Thread: Question RE: UL 489

The UL 489 Standard allows for two types of
ratings. Standard circuit breakers cannot exceed
a maximum of 50°C temperature rise at the wire
terminal connection at 100%current in 40°C open
air. 100% rated circuit breakers may have a
temperature rise of 60°C at the wire terminal
connection in the smallest allowable enclosure if
the circuit breakers are connected with wire rated
at 90°C wiring insulation sized to the 75°C chart

Just wondering when they speak of "rise", are they referring to the CB being at a 40 degree C exterior ambient temp and then allowing a 50 degree C rise?

That's what it says. And yes, at 226°F it's "hot" to the touch.

Fantastic, thanks.

Originally Posted by Bill Kriegh

That's what it says. And yes, at 226°F it's "hot" to the touch.

I do my best not to touch the "wire terminal connection".