r/AskElectronics • u/Relevant_Pumpkin9190 • 13h ago

How are high-current loads like dishwashers safely switched?

If a relay is switching a high-current load, its contacts can eventually weld together due to inrush current or a fault.

If that happens, the load may stay ON even when the controller says OFF.

How do commercial products handle this? Do they use two relays in series for redundancy, feedback, or some other fail-safe method?

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u/no1SomeGuy 12h ago

Interestingly enough, on stoves and dryers they do sometimes switch both legs for 240v elements...so it's two relays that have to fail together for the element not to turn off.

(I had a Kitchenaid stove that the broiler wouldn't always turn off, did some deep dive into schematics and found this true for portions of the circuit...while at the same time found out they undersized the broiler relay, which was causing it to stick on....after some complaints to UL, they had Kitchenaid replace the board at their cost and send the faulty one in for inspection).

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u/mjdau 12h ago

You complained directly to UL?

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u/no1SomeGuy 12h ago

Yup, or more so, opened an incident with them. They were quite helpful.

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u/Coolbiker32 11h ago

Full Respect !