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Is W2 an input to nest or an ouput?

Charles333
Community Member

I know W2 is a call for heat when the heat pump cannot cut it.  But who is asserting the signal?  It is not obvious.

1 Recommended Answer

Jake
Community Specialist
Community Specialist

Hey Charles333


I want to ensure you are good to go, and everything is working properly. Please let me know if you are still having trouble, as I will be locking the thread in 24 hours due to inactivity.

Best regards,
Jake

View Recommended Answer in original post

5 REPLIES 5

Charles333
Community Member

I do not understand why "Dual Fuel" is preventing "Heat Pump balance".   Why does this need to be?

If the heat pump is requesting AUX heat, why not have the Nest turn on the Furnace?

My York heat pump has W, W1 and W2 terminals.  Not sure why W has to go to the heat pump.  My understanding is that W1 and W2 are heat pump outputs asking for heat.  They are jumper in my case.  So lets call it W2.

I assume W2 (from hp) could spark up the furnace directly and carry on to be an input to the Nest so Nest knows what's going on.   But then they are times when the Nest wants to do a hurry-up and asserts W2,  So I assume W2 is bidirectional.

Ideally W2 would be just an input and the Nest would assert W (W1) when appropriate.  Problem is, if W1 and W2 are both connected the system is classified as Dual Fuel and no balancing happens. 

My goal is to get Balancing to work.   Problem is, that to do that I need to only have only W2 connected.  Which implies W2 must be bidirectional.   Either the heat pump or the Nest can call for furnace heat.   

Weirdly, one would then have to connect W2 to W1 at the heat pump or control.

Seems this should work.  Does this seem reasonable?

Charles333
Community Member

To answer some of my own questions.   W goes to the Heat Pump to trigger Emergency Heat if desired (W with no Y).  No need for that really - assuming both the Heat Pump and the Nest are driving W2.   Nest will keep things OK by driving W2 - which is what the Heat Pump would have done.

So looks like no W1 is required to the Heat Pump W line.  W2 needs to go to the furnace/air handler W.  Sounds all well and good - assuming both the Nest and the Heat Pump can drive W2 - occasionally/possibly at the same time.  Should not be a problem as long as the Nest and the Heat Pump are getting the same 24VAC from the furnace/air handler. 

It would be nice if Nest would give this the nod.

Hopefully final tidbit.  W from the Heat Pump is used during the defrost cycle.

So it seems one would connect all W, W1 and W2 lines at the Heat Pump (call the result triple-W);  connect the triple-W from the Heat Pump to the W for the Heat Source (furnace/Air Handler); and finally take the triple-W to the Nest thermostat's W2.

Jake
Community Specialist
Community Specialist

Hey Charles333

 

Sorry for the late reply. I wanted to follow up and see I could be of any help. It seems you may have resolved your own issue, but I wanted to be sure. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further. 

Best regards,
Jake

Jake
Community Specialist
Community Specialist

Hey Charles333


I want to ensure you are good to go, and everything is working properly. Please let me know if you are still having trouble, as I will be locking the thread in 24 hours due to inactivity.

Best regards,
Jake