Oversizing control panel circuit breaker

[ATC]

I have a control panel with 3 480V 1 HP starters. I want to oversize the main disconnect circuit breaker for the panel so that I can add more starters in the future. Is there a limit as to how large the breaker can be?

 

[petersonra]

I have a control panel with 3 480V 1 HP starters. I want to oversize the main disconnect circuit breaker for the panel so that I can add more starters in the future. Is there a limit as to how large the breaker can be?

In general, I would probably never put less than a 15 or 30A CB as a main disconnect on such a panel regardless of the calculated load. There is no cost difference, and there is always the chance of needing more juice down the road.

The only exception I might make is if I did not have individual OCPD for each starter. That might well dictate a maximum size. However, I cannot recall ever actually doing this.

 

[Smart $]

I have a control panel with 3 480V 1 HP starters. I want to oversize the main disconnect circuit breaker for the panel so that I can add more starters in the future. Is there a limit as to how large the breaker can be?

Depends. First, are they individual motor loads or combination motor loads?

See 430.53 then (A) and (D) thereto and 430.87 Exception No. 1...

 

[augie47]

You might want to look at Art 409 and see if your situation meets the definition of an "industrial control cabinet"... sounds like it might.
If so, check 409.21 concerning the rating of the overcurrent protective device.

 

[ATC]

Thank you for your replies. Yes, this is an industrial control panel and the 3motors (FLA 2.1A) have their own starter, overload, and fuses (4A).
I did a little searching and saw this post here so I'm thinking that the OCPD could be sized larger as long as the feeder is size larger as well?

 

[ATC]

Yes it's an industrial control panel and the motors have individual fuses and overload for protection. From this post, it appears it's ok to oversize the OCPD.

 

[petersonra]

Thank you for your replies. Yes, this is an industrial control panel and the 3motors (FLA 2.1A) have their own starter, overload, and fuses (4A).
I did a little searching and saw this post here so I'm thinking that the OCPD could be sized larger as long as the feeder is size larger as well?

The source OCPD has to be sized to protect the feeder conductors regardless of the size of the OCPD at the control panel. Keep in mind the tap rules which may be applied.

 

[augie47]

Yes it's an industrial control panel and the motors have individual fuses and overload for protection. From this post, it appears it's ok to oversize the OCPD.

Generally, I would agree with you. It is common practice to tap disconnects, panels, etc. from a larger feeder, however, unless I am mis-reading (highly possible), it appears that in a Art 409 situation, unless the panel has a single main overcurrent protective device, you can not size the feeder OCP larger than specified in 409.21(c).
It seems this falls in line with the 240.21 tap rules which often require
singular OCP at the end of the tap.

 

[Smart $]

Generally, I would agree with you. It is common practice to tap disconnects, panels, etc. from a larger feeder, however, unless I am mis-reading (highly possible), it appears that in a Art 409 situation, unless the panel has a single main overcurrent protective device, you can not size the feeder OCP larger than specified in 409.21(c).
It seems this falls in line with the 240.21 tap rules which often require
singular OCP at the end of the tap.

As I mentioned in post #3, "See 430.53 then (A) and (D) thereto..." 430.53(D) covers "Single Motor Taps", while (A), (B), or (C) covers the permitted OCPD of the "feeder"... which is called a branch-circuit in that section (don't ask me why, 'cause I don't know). 430.53 requirements must be met in addition to those of Article 409.

If each motor has individual OCP/SCFP then 430.87 also mentioned in post #3 does not apply.