Switchgear and panelboard section 408

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NTesla76

Senior Member
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IA
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Electrics
I scoured through some switchboard literature and what I could access of UL 891, and I could find no mention of any requirement from UL or the manufacturer that they be protected at their ratings. Just speculation, but perhaps the code writers don't require this protection for switchboards because they figured these are more likely used in situations where there is proper sizing, design and engineering. Plus, as I said, you already typically have section buses rated less than the through bus so it is already not protected at its rating anyway.
I think this explains it well.
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
I scoured through some switchboard literature and what I could access of UL 891, and I could find no mention of any requirement from UL or the manufacturer that they be protected at their ratings. Just speculation, but perhaps the code writers don't require this protection for switchboards because they figured these are more likely used in situations where there is proper sizing, design and engineering. Plus, as I said, you already typically have section buses rated less than the through bus so it is already not protected at its rating anyway.
Really? You weren't able to find any reference to the UL definition of continuous current or maximum ampere rating?

I know the old UL Whitebook guide #WEVZ said that switchboard sections are marked with the current rating of its supply bus. It goes on to talk about the adequacy of the supply with respect for the calculated load, per the NEC, is determined by the AHJ.
 

jim dungar

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Retired Electrical Engineer - Power Systems
I think this explains it well.
But it is not completely factual. A Listed piece of equipment is allowed to contain internal components which are not sized or applied per the NEC, but have been tested as a complete assembly with a single overall maximum current/amperage rating on its nameplate.
 
But it is not completely factual. A Listed piece of equipment is allowed to contain internal components which are not sized or applied per the NEC, but have been tested as a complete assembly with a single overall maximum current/amperage rating on its nameplate.
And we might end up going Round in circles and never really agreeing here. My personal opinion is I cannot find SPECIFIC requirement that a switchboard be protected at its rating by an OCPD. It is also my opinion that wording such as "used at its rating", "applied within it's rating", " this equipment is rating X amps" does not necessary mean that OCPD protection at or below that rating is required or the only way to meet that wording is by protection by OCPD. I respect that such wording could be interpreted that way, but it's a bit too much of a leap for me unless it is specifically stated.
 

hhsting

Senior Member
But it is not completely factual. A Listed piece of equipment is allowed to contain internal components which are not sized or applied per the NEC, but have been tested as a complete assembly with a single overall maximum current/amperage rating on its nameplate.

But wait what you are saying also applies to panelboards yet NEC 2017 section 408 part III specifically calls for OCPD ahead or main panelboard?

Why not remove such pharse from panelboard too then?
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
Exactly. if the arguments made by the others are correct then that 408.36 wording is completely unnecessary and should be removed.
No it is not.

A MLO panelboard is no longer allowed as service entrance equipment while a MLO switchboard still is.

People need to get over the fact that panelboards and switchboards have different NEC requirements.
 
No it is not.

A MLO panelboard is no longer allowed as service entrance equipment while a MLO switchboard still is.

People need to get over the fact that panelboards and switchboards have different NEC requirements.
there is some confusion here, several different things being discussed. For the purposes of my comments consider panel boards and switch boards only served by feeders. Thus when I reference 408.36, ignore the exemption for service panel boards.
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
there is some confusion here,
I am not confused.
I have repeatedly stated one of the governing NEC references is 110. Listed switchboards have a maximum or continuous current on their nameplate and must be protected at not more than that value.
I also acknowledge the NEC has different rule for similar but not identical equipment.
 

hhsting

Senior Member
No it is not.

A MLO panelboard is no longer allowed as service entrance equipment while a MLO switchboard still is.

People need to get over the fact that panelboards and switchboards have different NEC requirements.

Who says MLO panelboard with six service disco is not allowed to be as service equipment?

Did you look at previous post? Did you see NEC 2017 section 408.36 i think thats in part III exceptions?
 

hhsting

Senior Member
I am not confused.
I have repeatedly stated one of the governing NEC references is 110. Listed switchboards have a maximum or continuous current on their nameplate and must be protected at not more than that value.
I also acknowledge the NEC has different rule for similar but not identical equipment.

What? Where does above says for switchboard , switchgear?
 
I am not confused.
I have repeatedly stated one of the governing NEC references is 110. Listed switchboards have a maximum or continuous current on their nameplate and must be protected at not more than that value.
I also acknowledge the NEC has different rule for similar but not identical equipment.
Can you provide a reference from UL 891 or manufacturers instructions for that?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
Who says MLO panelboard with six service disco is not allowed to be as service equipment?
NEC 408 has required a panelboard to have either a local or remote protective device, for several editions.. Now codes require multiple main devices to be in individual enclosures, which for now precludes panelboards.
 
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