Oven heating element receives power when off?

Question

I don't usually pay much attention to this when cleaning the oven, but the instructions for the cleaner say not to spray on the heating element. So today before cleaning, I decided to remove the heating element.

I guess that was a dumb idea, but the oven was off. When I was pulling out the element, it arced between the electrical connection and the oven frame. I turned off the circuit breaker and when I got back upstairs the element was hot.

Why is there still power going to the element when the oven is turned off? If this is a common design, it does not seem very idiot proof (as proven by me deciding to remove the element while it is plugged in).

To me it is like the difference between a properly wired light switch, where it is connected to the hot wire, vs improper, where it is on the neutral.

Answer 1

Probably because it's a 240V oven, and the oven thermostatic switch only switches one side of the 240V.

American power is 240V, but wired with a center-tap on the transformer, with neutral attached at the center-tap and ground bonded there. This gives 120V from either "hot" wire to the neutral, which is how most of your receptacles are wired. Your oven uses both "hot" legs, with 240V between them. It is also grounded to the center. If the thermostat switch only switches one leg, that is adequate for controlling the oven, but it means the other leg is always connected to the heating element, so it is 120V above the grounded oven chassis.