Atwood water heater circuit board meltdown

well, I'll tell you how a friends new trailer roasted the controller on his water heater. The factory wired the 12V relay switch for the 120V element directly to 120V. He had been using only propane, but this weekend hit the electric element in the AM, and put 120V on the board, smoke rolling out of the water heater and the puny 16ga 12V wiring. fried the WH controller board at the least.

A circuit has to "fault" low impedance for a fuse to open. If resistance remains high or open circuit the fuse for the circuit will continue to (be able to) pass current. I have seen various electronic boards catch fire because of unrelated outside ignition and burn the logic circuit to a pulp leaving the power side with fuse intact.

Any place that uses a controlled gas flame has a potential to become unstable. If flammable material sees the flame, then problems galore. Refrigerators and water heaters need to be inspected and serviced before they can damage themselves or thir surroundings.

Don't think it was voltage spike, as I have a Progressive Dynamics EMS hard wired since day 1. It is supposed to protect againt over/under voltage. And all other electronic's are ok, 2 tv's, laptop,stereo,micro etc.
I am having trouble understanding why a fuse didn't blow as well. I removed the module today, and it has an area the size of a pencil melted out and bubled up on the back side.
Also no indication of flame out. The thermal fuse is intact and the plastic sleeve is ok.
Thanks for the replies.

X2

Difficult to believe an electrical probkem did not fail a fuse.

There is a Thermal FLAME fuse by the Burner tube. That is there in case you have a Blockage(insect nest) IN THE burner flue that will cause a Flashback Flame. When that happens it may indeed melt the Circuit board and then melt that Thermal fuse. Completely check the Burner flue for blockage as that is the ONLY thing that usually causes your type problem. Doug

Could have been a power spike or it could have just cooked on its own. Sorry to hear about this on your trip.

Look at this on eBay http://www.ebay.com/itm/172098009406

Maybe they can overnight this to ya.