Transformer on airhandler (Goodman) keeps burning out the primary side.

[keno]

I've got this Goodman Heat pump that keeps burning up the primary side of the transformer (240V)... Put a new transformer on it and the next morning I get a call that it's not working again. I've seen them blow the secondary side due to low voltage wiring issues but never run across one that does the primary side..... what am I missing.... all the relays (blower, heating element) look good..... what would cause this to be happening...... Electrician came and checked the incoming power and neutrals said everything looks good said I probably just got a lemon transformer..... Any Ideas??

[RoBoTeq]

How are you checking it to know that it is the primary side that is burning up?

[air1]

Is the secondary side fused?

[captube]

Did you check the defrost circuit for shorts?

[waregl82]

I've always heard that when the secondary side is grounded, shorted, etc., it will be the primary side that burns. Make sure to fuse your secondary side, so you can find the short without constantly replacing transformers. I'm going to go do a little more research on the first statement I made. See what I can find out.

[waregl82]

Check the archives. There is a long discussion about primary/secondary. It seems to me that what I said above is correct. When the secondary side is over amping, the primary side will be the first to burn. Keep checking the control side for a short or ground. Hopefully it will not be an intermittent ground. Pulled an all nighter on those before.

[terpfan_]

Yes, a secondary side short can cause primary coil to burn up. Make sure the secondary side has a fuse on it then see what happens. Loose wire, bad contactor, relay could cause this on a unfused transformer.

[Rob_in_WV]

Also get one of these to help out with when troubleshooting.

http://fierychill.com/lil-popper-3-a...-products-pop3

[keno]

No the secondary isn't fused so I'll do that and start tracking the 24 v side

[keno]

Thanks I'll get one for sure

[keno]

Thanks.... going to check the defrost...... stayed for about 1hr after starting system with the new transformer and everything was fine so it very well could be in the defrost side.

[keno]

With a meter checking continuity

[RoBoTeq]

Did you check the defrost circuit for shorts?

That would be on the secondary side.

[RoBoTeq]

I agree that the problem is more likely on the secondary side. An easy way to fuse the transformer is to cut the hot wire from the transformer secondary side, put insulated female spade connectors on both ends of the cut wire and plug a 3 amp automotive fuse into the connectors.

[pacnw]

could use a new transformer with built in resettable fuse, too.

[waregl82]

I agree with pacnw. I now use a 50va transformer with a resettable fuse. For a few bucks more I get a little safety margin and a resettable secondary fuse. No more manually tieing fuse holders to transformers. Don't know if I am allowed to tell the brand name or not? Somebody let me know if you want brand name.

[jtrammel]

Most times I've found a bad xmfr it was the primary side open or shorted caused by a secondary side short. Bad RV coil is a pretty common cause for lv short.

[littlebigdad]

Make sure you check the wiring outside especially around the wire ties