flange]

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.

[hands]

Are the burners staying on all the time, or are they cycling on the limits. Were they operating good at one time, if so when. Was any electrical work done on the building where the phases could of been changed and the blowers are running backwards.

[breegle1313]

The burners are staying on the whole time. They are on a door switch where when they open a roll up door the units shut down and once it is closed the units start back up... Sometimes (probably about once every week or once every two weeks) we will have to reset the units in order for them to fire again. They were installed when the building was built around seven years ago and worked perfect for the first two heating seasons then they started getting worse and worse every year since then. The blowers are not running backward. The air is definitely blowing out at high volume. The blowers are operated by a VFD which can be controlled. About three years ago they had a company come in and install a/c coils to each of the units and they did it by removing the units from the wall, moving the structural steel that the units were mounted to (because with the new coil box for the a/c the unit would be in the way of the crane located in the building) and then the units were mounted back on the walk and ran the same as they did before the a/c was installed. This is just all hearsay because neither I nor my coworker have worked on the site at the time it was happening. We started and then the guys that took care of the site before retired shortly after. They didn't seem like they were worried about it because they were retiring but now we are stuck with the problems of these units.

[alcomech]

Have you checked what the main gas pressure is while the 3 units are running, and all of the heat stages on. I know you said 3.5 in.w.c.

Is that a sealed combustion system. If so what is the combustion air pressure and what is the draft pressure. Have you checked the design pressure for both.

[breegle1313]

There is a software that you have to plug a laptop into the board on the unit and you can read the rpm of the combustion blower and the percent of gas at all six stages. They are all where they are supposed to be. I am thinking that the heat exchanger might be getting clogged because of the draft reading of the flue and the lack of the transfer of heat from the heat exchanger. My coworker swears that it cannot be the heat exchanger being clogged because there was no black soot coming from the flue.

[breegle1313]

Yes it stays at the 3.5 " w.c. during all the stages

[breegle1313]

Yes it is a sealed combustion system and we have not checked the combustion air pressure. The draft pressure is around zero (I say "around" because it will fluctuate between a negative and positive draft pressure... That is why I think that the heat exchanger is constricted.

[alcomech]

So how are you controlling draft and combustion pressure. Does the system have a power draft and combustion blower external to the Heater?

What are the actual readings of the draft and combustion air. Have you verified that the pressure readings are correct with say a magnehelic gauge. Does the controller use a pressure transducer for draft and combustion pressure, and if so have you checked that the pressure pick up tubes are installed correctly. Make sure that they have not been installed in a way that they are reading velocity.

So what is the manifold gas pressure on the units while running with all stages on?

You think that there is a restriction in the heat exchanger but if that's the case have you experienced any sort of high temperature limit failure or short cycling of the heat?