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All, I am trying to upgrade my Thermostat and am very confused how to connect the wires correctly (Florida house built 1991, AC and heat strips, no furnace): As is, Trane XT500

  1. Blue to B
  2. Red to R
  3. White to W
  4. Green to G
  5. Tan to O (I think this is supposed to be Orange)
  6. Yellow to Y1
  7. Jumper W to X2

On the Honeywell:

There is B/O not B and O as separate connections. There is no W. There is no X2.

Available Connections are:

on Left:

  • Y2
  • L
  • A
  • W1
  • S1
  • S2

on Right:

  • RC
  • R
  • O/B
  • Y
  • G
  • C

I would greatly appreciate any help!!!! This should be easy, but I don't want to guess. Here is the Trane (before) image:enter image description here

Here is the Honeywell Replacement (VisionPro 8000 TB8220U1003):enter image description here As you can see we ran the wires from what seemed obvious/reasonable, but didn't know what to do with the white wire. Also, we connected the Blue and Orange (tan) wires together into the O/B slot. Don't know if that is good or bad.

tag on air handler tag on air handler tag on air handler

enter image description here

enter image description here

![mid wiring diagram ]8

Diagram from booklet

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    Hello, and welcome to Stack Exchange. Pictures of the old and new thermostat's terminal strips would be really helpful. If you can't post the images, post the URLs and someone will be by to edit them in. – Daniel Griscom Apr 2 '18 at 2:04
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    Can you post photos of the wiring at the old thermostat and the air handler? – ThreePhaseEel Apr 2 '18 at 2:43
  • Inside your Air handler Cover Panel there will be a wiring diagram of how the unit should be wired. Your thermostat might not be compatible - you MIGHT be able to make it work by hooking the TAN wire that is on O to Y2 on the new Tstat and leave B on the O/B - but without your diagram - don't chance it. You have two reversing valve controls in your unit from what little I can find on the net. Your Diagram inside that panel is really important. – Ken Apr 2 '18 at 21:08
  • Ken, thx for help. I was called out of town for a few days on biz. I will get back up in the attic (ugh) as soon as I get back. I'll post by Sat. My wife is already ready to kill me cause it is already hot in FL. – davef Apr 3 '18 at 16:36
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Trane nomenclature's a bit different

Trane decided to be different (and a bit difficult) with their heat pump thermostat nomenclature: while O is indeed the reversing valve connection, they called the common B (blue) instead of C (for Common). So, your correct wiring is:

  • White (W on the old 'stat) goes to W1 on the new 'stat
  • The jumper from W to X2 on the old 'stat gets discarded (X2 was emergency heat, but the Honeywell is smart enough to mux that onto W1 in heat pump mode)
  • Red (R on the old 'stat) goes to R on the new 'stat (the R-RC jumper stays put)
  • Tan (O on the old 'stat) goes to O/B on the new 'stat (some other people designate the reversing valve terminal as B, but Trane went and used that for the common terminal instead)
  • Yellow (Y1 on the old 'stat) goes to Y on the new 'stat
  • Green (G on the old 'stat) goes to G on the new 'stat
  • and Blue (B on the 'old stat) goes to C on the new 'stat (not to O/B where you have it now)
  • If B really is common the op should be able to measure 24VAC on that lead when it is disconnected from the TSTAT. Apparently installer did not have orange in the jacket ..either.. – Ken Apr 3 '18 at 7:58
  • @Ken -- if he had a tester that could measure that, seconded :) – ThreePhaseEel Apr 3 '18 at 11:36
  • I climbed up into the attic and opened up the cover and took pics. Light was not too good. I'll post the sort-of clear ones. Also took the paper with the wiring diagram. Will post shortly as soon as I can get it scanned. I'll post pics now a scanned wiring diagram later this afternoon – davef Apr 7 '18 at 19:09
  • I have a voltmeter. Are you saying that I need to disconnect the blue wire from the thermostat and turn on power? If I measure AC Voltage between Red and Blue (w/Blue disconnected) that I should see 24 VAC? Also, I should see 24VAC between Tan(Orange) and Blue? Should I disconnect all thermostat leads first? – davef Apr 7 '18 at 19:52
  • You should read 24-30VAC between Red and Blue at the thermostat, yes -- don't run around disconnecting wires though, please! – ThreePhaseEel Apr 7 '18 at 20:53
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Ok I want to explain some things for you and also at the link here you can see the standard wiring code for Thermostats.

You do not post your Air conditioner / heater / Air handler make and model so you will get a generic map until that is posted. I can't be sure if your new thermostat really is compatible - looks like you are missing your c wire. Pictures of old thermostat with visible labeling and current wire hook up would be helpful. Pictures of new thermostat would also be helpful.

Here is the system function map - so if your wires are correctly colored and connected - it should be pretty clear to map it across. However with out your make and model of AC / Heating unit - there is no certainty that your new thermostat is compatible.

  1. Blue to B REVERSING VALVE - a HEAT PUMP. Activate the valve for Heat Mode
  2. Red to R 24 VAC
  3. White to W HEATER
  4. Green to G GROUND
  5. Tan to O Orange REVERSING VALVE - a HEAT PUMP. Activate the valve for Cooling Mode.
  6. Yellow to Y1 COOLING ON Stage 1 or only unit -
  7. Jumper W to [ X2 HEATER AUXILIARY - HEATING UNIT 2]

On the Honeywell:

There is B/O not B and O as separate connections. There is no W. There is no X2.

Available Connections are:

on Left:

  • Y2 2nd Stage Cooling [NO WIRE]
  • L Heat pump Failure Lamp
  • A (Never saw this before - possible ALARM ..) or is it AUX for Auxilliary
  • W1 Heater 1 [WHITE WIRE]
  • S1 Outdoor temperature sensor
  • S2 Outdoor temperature sensor

on Right:

  • RC 24VAC Cooling [RED for Cooling ]
  • R 24VAC [ RED ]
  • O/B Reversing Valve [ ORANGE OR BLUE ]
  • Y AC Cooling On Signal [YELLOW]
  • G Ground [GREEN]
  • C 24VAC [BLACK]

Like I said if you posted more information we could all help you better...

  • Ken, thx for info. I have posted the photos. I will be glad to post additional info if I know what/where to find it. I will go outside to the main unit to look for model#. The Air Handler is in the attic (in FL that is a crazy idea) and try to get whatever I can find. BTW, is tying the Blue and Orange together a good idea? I've been reading and it seems supposed to be one OR the other, not both. – davef Apr 2 '18 at 16:12
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    Outside Unit is a Trane XL14i – davef Apr 2 '18 at 16:18
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    Air handler Model # is Trane Variable speed TWE031E13FB1 – davef Apr 2 '18 at 19:08
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    I've posted the additional pics. I believe from what you posted that the White wire should be put in W1. I still don't know about if I'm supposed to tie the Orange (tan) and Blue wires together in the O/B? Also, there is no Black. Does the lack of a Black wire mean that I am FUBAR'd? – davef Apr 2 '18 at 19:31
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    Ken, On the tag on the outdoor unit it says model# 2TWX4024A1000AA. I do not have an owners manual. We moved here in 2009 and there was no history, manuals or info on anything. We bought from the bank after foreclosure. – davef Apr 2 '18 at 22:12

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