I want to know

[Whacheong]

want to check the compatibility for this Trane HVAC system  is it works with google nest thermostat?

 

[Jenelyn_O]

Hi Whacheong,

Thanks for posting in the Google Nest Community forum. I'm sorry for the delay. It looks like you have a heat pump system. It is compatible with the Nest Learning Thermostat. 

You can follow this wiring guide:

• Y1 - Yellow (Cooling)
• G - Green (Fan)
• C - Black (Common)
• OB - Black wire connected to O (Reversing Valve)
• * - Yellow connected to E (Emergency Heat)
• RC/RH - Red (Power)

Best,

Jenelyn

[Whacheong]

Hi Jenelyn，There are a total of seven wires here, and the five connectors on the right are respectively connected to R, O, G, Y, and C; the yellow wire on the left is connected to w and connected to w2 through a red wire; however, the seven wires share six, and there is a green wire The wiring is not used, so my question is: do I still follow the wiring method you said?

[Jenelyn_O]

Hi there,

Thanks for confirming. Yes, you can follow the wiring guide I provided. Since you have a heat pump system, the labels that you have to use as your guide is the heat pump side.

If you notice above, there's a specified group of labels for heat pumps and conventional. The yellow wire on the left side is actually your emergency heat with a label of (E).

You can disregard the unused green wire and red wire that is connected to the E terminal and Aux terminal, since the Nest Thermostat doesn't use jumper wires. 

Regards,

Jenelyn

[Whacheong]

I tried to connect and it didn't work. It took me three hours. Where should the red wire on the right be placed in？ The yellow line on the left is connected to the one on E, I let it free?the green line on the left it’s free now ,it’s still free?I tried it for more than three hours and the result is that when it is cooling, it is heating

[Jenelyn_O]

Hey Whacheong,

Thanks for keeping me in the loop. The yellow wire that is previously connected to the E terminal on your old thermostat should be connected to the star (*) terminal in the Nest Thermostat. You can connect your red wire (power) to the Rc or Rh terminal in the Nest Thermostat. 

Please go to your thermostat's Settings > Equipment > Heat Pump. Check if your heat pump is set to O or B. If it's currently set to O, change it to B. If it sets to B, change it to O. After that, test your system. 

Kind regards,

Jenelyn

[Whacheong]

It has not been completely solved yet. I invited a professional man. He said that the aux heat could not be started when heating. He asked: When the yellow wire originally connected to E  we  have connected this yellow wire to * key ; then do we need to make equipment settings to set this * key to aux heat? thank you

[Jenelyn_O]

Hi there Whacheong,

That's correct. Nest thermostat’s star connector can be used to control several different system functions, depending on what type of system you have, and that's the reason why you have to set it to what function of the specific wire connected to it.

Best regards,

Jenelyn

[Whacheong]

Hi Jenelyn ! but if I have let the yellow wire connected to * ,and the Heat Pump Balance doesn’t appear in the app or on my 
thermostat, if I have let the yellow wire connected to W2(aux) there is the pumb balance for select,and? Then?

[Markjosephp]

Hello folks,

I'm chiming in to see how I can help.

Thanks for looking into this, Jenelyn.

@Whacheong, if the Heat Pump Balance doesn’t appear in the app or on your thermostat, you might have an incompatible system, or there could be a wiring issue that makes your thermostat think you have a different system. To be sure, can you share with us your Nest Thermostat's wiring setup? This is to see how you installed it.

I'll look forward to your response.

Best,
Mark

[Whacheong]

 

 

Hi Mark,now I change the wire as the photo1, there is a heat pumb balance ,but before as the suggestion of Jenelyn,the wire to  W2 Aux  is connected to *(photo 2).and i wonder if it correct for this?

[Whacheong]

Hi Mark, Before this my thermostat is as follow :There are two main same lines here.（but one green and one red is useless，it means every color there is two the same in two different different main line） What I want to ask is that w1 and w2 are connected in series. Do we still need instruments? in google thermostat

 

[Markjosephp]

Hi Whacheong,

The wires from your old thermostat have two identical wiring colors. To avoid confusion about which terminals they should be connected to, can you share with me the actual photo of your Nest Thermostat's wiring setup? Also, after the wiring changes made in your screenshots above, have you tried to reconfigure it in the Equipment settings on the actual thermostat as well?

Keep me posted.

Best,
Mark

[Whacheong]

 

Hi Mark ,cooling and heating is ok that the yellow wire (connected W1 and W2 with the red wire ) is connected to *(According to Jenelyn's suggestion)

but there is no aux heat in the furnace, i mean there is no Voltage(The heating rod relay is open),but heating is ok only heat pumb (i think) ; also the Heat Pump Balance doesn’t appear in the app or on your thermostat. So i changed the line and it appears now. Now as this,please check if it’s correct?Green wire wrapped with black tape is useless.

[Markjosephp]

Hello Whacheong,

Perfect! It appears to be wired correctly as you don't have emergency heat, so it should be on the W2/Aux terminal for the auxiliary heat. But I'm glad to hear that the Heat Pump Balance is now showing.

I wanted to ensure you were good to go. Let me know if you have more questions, but here's an article about the Heat Pump Balance settings. You can also reach out to us by starting a new thread for any future questions or concerns; we're here to help.

Best regards,
Mark