tap rule?

[buzzlectric]

we have a 4160/480 trans 20' from 800amp fused disconnect,then to apprx 100'to 600amp I line , problem is our boss ,non electrician, wants us to tap the line side of the 600 and run apprx 35' to a 225 I line ,we say tap rules are not met, what do you think?

 

[iwire]

Re: tap rule?

Unless this tap is outdoors I do not see how you can do it as described.

If you use the 25' tap rule you will need a 225 amp OCPD within 25' of the connection to the 800 amp feed and these tap conductors will need a rating of 267 amps minimum (1/3 of 800). 300 Kcmil CU or 400 Kcmil AL

Also the EGC if used between the tap and the 225 OCPD it will need to be based on the 800 amp fused disconnect. 1/0 CU or 3/0 AL.

Once you get past the 225 amp OCPD the circuit and EGC conductors can be reduced in size.

Or you could try to use the 10' tap rule.

Which does not have the 1/3 rating requirement that the 25' tap rule has.