round humidifier (the Neptronic SKR-40). This humidifier turns on the furnace fan when there is a call for increased humidity. In other words, the humidifier will operate year round and simply turn the fan on when the humidity drops below the set-point.
The humidifier dry contact relay was wired to the furnace across the G and R 24V connections.
When the humidifier turns on the furnace fan, the ac unit is also turned on. I've traced this down to the fact that the White-Rogers thermostat is shorting it's cooling system control (the Y terminal) if the thermostat fan control is set to 'AUTO' and the humidifier turns on
the fan. I've demonstrated the Y contact is being turned on by the thermostat by disconnecting the wire to the thermostat and seeing that the wire remains at 24V while the thermostat Y pin is taken to 0V. I've
temporarily worked around this problem by simply dropping power to the a/c unit. Clearly this won't work when it gets warmer outside!
My question is, is there a way to wire up the White-Rogers thermostat so it doesn't turn on the a/c when the humidifier forces the furnace fan to turn on? Or do I just need to buy another thermostat?
Thanks for any help.