System Bonding Jumper for a SDS

[Pitt123]

I have an application where I am installing an outdoor transformer right next to a disconnect. I am using (4) wires with the 4th wire being used as the grounded wire. This grounded wire will be connected to the neutral at the transformer and at the disconnect. The grounded wire will also be bonded to the two enclosures. I know typically that you also need to have a ground rod driven at both the transformer and the disconnect with the grounded wire bonded to both at each end. However since these two units are right next to each other can I only drive one ground rod and bond this rod to both the enclosures and therefore grounded conductor at both ends?

 

[don_resqcapt19]

You can't bond the grounded conductor to both the transformer and the disconnect for a SDS. 250.30(A)(1).

 

[Pitt123]

You can't bond the grounded conductor to both the transformer and the disconnect for a SDS. 250.30(A)(1).

I thought when only using 4-wires you bonded the grounded concuctor at both ends? Isn't this how most utilities install these systems?

 

[raider1]

I thought when only using 4-wires you bonded the grounded concuctor at both ends? Isn't this how most utilities install these systems?

Utility companys installations don't fall under the scope of the NEC.

Chris

 

[philly]

So we are saying that a 4-wire connection between transformer and disconnect is not allowed inside a facility? Must we run 5 wires then and only bond at one end?

 

[raider1]

So we are saying that a 4-wire connection between transformer and disconnect is not allowed inside a facility? Must we run 5 wires then and only bond at one end?

Yes, unless you can meet Exception #2 to 250.30(A)(1).

Chris

 

[philly]

Yes, unless you can meet Exception #2 to 250.30(A)(1).

Chris

So all utilities can use 4 wires b/c they are not covered under NEC however inside a facility we must use 5 wires to comply with NEC?

In that case we have grounding electrode at one end, and only bond grounding conductor at one end?

 

[raider1]

So all utilities can use 4 wires b/c they are not covered under NEC however inside a facility we must use 5 wires to comply with NEC?

Correct in most cases.

In that case we have grounding electrode at one end, and only bond grounding conductor at one end?

You would have a grounding electrode conductor and system bonding jumper connection at one end and an equipment bonding jumper connection at the other end.

Check out 250.30.

Chris