I have an Aprilaire 600a humidifier from a few years ago and currently it's wired into my furnace with two control wires labeled "W/G" and "Cf". The "W/G" is connected to the W terminal on the furnace (call for heat). The "Cf" is connected to "C". My understanding is that any time call for heat occurs, W is shorted to C, which is detected by my humidifier and it enables the flow of water.
I would like the humidifier to run any time the fan is on, not just when there's a call for heat. The fan control is determined by the "G" terminal. Is there a way to change my wiring to do this?
Edit: Furnace model is Bryant 925t. Per the manual:
The HUM terminal is a 24 VAC output, energized when the gas valve
relay is operating during a call for heat.
This seems like it wouldn't help since it's only available during the call for heat.
Edit 2: There is also a "EAC-1" terminal that is energized "whenever the blower operates". However, this operates at 115 VAC, not 24VAC. Is there a way I could use this?
Best Answer
You could use the
EAC-1
terminal to power a step-down transformer. This is common with furnaces that energize theHUM
terminal to line voltage.Check the humidifier manufacturer, they should have a properly sized transformer to fit this exact need. They should also have a wiring diagram for this type of setup, in the installation instructions.
Basically, the primary side of the transformer will connect to the
EAC-1
terminal, and a neutral terminal on the furnace control board. Then the secondary side will power the humidifier.Whenever
EAC-1
is energized, it will power the transformer, and the humidifier will turn on.As noted in the comments on the question, you may not get the expected results.