(2) 225A Breakers feeding (1) 400A Fused Disc?

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jim dungar said:
The panel itself does not need to be an MCB type. What is important is to not 'tap a tap'.
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True, but if MCB, that's all the verification necessary to confirm no 'tap a tap'. If the panelboard is MLO, the panel feeder may or may not be a tap. Verification not a tap req'd before proceeding.
 
Smart $ said:
True, but if MCB, that's all the verification necessary to confirm no 'tap a tap'. If the panelboard is MLO, the panel feeder may or may not be a tap. Verification not a tap req'd before proceeding.
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PS: If the panelboard is MLO and fed by tap, that may make it in violation, yes? Details would determine compliant or not. OP stated fed by MDP a few hundred feet away, which tends to make me think it not a tap... but only a guess.
 
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jim dungar said:
Square D makes plug-on lug kits that are the same size as a 200A breaker. You could use two of these plus a rule from 240.21(B), to feed your 400A switch, as long as the 600A is not already being fed using a tap rule.
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Now if we only knew what kind of panelboard the OP has and whether or not there is a similar device available for it.
 
kwired said:
Now if we only knew what kind of panelboard the OP has and whether or not there is a similar device available for it.
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You are correct, the OP did not say. I assumed that a 600A panel limited to 225A breakers would have to be I-Line construction, which has been around for almost 45years.
 
Smart $ said:
Aside from what kwired said, the AHJ may have the authority to permit you to do something questionable, but consider AHJ permission is no substitute for a UL listing. Altering a listed panelboard by doing something not consistent with its listing will render its listing void. Doing such puts unnecessary liability on the EC.
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Here is a UL statement on this in

http://www.ul.com/global/documents/...newsletters/electricalconnections/april10.pdf

There are many safety concerns to consider
when busbars are tapped in the field. If the
product is not Listed for field tapping, the
code official must determine whether to
approve the modified product or not. A UL
field evaluation can provide assistance to the
code official in particular cases, but not all.
 
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Smart $ said:
Though it may be, I'm saying AHJ approval is Code req'd, AHJ permission is not...

...but if the AHJ is asked and permission is granted beforehand, get it documented.
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90.4

By special permission, the authority having jurisdiction may waive specific requirements in this
Code or permit alternative methods where it is assured that equivalent objectives can be
achieved by establishing and maintaining effective safety.
 
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