ground conductor for service

[WirenutNH]

I am looking for some input on a job we are doing. The existing conditions


private service transformer secondary 120/208 3 ph. feed under private road to a 1200 amp 120/208 3 ph service. We are planning on intercepting 3-4" pvc conduit running from transformer to service across street. Installing a spiceing hang hole, where we will run feeders from transformer to new 3R service rated transfer switch. which will be feed from new generator and existing service. My question is this:

The exiting transformer has a bond grid in place with ground rod driven. The exisitng service across the street has a ground grid with ground rods/building steel. I am planning on installing ground grid 2- ground rods at new generator. The exisitng triple 600 mcm in 3 -4" pvc conduits running across street do not have a ground conductor in conduit. Will I need to install one once I intercept at new hand hole? I looked at 250-32 and I am looking at this as a seprate building and I am under the impresion that I will not need them. Any imput will be appreciated.

 

[iwire]

The service rated transfer switch becomes the service disconnect the bonding will have to be done there, anything on the load side of that ATS will require an EGC and the original service disconect will have to be 'unbonded'.

I hope that 1200 amp gear is able to float the neutral.

 

[WirenutNH]

If the neutral is switch, doesn't this make this a sepratley dirived system and then all down stream equippment will still have it origina;l service disconnect as it was?

 

[WirenutNH]

If I read 250-32B2 It tells me that:1)If no equipment grounding cond is run with supply conductors 2) If there are no contunuse metalic pathsbonded to grounding systemin both buildings involved 3) If the grounded conductor is run with the supply conductors to the building or structuredisco means and to the GE shall be used forgrounding or bonding of equipment,strucutre,or framesreq to be groundedor bonded. Does this allow the conductors from the transfer switch acorss street to be run with out grounding conductor?

 

[augie47]

IMO, If the existing transformer is 208Y/120 then 250.24(A)(2) requires a grounding electrode at the transformer which you have. From the transformer to your transfer switch (service rated) you would need a grounded conductor per 250.24(C).
From the transfer switch to the building, a grounded conductor is not required if you don't need the neutral at the building, but a grounding conductor is required.