Hi folks,

I have an old Trane heat pump (Wethertron TWR736A100A1) and the air handler is under our crawl space. My old contactor had gone bad and a buddy dropped off a new contactor, but it's altogether different. But after researching, I thought I could replace the old with new.

This is the old contactor:



Here is the new as I have it wired up. It blows the breaker!






I hope there's something obvious someone can tell me where I went wrong. Thanks so much!

Howard in NC

 

Can you post a picture of the wiring diagram? The two Blk/blu wires on the same terminal looks suspicious.

 

Thanks for trying to help. I located the wiring diagram and it's not in very good shape. It was sitting in the unit since it was new, I reckon. I tried piecing it together as best I could and took some high res photos.

If it's any help, after I had wired it up and turned the breakers back on, the heat pump fan turned on even though the system was turned off at the thermostat. When I turned a/c on at the thermostat, the air handler came on as usual, but the compressor fan stopped.

These are very large files, hopefully you can make heads or tails of them:

http://www.ochsart.com/trane/trane10.JPG

http://www.ochsart.com/trane/trane11.JPG

Thanks again for helping me out!


Howard

 

Ok I see whats going on now. Remove the 3 black/blue wires. Then move the 2 red wires and connect the where the Blk/Blu wires were. Then move blu/wht wire to where the red wires were.

Then attach blk/blu wires where the purple/wht wire is. Hope this makes sence to you. Let me know.

 

I'll get to it first thing in the morning and report back.

Thanks for your time, much appreciated!


Howard

 

Well, I believe we have success!!

I do have one question though. With the system turned off at the t-stat, I switched on the breakers and the heat pump fan came on. Should that happen even with it turned off at the t-stat?

But otherwise, I turned on the air, the air handler fired up and I do believe we have cool air, although it was tough to tell since it's cool outside today. Temp in house was 78 when I turned it back on, should know if it's cooling off soon enough.

Can't thank you enough! I'll report back later to say all is well!

Have a great weekend.


Howard

 

No, the fan should not be running. Let me dig through the drawing again. Can you send pic of new contactor wiring?

 

I don't believe the compressor is coming on, no cold air. Be back in a few with a photo.

 

As it is now. Forgive my rudimentary drawing, though it may help. i forgot to add the all Black wire, it is connected with the brown wires. oops.

With the compressor fan and air handler both running, the contactor is making a slight buzzing noise. Don't know if that's normal or not.






Thanks.

 

The thick black wire to the sump heater is on the wrong side of the contactor.
It should be with the brown/red wires, not the red wires.

 

Thanks Houston, it does appear that way, but the thick black wire is indeed connected with the brown/red wires.

 

After looking at the original diagram, I followed it to the letter and am fairly confident it's wired correctly now. Provided I have the T2/T1 and the L2/L1 properly identified:

T1 = RED wire and RED wire
T2 = Blue/white
L1 = 2 Brown/Red wires and all Black wire
L2 = 3 Black/blue wires and Purple/wh wire




Same results. With system off at t-stat and breaker switched to on, the compressor fan comes on. When A/C turned on at t-stat, air handler starts up, compressor fan stays on but no compressor and not cold air. The compressor fan never turns off.

Could the contactor switch perhaps be bad?

 

The only wire on T2 should turn off power to the fan motor when demand is not present.

You can measure between T2 and L1 for 240 volts AC when demand is not present or, unplug and isolate the T2 wire controlling the fan motor then restore power to prove that your fan motor does not have an internal short to ground that is allowing it to run when no power is present at T2.

Be Careful. There is a chance that you have a short and a faulty or non existent ground connection to your unit. Touching the unit when power is present and touching ground simultaneously could run high voltage through you if this condition exists.

 

Thank you for the warning!

There is 240 volts across T2 and L1 when no demand present. The fan does not come on when T2 (Bl/Wh) is disconnected and unit powered on.

 

Faulty contactor.

If you turn off power to the unit and remove the 2 small phillips screws on top of the contactor, do you see anything wrong with the T2 contacts (like a piece of wire in there or the contacts have partially flipped)

 

Is contactor single pole? What voltage are you getting across L1-L2 and T1-T2?

 

It is a double pole contactor.
I can already tell you that you have 240vac L1 to L2 since the compressor runs with demand, and 0vac T1 to T2 (without demand) since the compressor does not run when demand is not present.

 

Okay, I removed the contactor, removed all the screws and blew it out. I see nothing amiss. I re-installed it and wired it up the same way, only I flipped it.

Now, when I switch breakers on with the t-stat in the off position, the compressor is humming. When I turn on the a/c at the t-stat, the air handler clicks on and the compressor continues to run, but no fan at the compressor. It would seem obvious that perhaps the contactor is faulty but it seems like the same symptoms as the original contactor I am replacing. Maybe it's just coincidence, but I'm not a huge believer in coincidence!

 

So before the condenser fan was stuck on and now it will not turn on?
The old L1 is now L2?
Is the same contactor pole giving you the problem?

 

It appears the same pole is the problem. I was having much the same problem with the original contactor and I am working with this new one. Either it was faulty to begin with or I muffed it up by wiring things up incorrectly. Either way, i am going to just get another new one instead of going through testing this one. If it's still not right, something else is going on and I have a spare. Naturally will have to wait until Monday now......but we'll have 60 degree high tomorrow instead of the mid 80's!

Thanks a lot for taking the time to help, fellas. Hope you have a good rest of the weekend.


Howard

 

I thought myself pretty handy, but this HVAC stuff is too confusing for my feeble brain.

I bought a new contactor this morning, hooked it up and voila, everything functioning great!

Never to leave well enough alone, my wife complained about the difficulty of this (POS) Hunter programmable t-stat I had bought years ago. So I thought hey, I am going to pick up a simple Honeywell. I tried wiring up the Honeywell, but the wires didn't match up right no matter where I read on their instructions. I thought the heck with it, I returned it. Once back home, I install the original t-stat and it states "No AC Power". I checked and no 24 volt at the heat pump. What could be wrong. After tearing my hair out, I remember the little fuse at the air handler. Bingo, that cured it.

But now I swear we're not getting cold air. My wife says different and I have a frosty line at the heat pump. But the air leaving heat pump feels air temp to me. Heck, maybe it just needs a charging, I don't know. We've been here 11 years and have never had it serviced.

Well, at least it's running now! I've been at this most of the day and I'll give it until tomorrow. Then I might just throw in the towel and let my fingers do the walking. $$$$$

On edit. If the compressor were running and needing a charge, the air coming out the fan of the heat pump should still be plenty warm, no?

 

If your seeing ice on the large pipe out side then it could be low. No, if comp is running and low on charge the you won't get warm air. The only way to test the charge is with gauges.

 

Thanks, I think it's time for a service call. I was THIS close to success!