Steam humidifer causes a/c to start when furnace fan turned on

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Hello, I have a White-Rogers model 1F80-51 digital thermostat. It controls my forced air furnace and my a/c. I recently installed a whole house, year

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.

[SJF]

I expect you'll get more comprehensive answers on this but --

When you're using the AC this summer you probably won't need the humidifier. Warm summer air contains more moisture and the AC generally extracts the excess to provide air at 75 degrees, more or less, and humidity around 40 to

50 percent. I live in the desert, I humidify to 40 percent in the winter with a cabinet humidifier but store it when spring comes.

SJF

[John Taylor]

You won't want the humidifier running in the summer with the a/c, it's rather counter-productive.

You should install a relay that would that would control the line voltage to the blower motor. When energized by the humidifier, the relay should open the line voltage tap connected to the furnaces cooling speed (usually high speed) and would close (send line voltage) to the heating fan speed (usually lower than cooling speed). This is assuming you have a multi-speed blower motor. It would be best to utilize low speed since the furnace may not be operating at the time and the air will feel cool when exiting the registers (less noise also).

Did you install this yourself? This info should be in the install instructions. Don't fry any circuit boards (or yourself of course) :)

Hope this helps.