Under the Glass: Testing Ceramic Hob Elements and Limiters

⚠️ SAFETY FIRST: IMPORTANT

Ceramic hob elements operate at very high temperatures and involve exposed high-voltage wiring beneath the glass. Always isolate the appliance from the mains before removing the glass top. Never touch an element immediately after testing, as they retain heat significantly longer than they appear to.

Ceramic hobs use radiant heating elements nestled in a circular tray. While they look high-tech, they are relatively simple to test. The key is understanding the "common" terminal and the role of the safety limiter.

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Testing the Radiant Element

A ceramic element can be single, double, or even triple-ringed. To test if it’s "healthy," you need to check for continuity across its coils.

• Single Element: Two terminals.

• Double/Triple Element: These have a "common" terminal where all circuits meet. To test, place one multimeter probe on the common terminal and the other on each individual "incoming" terminal.

• The Reading: A healthy radiant element typically reads between 10 and 30 ohms. If you get "OL" (Open Loop), the coil is broken and the element must be replaced.

The Energy Regulator and Hot Light

The switch for a ceramic hob is an Energy Regulator. It’s a thermostatically controlled switch that cycles the element on and off to maintain the heat level you selected.

• The Warning Light: Ceramic hobs have a "Hot Surface" indicator. This is controlled by a separate bimetallic switch on the element's limiter. It cuts in the warning light once the temperature reaches a certain threshold and keeps it on until the glass is safe to touch, even if you've turned the hob off.

The Wire Limiter

Attached to the element is a long metal rod (the limiter). This is a safety device that prevents the ceramic glass from overheating and shattering. If the hob gets too hot, the limiter breaks the circuit to the element until it cools down.It easy to test the elements on these but the switches need temperature to operate.

On single element version there will be 2 terminal to the element of double there will be 3, 2 incoming single and the common will be the terminal where both element terminal into one connection on  triple element there will be four connection 3 incoming and one common.

here is a double element for comparison to below single i test on.

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To test element find the common terminal on and test between each incoming for continuity it does not really matter about ohms reading as long as it looks healthy for an electric element 10-30 oms.

Connect test leads between the single incoming and the common terminal

Here i get continuity and good healthy reading for an electrical element of 26.5 ohms 

Here is the switch for the element and the hot light ( Warning indicator )

This is just  thermostatically controlled set of switches on controls the cycling on and off of the heating element the other switches the heat or hot warning indicator lamp on when it reaches a certain temperature.

they can be wired different but the terminal of the switch are usually 

1a to 2a and 1b to 2b in one of below photo configurations. 

See video of this process below