Rack Mount Circuit Breaker - NEC Codes?

Thread Starter

SOENCO3235

Joined Nov 7, 2023
2
Please delete if this is posted in the wrong section. I'm trying to add a rack mount circuit breaker into a custom enclosure for a new product being released. I'm looking to see if it might conflict with any of the NEC guidelines before implementing into the design; any thoughts? Inside the enclosure will be 240V (contactor, SSR, panel mount controllers) and 24V circuits. Below is the link for the type of breaker we're considering. Thank you in advance!

https://www.grainger.com/product/CARLING-TECHNOLOGIES-Panel-Mount-Circuit-Breaker-3XC73

Gerald
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
28,494
That is typical of a NFB, Non-Fused-Breaker, it is customary to wire them just as you would any fuse block.
I assume this would be for feeding the whole enclosure?
Other devices may need their own individual fusing or other protection.
Obtain a copy of NFPA79 if in N.A.
There is also an older copy out there on the web.
 

Thread Starter

SOENCO3235

Joined Nov 7, 2023
2
That is typical of a NFB, Non-Fused-Breaker, it is customary to wire them just as you would any fuse block.
I assume this would be for feeding the whole enclosure?
Other devices may need their own individual fusing or other protection.
Obtain a copy of NFPA79 if in N.A.
There is also an older copy out there on the web.
Correct, This would act as the main breaker feeding into a contactor and out to the rest of the circuit, The enclosure depth is ~5-7 inches would contain all of the PID controllers and SSRs.
 

MisterBill2

Joined Jan 23, 2018
17,745
If the breaker is mounted on the enclosure door, and the leads run back into the enclosure, it may be inconvenient with the door open to adjust modules inside the enclosure. Also, the live posts on the rear of the breaker can be a pain becuase bumping them will deliver a shock. So a protective insulating cover is a good idea. "Wire Nuts can serve that purpose fairly well.
 

MisterBill2

Joined Jan 23, 2018
17,745
One more rather important consideration is relative to the depth of the enclosure. It is entirely possible, with a more shallow depth, to have the panel mounted devices crash with items mounted on the back panel. That is the unstated secondary motivation for operator portions on the door to be mechanically linked to the switch mechanism on the back panel. Also, it avoids flexing the main power feed wires.
 

MaxHeadRoom

Joined Jul 18, 2013
28,494
@SOENCO3235 NFPA79 states that the operating handle of the disconnect means, shall be readily accessible on the outside of the cabinet.
Not more than 6.5ft above floor level, Mounting the type of switch I showed in the door is very common in the control industry for some years now.
Also the method I have always used.
 

MisterBill2

Joined Jan 23, 2018
17,745
OK! This is "a new product", NOT a controls cabinet. That makes quite a big difference. All of Max's comments and some of my comments relate to controls cabinets for industrial machines and equipment.
So now a question: what size is the enclosure that the circuit breaker would be mounted in (inches), and is the panel that the breaker will mount in the access panel? If that is not the access panel then it seems to me you are all set, and none of the issues I commented on apply. Likewise none of those from Max.
What happened is that we guessed wrong, thinking it was a controls cabinet like the ones we have designed or worked with. It seems now that it is something different from that. Can yo verify that for us, please.
 
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