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Brian1080P 12-31-2012 03:08 PM

Nest 2nd Generation
I am having a power issue with a new 2nd Generation Nest T-stat that I recently installed. I am almost certain that it pertains to the abscence of a C common wire.

I hooked up the 4 wires from my previous Honeywell T-Stat (Yellow, Green, Red and White) to the Nest with no issues. There is a 5th unused blue wire (that I assume could be a common wire.

On the circuit board of my forced air furnace (Armstrong) there are the same corresponding wires (Y, G, R, W and there is a C.

Connected to the C terminal is a white wire that goes to the Nuetral of the Aprilaire Humidistat and the Red wire is connected to the Yellow on the circuit board.

My question: Is the C terminal a common? Can I attach the blue wire to the C at the furnace and to the Common on the nest? will this alleviate the power loss on the Nest?


beenthere 12-31-2012 04:42 PM

Yes, its a common. You can connect the common of the stat to it.

Brian1080P 12-31-2012 09:33 PM

Thanks for reply!

I connected the blue wire (common) to the (C) terminal on furnace that also shares the condenser and I connected it to the common slot on the nest.

I charged the Nest faceplate externally for about an hour. I re attached faceplate and it worked fine for about 45 minutes. The Nest apparently will not charge via the 24v common wire unless it takes 24 hours. This is becoming very aggravating for a $250.00 T-Stat.

I have rebooted several times etc and still it disconnects from the network due to low battery.

Maybe I have a lemon, but very frustrated.

beenthere 12-31-2012 09:35 PM

Might call Nest for technical support.

Brian1080P 12-31-2012 09:43 PM

Yeah I can put them on speaker for the 45 min wait ;o)

beenthere 12-31-2012 10:27 PM

LOL. Sorry, I'm not well versed on the Nest.

Missouri Bound 12-31-2012 10:44 PM

Take it back and get a refund or a credit towards a traditional thermostat. I know the Nest has a lot of appeal because of it's learning capabilities but it's not a proven entity. You can get a much better thermostat (almost 2) for what you paid for the Nest. If you fiddle with your thermostat enough to want a Nest you are wasting money anyway. A thermostat with defined settings is much more capable of energy savings than a continuously programmable one. Enough of my rant. You will have to open up your furnace to see which is the common, but I suspect you already have it wired correctly.:whistling2:

Brian1080P 12-31-2012 11:08 PM

^^ You are correct, this is too much trouble for a thermostat. I will call their tech support when I get home tomorrow, but I'm sure it's wired correctly.

Any recommendations for a Tstat that can be controlled via smartphone etc?

beenthere 01-01-2013 05:10 AM


Missouri Bound 01-01-2013 02:38 PM

RTH8580WF | Programmable Wi-Fi Thermostat
This one will work.:thumbsup:

sgip2000 01-01-2013 03:21 PM


Originally Posted by Missouri Bound (Post 1084044)
RTH8580WF | Programmable Wi-Fi Thermostat
This one will work.:thumbsup:

I have the "PRO" version of that model and it has been awesome!

gregzoll 01-01-2013 03:32 PM

I use the 3m-50 filtrete with the home spaces radio The only app available is for the iPhone, no android or windows phone 8 app available.

As for the problem with the C wire, did you ever check for continuity, to make sure that the wire was not broke somewhere along the line? You can also use a external power source for these thermostats, that would plug in and then connect to the NEST.

Nest may send you out a new thermostat if the one you had did not work after making sure all wiring was properly connected at the furnace, and same at the thermostat. There are also some setup that you have to do on the thermostat, once you get it powered up, for type of furnace, ac/heat-pump, etc..

Tator1076 01-01-2013 03:37 PM

Good luck with that crap stat. I been on 7 of them so far that customers had to replace them. The display will go away or stat will read 80 deg's for room temp and never change

sgip2000 01-01-2013 03:55 PM

I looked at the "Nest" when I purchased the Honeywell. The Nest just felt too cheap to me considering the price.

Brian1080P 01-02-2013 03:49 PM


Originally Posted by Missouri Bound (Post 1084044)
RTH8580WF | Programmable Wi-Fi Thermostat
This one will work.:thumbsup:

My wife bought me this exact model for Xmas and sadly I returned it for the nest.

I did spend an unnecessary 90 minutes on the phone with Nest CSR and they think my Tstat needs replacing and they are going to send me another unit.

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