Drying Oven - Preset Temp Fail

[CapLeaker]

Originally Posted by redwire

I don't get the fuse box affecting the heating element. Usually there is high temperature wire/spade connectors from the heating element to the control circuit, and then that goes to the fuse.
Corrosion I find causes hot spots whichs melt things such as PVC wire or switches etc.

All I can tell you it was one of the old screw in fuses with the fuse block that needs to be inserted in the panel. The fuse was hot and there was some arcing going on between the blocks fingers and the bars inside the box. I think I exchanged the upper heating element 3 times until I got it. After that my dryer started popping fuses. Same corrosion on the fuse block and arcing to the bars. Must be the very high humidity we have.

[stj]

if the element is not plated with something like nickel and is pure copper then it can develop tiny pinholes in the surface,
combine that with moisture and the internal winding can rust and bridge to the copper shell.
very common in imersion water heaters - the rust will build up until the pressure splits the copper open if you dont have an RCD breaker on it!

[redwire]

These heating elements expand so much when hot, that the wire gets longer and can push through the MgO and short. I think most failures are thin spots in the wire element which run super hot and expand too much, short to the tube or just go open-circuit.
They seem to be NiCr or Kanthal wire inside. I don't believe the (oven) moisture problem because it's near impossible to get enough past the end seal and inside the tube, to corrode the element so badly. MgO is hygroscopic though.
Tubular heating elements data.

Immersion hot water water heating elements, I've seen the sheath get covered with mineral deposits and develop hot spots. Or corrode and micro leak inside.

With clothes dryers, the heating element is open coil? I find if the vent is not connected, duct not sealed good or partially blocked- it blows the moist air into the dryer and laundry room. Lots of lint dust too. It might be what is eating the fuse blocks, unless you live seaside or something.