Trane Thermostat and Emergency Heat Wiring.

Other Devices & Integrations Climate Control & Temperature Sensors
1

I recently installed a Trane TZEMT400BB32MAA thermostat on a heatpump system with 2 stage heat (as determined by previous thermostat wiring). The previous thermostat had an E wire connected to the emergency heat terminal.

The Trane says to connect the 2nd stage heat to W1 and ALSO connect the emergency heat to W1. Won’t this activate the heat strips all the time? What am I missing?

The other connections are:
R 24vac “hot”
C 24vac common
O heat pump switch over
G fan
Y1 first stage
W1 second stage heat (was W2 on the old thermostat).

THanks for any help. I never was able to get anyone on the 877 number included with the instructions.

2

No, W1 is the second stage.
When it needs a little heat (a few degrees from setpoint) it will do the heat pump cross over O (Heatpump mode) and the Y1 compressor stage1 and the Fan G.

When it needs a lot of heat (more than a few degrees) it will ALSO fire stage2 of the Heatpump (If you have a second stage) AND the emergency heat (also known as auxiliary heat) strips.

3

Thank you! I think I was wondering if there are three “stages”. On the thermostat I see the first stage, then the 2nd stage kicks in, finally Auxilary heat.

My question is if the software thinks there are three different “stages”, why are the second and aux wired together? What is it really doing when it hits that Aux stage?

BTW - I’ve asked for a maintenance call and will see if they can tell me if I have 2nd stage heat. I know I have the Aux/Heat strips.

Thanks!

4

It does support 2 or 3 stages depending on how it’s configured.
If you only have a Y1 then you only have a single stage heat/cool heatpump.
You should configure the thermostat for a single stage heat/cool heatpump.
The second stage HEAT is the aux heat pannels.
I
t does support 2 or 3 stages depending on how it’s configured.
If you only have a Y1, and a Y2 then you only have a dual stage heat/cool heatpump.
You should configure the thermostat for a dual stage heat/cool heatpump.
The third stage HEAT is the aux heat pannels.