Jumper wire Y and W

[Wallsroy]

Is this wiring compatible with the Google nest thermostat? I just ignore the W of the jumper? How will the heater work? Through the O/B? 

So, do i connect everything as labeled without the W?

 

[CoolingWizard · Accepted solution]

That thermostat is not fully heat pump smart.  So if the system called for auxiliary heat, it called the compressor to run. You have an O model heat pump. You heat pump defaults to a heater.  To make it cool the thermostat energizes the O wire with the Y.  The Nest Learning Thermostat is very flexible and knows how to handle Axillary Heat and Emergency Heat when working with heat pump system’s.

AC Cooling Wizard 

The AC Cooling Wizard. 

[Wallsroy]

Thanks Wizard! Great explanation

[Wallsroy]

Hi. What about the B and O wire, I only see OB on the nest thermostat. Which one do I connect?

[Wallsroy]

This is how it's connected inside the furnace 

 

[Wallsroy]

It's a Trane thermostat. It's only heating with I connect the B or O from old thermostat to the Nest O/B. I tried with first with B and then with O. It heats but doesn't cool

[CoolingWizard]

You need to tell the Nest how to treat the OB wire.  The two choices are O energize for Heat, or B energize for Cooling. My gut feeling is your reversing valve is the O and the B wire is your Common.  You will need to have a volt ohm meter to verify. 

The AC Cooling Wizard

[Jenelyn_O]

Hi there,

Thanks for reaching out. Were you able to verify which wire is your reversing valve and which is your common wire? You can try to use a volt meter to check the voltage of those wires. 

I appreciate your help, @CoolingWizard.

Best,

Jenelyn

[Wallsroy]

Hi

What voltage should the reversing valve show?

[CoolingWizard]

The reversing valve is a coil. If the wire is energized you will gate the same voltage as measuring R and C.

AC Colling Wizard 

[Jenelyn_O]

Hi Wallsroy,
 

I just want to check if you're already able to find the wire which is responsible for your reversing valve. Please let us know if you still need help. 
 

Thanks for your help, @CoolingWizard.
 

Regards,

Jenelyn

[Markjosephp]

Hi Wallsroy,

I'm checking back in — how's it going? Still need our help?

Thanks,

Mark

[Wallsroy]

Thanks for your help. All good

[Markjosephp]

Hello Wallsroy,

Awesome! I'm glad to hear it was sorted out. It looks like we have come to a solution, so I'm going to lock this thread in 24 hours. If you have any other concerns or questions, please feel free to create a new thread.

Regards,

Mark