Testing 48A Charging on 40A Circuit

[mongo]

Hmmm... lots of failed breakers out there then. I've never met a breaker that could take >80% of its rating continuously overnight without tripping by morning.

There must be: Repost of QO data sheet:

It does call out free air, so in a close breaker panel with other heat sources it could trip if the enclosed space is above 40C 104F.

 

[mspohr]

Hmmm... lots of failed breakers out there then. I've never met a breaker that could take >80% of its rating continuously overnight without tripping by morning.

My only experience with intentionally maximum loading a breaker was at a campground in Death Valley. 30 amp breaker and I was desperate for a charge so I charged at 30 amps. Breaker was warm (so was the air) but no problems overnight. I think this was an old Zinsco breaker so I probably could have pushed it to 50 amps

 

[nwdiver]

There must be: Repost of QO data sheet:
View attachment 356446

It does call out free air, so in a close breaker panel with other heat sources it could trip if the enclosed space is above 40C 104F.

104F is pretty easy to achieve.