Nest 3rd Generation Thermostat E83 code

[JohnInVA]

I installed my Nest 3rd Gen thermostat but had a E83 code, am I missing something or connected something wrong.  My system is a Heat Pump with electric aux/emer heat, not dual fuel or furnace.

I don't have permission to post a picture so the following tables are submitted to show my old Tstat to new Tstat wiring.

My old Thermostat Top Tech Model TT-P-421 had the following wiring:

Terminal	Wire Color	Description
R	Red	24 VAC
O	Orange	Reversing Valve (Cooling)
Y1	Yellow	Cooling or Compressor for HP System
E/W1	Purple or Brownish	1st Stage Heat Pump or Em Heat
G	Green	Fan Control
C	White	24 VAC Common
W2	Blue	2nd Stage Heat Pump

I had to disconnect the W2 wire below to clear code and everything seems to work but without that connected, won't I lose Aux Heat?

I connected to Nest 3rd Gen as follows:

Label	Color	Function
Y1	Yellow	Compressor Relay (stage 1)
G	Green	Fan relay
O/B	Orange	Heat Pump Changeover Valve
Rc	Red	24 VAC power
W1	Purple/Brownish	Heat Relay Stage 1
W2/AUX	Blue	Heat relay Stage 2 (Aux Heat)
C	White	24 VAC Common

Any assistance would be greatly appreciated.

[GBD · Accepted solution]

You're getting the error because you have the nest thermostat setup as operating a heat pump and it's sensing connections to both the W1 and W2 connections where it is only expecting one of them. From looking at your photo the Purple/Brownish and Blue wires are jumped together with an orange jumper wire so if it was me, I'd put them both on the W2 connector of the nest thermostat and leave the W1 connector empty.

[JohnInVA]

Old ThermostatNew Display

The old thermostat wiring in picture and what I get on my display, the colors are not correct on display on new nest thermostat for W1, W2 and C.   A better chart showing each compared to labels is below:

TT-P421				Nest Tstat
Terminal	Wire Color	Description		Label	Color	Function
R	Red	24 VAC		Rc	Red	24 VAC power
O	Orange	Reversing Valve (Cooling)		O/B	Orange	Heat Pump Changeover Valve
Y1	Yellow	Cooling or Compressor for HP System		Y1	Yellow	Compressor Relay (stage 1)
E/W1	Purple/Brownish	1st Stage Heat Pump or Em Heat		W1	Purple/Brownish	Heat Relay Stage 1
G	Green	Fan Control		G	Green	Fan Relay
C	White	24 VAC Common		C	White	24 VAC Common
W2	Blue	2nd Stage Heat Pump		W2/AUX	Blue	Heat relay Stage 2 (Aux Heat)

[GBD · Accepted solution]

You're getting the error because you have the nest thermostat setup as operating a heat pump and it's sensing connections to both the W1 and W2 connections where it is only expecting one of them. From looking at your photo the Purple/Brownish and Blue wires are jumped together with an orange jumper wire so if it was me, I'd put them both on the W2 connector of the nest thermostat and leave the W1 connector empty.

[JohnInVA · Accepted solution]

Thanks, I kind of figured it was along those lines. Now, this is how I fixed it.  I used the asterisk for the Emergency Heat which used to be W1.  It works great, passes all tests.