Help with a Nest on Trane heatpump


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Old 10-17-15, 08:07 PM
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Help with a Nest on Trane heatpump

i am kind of in the same boat but i have already installed my nest and everything is working except my alt heat. i do have a heat pump with gas alt i believe my black wire is my emergency heat which also works. My wiring is as follows y -y1(yellow), g -g(green), o -o/b(orange), r -rc(red), w1 -w1(white), b/c -c(blue), bk -*(black) any help would be appreciated.


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Last edited by PJmax; 10-17-15 at 10:34 PM. Reason: started new thread
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Old 10-17-15, 10:41 PM
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Welcome to the forums.

Your system is completely different from the one in the thread you posted in. That was a furnace with A/C...... you have a Trane heatpump with electric reheat so will treat your thread differently.

I'm familiar with nest wiring but not their programming.

What terminal was the white wire connected to on the old stat ?
What terminal was the black wire connected to on the old stat.

One of those two is the backup heat. You probably don't need both. You do need to program the nest for heatpump operation with backup heat. I'd imagine the backup heat is activated by the W1 terminal and you won't need the *.
 
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Old 10-19-15, 07:58 PM
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yes my heat pump is also an a/c unit but also have gas furnace up as well. The old thermostat was w1 to w1 and my black went to x2 which i assume is the back up or emergency heat that you are talking about. That worked fine when i had the nest programmed for emergency heat but my w1 was not activating the alternate heat like the old therm with the white wire so i have since moved the black wire which was in x2 and * on the nest into w1 and now alt heat works through the black wire but now the white wire is just in there doing nothing. I wasn't sure if i needed to have it hooked to work properly or if that black back up heat wire in the w1 would be suitable. Oh and yes the heat pump orientation is correct it works fine as well the a/c works too was just the alt heat coming through the white wire wasn't working but does through the black, the furnace is a trane xv90
 

Last edited by cableguy83; 10-19-15 at 08:16 PM.
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Old 10-19-15, 08:54 PM
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A question....why a heat pump and a gas furnace ?
Why not just use the gas furnace for heat ?

That is what is called a dual fuel setup. That will need to be set in pro setup.
 
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Old 10-19-15, 09:18 PM
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it was that way when we bought the house. Yes you are correct i have set up the nest as dual fuel and it all worked except the white wire in the w1 but the black is acting as my w1 for my alternate fuel. i was just wondering why the white wire would not be working on the nest when i move the black wire to w1 the furnace works just fine
 
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Old 10-19-15, 09:23 PM
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It would appear that the black wire is the gas furnace. You'd have to check where the thermostat wiring joins the equipment to see where the white wire is connected. Maybe the white wire is connected to nothing.
 
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Old 10-19-15, 09:26 PM
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on the air handler there is a heat pump kit and the set of wires hit that then wire nut off to the furnace and on the board of the furnace itself the white wire goes to the corresponding w1 slot and there is a small jumper connecting the the w1 and w2 from which i understand would be a secondary stage but since its jumped makes it a single stage so i guess my question is will that black wire be sufficient to run the furnace or am i missing some thing by not using the white
 
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Old 10-19-15, 09:33 PM
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And where does the black go on the furnace..... to W ?
 
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Old 10-19-15, 09:34 PM
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no the black goes to BK on the board this is why i assumed the black was emergency heat
 
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Old 10-19-15, 09:42 PM
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This is the control board inside or for the furnace ?
Can you post a pic of it or post the board part number.
 
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Old 10-19-15, 09:48 PM
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My partner, Houston, is the forum pro on Trane wiring. Here's a thread with similar setup to yours. From what I'm seeing.... BK is for dehumidifying. The thing we need to make sure of is that the heatpump can't be in heat mode and the furnace running at the same time.

http://www.doityourself.com/forum/th...ic-wiring.html
 
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Old 10-19-15, 09:54 PM
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this is the board itself the wires coming from that also go to the heat pump kit i mention earlier. At first i thought that too about the dehumidifier but when i had the nest set the* for dehumidifier the white did nothing in w1 so i tried setting the * to emergency heat and the furnace came on so i moved it (the black wire) to w1 to use as my alternate heat and left the white wire unhooked, it does work i just dont want to damage either my system or the therm
 
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Old 10-23-15, 01:05 PM
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I'm having issues with my alt heat working on a nest thru my white wire which is in the w1 slot of the nest and white goes to w1 in furnace as well. i have my black wire in the * slot of nest which hits bk in the furnace. I have the nest set up for dual fuel since i do have heat pump as well as a backup gas furnace. I initially thought the black wire to be a (de)humidification wire, but since my alt heat was not coming on i played with some of the * setting in the thermostat and found an emergency heat. I switched the * (black wire) in the settings of the nest to emergency heat and then i had heat from furnace. Although the white wire wire(w1) was not doing anything i since changed the * (black) to the w1 and left my white wire off inside the thermostat i do have alt heat now and everything seems to be working fine. However i believe this white wire should not be disconnected as it was connected in my old therm any help or thought would be great thanks
 
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Old 10-23-15, 06:20 PM
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I asked Houston to check in here for you.


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Old 10-23-15, 06:32 PM
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That black wire on BK is for reduced blower speed on demand for dehumidification.

I will see if I can bring up a manual to review the BK jumper and any other jumpers that may be required.
 
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Old 10-23-15, 06:45 PM
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The BK terminal is for dehumidification but the factory jumper between R and BK must be cut ( this is a toggle switch on newer models and replacement boards).

I have a few questions...

Do you have any splices between the thermostat and the furnace that could be changing the wire color?

How long did you wait before giving up on white for W1?

Do you have any extra conductors to use for W2?
 
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Old 10-24-15, 07:54 AM
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yes there is a heat pump kit (small metal box) attached to the air handler with a terminal board similar to what is in the furnace and a few wire nuts. They all seem to be attached to the same color though. I gave up on the white wire after a couple hours on the phone with nest support telling me something in my furnace was bad which i knew wasn't true because it had worked with the old trane therm just fine. There is an additional wire in the furnace and in the therm for what looks to be the w2 however there is a jumper in my w1 and w2 at the furnace for which i believe is to make a single stage where the second stage comes on after ten minutes of heat being called for at least thats what my furnace indicates as well as the pic u posted below
 

Last edited by cableguy83; 10-24-15 at 10:30 AM.
 

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