240.21(B)

[Isaiah]

Construction wants to tap a 3 phase feeder from a 480V SWGR CB at three locations all within about 10 feet of each other: first a 400A fused disconnect; second a 150A fused disconnect and third, a MLO panelboard with a max rating of 800A and has seven branch circuits ranging from 30A to 100A.
I’m primarily concerned about the MLO panelboard
Is this Code compliant?


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[LarryFine]

I'd want to know the load and the short-circuit calcs.

 

[Isaiah]

I'd want to know the load and the short-circuit calcs.

Right but aside from the engineering aspect is it conceptually code compliant?
If the panelboard had a MCB I wouldn’t be too concerned


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[LarryFine]

Yes, with proper taps.

 

[dkidd]

Construction wants to tap a 3 phase feeder from a 480V SWGR CB at three locations all within about 10 feet of each other: first a 400A fused disconnect; second a 150A fused disconnect and third, a MLO panelboard with a max rating of 800A and has seven branch circuits ranging from 30A to 100A.
I’m primarily concerned about the MLO panelboard
Is this Code compliant?


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What is the rating of the SWGR CB?

 

[wwhitney]

Right but aside from the engineering aspect is it conceptually code compliant?

Tap-wise, it may be OK under 240.21(B)(1) (10' tap rule), but as the informational note says, 408.36 requires that the panelboard be protected at not above its rating. So if the feeder being tapped is over 800A, the tap can't terminate in an 800A MLO panelboard. But if the feeder is protected at 800A or less, then 408.36 is satisfied.

Cheers, Wayne

 

[Isaiah]

Tap-wise, it may be OK under 240.21(B)(1) (10' tap rule), but as the informational note says, 408.36 requires that the panelboard be protected at not above its rating. So if the feeder being tapped is over 800A, the tap can't terminate in an 800A MLO panelboard. But if the feeder is protected at 800A or less, then 408.36 is satisfied.

Cheers, Wayne

Yes it’s protected at 800A
Many thanks to all!


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