Outside SDS

[augie47]

Little lengthy .,..sorry

Every-time I think I know just a little something about the NEC, I stumble across a job that humbles me.....

I've been working on this for some time now and need some assistance...

In inspecting, I keep finding stumbling blocks.

Here is what I have:
(a) an outdoor pad transformer 13.2kv-/208Y120 privately owned. Fed by a privately owned system (college campus). As I see it, the secondary conductors from this pad to the building would be SDS conductors and not service conductors.

(b) the secondary conductors come from the open bottom pad thru (6) 4" GRS Conduits each with (4) 600 kcmil Cu and a equipment bonding jumper.

(c) The (6) conduits terminate open ended in an old high voltage vault. The conductors are then protected by a steel
plate a short distance until they enter a meal j box thru chase nipples.

(d) On the opposite side of the vault (9) GRS conduits terminate open ended then the conductors ( 500 kcmil AL) also enter the j box. The conduits feed an open bottom 2500 amp switch gear.

The (6) GRS conduits from the transformer have a 2/0 Cu System Bonding jumper in each conduit accompanying the 600 kcmil phase conductors.
The (9) GRS from the gear have a 3/0 AL system bonding jumper in each conduit. All of these connect in a 14 port Polaris connector.

Question 1: Does the above seem Code compliant so far ?

Now the problems:
The (6) conduits (c above) are "floating". They have bonding bushings on the vault end but no jumpers.
Likewise the (9) conduits from the gear are "floating" with non terminated bonding bushings on the vault end.

The contractor proposes to add a 2/0 bonding jumper to each of the conduits based on 250.102(C) and 250.66
The contractor proposes to add a 500 kcmil bond jumper to the j box based on 250.102(C).

Question #2: If the j box jumper (500 kcmil) terminates in the polaris connector with the system bonding jumpers, can the individual 2/0 conduit bonding jumpers terminate on lugs bolted to the j box ?

There is a grounding electrode in the transformer and a multiple ground-rod electrode system at the gear.

Question 3: can the grounding electrode system at the gear legally connect to the grounding terminal where the system bonding jumpers from the transformer terminate in the gear ?

 

[Smart $]

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Question 1: Does the above seem Code compliant so far ?

9+6=15 grounding conductors

With a 14-port splice block, at least two conductors have to be doubled in one port. Is the block rated for terminating two conductors in a port?

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Question #2: If the j box jumper (500 kcmil) terminates in the polaris connector with the system bonding jumpers, can the individual 2/0 conduit bonding jumpers terminate on lugs bolted to the j box ?

Technically, you could use one continuous 2/0 Cu jumper for all of the bonding bushings and the j-box. Two or more may simply be more practical. While many electriciains use enclosure metal as a bus, I do not believe this meets the intent of the Code.

The 500kcmil jumper is not required. 250.102(C) is for service supply side bonding. See 250.102(D)...

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Question 3: can the grounding electrode system at the gear legally connect to the grounding terminal where the system bonding jumpers from the transformer terminate in the gear ?

I'm thinking you are misunderstanding the term "system bonding jumper". It connects the equipment grounding system to the grounded conductor at one location. Both ends connect in a single enclosure and no part leaves that enclosure.

With an SDS, only one of two electrodes is required. Water pipe or building steel electrode. Auxiliary electrodes are not prohibited. Where neither required electrode exists, general building or structure grounding electrode system requirements apply. As usual, connection can be made at any point from source to disconnecting means enclosures.