industrial tap rule violation?

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slc410

Electrician
Location
Madison wi
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Electrician
I just started working for a company wiring cabinet panels and ran across what I believe is a tap violation. Main power enters the cabinet and terminates on a 150A breaker. The load side of the breaker then runs approximately 5 feet then terminates into a distribution block (tap). Here is where the problem begins, out of the distribution block there are several #14awg wires which then run to various small breakers which are no more than a couple feet away from the block all within the same panel board.
My concern is what is going to keep the #14's from turning into molten magma if there would ever be a ground fault to the backplane of the panel?
Its my understanding that the tap conductors can be no smaller than 10% of the breaker feeding the taps.
 
slc410 said:
I just started working for a company wiring cabinet panels and ran across what I believe is a tap violation. Main power enters the cabinet and terminates on a 150A breaker. The load side of the breaker then runs approximately 5 feet then terminates into a distribution block (tap). Here is where the problem begins, out of the distribution block there are several #14awg wires which then run to various small breakers which are no more than a couple feet away from the block all within the same panel board.
My concern is what is going to keep the #14's from turning into molten magma if there would ever be a ground fault to the backplane of the panel?
Its my understanding that the tap conductors can be no smaller than 10% of the breaker feeding the taps.
Click to expand...

240.21(B)(1) not %10..........10 times
 
I believe the 1/10th rule does not apply if they are within the enclosure as mentioned. As long as they can handle the load of the OCPD they supply then it's OK.

Odds are the only thing protecting them from melting, but they are likely a million to one and they are inside an enclosure so unless you short it out while inside you should be OK. :)

(1) Taps Not over 3 m (10 ft) Long. If the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:
(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors.
(2) The tap conductors do not extend beyond the switchboard, panelboard, disconnecting means, or control devices they supply.
(3) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which shall extend from the tap to the enclosure of an enclosed switchboard, panelboard, or control devices, or to the back of an open switchboard.
(4) For field installations, if the tap conductors leave the enclosure or vault in which the tap is made, the ampacity of the tap conductors is not less than one-tenth of the rating of the overcurrent device protecting the feeder conductors.
Click to expand...
 
buddhakii said:
I don't think the 10 times rule even would apply in this situation since the taps are made in the same cabinet as the overcurrent protection.
Click to expand...

They would have to be longer than 10 feet before that needs considered, not that it is impossible for them to be that long. Then 25 foot tap rule comes into play and tap must be 1/3 ampacity of overcurrent device on line side.
 
Most "cabinet panels" are wired to Codes other than the NEC and often certified by UL or another NRTL. They do not need to meet NEC rules.
 
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