The humidifer has it's own drain, it's not going to overflow into the furnance.

The outdoor sensor is a thermistor ( a resistor that vaires resistance with respect to temperature ). I would guess that it uses thermostat wire.

http://www.alpinehomeair.com/related/700M-700A%20Series%20Installation%20Instructions%2004.10.pdf

Thanks, I have a copy of that PDF. I had never noticed that the water panel w/associated hardware was entirely outside of the plenum, so notwithstanding some PROs arguing in favor of a bypass unit to avoid water flooding electronics, there appears to be little possibility of that happening.

My biggest concern regarding the sensor deals with gauge of wire and shielding requirement. Length (resistance) might also come into play. Aprilaire's contact email line if very subject oriented. Will take a look at Alpineair's site.

T

V

They are measuring the resistance in the thermistor. My guess they are using the 24 volt power. As I said, it probably uses 18 gauge thermostat wire. You don't need any shielding with low voltage wiring.

"As I said, it probably uses 18 gauge thermostat wire. You don't need any shielding with low voltage wiring."

I'm not disagreeing with you, but just concerned. My A/C unit has an outdoor temperature sensor installed. The installation sheet states that the wires be separate from the thermostat bundle.

V