AC Unit/Gas furnace

[rcrawford83]

I am replacing my honeywell thermostat with a Google nest learning thermostat I wired it up ran a test and when I ran the heat the ac unit came on so I just need to know it this is even compatible or if I just need to maybe move a wire into a different place to control my has furnace. 

Wires I have are

Red

Yellow

White

Green

Blue 

[CoolingWizard]

Please post the picture of the base of your old thermostat so we can see where the wires were connected to which labeled terminals.  

Ken, The AC Cooling Wizard

[rcrawford83]

 

[CoolingWizard]

Ok,

Red wire on R terminal, goes on Rc of Nest Learning Thermostat 

Green wire on G terminal, goes on G of Nest Learning Thermostat

Yellow wire on Y terminal, goes on the Y1 of the Nest Learning Thermostat 

White wire on W terminal, goes on W1 of the Nest Learning Thermostat

Blue wire on B terminal, goes on the C of the Nest Learning Thermostat 

Ken, The AC Cooling Wizard 

[rcrawford83]

So I just hooked it up like you said and had no power to it. placed to blue wire in the ob slot have power but when run heat test it still turns on my ac unti and not my gas furnace 

[CoolingWizard]

The O/B is for a Heat Pump.  Do you have a Heat Pump also? Sometimes the Common is hooked up at the thermostat but not at the Furnace.  It is rare to have a Heat Pump with a Gas Furnace. 

Ken, The AC Cooling Wizard 

[rcrawford83]

no heat pump just gas furnace. but the thermostat itself would not even turn on until I had it plugged I to the ob so after I got it on it was still showing on the screen at the wire in the nest y1 heat pump/ac I unhooked the blue wire completely and it labeled the wires on screen correctly y ac g ground red power wagon heat and everything worked correctly but the blue wire is not connected so I just put my old thermostat back on for now because I was unsure about the blue wire not being connected

[CoolingWizard]

How mechanically inclined are you? The blue wire can be checked in the Furnace.  And If not connected it can be.  Your thoughts?

[rcrawford83]

I can figure things out fairly easily. I'm just really confused right now with everything working correctly when the blue wire is not connected but when it is connected it throws it into saying I dont have 2 different units but disconnected it works right it just doesn't charge the nest thermostat. If that makes sense it has power it just says low battery and will not charge the nest.

[CoolingWizard]

When go through the setup of the Nest thermostat, you stated the wires as I suggested correct? Now, here is something that will help. The Nest learning thermostat has the ability to be charged via a USB on the back of the display.  Charge for 24 hours.  In the meantime, go to the furnace, locate the thermostat cable where it enters the cabinet.  That will be the cover that will need to be removed.  Locate the blue conductor and see what, if anything, is it attached to.  Post a picture and if possible the model number of the Furnace.  

Ken, The AC Cooling Wizard

[rcrawford83]

okay it will be tomorrow before I will be able to do that but I will as soon as I get home thanks

[rcrawford83]

so I'm going to attempt to get a picture of the blue wire like you ask. however when I got home my nest is charged everything works properly could it be I don't need the blue wire connected

[Markjosephp]

Hello folks,

I wanted to drop by and see how I could help.

Thanks for assisting, Ken.

@rcrawford83, Nest Learning Thermostats typically do not require a C wire. If you're receiving any wiring reports about "no power to R wire detected," Your C wire may not be properly grounded, so your system uses power sharing but doesn't get enough energy. Leaving it disconnected would be fine. Please take a look at this article and let us know if you need more help.

Regards,

Mark

[EmersonB]

Hi everyone,

@rcrawford83 I'm dropping by to ensure that everything is covered here. How's it going with your Nest Thermostat? Were you able to read the information and check the link that Mark has shared? In case you have an update, you know where to find us.

I appreciate the help, Mark and Ken.

Best,
Emerson

[EmersonB]

Hello rcrawford83,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let us know.

Thanks,
Emerson