I live in western NY and we've had the furnace on for weeks now. Lately, highs are near 30 degrees and lows around 20.

My (Trane) thermostat has two fan settings - Auto and On. In On mode, the fan runs 24/7 at very low speed. In the winter, with the heat on, I prefer Auto mode which is where I have the Thermostat set.

I had a feeling my new Aprilaire 600 wasn't working since the RH was slowly dropping (over a few days) down to 30%. I was looking for 40% so I had been slowly moving the adjustment dial up to 7 with no corresponding increase in RH.

I also noticed that when the heat kicked on, nothing happened at the humidifier control panel - i.e. no green light, no water. However, the humidifier did work properly in Test mode.

So I checked around the Internet and found a post that suggested switching the Thermostat fan setting from Auto to On. Bingo! The next time the furnace kicked on the green light on the humidifier panel came on and the water flowed. It now continues to work "properly."

The bad news, as I mentioned above, is that I prefer to have the Thermostat (fan) setting on Auto, not On. So my questions:

1) Is this normal?
2) If not, which device is probably at fault?
3) Can the thermostat and/or the humidifier control panel be rewired by my service rep to "fix" this?

Thanks ...

Humidifiers - Aprilaire - 600 Humidifier