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An old oven (20+ years) plugged into an 220v 3-pronged outlet suddenly caught fire when we tried to use the oven a week ago. We replaced the appliance today but found that it would not power on when plugging it into the outlet. I took a look at the circuit breaker but there was no tripped circuits. I turned off/then on all of the circuits and, after plugging the new oven in again, I get power (clock on oven turns on).

My concern is that the fire was not caused by the appliance but faulty wiring and I was hoping to get some advice on whether this is safe or not. If it helps, the home is from the late 60-s and the outlet itself is not GCFI.

Thanks in advance!

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  • Hello, and welcome to Stack Exchange. Was the oven working in that outlet before you had the problem, or did you plug it in, turn it on and boom? – Daniel Griscom Sep 19 '16 at 22:03
  • @DanielGriscom Thanks! The oven was working for several years on that same outlet. – Columbusdiy Sep 19 '16 at 22:22
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    Can you get us photos of the fire damage? (And the innards of the box, if the fire was in the box itself.) – ThreePhaseEel Sep 20 '16 at 0:06
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    Where in the oven was the fire located, or could you not tell? – ThreePhaseEel Sep 20 '16 at 0:18
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    When breakers trip, they don't typically flip all the way to the OFF position. You'll usually find them in the middle (tripped position), though some brands can almost appear to still be in the ON position. To reset a breaker, you have to turn it to the OFF position, then back to the ON position. – Tester101 Sep 20 '16 at 15:47
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Resistive heating elements (calrods), such as those in an electric oven, can break down and fail after a period of time due to deterioration of the internal insulation. When they do, the results can be quite spectacular, involving arcing from element and shell to the oven floor and a resulting fire when the arc ignites whatever grease deposits are present. However, this doesn't damage anything outside the oven, provided the fire itself stays inside the oven.

I would kill the power to the circuit and check the receptacle for any signs of damage (such as burn marks or metal spatter from arcing) anyway, though, just to be on the safe side.

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It should be noted that the 3-prong oven receptacle is an obsolete type, with one serious vulnerability: it uses an exception on Code to ground the chassis to the neutral wire. If anything goes wrong with that neutral wire, at the oven, oven cord, plug, socket or run back to the panel, this has the effect of electrifying the chassis of the oven. This is allowed because failures are considered rare.

Also, some range/ovens use 50A connections (6 AWG wires). 6 AWG can actually carry 60A. The upshot is that if you are thinking of replacing the wire, you will gain both a safety and future-proof by upgrading to 6/3 cable.

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