Heating Help

AprilAire 500 controls

I am connecting an Aprilaire 500 humidifier. There are several ways to control it.

One way is set it to run when the fan runs using the ACC connection. But that is 120 volts on the Lennox I'm working on and will require a transformer.

Another way is run it when the heat comes on by connecting it to the W. 

Is there any reason I couldn't connect it to the G, thus tying it into the fan and a 24 volt line.

HI Bob:

The "G" terminal is energised only when the stat calls for cooling or is turned on at the t-stat fan on switch.  I have used current sensing relays which connect around the common leg of the blower.  This way you have potential any time the blower energises.  The reason the W" circuit is not used is because in the past when anticipators were used, the water solenoid would affect the t-stat.
     You can use lennox Aux terminal, just install a cheap 20 VA t-former.

Mike T.

Aprilaire 500

I am connecting an Aprilaire 500 humidifier. There are several ways to
control it.



One way is set it to run when the fan runs using the ACC connection. But
that is 120 volts on the Lennox I'm working on and will require a
transformer.



Another way is run it when the heat comes on by connecting it to the W. 
I like using W because it starts the water running across the pad before the fan starts



Is there any reason I couldn't connect it to the G, thus tying it into
the fan and a 24 volt line.
1. If you have A/C and it is not wired correctly you may backfeed to Y and bring on the compressor, depending on the stat you have.
2. Although running the fan is preferred over running with heat, often people don't like the "drafty" feeling of room temp air circulating.
This is a drain type humidifier. Make sure your condensate pump is pumped inside and not outside. Also get a pump with a float switch and connect it