Hacker News Reader

Comment by rtkwe | Hacker News Reader

Doesn't work and would likely cause fires.

First the smaller circuits will trip first, that's where the current is actually flowing, there wouldn't be any actually flowing through the whole house breaker in your idea. The main circuit to your house is 100+ Amps (this would be a tiny old circuit most houses have larger main feeds these days) at least. You'd have to feed at that much through the main disconnect for it to trip.

Second even if you could push that many amps through the main breaker somehow to trip it you'd be feeding it through wires designed for 15-20 amp nominal loads which would cook them.

View on HN

> Second even if you could push that many amps through the main breaker somehow to trip it you'd be feeding it through wires designed for 15-20 amp nominal loads which would cook them.

Well, you'd end up tripping the 15-20 amp breaker protecting those wires first.

Probably but I'd rather never send that big of a pulse down a 15/20 amp line at all.

It's no more of a pulse than any other dead short that would trip the breaker instantly rather than on a delay.

The fault current that a breaker is required to be able to interrupt is two orders of magnitude larger than we're talking about feeding into the wire, and a 15 amp breaker is designed to _not_ interrupt a 150 amp load until a second has passed (there's a rating curve for this): some loads might require that much current briefly, and the wire in the wall is not going to overheat in that time (that's why the breaker has the curve that it does: to model and therefore protect the allowable heating of the wiring).

Yeah should be fine but I'd still rather not intentionally try it and count on it. Breakers can fail closed.

Doubly so because it doesn't even do what we want it to which would be to switch the main breaker off.

Don't get me wrong, it's still a stupid thing to do, but not because there's any danger to the wiring.

You’re right, my mistake.

Reply on news.ycombinator.com