old topic another on secondary conductors 2008 nec

[grumpy11]

ill keep the question short

75 kva 480 delta primary 120/208 wye secondary

primary protection 125 amp fuse. 3 #1 1#6 egc
secondary im taking the full 300 amps from the secondary 4#350 1# 2 egc

question is can i or can i not take the secondary conductors bring them into a wiring trough and tap them to 2 150 amp panels.

it is my understanding of the code that secondary conductors must be connected to a single over current device.

i know i can come out of transformer twice to the two panels.

i say taping the secondary conductors is taping a tap and that should not be done.

[cadpoint]

MH and EC&M post here

Second paragraph answers you last question, yes you are correct!

Here's another MH and EC&M here ; with scenario 1 - or scenario 2

[don_resqcapt19]

I think the 2008 code is clear that you cannot do that. There was no change in the following part of 240.21 between the 2008 and 2011 codes.

240.21 Location in Circuit. Overcurrent protection shall be provided in each ungrounded circuit conductor and shall be located at the point where the conductors receive their supply except as specified in 240.21(A) through (H). Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.

The 350's are installed without overcurrent protection at their source so you can't "tap" off of them to feed the two panels.

[grumpy11]

thank you . i think some people get confused. when they look at 450.3 B

this article is only for the transformer winding's, not the secondary conductors.

if you ocpd is 125% of the full load current is on the primary then the secondary winding's are protected.

this has nothing to do with the protection of the secondary conductors.