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#101223 02/26/07 04:33 PM
Joined: Apr 2002
Posts: 178
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We`re working in a plant wiring a machine and they have in switch gear room a 600 amp breaker 3 500`s feed a JB from there a set of 3/0`s tapped to a 225 amp breaker and then another set of 3/0`s tapped to 200 amp. Is all well with this? I read the feeder tap rules but wasn`t sure about the loading of the main 600 amp is this considered cont load or non or does this effect calculations? Do you figure .80 which would be rughly 480 amps continuous? Thanks for some insight. These are textile machines many motors.

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#101224 02/26/07 05:18 PM
Joined: Nov 2000
Posts: 2,148
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The load calculations and the tap rules are two different issues. This installation appears to comply with 240.21(B) assuming the 3/0s are 25' or less. You would have to do a load calculation as to the total loads, however with only 425 amps of overcurrent protection on the taps, there is no way that the 600 amp circuit is overloaded.
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