Vertical bus section without switches and breakers (used for taps only)

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Tainted

Tainted

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Location
New York
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Engineer (PE)
Can we have a empty MLO switchboard with vertical busses only used strictly for taps only? No switches or breakers to be installed inside

Should I call manufacturer if this is allowed? Has it been done before?

Need it to feed a 3000A switchboard and a 2000A switchboard via the taps
 
1. What is the rating of the MLO switchboard?
2. What provides overcurrent protection for it?
3. How do you intend to provide overcurrent protection for the two downstream feeders and the switchboards to which they will be connected?
 
charlie b said:
1. What is the rating of the MLO switchboard?
2. What provides overcurrent protection for it?
3. How do you intend to provide overcurrent protection for the two downstream feeders and the switchboards to which they will be connected?
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1. Rating will be 3000A

2. 3000A fuses

3. Instead of 2000A switchboard as I previously mentioned, I will use 3000A. If I use full size 3000A feeders, do I need overcurrent protection in this case?
 
electrofelon said:
But technically doesn't the switchboard have to come that way or have manufacturer approved or supplied parts? While I have no issue with bolting lugs to a bus, some people do.
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I am in general opposed to drilling holes in existing bus work, but if there is already a hole there, I am less offended.

However, I feel the need to point out that these days a lot of bus work is not fully rated for anything you might come up with. For instance, some MCCs come with sections rated for 600 Amps, but that boils down to 300 Amps fed from the upper part of the vertical bus (above the center horizontal bus) and 300 Amps from the lower part of the vertical bus.
 
electrofelon said:
Charlie, note that switchboards do not require overcurrent protection.
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Forgive what may be a display of ignorance on my part (it's too late in the day to blame insufficient coffee), but I believe that anything and everything that carries current is required to be protected against overcurrent. Most of the time, that is achieved by a device upstream of the component under discussion. The tap rules give some exceptions, but overcurrent protection is still at play.

Would you please explain your thoughts?
 
electrofelon said:
There is no such general requirement in the NEC



If you can cite me a code requiring that a switchboard be protected at it's rating by an OCPD, i'm all ears 🤠
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hmmm... I think what you're trying to say is that OCPD amp rating is to only protect the conductors, not the switchboard itself?

are you being technical? lol
 
petersonra said:
I am in general opposed to drilling holes in existing bus work, but if there is already a hole there, I am less offended.

However, I feel the need to point out that these days a lot of bus work is not fully rated for anything you might come up with. For instance, some MCCs come with sections rated for 600 Amps, but that boils down to 300 Amps fed from the upper part of the vertical bus (above the center horizontal bus) and 300 Amps from the lower part of the vertical bus.
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I believe there is a UL white paper that discusses tapping the bus of a switchboard. IIRC, existing holes are marked with wording (tap?) If you can bolt on lugs. I don't have a problem with adding a lug to unmarked holes or say longer bolts and a lug to a splice or joint on the bus, but the AHJ may deem it no longer approved without a field eval.
 
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