||02-24-2013 02:04 PM
Wiring new Nest thermostat
I'm new to the forum and am looking for a little help. I bought a nest 2nd generation thermostat and will be installing it in a few days. I have a gas furnace with access and 4 wires coming into the old state. This is how it's connected: Red - rc, white - w, blue - y, green - g. No common. Nest says no common wire is needed, but I have read issues with the system stealing power causing problems with furnaces. Is this a valid concern? I am thinking I need the common wire to avoid any issues.
Now I also have 2 wires coming in to the stat area from a humidifier we don't use. Red and white.
Down at the furnace, I have the connections above plus c for common. There are 2 red wires connected there. I'm pretty sure they are for the humidifier and ac.
So my question is does it make sense to run a new 5 wire from the stat to the furnace or steal the humidifier red wire for the common after disconnecting it from the humidifier entirely? Running new wire is a clear shot and doesn't look too bad. Just concerned about messing up the connections at the furnace.