MOCP for 143 FLC ---50HP

[Npstewart]

Doing a project with a 50 HP air compressor, according to 430.250 its about 143 FLC. I suppose a 200A breaker would be required, everyone agree with that?

I know I would need a motor starter for this application, does the motor starter get connected to the panel, or does the feeder go directly into the motor starter prior to entering the compressor. Thanks for your opinions!

Nick

 

[augie47]

Doing a project with a 50 HP air compressor, according to 430.250 its about 143 FLC. I suppose a 200A breaker would be required, everyone agree with that?

430.52 under normal conditions will allow a breaker sized up to 400 amp as Branch Circuit Short Circuit-Ground Fault Protection.
Depending on the compressor 200 amps may be too low due to inrush.

I know I would need a motor starter for this application, does the motor starter get connected to the panel, or does the feeder go directly into the motor starter prior to entering the compressor. Thanks for your opinions!

Nick

Starter can be located anywhere between the Branch Circuit SCGF device and the motor. 430.120 might effect the decision.

95% of the larger compressor installs I have seen have included manufacturers recommendations on SCGF selection, and when that info is present 110.3(B) will take precedence.

 

[Npstewart]

I dont have information on what model or manufacture the client will be using. He gave me an equipment list with voltage, phase and horsepower of his equipment. Ive been using the NEC for my FLC information because thats all I have. I wish I had some manufacturers specifications.

 

[bob]

Doing a project with a 50 HP air compressor, according to 430.250 its about 143 FLC. I suppose a 200A breaker would be required, everyone agree with that?

Do not agree. The starting amperage will be 5 or 6 times the 143 FLC. You can check the breaker curves and see how long the breaker will hold the starting amperage. You can go a high as 250% of the FLA for the breaker size.

 

[mcclary's electrical]

Do not agree. The starting amperage will be 5 or 6 times the 143 FLC. You can check the breaker curves and see how long the breaker will hold the starting amperage. You can go a high as 250% of the FLA for the breaker size.

that's especially good advise for a compressor