I've got a Rheem air handler that has just recently started making a odd hissing/screaming noise. It's not real bad, but bad enough that I have quit running it until I find the problem. I have a wood burning furnace that is tied into my ductwork and when the blower kicks on with it, I have the air handler wired to come on too. There is also a bypass humidifier tied into the system that runs when the humidistat calls and has a current sensing relay to make sure the air handler fan is running before it turns the solenoid on.
So I turned off the air handler fan on the thermostat controller and the humidifier solenoid kept running. So my first thought was it was just a coincidence and the solenoid was bad. Well I flipped the breaker on the air handler off and the solenoid clicked off too (they are on different circuits). So that means the current sensing relay was keeping the solenoid open which means that the fan motor was still drawing power.
Now I'm to the point where it's over my head. I thought it may have something to do with a capacitor but I don't know. This system has been working just fine for about 3 years with this setup. Any and all help would be greatly appreciated.