Siemens NGB1B020 Thermal Magnetic breaker

[Danny89]

For a 1/2 Hp motor pulling 4 amps single phase 277. with internal motor thermal protection. What size breaker should be used. Can NGB1B020 be used or does it have to be sized at 800 percent ...code reference T.430.52

I'm not sure if this breaker qualifies as instantaneous trip or inverse time breaker. I want to size the protection correctly for the the short circuit and ground fault protection. Motor it is supplying already has wired up internal overload protection. Any answers anyone?

 

[Little Bill]

Bump

 

[Jraef]

That’s an inverse time breaker. 250% max.

 

[kwired]

I didn't look up the cat number but if it is "thermal magnetic" I agree with Jraef, thermal magnetic is an inverse time breaker and 250% max - though in this case since 250% is less than 15 you still can use a 15 amp breaker as it is the next higher standard size.

If you were using time delay fuses - it would be 175% - and you would need to use a 10 amp fuse since that is the next standard size for fuses.