In a ring circuit, a continuity fault has the potential to overload the ring and melt some wire. Detecting such fault at the outlet requires impedance testing (expensive), while doing so at the panel would be relatively cheap. So why hasn't anyone invented a continuity protection to put in the panel?
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opinion-based? dumb modding like this is why stackoverflow tanked – capr Nov 08 '23 at 23:05
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Ring wiring was a very old solution (predating the sort of components that doing it cheaply at the panel would require) to a problem that no longer really exists.
The solution to ring faults now is to use spur, rather than ring, wiring.
Retrofitting existing panels would not be cheap.
Engineering new panels for a shrinking market would not be commercially worthwhile.
Neil_UK
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Currently UK requires checking ring continuity every 10 years (less if you have tenants) which to me seems more expensive than changing one or two protections in the panel. I get that rings are "old school" but they are more efficient. How come you need a world war to think efficiency? – capr Nov 07 '23 at 17:09
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@capr unless you are a landlord in England, the 10 year "requirement" for a test is wishful thinking. As is people pushing the test button on an RCD every 6 months. It's not enforced by anybody, and most householders don't do it. – Simon B Nov 07 '23 at 22:31
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It will be down to cost.
The only place I know that regularly uses ring circuits is the UK. They are normally wired using a European standard MCB (miniature circuit breaker) or RCBO (residual current breaker with overload - an MCB and RCD combined). These components are cheap and available for every brand of consumer unit.
A device with automatic ring fault would be more complex, and so more expensive. Especially if most countries don't need them. Each consumer unit manufacturer would have to offer a version certified for use in their units. The device may be larger than a standard MCB or RCBO, requiring a larger board.
Ring circuit failures aren't that common. When they are discovered, they may have been like that for years without causing any problems.
Simon B
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"for years without causing any problems" -- but that's true even for a completely unprotected circuit, eg. from an incorrectly sized MCB. Everything works until it doesn't. – capr Nov 07 '23 at 17:18