- Location
- Illinois
- Occupation
- retired electrician
but that is not my opinion
Switchgear and panelboard section 408
- Thread starter hhsting
- Start date
- Status
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Nor the opinion of manufacturers and therefore NEC 110.but that is not my opinion
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
but that is not my opinion
Guys, see 240.3. Note article 408 is on there. Bottom line is 408 requires OCPD protection at or below rating for panel boards but not switchboards.
Another example, clearly 240 doesn't apply to the wiring inside water heaters and most other appliances, those sizes almost never comply with article 240 protection.
Also, see 310.1.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It is true, the NEC conductor sizing does not apply to the wiring inside of Listed equipment.
But that does not mean that proper overcurrent protection is optional.
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
Where is the code? Oops did code writers missed it for switchboards, switchgear or something else is going on?
Lets all write to the code panel NEC what is going on for switchboards, switchgears
- Location
- Illinois
- Occupation
- retired electrician
There is a procedure for that. It is called a Public Input. The system will be open for PIs for the 2026 code sometime in Aug or Sept of 2022.
Just writing to the panel members does not accomplish anything. Changes are only made through the Public Input process.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Why is something required more than what is in 230 and 110?
As I recall, the 408 panelboard main breaker requirements were added when the NEC removed the difference between 'power' and 'appliance and branch circuit' panelboards. Evidently the industry did not think there was a problem with switchboards at that time, nor later on when they added switchgear.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Say I install a 1200A MLO switchboard supplied by a 2000A feeder. Say the NEC load calc for the switchboard is 1000A. Compliant or not? If not, what code section would you cite?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It is not compliant. The only provision for protecting based on load is found in an exception in 230 for services. Both UL and the manufacturer would expect feeder equipment to be protected at not more than its nameplate thus 110.3 would apply.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
they may expect but is this specifically stated in UL 891 or any manufacturers literature? Section busses are already typically rated lower than the through buss. Maybe this is just a silly academic debate, But I just dont see a requirement.
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
Same goes for panelboard but has NEC 408 requirement. Why not switchboard, switchgear?
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
No.
The panelboard has the added requirement of a main device, but that is not a relaxation of any protection at all for the other items.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I am not aware of any requirement for a main device in a panelboard.
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
2017 nec 408 part III for panelboard
Be careful.. no requirement for it to be in..... within OR.........
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
Yes it can be within or outside supply side panelboard but its their for panelboard Not for switchboard switchgear
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
And prior to 2017 it was only required for appliance and branch circuit panels. Power panelboards were treated the same as switchboards.
CrapperEpiphanies
Member
- Location
- MD, USA
- Occupation
- EE
I agree 408 is lacking on the switchboard/switchgear, but I agree with this statement the most.
Unless you have some existing installation of some sort that you're trying to work around - I don't see any reason for the MLO swbd/swgr to be rated less than the upstream OCPD.
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
What I am saying is same holds for panelboards but its stated clearly in nec 2017 section 408 part III?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
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.
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