3 ms·
Most breakers do not trip instantly. They are designed to protect the wiring insulation from melting. Because the wires have thermal mass, a brief pulse above
by invalidator 4y ago
Most breakers do not trip instantly. They are designed to protect the wiring insulation from melting. Because the wires have thermal mass, a brief pulse above rated power is fine. Your 15A A/C may pull 30A or even 45A for 100ms while starting, and that's okay because the wiring won't overheat that quickly. It does drag down the voltage on the wiring though, which is why some lights may flicker when it starts.
- kube-system 4y agoResidential breakers (in the US at least) have two trip modes -- a delayed trip thermal mechanism, and a fast trip magnetic mechanism. What it essentially does is trip faster if you overload it more. There are requirements for how long a breaker can take to trip at 135% of the rating, and a faster trip time required at 200% of the rating. I think some people have probably experienced this first hand -- if you just barely overload a breaker, it might take a little while for it to break, and if you turn it back on, it might stay on a little bit before breaking again. And if you really overload it or short it out, it'll break right away. This is all by design.