Service Taps

[MNSparky]

Hello everyone, I'm having a debate with a fellow electrician. We are doing a new restaurant with a 600A service. My plan is to feed the CT with 3 sets of paralleled 250 kcmil AL quadruplex USE-2 from the service providers transformer and then leave the CT with three more sets of the same, run under the building (which has a half basement) to the basement mech room and run each set into three 200A MCB panels. The other guy doesn't think I can tap and split the CT like that since they are service conductors but I think I can under 240.21(C)(4). He feels we need to run them into a 600A service disconnect in the mech room and then distribute as feeders to the panels. The tap conductors would be around 60' long. Am I interpreting the code right on this one? Thanks!

 

[infinity]

Since your three sets are before the service disconnect there are no tap conductors what you end up with is three sets of service entrance conductors so the tap rules in Article 240 do not apply.

Welcome to the Forum.

 

[MNSparky]

I don't use the tap rules too often. I've looked in the past and just now but it's not slapping me in the face; where in the code does it suggest that 240.21(C) doesn't apply to service conductors? Is it because they get called out separately in 240.21(D)?

 

[kwired]

I don't use the tap rules too often. I've looked in the past and just now but it's not slapping me in the face; where in the code does it suggest that 240.21(C) doesn't apply to service conductors? Is it because they get called out separately in 240.21(D)?

240.21(C) is titled transformer secondary conductors, and I can see how that can be misinterpreted, but it is intended to cover secondary conductors of a separately derived system. Service conductors are covered in art 230.

240.21(D) does point you to a 230 section.

Service conductors do not (ordinarily) have overcurrent protection on the supply side. Everything else in 240.21 has some overcurrent protection level on the supply side.

 

[Smart $]

... then leave the CT with three more sets of the same, run under the building (which has a half basement) to the basement mech room and run each set into three 200A MCB panels. ...

If by "run under the building (which has a half basement)" you mean in the space of the half basement, I do not believe that qualifies as being considered outside the building [230.6].

 

[kwired]

If by "run under the building (which has a half basement)" you mean in the space of the half basement, I do not believe that qualifies as being considered outside the building [230.6].

I sort of assumed he meant underground, under slab, etc. But if within the building could still be encased in 2 inches of concrete and be considered effectively outside the building.

 

[Smart $]

I sort of assumed he meant underground, under slab, etc. But if within the building could still be encased in 2 inches of concrete and be considered effectively outside the building.

That goes along with what I was thinking. Compliance with 230.6 is required within the footprint of the building.

 

[MNSparky]

Thanks for the explaination, that makes sense. I'll make a note in my code book for future reference. :happyyes:

kwired's assumption is correct, I'll be running them in the dirt under the slab of slab-on-grade portion of the building to the basement wall. I still don't feel like the 600A service disconnect in the basement is necessary, since I'll only have 3 panels with a SDM in each so I meet the 6 or less rule. Is there a reason one would want to put in the extra gear? Seems redundant and an unnecessary cost.

Thanks!

 

[Smart $]

... I still don't feel like the 600A service disconnect in the basement is necessary, since I'll only have 3 panels with a SDM in each so I meet the 6 or less rule. Is there a reason one would want to put in the extra gear? Seems redundant and an unnecessary cost.

You are correct. A 600A main is not required. (3) 200A SDMs are compliant as long as they are grouped.