TIL that a standard 20-amp circuit breaker can actually handle a continuous load of only 16 amps. I was reading the fine print on the side of a Square D Homeline breaker in my truck this morning.

4 comments

4 Comments

Hold on, that's not quite right. The 80% rule is for continuous loads, like an oven or heater running for three hours or more. A standard breaker can handle 20 amps for normal, non continuous use. The fine print is about a specific safety margin for those long running appliances.

miles_chen2mo ago

Oh great, so my breaker is basically a teenager promising to clean its room. It can do 20 amps for a little while, but ask it to actually work for three hours and it taps out at 16. Makes total sense, why would we want things to be simple?

valcampbell2mo ago

Actually that safety margin is the whole point, isn't it?

oscar_gonzalez451mo ago

Exactly, it's like building in a buffer so your wiring doesn't get stressed and heat up over time.