Trane XV80 furnace and Nest Gen 3

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  #1  
Old 06-16-19, 08:01 PM
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Post Trane XV80 furnace and Nest Gen 3

My Kids bought me a Nest gen 3 for Christmas and am now trying to install it. i wanted to wait for warmer weather.
I tried to get a Yes from the compatibility web page but it insists I need a Pro to install It and it may not be compatible. I am a Electronic engineer but not an HVAC Guy.
I have an XV80 Trane Furnace but have a XL16i Air conditioner 2 Stage scroll compressor. My Thermostat is a TCONT802AS32DAA. Notice the 3 cables going to the Main furnace board. One goes to the thermostat and one to the xl-16i compressor and the larger wire that is kind of back behind in the photo goes to the electrostatic air cleaner.
i WILL ATTACH PHOTOS OF THE WIRING. can You Help me connect this up and set it up.
Thanks So Much for being here to help. I tried to return the Nest but the store wouldn't take it back and its a good gift. I would like to get it working. I can't believe it won't work.

Thanks Again

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Last edited by PJmax; 06-16-19 at 10:33 PM. Reason: cropped/resized pictures
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  #2  
Old 06-16-19, 08:56 PM
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Here is a Schematic I found online for the xl-16i.I noticed that there is a MS contactor coil that is driven by the Y output through the Hi and low pressure switches. How much current does these 24 V Coils typically draw.
Could the coil resistance of this contactor coil be an issue for the Nest to drive. Most modern FET drivers can handle up to 10 Amps. Just Thinking out loud. I also noticed no mention of a 2 Stage function Here?????
My Understanding is the 16i is a 2 stage unit. How Does this work?
OH would you send me the pro programming guide for the gen 3 nest?
 
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Old 06-16-19, 11:02 PM
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Welcome to the forums.

I moved you to your own thread. Left a link to the old thread in your post.

So you have a two stage furnace and a two stage A/C system.
Modern thermostats can handle a maximum of 1A per function. That's 24va.
A contactor coil is approx 10va

Red -------> Rh
White ------> W1
Yellow -----> Y1
Green -----> G
Black ------> C
Orange ----> Y2
Brown -----> W2/AUX

Send me a PM with your email address and I'll get you some pro info.setup.
You'll need to set the nest for two speed cooling and two stage heating.
 
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Old 06-17-19, 03:31 PM
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Wow that was fast. So you think this will work. I was told by some one at NEST it was not compatible.
I couldn't believe it wouldn't work. I know a lot about electronics but not so much about HVAC.
I will set this up next week when I have more time.
Thanks so much for your Help!
Again Thanks Pete
 
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Old 06-17-19, 06:29 PM
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I've never set up a Gen3 for two stage heating and cooling but it is in the wiring diagrams.
 
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Old 06-29-19, 04:08 PM
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Hey Pete
I have noticed that there are some inconsistency in the wire colors and where they are connected.
If you look at the picture of the furnace control board the wire cable coming from the thermostat and going to the main furnace board, the orange wire is connected to Y and the yellow wire is connected to O. On the thermostat end of the Cable the yellow wire goes to the y. And the Orange wire goes to the Y2. I know the wire color doesn't matter but the thermostat connection does. The Yellow and orange wires on the furnace end Looks to me to be swapped. Additionally there is a Cable that goes to the XL16i Air conditioner compressor. There are three wires, the White wire is the 24vac return and there is a yellow wire tied to the main furnace board Y terminal and a red wire tied to the main board terminal O.
I connect my current meter on the 10Amp range and measured 0.31 amps when connected between the Rh and the Y terminal at the thermostat. I also tested between the Rh and the Y2 at the thermostat and measure 0.62 Amps. Does this sound like normal current values. It appears to me the the Y2 turns on 2 relay coils and the Y only one.
If the Y and Y2/O are swapped on the Main board with the thermostat, that may be a problem. But if there are no connections to board logic or intermediate circuitry on the furnace board and the terminals are just that, "Terminals ONLY" this may not matter. If the O and Y terminals are swapped on the thermostat wouldn't that affect the operation of the air conditioner and how the Thermostat controls the Temp. Does the thermostat call for cooling with one stage on "one relay coil on" and after a time if the cooling requirement is not met turn on both stages. Or does the Thermostat turn on both stages initially and then cut back to one?
is Y supposed to turn on one stage and Y2 2 both compressors. or does Y turn on stage 1 and Y2 turn on stage 2. How does this work?
 
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Old 06-30-19, 10:11 AM
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Hey Pete.
Please teach me!!
How Does the 2 Stage XL-16i compressor switch between Stage 1 and stage 2. Is it a Valve coil or a switch in motor winding. What??? How is this accomplished. I have looked at their schematics and can't figure it out. I understand some how it changes the compressor from about 50-60% output to 100% output. How is this done?
 
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Old 06-30-19, 10:38 AM
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With a two stage compressor..... the Y1 is powered to start the compressor. The Y2 is powered to reduce the compressor output by activating an internal solenoid that changes the valve configuration. More details are shown in the video below. The Y2 or Yo terminal on the air handler can be used to slow down the air flow.


Two speed scroll operation
 
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