Installing a Nest Thermostat - Wiring Question
#11
The Nest wiring instructions seemed clear until I actually did it.  My existing T-stat is a Trane.  It has separate wires labeled O and B on the terminal block, the colors of the wires are Orange and Blue.  The Nest instructions don't cover that.  They do say that the B wire may be a common wire and it should go to the C terminal on the Nest but that I need to look at the orignal t-stat installation instructions to make sure.  Looking at the installation instructions for the T-stat, this appears to be the case.  I found the instructions for my existing t-stat here:

http://www.munchsupply.com/docs/default-...f?sfvrsn=0

Figure 5 on page 3 seems to indicate this is a common wire, but I also see references to it controlling a reversing valve.  Should I treat it as the common?  I don't have a separate wire labeled 'C'.
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#12
The B wire is blue and is common.
The O wire is orange and energizes the 4 way (Reversing) valve for heat or a/c on a heat pump.

O- energized is cooling on Trane systems.
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#13
Thanks. I found indications of that elsewhere but I trust the answers I get here more than nearly everyplace else.
Wink
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#14
I ran into an issue.  My old tstat has connections for R, W2/X2,W1,Y,G,O,B  

I had wires connected to each of those.  I ran the system tests.  Everything seems to work except Aux Heat.  I connected the wire from W1 on old to W1 on the Nest, and the wire from W2/X2 to W2/Aux on the Nest.   I might have a loose wire.  I didn't check that yet, but the Nest detects the wires connected - it shows me a picture on the display of where they are connected.  Is something on the heat pump overriding the heat strips?  It's summer time after all.

Here is a picture of the Nest.  This isn't mine.  My connections are Y to Y1, G to G, O to OB, W1 to W1,W2/X2 to W2, B to C and R to RH:
[Image: aHR0cDovL21lZGlhLmJlc3RvZm1pY3JvLmNvbS9R...qcGc=?.jpg]
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#15
Be sure RH and RC are jumped.

Aux heat may be time delayed, it may run through an outdoor thermostat and the temp setting must be set 2* higher than the room temp.

On some thermostats, W1 is used for Gas/Fuel heating (Non- Heat pump).

Check the programing if there is one.

See if there is a "Sequence of operation" with the thermostat.

Frankly, I haven't dealt much with nest- too many complaints.
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#16
Nest instructions say no jumpers needed. R by itself can be connected to RH or RC. The Nest tells me that there may be a time delay - I waited several minutes. I'm wondering if it is running through an outdoor tstat. Temp setting was set to 75, which is room temp. this was a test using the Nest testing utility - it would call for heat no matter what the temp was. testing regular cooling and heating worked.


what do you mean by sequence of operations?
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#17
Sequence of operation means what the thermostat does at a particular setting.
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#18
(07-08-2018, 10:55 PM)daddo Wrote: Sequence of operation means what the thermostat does at a particular setting.

thanks.  in this case, the Nest has a Test mode.  you can test heat/cool/etc.  In test mode I don't think it matters what the t-stat temp is.   Testing cooling and basic heat worked.  testing aux heat nothing happens.  I checked the wiring, it all looked good, no loose connections.  I'll have to see if I can find a schematic for my heat pump to see whether there's an outside thermostat.
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#19
Worst case scenario can you temporarily replace the old thermostat and see if aux heat works?
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#20
I figured it out. I spoke to Nest support and I had the aux wire in the wrong spot.
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