I just read that a standard 15-amp circuit can actually handle more than 3,600 watts.

Found it in an old code book from the 80s my boss keeps in the office. It said the 80% rule for continuous loads wasn't always a thing. Anyone know when that changed for sure?

3 comments

3 Comments

mark6763mo ago

Wait, does that explain my old apartment wiring?

piper_dixon451mo ago

That bit about "old, warm junction boxes" really hit home for me. My dad bought this fixer-upper back in the 80s, and I remember him running a heavy duty space heater in the basement workshop all winter. The outlet plate got so hot you could barely touch it. He just thought that was normal. It was probably a 15 amp circuit with nothing but 14 gauge wire going back to a panel that had been there since the 60s. @mark676, I bet your old place had that same kind of setup. Makes me glad the code changed when it did.

robin_wright3mo ago

That old code book is a trip. So the 80% rule for continuous loads, like a space heater or an air conditioner running for hours, came in with the 1996 NEC. Before that, you could technically load a 15-amp circuit to its full 1800 watts, which explains a lot of old, warm junction boxes. @mark676, your old apartment wiring was probably running right at that edge, which is why those outlets felt hot. Makes you wonder how many houses are still out there wired to the older, sketchier standard.