LF: Electrician / Furnace Guy

[jwslam]

Bought myself a smart thermostat.
Opened up the furnace and found no C wire. No clue how the last owner had a Nest.

The current thermostat is a dumb programmable. Seems like there's a lot more than 4 wires though.

Anyone on here can help me?

[iggy_oi]

http://forum.calgarypuck.com/showthread.php?t=104907

Everlast seems to be the cp furnace guy, if he can't help you he can probably point you in the right direction.

[jwslam]

Originally Posted by iggy_oi

http://forum.calgarypuck.com/showthread.php?t=104907

Everlast seems to be the cp furnace guy, if he can't help you he can probably point you in the right direction.

I called him up earlier and he says any guys he could recommend at this time of year are going around for emergency repairs and would charge an arm/leg.

[Ducay]

Its dead easy to be honest (depending on the furnace). The hardest part would be running additional wires to the thermostat, but if you have extra wires to use, whole job should take you like 20 minutes.

Dumbed down version for a normal forced air gas furnace running at 24Volts AC (which vast majority of Calgary is): Kill power to furnace. Check in furnace at panel which wires running from the thermostat are unused (they're normally capped and/or loose). Connect that wire to the C on furnace panel, then connect same wire to C on nest. Bingo bango you're done.

I did the same thing, had only Rh and W (power and heat) on both mine when I got the nests. Had additional 4 wires to spare (some buried in wall), connected the C as well as G (fan) and * (humidifier) to the nest and now I have pretty sweet control over the whole system. I lucked out the builder ran 2 runs of 3-wire cable to each thermostat, which was not really needed or common back in the 80s.

I'd start by doing the C as it is pretty easy and requires no additional "setup" or tinkering like the humidifier often does. Tonnes of resources online or just ask here.

[jwslam]

The basement is developed... so running wires is something I'd rather not do and pay a fellow CP'er for, maybe in beer and food? =D

[Ducay]

I thought you said there were more than 4 wires at the thermostat? A basic furnace here needs 2 wires. Power and Heat.

Newer/upgraded models will often have a third for the fan, maybe another for humidifier, perhaps another if you have central air.

That said, to start, I'd look for the thermostat wires running into the furnace, and then you can determine how many there are and if any are unused @ the thermostat.

You'll need to know even if you're paying someone to connect it, as if there are extra wires it'll be minimum charge for the trip, versus a few hours (at least) and potentially some drywall repair, etc, if additional wires are needed (but it sounds like if you have 4 you might have some unused or it could be a 6 wire cable).

[jwslam]

Top is current thermostat
bottom is furnace

basement is developed

[jwslam]

So I was reading that because I have both Rc and Rh, I can jumper that to the 24V C?

[Ducay]

I believe that is the case. I'd just google to confirm, lots of help on Nest forums.


What about the blue and orange lines @ the thermostat? Are those connected anywhere? If they just terminate in the furnance without being connected anywhere, I'd just use one of those as the 24V C line. (And then can always still disconnect the second R as well).