Re: Basic advice for an oven bake element house fire (GE JBP24B0B4WH)



The element is normally fed from 240 V.  The heat is generated in an
inner resistance component which is completely insulated (electrically)
from the element's outer metal jacket, which is grounded by touching
other metal parts of the oven (and possibly by an explicit ground wire).

In normal operation, the jacket of the element is always grounded, so
there's no voltage on it.  *But* if the element breaks or the insulation
between the core and jacket fails, you can get current flow between the
centre core and the jacket - there is 120 V from *each* side of a broken
core and the jacket.  You could get an arc from the core to the jacket
even with a gap in the element - the 240 V path through the element is
broken, but there's still 120V at high current available.


This is correct... it is a dangerous failure mode...

Many appliances switch only one side of the 220 line so a fault to
ground in the element can't be shut off with the switch...

You have to pull the plug or the breaker.

Yep it's a dangerous failure mode.

Mark


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