Heat Pumps and Electric Heating - Trouble with control transformer
Doityourself.com community forum was created to provide answers to all questions related to home improvement and home repair. Doityourself community can help you find information about how-to topics on small fixes to large remodeling projects. With comprehensive how-to content and expertly moderated community forums DoItYourself.com makes it easy to tackle even the most complex home improvement projects.View Full Version : Trouble with control transformer
DeanP
03-05-08, 06:41 PM
Hello:
I need your help!
Let preface this by saying I’m not an HVAC guy but I do have some “sparky” experience.
I have a Bryant heat pump/electric furnace that’s driving nuts. The control transformer trips the breaker (on the side of the transformer) and I just can’t seem to isolate the problem. I believe I’ve isolated the problem to the heat pump, but here I’m hitting a brick wall. Here’s what I’ve determined to this point:
With all control wiring in place the transformer trips; some times right a way, sometimes not. If I disconnect the control power to the heat pump from the terminal board at the furnace, the furnace will run fine on AUX or emergency heat. As soon as I reconnect the 24V to the heat pump, the transformer may trip.
Last week I pulled new control wiring from the furnace terminal board out to the heat pump thinking there was probably a short in the old wiring. This didn’t help – same problem still present.
Next I replaced the heat pump control board. This didn’t help – same problem still present.
Next I unplugged the reversing valve power from the heat pump control board. The heat pump ran until the timer called for defrost. At this point I thought I had found the problem. When I reconnected the reversing valve spade connector on the control board, the valve reversed as it should and didn’t trip the transformer breaker so I let it run all night. It was still working when I left for work the next morning, but had tripped the transformer again by the time I got home. At this point I still thought it might be the valve. I tried running the heat pump again with the reversing valve unplugged from the control board and this time the transformer tripped. Now I’m back to the same problem again.
In one last attempt, today I replaced the contactor on the heat pump. The transformer still trips.
What’s left??????????
Thanks for you help.
Dean
I need your help!
Let preface this by saying I’m not an HVAC guy but I do have some “sparky” experience.
I have a Bryant heat pump/electric furnace that’s driving nuts. The control transformer trips the breaker (on the side of the transformer) and I just can’t seem to isolate the problem. I believe I’ve isolated the problem to the heat pump, but here I’m hitting a brick wall. Here’s what I’ve determined to this point:
With all control wiring in place the transformer trips; some times right a way, sometimes not. If I disconnect the control power to the heat pump from the terminal board at the furnace, the furnace will run fine on AUX or emergency heat. As soon as I reconnect the 24V to the heat pump, the transformer may trip.
Last week I pulled new control wiring from the furnace terminal board out to the heat pump thinking there was probably a short in the old wiring. This didn’t help – same problem still present.
Next I replaced the heat pump control board. This didn’t help – same problem still present.
Next I unplugged the reversing valve power from the heat pump control board. The heat pump ran until the timer called for defrost. At this point I thought I had found the problem. When I reconnected the reversing valve spade connector on the control board, the valve reversed as it should and didn’t trip the transformer breaker so I let it run all night. It was still working when I left for work the next morning, but had tripped the transformer again by the time I got home. At this point I still thought it might be the valve. I tried running the heat pump again with the reversing valve unplugged from the control board and this time the transformer tripped. Now I’m back to the same problem again.
In one last attempt, today I replaced the contactor on the heat pump. The transformer still trips.
What’s left??????????
Thanks for you help.
Dean
tater1800
03-05-08, 07:21 PM
Dean,
Finding this problem may be a bear. The first thing you must do is stop the breaker from tripping. Do this by placing a 60 watt standard lamp in series with the transformer primary. The lamp will control the current and allow you to find the short, hopefully. A clamp-on amp meter and a helper will be needed. Check the meter as you check the circuits. When the current spikes your problem is active and hopefully you can find it. Check the transformer occasionally and don't let it get hot. Also check for hot components such as contactors. Good luck.
Finding this problem may be a bear. The first thing you must do is stop the breaker from tripping. Do this by placing a 60 watt standard lamp in series with the transformer primary. The lamp will control the current and allow you to find the short, hopefully. A clamp-on amp meter and a helper will be needed. Check the meter as you check the circuits. When the current spikes your problem is active and hopefully you can find it. Check the transformer occasionally and don't let it get hot. Also check for hot components such as contactors. Good luck.
DeanP
03-07-08, 07:52 AM
tater:
Found it!
A themostat wire was laying against a hot line inside the heat pump and the insulation had melted/worn away and was shorting to the line.
Thanks, I really appreciate the help.
DeanP
Found it!
A themostat wire was laying against a hot line inside the heat pump and the insulation had melted/worn away and was shorting to the line.
Thanks, I really appreciate the help.
DeanP