breaker sizing

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fifty five

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is it acceptable to feed a control center with a 3 pole 70 amp breaker when
the supplementary protection in control panel has factory installed 60 amp fuse protection.their is a 70 amp breaker not being used in I.line m.l.o.
panel. thanks for any info
 
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fifty five

Member
breaker sizing

the #3 wire was already available. I was conserned with brk. size and if
their is an article for control centers any one knew of off hand i could use.
thanks
 
infinity

infinity

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#3 is fine if it's available. If you're pulling an EGC you'll need to up size it according to 250.122(B).
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Is this a motor control center ? If its not than don't read on...

If that's the Case then you really need to follow some of:

Figure 430.1 Article 430 Contents if it is a motor CC than it could go anywhere based on that!

I frankly went looking for conductors based on the nameplate rating,
I didn't find that Code but motor control center is the basis of my pitch!

I don't know why you want to use a 70 AMP breaker on a nameplate required service, and the Breaker is supplied. I just installed and passed 50 to 50 AMp breaker on a self contained breaker. panel to device, no voltage drop or distance to consider.

This will be protecting your 60 self contain-factory wired (430.7(D) Multiwired and Combination-Load Equipment(1) Factiory Wired)equiment, maybe. ? ?

If I read to much into it, well you know it me posting :cool:
 
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mull982

Senior Member
I've wondered a similar question myself. If you are feeding a panel that has a CB or fuse for the panels main then can your feeder wire to this panel be based upon this panel OCPD or does it have to be protected and based of of an upstream OCPD?

As an example I had a #2 AWG being fed from from a an 125A feeder breaker. It is obvious that a #2 copper is not rated for 125A but someone here stated that is was o.k. because it terminated in a control cabinet which had a 70A main breaker. They claimed that this 70 main breaker would protect this feeder from an overload even know the cable rating was smaller than the feeder breaker. I could not find any evidece if there was any truth to this statement.

Any code references?
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
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Electrical Contractor
mull982 said:
I've wondered a similar question myself. If you are feeding a panel that has a CB or fuse for the panels main then can your feeder wire to this panel be based upon this panel OCPD or does it have to be protected and based of of an upstream OCPD?

Any code references?
Click to expand...
It depends on the length of the conductors. See 240.21(B).
 
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mull982

Senior Member
LarryFine said:
It depends on the length of the conductors. See 240.21(B).
Click to expand...

Thanks for the reference Larry. So for conductors loacated in an enclosed raceway outdoors there is not limitation on lenghts even if the circuit originates on a feeder located indoors at its source termination point?
 
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fifty five

Member
breaker size

breaker size

i just had this job inspected.He quoted 240-10. so i'll be changing to a 60.
just thought i would pass on the info.
 
Pierre C Belarge

Pierre C Belarge

Senior Member
Location
Westchester County, New York
1. How did the inspector determine the overcurrent device was a "supplementary" device as per 240.10?

2. Is the control enclosure/bus rated at 60A?



The Tap rules of 240.21(B) may permit this installation, as long as one meets all of the requirements of the pertinent section.
 
infinity

infinity

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fifty five said:
i just had this job inspected.He quoted 240-10. so i'll be changing to a 60.
just thought i would pass on the info.
Click to expand...


Even if 240.10 is applicable, why wouldn't a 70 amp OCPD be permitted to protect a #3 conductor which has an ampacity greater than 70 amps?
 
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