W2 for Heat Pump Balance

[Charles333]

I had a previous post which has got stale.  "Is W2 an input to nest or an ouput?"   (missing the 't')

Jake reached out to see if everything was solved - and I did not respond in time.

I will not repeat that post here - because there was a LOT - and it not all so good.   I think I finally figured it out.

I was getting hung up on the "need" to use 'W2' to get balance operation.  I am pretty sure the simple answer is - connect Nest 'W2' to Heat Pump 'W'.  Maybe that is obvious - but it would have been nice if it was explicitly stated.

W2_OUT is a heat pump output and hence my confusion - connect that to Nest W2? - NO. 

[Jhonleanmel]

Hey Charles333, 

Awesome — glad to hear that your issue is fixed and thanks for sharing your thoughts about this. It looks like we can consider this one complete, so I will lock the thread shortly unless I can help out with anything else. 

Best, 
Mel

[Charles333]

Hi Mel,

I was looking for confirmation of my thinking.  I am surprised there has been so little interest.

I started this whole process by trying to understand whether the W and W2 signals were bi-directional.  I have never gotten an answer from Nest.

I am looking at a possible equipment setup where W1 is connected to the Thermostat, the air handler, and the heat pump.   This means this signal must be bi-directional (or at least able ton handle other equipment driving "its" output).

The heat pump drives W when defrosting and the thermostat drives W when calling for heat.  So certainly bi-directional at the heat pump.  And the Nest needs to handle W asserted from the heat pump.

Different heat pump vendors handle these signals differently.  My current York unit takes W in and then provided a W_out (weirdly named as W1/66)  that then goes to the air handler.  In this and other cases, two pieces of equipment were never driving the W signals.  Until I came across the case mentioned above (Goodman/Amana heat pump).

/Charles

[Jhonleanmel]

Hi Charles333,

Thanks for clarifying that. I suggest reaching out to a Nest Pro so they can provide more accurate suggestions for this. 

Best,

Mel

[Jhonleanmel]

Hey Charles333,

Checking back in should you still have some questions here. Let us know by replying to this thread.

Best,
Mel

[Jhonleanmel]

Hi Charles333,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Mel