Tapping 400 to 600

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POSTELEC19

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A building has a 600 amp fused service disconnect. On the load side of the disconnect are parallel lugs with 350mcm feeding a 600 amp main lug panelboard 120/208v. This main lug panelboard is 6ft. away from the service disconnect.
I am taking this job because the other contractor could not finish the job.
He had mounted a 400 amp panel box right next to the service disconnect and intended to put triple lugs in the disconnect and also feed the 400 amp main lug panel with 500 mcm.
I think the 400 amp panel should have a 400 amp main breaker. The buss is rated for 400 amps.
Would the tap rule cover this?
(The load will not change on the service disconnect, it will be a redistribution of power)
600 amp fuses in service disconnect.
Total connected load on 400 amp is 263A
Thanks
BP
 
Yes the tap rules can be used but the tap has to terminate in an over current device and the panel will require over current protection unless it is a "power panel board".

So as you thought the best way to handle both of these issues is the use of a main breaker panel.
 
can the ampacity of the tap conductors be less than the 400 amp breaker at the termination end? 240.21 (B) (1) b
 
can the ampacity of the tap conductors be less than the 400 amp breaker at the termination end?
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No, see below.
(B) Feeder Taps Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The provisions of 240.4(B) shall not be permitted for tap conductors.
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thanks don, looked right at that section and didn't see it, the OP cannot use the 500's on a 400 amp breaker for his propsed feeder tap
 
mpd said:
the OP cannot use the 500's on a 400 amp breaker for his propsed feeder tap
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The conductors to each of the three panels from the 400 amp breakers is a splice.If it were a tap, there would be a change in conductor size.
 
RUWired,
The conductors to each of the three panels from the 400 amp breakers is a splice.
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The 500's originate on the load side of a 600 amp OCPD and terminate on a MLO panel. If you extend 500's from the load side of a 600a OCPD, they must terminate on a OCPD rated 380 amps or less.
Don
 
don_resqcapt19 said:
RUWired,

The 500's originate on the load side of a 600 amp OCPD and terminate on a MLO panel. If you extend 500's from the load side of a 600a OCPD, they must terminate on a OCPD rated 380 amps or less.
Don
Click to expand...
Boy am i embaressed,i thought i was responding to Code Compliant with 500's to the three panels.
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