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gotoman for ac
gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5215
Experience:  51 years of experience install design and repair of all makes and models of AC
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I have an old Trane TWV730b140a0 air handler in my condo

Customer Question

I have an old Trane TWV730b140a0 air handler in my condo unit that I just bought. The condo association doesn't have a map of the outdoor units so as of right now I don't know which condensor unit is mine. In my closet I have 6 wires (red, yellow, green, blue, white, and brown) but no orange wire coming from the heat pump (XE800). If I follow the wiring diagram on the unit it connects to R, G, W1, W2, and B but not O. I'd like to install a new wifi thermostat and the wires inside the current tstat are Red-Rc/Rh, Yellow-Y, Brown-W, Blue-B, White-O, Green-G. When I goto the air handler half of the wires weren't connected and the time delay PCB was missing. I replaced it and the relay with a new RLY02807. The issue I'm having is the correct wiring from the Heat Pump to the Air Handler Terminal Block which has options for R, O, G, B, T, Y, W1 and W2 since I only have 6 wires for the 8 terminals. I assume I can skip the T terminal but since there's no diagram connecting an O would I then use W1 as my O and W2 is my aux heat?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

The O (which controls reversing valve can go straight to O in outdoor unit.It does not need to connect to air handler.It would be great if you could see how the wires are connected in outdoor unit as techs often used different colors.

On the old air handler B was "Common". If you had a C on new thermostat that B from air handler would go to C.

The B on newer thermostats control reversing valve in heat pumps such as Rheem or Ruud that reverse in heat mode.While O is used on Trane and most others as they reverse I cool mode.

So on a newer thermostat you will never use both O and B.

To be sure ,if you can provide model on new thermostat,and verify which wires currently go to each component , this will be pretty simple. If you can list in the following format:

Thermostat----------Air Handler-----------Outdoor unit






To determine which outdoor unit is yours. Go stand by units and have someone turn on and off at thermostat to see which unit responds..

I am leaving to go out of town shortly but if we can not finish before I leave I will open to other experts.

Customer: replied 1 year ago.
I'm at work currently so I don't have access to the units/someone to help verify the unit. So if you're going away I don't think this is going to be dealt with right this second. I appreciate your input but it would be helpful if you left it open.The question is less which Tstat hook ups to use but more what the hook ups at the terminal block in the air handler should be. The wiring diagram in the Air Handler doesn't correspond to values at the Tstat. As it stands I'd probably end up using a nest or the sensi (I have both debating which I like) and the hook ups at the tstat would likely be:Old Tstat-------New Tstat------Line Color
R/RH----------------Rh---------------RedBut per the wiring diagram the following connections are made at the LVTBWH1 & WH2 from the polarized plug goto W1 & W2 respectively at the LVTB
24VAC common is jumped between B & 4 at the PCB and goes to B at the LVTB
G goes directly from the PCB to G at the LVTB
24VAC goes to A at the PCB and then to R at the LVTBso if Y connects to Y and O connects to O and neither are wired through the air handler that's a total of 7 designations.So all of that to say if I have 7 terminal block designations (the 5 called for on the wiring diagram + Y & O) but at the tstat and from the heat pump I only have 6 wires run. So what gets omitted? Do I need W2? are W1 & W2 jumpered? Something else that I haven't thought of? Keeping in mind I obviously do not want the electric heat strip running everytime I call for heat unless it's required.
Expert:  airheatman replied 1 year ago.

Your wiring will be as you stated, except on new thermostat you will use W2 or AUX, whichever new thermostat has as the heat strips are second stage heat.

At board W1 and W2 can be connected together.

Since you are not there right now ,I am going to open this to other experts in case you need further assistance before I get back. Please wait to leave rating until we are done

Expert:  gotoman for ac replied 1 year ago.

Do you still need help. Russ