Tap Rule

[transman2]

I have a feeder breaker that supply's power to an electrical room with 3 underground raceways that have 3-500kcmil 5kv conductors and 1-500 thhn 600volt rated grounding conductor in each conduit. The voltage is 4160 and feeds motors and a transformer for 480 volt gear. My question, is it legal to tap off the existing conductors to feed some new 4160 gear because the 1200amp buss on existing gear might be maxed out maybe. Just curious if I could do this if the conductors can handle the load. The reason for this is the company is trying to avoid another substation and money of course is all ways a factor. Oh, another question, where is it in the code that shows underground 5kv rated ampacities. Shielded 5kv.

 

[transman2]

No takers on this Question?

No takers on this Question?

Did I not explain this good enough?

 

[augie47]

It depends on what you mean by "maxed out" ? Fully loaded or no more space ?
If you 1200 amp gear is fully loaded, your (3) 500s are loaded close to their ampacity and a tap would be of little value IMO.
(See Tables such as 310.77 that fit your install).

 

[transman2]

Augie

Augie

It depends on what you mean by "maxed out" ? Fully loaded or no more space ?
If you 1200 amp gear is fully loaded, your (3) 500s are loaded close to their ampacity and a tap would be of little value IMO.
(See Tables such as 310.77 that fit your install).

Originally we had a 600A buss for the 4160 gear in ER13 in the power model software causing the overload condition and the need for a new feeder from MS2. We have changed it to the 1200A field verified buss. The 3-500kcmil per phase in a D3 duct bank de-rated allows for a total of 869A. With all belts running and three north east feeders running the current draw is about 800A. The existing feed will have enough capacity with the additional equipment when running three or less feeders. If this is acceptable we will change the design to reflect the additions to ER13 utilizing the existing power feed.

Lets say that if the gear was rated for 600A and our feeder conductors were rated for the 869A . If we need to add new gear but our gear buss is not big enough, can we add new gear and just tap off somewhere along the conductors route.