NEC Table 450.3(B) Note #2

A

anbm

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NEC Table 450.3(B) Note #2 - Where secondary overcurrent protection is required, the secondary overcurrent device shall be permitted to consist of not more than six circuit breakers or six sets of fuses grouped in one location. Where multiple overcurrent devices are utilized, the total of all the device ratings shall not exceed the allowed value of a single overcurrent device.

Will the attached partial elec. one line with (2) secondary breaker configuration connection as shown - violates above rule?
 

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anbm said:
NEC Table 450.3(B) Note #2 - Where secondary overcurrent protection is required, the secondary overcurrent device shall be permitted to consist of not more than six circuit breakers or six sets of fuses grouped in one location. Where multiple overcurrent devices are utilized, the total of all the device ratings shall not exceed the allowed value of a single overcurrent device.

Will the attached partial elec. one line with (2) secondary breaker configuration connection as shown - violates above rule?
Click to expand...

How do you come up with 6000amps total?
 
If the primary is properly protected then there would be no problem.
There is a school of thought that having the transformer "tap" box would be in violation as the transformer secondary rules call for the conductors to terminate on an OC device.
 
augie47 said:
If the primary is properly protected then there would be no problem.
There is a school of thought that having the transformer "tap" box would be in violation as the transformer secondary rules call for the conductors to terminate on an OC device.
Click to expand...
450.3 does not care where the tap is made as it is about the transformer protection rating.
240.21(C) is the relevant section for where the taps are made as it is about conductor location.

Is this a supervised industrial location?
Is the tap box close coupled to the transformer with factory supplied bussing such that it can be considered one piece of equipment with multiple sections?
 
augie47 said:
If the primary is properly protected then there would be no problem.
There is a school of thought that having the transformer "tap" box would be in violation as the transformer secondary rules call for the conductors to terminate on an OC device.
Click to expand...
Even with the primary protection, per 240.21(C) we still need secondary protection, prefer the secondary protection is within 10 feet from xfmr.
 
Table 450-3(A) applies to this installation, not 3(B). 3(A) has columns for the secondary protection for secondaries both above and below 1000 volts.
 
anbm said:
Even with the primary protection, per 240.21(C) we still need secondary protection, prefer the secondary protection is within 10 feet from xfmr.
Click to expand...
agree,
my post was simply meant to point out that, as far as Art 450 is concerned, with proper primary overcurrent protection, there secondary protection is irrelevant ( I didn't bring size into account as Table 3A is far more involved than 3B)
as always, Art 240.21 must be taken into account in regard to conductor overcurrent (and as far as the tap box is concerned)
 
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