# Need help with honeywell TB8575A1000 Fan coil thermostat wiring



## Desihype (Oct 20, 2012)

I recently bought Honeywell fan coil thermostat TB8575A1000 to replace my older Honeywell thermostat T8575D2003 which is discontinued by Honeywell.I don't know much about HVAC wiring. There are 8 wires coming out from the wall which was connected to my older thermostat 








In this manner, By going through the manuals I figure out how to connected 7 wires out of 8 to the new thermostat 








There is one more wire which is Violet in color and hooked to connection number 6 in the older thermostat T8575d2003 it's mentioned as Fan Common wire in T8575D2003 literature 

I need someone to help me out by looking at the picture if the wiring is connected correctly and help me out where I can attach violet wire.

Thank You.


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## beenthere (Oct 11, 2008)

In the pic, the wire on 6 looks to be green. Does your fan coil have 1 or 2 transformers.


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## diyorpay (Sep 21, 2010)

From your pics, looks like older ts had 4 wires for fan control/speeds.
New one has only 3. Probably jumpered internally.
Your wiring looks correct. Extra wire not needed.


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## Desihype (Oct 20, 2012)

Yes it's green I have this diagram of the heat system I have in condo. May be this will help 









































Thanks for replying to my post 
Appreciate your help.


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## Desihype (Oct 20, 2012)

diyorpay said:


> From your pics, looks like older ts had 4 wires for fan control/speeds.
> New one has only 3. Probably jumpered internally.
> Your wiring looks correct. Extra wire not needed.


The new thermostat had Pipe sensor option the last slot does this green wire has anything to do with that ?


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## Desihype (Oct 20, 2012)

beenthere said:


> In the pic, the wire on 6 looks to be green. Does your fan coil have 1 or 2 transformers.


I think it's only one transformer


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## beenthere (Oct 11, 2008)

The wire to 6 was/is energized from the aquastat. If the new stat energizes the fan speeds from the R terminal, then you don't need to connect that violet wire.


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## tyassine (Dec 9, 2012)

Desihype said:


> I recently bought Honeywell fan coil thermostat TB8575A1000 to replace my older Honeywell thermostat T8575D2003 which is discontinued by Honeywell.I don't know much about HVAC wiring. There are 8 wires coming out from the wall which was connected to my older thermostat
> 
> View attachment 59133
> 
> ...


I have almost the exact same setup (only difference is the thermostat model) and can't figure out which wire goes into which terminal on the new thermostat - any chance you remember which colour wire matched which label? Need to figure out if the NEST thermostat is compatible.


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## pkaye1 (Jan 6, 2016)

*extra violet wire*

i just purchased the tb6575a to replace the old honeywell t6575b and have the same curiosity with the extra violet wire coming out of the hvac wall that was connected to terminal 6, labeled 'fan common' in the t6575b. The new thermostat doesn't seem to have room for the violet wire..would the advice to ignore it be the same in my situation as it was with the previous 24 volt thermostat posted by desihype..


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## beenthere (Oct 11, 2008)

Terminal 6 is usually fan high/GH.


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