Have not sized transformers for motor loads for a long time, but how many HP is your compressor? never mind I looked at your link 5hp 22A, looks like it is rated for 31A. The starting current for that compressor motor would be pretty high.

I believe that rating is for the boost/buck portion of the transformer(12/24v)

Follow the link shaun posted and it's 30/60 amp.

Pulled transformer apart, wiring is charred. No time for inspection. More to come.

Interestingly, the dryer did work plugged into it so it may be salvageable. Or not.

first thought is undersized

So would there be a benefit to oversizing a transformer for longevity purposes?

It's probably salvageable. Check continuity with a multimeter on primary and secondary. Check the operating temp with a laser thermometer. Hot=early death. Cool=infinite life.

I'll post some pics tomorrow of the wiring.

X2 and X3 got mighty hot.

http://forums.pelicanparts.com/uploa...1591532556.jpg



http://forums.pelicanparts.com/uploa...1591532556.jpg



http://forums.pelicanparts.com/uploa...1591532556.jpg

I think you can save it. It should be hi-potted to be sure it's okay.

Put a fan on it when it runs next time...and a cooling plate too if needed.

The wires actually look good to the transformer. Looks like (from hundreds of miles away) this connection in this spot arced and failed:

http://forums.pelicanparts.com/uploa...1591545281.jpg

Looks like the smoke released from the connections, not the transformer.

If you want to test the transformer, you should get a 'continuity' reading for each individual coil to see if it burned open. Disconnect all the wires, with an ohmmeter there should be able to get a measurement at each coil (greater than infinity). X1 & X2, X3 & X4, H1 & H2, H3 & H4. The 2 X coils should read about the same, as should the 2 H coils.

Thanks '90 and Dad.

The failure is at the junction of X2 and X3. That junction burned the connector off and melted away the exposed twisted wires.

http://forums.pelicanparts.com/uploa...1591546120.jpg

http://forums.pelicanparts.com/uploa...1591545993.jpg

What gauge is this wire? How many amp breaker on this circuit?

Based on the Compressor specs, should be 30A breaker, and wire at least 10AWG.

Just looked, it's 12/3 solid Romex.

Then I suspect you can clean up the connections, and your back in business.

Any idea why it did what it did? Should I at least get the 10/3 wire?

In general, 12 wire feeds are rated for 20 amps and protected by a 20 amp breaker.

The compressor specs say it draws 22 amps, and recommend a 30 amp breaker, which would typically be #10 wire.

If it's a long way to the panel, or if there is a 20 amp breaker on #12, you should probably address this.

it's a 30A breaker. A professional electrician ran the wire 60 feet or so from the box to the new outlet which was for a silkscreen exposure unit. I think it had a 4500W metal halide bulb. Took massive amounts of e-. The brightness was incredible. I will have to look at what gauge wire the electrician ran.

The transformer is next to the outlet with the compressor.

Probably a little oxidation over time. Doesn't take much. Make them clean and shine. Maybe a little anti-ox paste.

I didn't sleep in a Holiday Inn, and I'm more familiar with Residential than Commercial, but in general the wire is sized for the load, then a breaker is sized to protect the wire, if that makes sense. #12 is generally rated for 20amp, #10 for 30amp (copper).

The specs for the compressor say 22 amp, 30amp breaker. If you have been getting by not tripping a 20 amp breaker, and it's a short run to the panel, you can probably leave well enough alone. If it's a 30 amp breaker on #12 wire, that's not allowed residential, and I suspect commercial also.

If it's a long run to the panel, you would also get less voltage drop with #10 wire.

So the #12 just goes a few feet from transformet to the outlet? Definitely swap.

If I was closer I'd grab a hunk of wire and come over.