Nest Thermostat Install - Help w/ wire identification

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Old 01-04-12, 03:44 PM
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Nest Thermostat Install - Help w/ wire identification

So I installed my Nest Thermostat for my main living area just perfectly but now I am installing the second unit for our basement area that operates on it's own heat pump unit. The problem I'm having is wire identification from the old thermostat and where to place the wires into the new Nest Thermostat. Unfortunately Nest Support was unable to assist in the install as they can't figure out the wiring either. Any help is greatly appreciated! I have attached the Nest base picture and also a picture of the current thermostat install....

Original...


Nest...
 
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Old 01-04-12, 05:27 PM
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I'm unsure of those terminal designations myself. The solution is to open up your air handler and HP and check the wire colors VS. terminal designations in the equipment.
 
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Old 01-04-12, 05:34 PM
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Sounds like fun, but it's 20F outside, maybe tomorrow! Thanks for the help hvactech. After I open up the panels perhaps would you then be able to assist. The HP is definitely an older unit but I believe the blower is new, less than 5 yrs.
 
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Old 01-04-12, 05:35 PM
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yes, I'd be happy to help. Just list out the terminal designations and wire colors. Pictures are nice too......
 
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Old 01-04-12, 05:37 PM
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I love pictures myself. I shall try to post up some tomorrow. Thanks again for all your help!
 
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Old 01-04-12, 06:56 PM
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Hey hvactech. So I just went down and checked out the handler. I drew a description of how the wires are connected inside the handler itself but was unable to bear the cold so I have yet to open the HP. Does this help at all?



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So at the top, Red, Yellow, Blue, Black & Orange direct from HP to Stat. Brown is pigtailed into two wires, then continues to Stat, one that appears to go to AUX or Emerg Heat Unit and one that goes to what appears is the blower motor relay. Then the Emerg Heat sends 1 wire (Pink) to Stat and blower relay sends Green to Stat. Is this just crazy or what??
 
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Old 01-04-12, 07:37 PM
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that is not a common connection. Most connections are made at the air handler and also sent to the HP, but we will know more when you get info on the HP
 
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Old 01-04-12, 07:39 PM
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Ok. Thanks again for all your help. This just seems crazy!
 
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Old 01-05-12, 07:55 AM
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So here's the update today with pics....


Original Wiring Diagram Found inside HP


HP Wires


Updated Diagram
 
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Old 01-05-12, 07:59 AM
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I looked up the old stat, and this how it should be wired.

My question for you, is this t-stat controling a zoned system?? Reason I asked is B is wired up. But as HVAC wants more info.

X----C
A----Not used
O----O/B
Y-----Y1
B-----????????
R-----Rh/Rc(jumper the two together)
W2---Aux
G-----G
 
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Old 01-05-12, 08:01 AM
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So for the Nest I am going to jump out there and reach but....

Red wire goes to Rh...
Yellow to Y1...
Green to G...
BROWN to C... (As brown is apparently the common?)
Orange to O/B...
Pink to AUX/W2....
And then the big mystery....Will Black go to W1???
 
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Old 01-05-12, 08:16 AM
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Ok, Here's the update.


X----C
O----O/B
Y-----Y1
R-----Rh/Rc(jumper the two together)
W2---Aux/W2 (jumper the two together)
G-----G
A and B are not used with this new stat.


 
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Old 01-05-12, 08:43 AM
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Hi Jay. Even though B (Blue wire) is connected at TStat, it is not connected to HP or Handler. The unit is not zoned either.
 
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Old 01-05-12, 08:46 AM
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Ok, Here's the update.


X----C
O----O/B
Y-----Y1
R-----Rh/Rc(jumper the two together)
W2---Aux/W2 (jumper the two together)
G-----G
A and B are not used with this new stat.


Read more: http://www.doityourself.com/forum/th...#ixzz1ibCqU06N
Ok. Thank you so much! I will attempt this configuration later on today and report back with the results! By the way, what is the black wire used for??
 
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Old 01-05-12, 08:51 AM
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The old A-Black wire is used to "Trick" the t-stat when the temp gets colder outside to turn on the Aux heat strip.

The old B-blue wire may of been for another unit or installer at the time didn't know if O or B was going to be used, so they wired up both till the unit was in place, then hooked up the O instead of B.
 
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Old 01-05-12, 08:52 AM
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Thanks for the info Jay! You and hvactech are amazing. As soon as I can test this out I'll update the thread! Thank you again so much!
 
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Old 01-05-12, 03:07 PM
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So to update.....My Nest is working perfectly! Thank you so much Jay and HVACTech! You guys rockand I couldn't have done it without you!!
 
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Old 01-05-12, 04:18 PM
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Thanks for the update!

Don't get too carried away setting the temp back too far at night, Otherwise, the Aux heat will come on to help with recovery, and the savings are gone.
 
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