Advice on upgrading an old Trane/BayStat 339 thermostat

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  #1  
Old 08-01-14, 08:49 PM
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Advice on upgrading an old Trane/BayStat 339 thermostat

Dear Sirs,

Any advice and direction on the following would be very much appreciated.
I have a mercury Trane Weathertron Heat Pump thermostat (inside says Baystat 339) - and would like to change out both of these identical upstairs and downstairs thermostats for a modern programmable one. Name:  101_3266.jpg
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There's seven wires, and I would like to ask for you help figuring out what they go to in the new thermostats. The modern models I've looked at, don't have an x2, nor a T. I also don't understand why the white wire hooks through X2 and then connects to W.
If the pictures don't come through here's a description:
Green wire - G
White wire - x2, then W which is connected to U
- F
Red wire - R
Orange wire - O
Yellow wire - Y
Brown wire - B
Blue wire - T

I'm looking at purchasing a Robert Shaw 5220 thermostat - as it has all the features I'm looking for, and was wondering if my current wiring can be matched to the RobertShaw layout, and how the wires get hooked up.

(Robertshaw RS5220 24-Volt Digital 5/2 Day 2 Heat / 2 Cool Multi-Stage Programable Thermostat - Smarthome)

https://imageshack.com/i/pamT976aj
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https://imageshack.com/i/ezN4YBnij
 
  #2  
Old 08-02-14, 12:56 AM
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Green wire - G
White wire - W2 and E
Red wire - R (leave factory jumper installed)
Orange wire - O
Yellow wire - Y1
Blue wire - C
Brown wire - Tape off

Looks like Blue is B in your picture.
The old B is now C.

Make certain the HP switch is in the HP position.
 
  #3  
Old 08-07-14, 08:38 PM
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Thank you so much for your advice. Now that the replacement thermostats are there, I have removed the old weathertron/baystat unit and when it came off the wall, I noticed that in the drywall hole there's an unused wire. The wire looks to be pink in color, and if my pictures come through you will be able to see it. What to do with this one? Is there a place to connect it to on the new thermostat, or is it just an unused wire on the HVAC harness?Name:  101_3294.jpg
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The wall plate see in the pictures is the one from the new thermostat, as opposed to previously posted pictures.
Thank you, beforehand, for any advice and suggestions that may come my way.
 
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Old 08-07-14, 09:04 PM
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Any wires not used with the original thermostat will not be used with the new thermostat.
I hope you turned off power to the indoor unit before replacing the stat.
 
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Old 08-07-14, 10:26 PM
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Houston204,
Thank you, again, very much. Per instructions given, and a tiny bit of common sense, the breaker for heat pump and air handler was thrown before attempts were made to upgrade the thermostat.
 
 

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