Q?: Wiring a NEST Learning Thermostat

[77thor]

I just installed a NEST Learning Thermostat (Gen 3) for my son in his condo...
His old thermostat had a jumper from Y to W, so I installed the NEST with a jumper Y1 to W1.
Apparently, jumpers are forbidden (or not needed)...

So, should I connect the wire to Y1 or W1 terminal???

Thanks.

 

[jlv03]

Whoops, replied to the other thread first. Copy/paste from other thread:

Yes, pull the jumper. I'm guessing you would want the wire on Y1. The Nest likely energizes the Y connection for both heating and cooling (turns on outside condenser) when setup as a heat pump system.

 

[fitter30]

Y is for cooling
W is for heat
There shouldn't be a jumper
Rh and Rc would need a jumper if there was just one R wire old stat

 

[PoorUB]

The big question, what type of system?

I have never heard of jumpering Y to W. The set up in the thermostat should take care of that.

 

[77thor]

It is a heat pump system... and there definitely is a jumper on the old thermostat Y to W.
Also, a jumper RH to RC, which I did not add to the NEST (I just connected wire to RH).

I did add the Y1 - W1 jumper to the NEST and everything seems to be working, but if it's not required or not needed I would like to remove it.

jlv03 --- I'm thinking that you are correct in guessing that the wire should go to Y1.
Because I did connect it to W1 and the NEST setup config flagged that an ERROR.

I will try that unless somebody has a better idea.

 

[jlv03]

What was the old thermostat make/model?

Is this a heat pump? Or, you mentioned condo, is this a high rise with circulating water for heat/cool?

I suspect the old thermostat was pretty dumb - it couldn't be configured to turn on the "Y" in heat mode, so the jumper was put into place.

 

[77thor]

The old thermostat is a Robertshaw (says "ITEM 9610", not sure if that's a model number) dated Oct 07.
It was configured with 4 wires; RH, W, G, and O... With jumpers RH/RC and Y/W.

It is a heat pump... not really a "high rise" at 4 stories... unsure of circulating water for h/c.

 

[jlv03]

Here is my best guess of how to wire it. It sounds like you don't have a common wire? Nest can be very finicky without a common, so be prepared for that.

On the Nest connect:
Rc (was Rh on the old thermostat)
Y1 (was Y/W on old)
G (was G)
O (was O on old)

It should ask for system setup when the Nest boots up.

 

[77thor]

Yes. That is exactly what I thought.
No Common(C) wire.
Thanks.

FYI - - - Just tested it: Yes! Everything works with that wiring.