2005 nec art 250.30(a)(2)

[Zane Bailey]

As per this article, when the service entrance feeder conductors are paralleled, the equipment bonding jumper is to be sized as per 250.102(C)/250.66.

On separately derived, what size equipment grounding conductor would be needed between the transformer and the first disconnect means in each parallel conduit/
If I have 2 conduits with 4-350kcmil would the equipment grounds in each conduit be 1/0 AWG or 2/0 AWG?

Zane.

 

[Buck Parrish]

1/0 or you can use the metal pipe as your grounding conductor.

 

[Zane Bailey]

2/0 versed 1/0

2/0 versed 1/0

It has been argued that a 2/0 would be required in each conduit?

 

[raider1]

It has been argued that a 2/0 would be required in each conduit?

You are only required to size the equipment bonding jumper based on the largest secondary derived phase conductor in each conduit, not the combine size of the paralleled conductors.

Here is what the last sentence of 250.102(C) states:

Where the service-entrance conductors are paralleled in two or more raceways or cables, the equipment bonding jumper, where routed with the raceways or cables, shall be run in parallel. The size of the bonding jumper for each raceway or cable shall be based on the size of the service-entrance conductors in each raceway or cable.

Chris

 

[Zane Bailey]

Raider 1

Raider 1

I agree with Raider 1, and that is how I have interpreted the code as well; however, I have had trouble convincing people in the past.

Zane.

 

[ibew441dc]

As per this article, when the service entrance feeder conductors are paralleled, the equipment bonding jumper is to be sized as per 250.102(C)/250.66.

On separately derived, what size equipment grounding conductor would be needed between the transformer and the first disconnect means in each parallel conduit/

If I have 2 conduits with 4-350kcmil would the equipment grounds in each conduit be 1/0 AWG or 2/0 AWG?
Zane.

Neither are correct.

1/0 or you can use the metal pipe as your grounding conductor.

1/0 is wrong look again at Table 250.66.

It has been argued that a 2/0 would be required in each conduit?

Whoever was arguing that would be incorrect....where do they come up with 2/0?

You are only required to size the equipment bonding jumper based on the largest secondary derived phase conductor in each conduit, not the combine size of the paralleled conductors.

Agreed!:smile: That being said...all those who think it may be 1/0 or 2/0 take a better look at table 250.66 (assuming copper conductors).

 

[ibew441dc]

just trying to help

just trying to help

As per this article, when the service entrance feeder conductors are paralleled, the equipment bonding jumper is to be sized as per 250.102(C)/250.66.

On separately derived, what size equipment grounding conductor would be needed between the transformer and the first disconnect means in each parallel conduit/
If I have 2 conduits with 4-350kcmil would the equipment grounds in each conduit be 1/0 AWG or 2/0 AWG?

Zane.

Zane Bailey although I can decipher the question you have asked, I think it is important to give you some constructive criticism:smile:.

when the service entrance feeder conductors are paralleled

The conductors are either service entrance or feeders, they can't be both.Maybe your wondering why I pointed this out.....article 100 definitions are extremely important and often overlooked. There are rules for service conductors that don't apply to feeders, and if the terms are used in the same respect, the confusion begins.

Now since you mentioned that this is a separately derived system, are the conductors service conductors or feeders?

 

[raider1]

Neither are correct.



1/0 is wrong look again at Table 250.66.



Whoever was arguing that would be incorrect....where do they come up with 2/0?



Agreed!:smile: That being said...all those who think it may be 1/0 or 2/0 take a better look at table 250.66 (assuming copper conductors).

If I have 4-350 kcmil in each conduit then the largest ungrounded secondary phase conductor would be a 350 kcmil conductor.(This is assumming that we have a 3 phase wye secondary with a neutral) Therefore Table 250.66 would require a 1/0 copper equipment bonding jumper for each raceway.

Now since you mentioned that this is a separately derived system, are the conductors service conductors or feeders?

They would be transformer secondary conductors. 250.30(A)(2) requires that an equipment bonding jumper run with the secondary derived phase conductors be sized in accordance with 250.102(C).

Chris

 

[ibew441dc]

If I have 4-350 kcmil in each conduit then the largest ungrounded secondary phase conductor would be a 350 kcmil conductor.(This is assumming that we have a 3 phase wye secondary with a neutral) Therefore Table 250.66 would require a 1/0 copper equipment bonding jumper for each raceway.

Wrong, look again......the required conductor size is a 2AWG copper.

Over 3/0
through 350 = 2 AWG

Over 350
through 600 = 1/0 AWG

For argument sake......351 is over 350,

They would be transformer secondary conductors. 250.30(A)(2) requires that an equipment bonding jumper run with the secondary derived phase conductors be sized in accordance with 250.102(C).

Chris

The very important point I was trying to make is that they are ultimately Feeders and are not Service Entrance Conductors.(transformer secondary conductors in this example are feeders)

 

[raider1]

Wrong, look again......the required conductor size is a 2AWG copper.

Over 3/0
through 350 = 2 AWG

Over 350
through 600 = 1/0 AWG

For argument sake......351 is over 350,

You are correct, my bad, had a brain fart.

The very important point I was trying to make is that they are ultimately Feeders and are not Service Entrance Conductors.(transformer secondary conductors in this example are feeders)

I agree, but I think the OPer was refering to the wording in 250.102(C) that refers to service entrance conductors.

Chris

 

[ibew441dc]

I agree, but I think the OPer was refering to the wording in 250.102(C) that refers to service entrance conductors.

Chris

That's why I thought it was important to possibly clear up any misunderstanding the OP may have had because of the way the NEC will require certain rules to be applied.

You are right about the wording in 250.102(C) referring to service conductors but it is extremely important for one to have a firm foundation with the definitions of Service(and all associated), Feeder, and Branch Circuit. If one does not clearly understand those 3, one will get lost before he/she knows it.