I have a Honeywell IAQ thermostat controlling a Carrier Infinity furnace and A/C Condenser. I cannot get the IAQ thermostat to lower the fan speed via the furnaces DHUM terminal. I have the thermostat set as follows:
0379 Dehumidification Control *1* (Dehumidify with air conditioner)
0383 Over-cooling limit *3* (3 deg. F)
0390 Dehumidification away mode *0* (no)
I realize that there are more settings, but with the 0379 set to *1*, the others are blocked out.
If I change the setting to a whole-house dehumidifier (0379 set to *3*) (which mine is not) the relay on the EIM closes, so I know that works. I turned it back to the "use air conditioner" setting. It allows the temperature to be as low as 3 deg below setpoint, but it will not close the DEHUM contact on the EIM.
I understand that the infinity furnace uses reverse logic on the DEHUM terminal, that is, it lowers the fan speed when there is NOT a signal on DEHUM. I may have to install a relay to make that "forward logic" but I will cross that bridge when I get there
Does anyone have any thoughts on what is happening here?
Just a side note, I have read on other forums as well as in the owner's manual that I shouldn't see the Auto/Off option on the screen when dehumidifying with the A/C. I DO have that option, however. I am guessing that is a typo in the owner's manual??