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Burning up transformers

\015 Repair of blown Heat Pump Transformer.\015\012I am having some issues with the trouble shooting of a Goodman PHK048-1B heat pump that continues to blow the transformer. I am a home owner with plenty of mechanical experience and am looking to be able to ask all the right questions to a heat pump repair tech. I live 50 minutes from town so it is an automatic 2 hour charge when service is required.\015\012 \015\012The description of the problem the heat pump is having and the first attempt at repair goes like this.\015\012-The heat pump has been working fine for the 3 years that I have owned the property.\015\012-One day it does not work. Cooling or Heating.\015\012-Nothing I can find at this point, replaced batteries in thermostat. (simple thermostat, no programming, Heat, Off, Cool \342\200\223 fan is either Auto or On). I do not note any wires not connected behind the face plate.\015\012-Called for repair\015\012-Tech opens up the control/electric area outside on the unit. Pokes around for a couple minutes replaces the transformer and installs a 5 amp auto style fuse on what he describes and the low voltage side of the transformer.\015\012-After some more poking around the power disconnect is reinstalled. (push in blade type, no fuses here).\015\012-At this point I am not sure what he was doing but attempted to activate the unit from outside. Smoked the new transformer. His little fuse did not blow.\015\012-More poking around. Disconnected some kind of thing he called a crank case heater. With second transformer installed the unit was again activated. This time the 5A fuse blew a couple times while he was attempting to operate the unit from outside. (transformer not smoked) Not sure of everything he was doing but determined that the reversing valve solenoid was bad. Re connected the crank case heater, disconnected the rev. valve sol. Testing at this point and said it was ok, need a new reversing valve solenoid. He said that heat would work but not cooling.\015\012-A new solenoid was ordered for the reversing valve. Tech called and said that a generic solenoid was ordered because Goodman did not sell just the solenoid.\015\012-Rather than have another 2hr trip and charge I volunteered to install the new solenoid. Simple one screw affair with a two prong plug. No problem for me. He said that the plug could go on either way.\015\012-The new solenoid was similar to the old one hole in center and plugs (blade style) sticking out the side.\015\012-Just for drill I did an ohm test on the two units. New unit was 16 ohm old unit was 1. I do not know what the value should be.\015\012-I have attempted to get info from Goodman tech support but was told they only talk to repair technicians.\015\012-After installing the new solenoid I fired up the unit and set the thermostat to Cool and lowered the temp to cause it to come on. Just as a test I ran the unit on cool for an hour on two consecutive days. Seemed fine.\015\012-Then it got cold again so I turned the thermostat to heat and set the temp up to cause the unit to make heat. No Response, second day attempted to get heat, No Response.\015\012-I opened up the electric area on the unit and the transformer was very thoroughly smoked, melted wires and lots of ugly black stuff stuck to the lower side. The little 5A fuse was in tact. The other transformers that were bad did not look like this.\015\012-Further investigation showed that the blue wire in the thermostat was not connected.\015\012 \015\012Please advise any questions to ask the service tech when he comes back out. \015\012Is there any testing I can do before he arrives?\015\012Is the ohm reading for the new solenoid correct? (16 ohm) \015\012 \015\012I appreciate any help or advice you can offer.\015\012 \015\012George\015

Answers :

YOUR the first person that has gave enough information to help in a WHILE THANK YOU SO MUCH!!

Start all over from first
I'm betting that you need a fuse in both sides of the transformer until you find the real reason they burn up.

A solenoid valve that sticks can cause the transformer to blow but so can a lot of other things, namely anything in the control circuit that uses the 24V power. A relay or contactor that doesn't pull in or a defective defrost control, a shorted wire from the thermostat.

I'm wondering if you have what we call a package heat pump meaning the\015\012both the indoor blower and out door compressor & fan are in the\015\012same section out side? OR is your a split system with an indoor\015\012section and an outdoor section?
\015\012I'm betting on the split section. In some miss-matched systems (like a Lennox indoor and a GMC out door for example) Some of the origonal Lennox heat pumps had an out door and an indoor transformer. If these trans formers were not "phased" together it could cause a problem like your having. Now you just have it in the heatign mode if I read between the lines correctly. So it makes snece that it's something with the heat. The out door unit can opperate withits own 24v but if you have back up heat inside (gas or electric Im thinking you have electric) the indoor section will come on atfter a few more degrees of heat loss (2-4'F). This is where the transformer inside will buck the one outside and somethjing has to give. The weakest point.

From what ive been told by some of the old hands I've been around if the high volt side burns out look for a low volt problem if the low volt burns out look for a line volt problem.

If this has 2 transformers like I suspect try the fuse on both sides but remember the one is hot and will remain hot all time on 220V or 1 leg of it or it might remind you. To phase these transfoprmers I believe you swtich the main lines L1 & L2 at either of the transformers. Now 1 more thing the indoor section may be using ground on the low volt side as a path for 1 side of the transformer. I believe you will ahve to do same for the other transformer too.

Hope this helps Id really like to know what you find and do.
Please ask more and you give such detail I can follow you with little trouble. Please rate me as high as you can and good luck.

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YOUR the first person that has gave enough information to help in a WHILE THANK YOU SO MUCH!!Start all over from firstI'm betting that you need a fuse in both sides of the transformer until you find the real reason they burn up. ... Goodman Air Conditioners

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