The A/C contactor and humidifier solenoid share the same 24vac transformer.
They are both ac relay coil loads, zero-crossing would snuff any serious
transients.
--
Rick

snip...........
Hcac Tech2 wrote:
Well, there are 2 different ways you can do it. first you could just
break the commons to the humidifier and a/c
++++++++++++
John wrote
To do the above, the Aprilaire would have to be using the same
transformer as the furnace/ac and have to be 24vac of course. This I do
not know but If that is true, you could do it that way. I would not
prefer to do it this way but granted you could and be acceptable.

++++++++++++++++++++++
John wrote:
I would not even consider this due to the transits and current draw of
the solenoid. It could damage the thermostat or the cooling anticipator
circuit. It might work one time or a hundred times, depending on the
thermostat circuit. I would put this approach in the "jerry rig"
category. It would be very confusing for the service people down the
road also.

Not bad though HvacTech2, not bad

John Williamson