AAON Dehum question

[dmd-marc]

I recently came across a Aaon RTU 6ton I believe R-22. This RTU controls a testing room for a car part supplier. They are trying to control 45-55% rh in this space. Lately the humidity has been creeping up and the dehum mode doesn't seem to be keeping up. Any suggestions? I did notice that the dehum is activated and the first stage compressor is running with the cfm. Also the first stage has hot gas bypass. I'm not sure if I'm just having a brain fart or I am overlooking something. The space temp has been steady between 70-72. But the humidity is my problem. Any help would be appreciated.

[dunkman]

I can't speak specifically of AAon, but I worked on a new Trane 8.5 ton plenum fan style RTU with dehum. It's logic runs both stages of cooling, and energizes a 4 way valve for reheat on a call for dehum. The reheat coil is connected only to 1st stage compressor. There's no way to run only 1st stage comp during dehum on that unit. Even with both stages running it yields a 4* delta t. Hope this info helps some. Maybe your 2nd stage only starts when the temp rises enough in the space to call for cooling? Have you checked the charge? Make sure your hot gas bypass isn't messing you up. I;m guessing that should only be active during low ambient conditions.

[acwizard]

I recently came across a Aaon RTU 6ton I believe R-22. This RTU controls a testing room for a car part supplier. They are trying to control 45-55% rh in this space. Lately the humidity has been creeping up and the dehum mode doesn't seem to be keeping up. Any suggestions? I did notice that the dehum is activated and the first stage compressor is running with the cfm. Also the first stage has hot gas bypass. I'm not sure if I'm just having a brain fart or I am overlooking something. The space temp has been steady between 70-72. But the humidity is my problem. Any help would be appreciated.

Is it a safe assumption that this unit has worked correctly for several years. If the answer is yes then there is either a problem with the controls, or refrigerant charge, or something has changed in the room which is adding more humidity to the space. Post the model number of the unit.

[ewang]

Aaon has a mess of controller's out there. Post a model number of the unit, and try to get a model of the controller.

[fireye03]

Is it a safe assumption that this unit has worked correctly for several years. If the answer is yes then there is either a problem with the controls, or refrigerant charge, or something has changed in the room which is adding more humidity to the space. Post the model number of the unit.

agreed if the unit has been working i would start looking at ref charge.
is there bldg automation co controlling it or is it wattmaster

[JWOO]

need more info, does this unit have a reheat coil, do you have a mhgrv board that controls your stepper motor