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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 15097
Experience:  15yrs in the HVAC industry with certificates and degrees.
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I'm trying to install a nest thermostat and there are two

Customer Question

I'm trying to install a nest thermostat and there are two wires going into the aux/e / w2 port (for a honeywell thermostat) and I'm wondering if both should (or can) be installed for the nest...
I have pictures of the existing connection. The unit outside is a carrier tech 2000ss (not sure if that is useful). There is also a black wire that isn't connected to anything...
Submitted: 1 year ago.
Category: HVAC
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset. I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. I just picked up your question now. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly I am not paid anything until you rate my service good using the STAR RATING LINK at the top of your page, the money is paid to the site not me directly.

Yes if you have a picture of the current connections that would help

Customer: replied 1 year ago.
here is a picture of the current wiring setup
Customer: replied 1 year ago.
I am unsure of what to do with the two wires going into the aux/e port (white & brown) as well as the unused black wire.
Expert:  HVAC Guru replied 1 year ago.

I would leave the black wire capped....the white should be your regular heat and Brown is likely emergency heat... So White should go to the normal W connection or AUX for heatpump purposes and Brown if you can on the next it would go to W2

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

Customer: replied 1 year ago.
the pink / salmon wire is going to 'W' and the nest attachment only has one W2/Aux connection. How do I know which wire to use in the W2/Aux slot since there are two going into the current thermostat?
Expert:  HVAC Guru replied 1 year ago.

You have a heatpump correct?

Customer: replied 1 year ago.
I'm not sure - it says Carrier Tech 2000ss on the unit outside...
Expert:  HVAC Guru replied 1 year ago.

Yes it is a heatpump for sure, you need to read the labels on the bottom of the original that is where you need to hook them up on the new one, disregard the top labels.

Customer: replied 1 year ago.
is there a way to tell which of the two wires going into aux/e to use? the white and / or the brown one? Nest says not to use two wires in one port...
Expert:  HVAC Guru replied 1 year ago.

You should use White...in there and cap off brown for now...Brown is likely the EMERGENCY heat wire they should not have put in there...

Customer: replied 1 year ago.
does white also control the emergency heat? should I switch them if it doesn't work with white (use brown instead?) Is there a way to tell by going to the heatpump and seeing what wires are being used (assumed the colors hold)? Will nest be able to tell if everything is working during its self tests?thanks
Customer: replied 1 year ago.
this is what the attic looks like?!... It's my mother's house and a local neighborhood handyman repaired the ac last summer...the thicker red wires are running around the corner to some water leak monitoring system (I'm guessing as a power supply?)
Expert:  HVAC Guru replied 1 year ago.

Try to put White to AUX terminal and try it if it does not work you can connect Brown to it as well, even though the NEST says not to connect two wires to one terminal you still can do it just like the old one. It will not hurt anything.

Customer: replied 1 year ago.
it looks like from this picture:
http://graph.darren-criss.org/2016/02/06/honeywell-thermostat-wiring-color-code-l-b5cb02603cfc52d1.jpg
that aux and e can be separated... the nest has a slot for an 'e' and 'w2/aux' - how do I distinguish which wire is 'e' and which one is 'aux'???
Customer: replied 1 year ago.
could that be done by examining the wires in the attic?
Expert:  HVAC Guru replied 1 year ago.

Yes so put WHITE in AUX and BROWN in E

Customer: replied 1 year ago.
is there a way to tell if that doesn't work? will it be obvious (emergency heat won't work or?)?
Expert:  HVAC Guru replied 1 year ago.

Yes it would be pretty obvious, but WHITE is always AUX and Brown is always Emergency heat so I doubt it is wired backwards.

Expert:  HVAC Guru replied 1 year ago.

Hi there,

I was just touching base with you because I have not heard back from you and the question is still open and unrated, if there is something else I can help you with follow up questions are free and can still be handled even after you rate the service thanks.