Converting Bryant 2 wire thermostat to Nest

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Old 07-20-17, 09:21 AM
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Converting Bryant 2 wire thermostat to Nest

Currently I have a serial thermostat for Single unit HVAC (gas) which I would like to convert to Nest thermostat.

There are six wires coming out from the HVAC system to the two wire conversion module.

I have wires in place for 5 wire system.

I need some help in installing to Nest compatible set up.

Here are the pictures of the current set up.

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Old 07-20-17, 09:25 AM
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There is a brown wire from HVAC which is going into D1 and then D2 is jumpered to Rc.

I can bring down the Red, White, Green, Yellow, and Blue to the Nest but what do I need to do with the brown wire? Also, Should Red wire be connected to Rc or Rh on the Nest?

Are there any switch setting inside the HVAC system to convert to legacy wiring?

TIA.
 
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Old 07-20-17, 11:00 AM
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Welcome to the forums.

You will need to bring the thermostat cable down to the furnace connections or you will need to remove the wires from the EIM and splice to them.

I can't guess what the brown wire is doing connected to the D (aux) switching circuit. It appears to supply an external device with power. You should open the furnace up and trace that brown wire. There is a chance it goes to a humidifier.

You should be able to get system running now without the brown wire.
Turn furnace power off before changing any wiring.

connections to nest...
Red = Rh
White = W1
Yellow = Y1
Blue = C
Green = G
 
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Old 07-20-17, 11:38 AM
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Thank you. I will give that a shot.

-----

Okay that worked fine. Didn't get to test the heating but I would assume that will work too.

Thank you for your help.
 

Last edited by csrow; 07-20-17 at 12:23 PM.
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Old 07-20-17, 08:58 PM
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You're welcome.

Do test the heat before winter sneaks up on you.
You could return to this thread and tell us what the brown wire was used for too.
 
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