ATS question

[RUWired]

my point exactly,Pierre,. how do we make it code correct?
seems like its quite the dilemma..:-?

switch the grounded conductor in building 2 via the 4-pole ats. by not switching the neutral in building 2 you violate article 250.24(A)5.

 

[Pierre C Belarge]

The first objective is to eliminate the parallel path between the 3 pieces of equipment, (service disconnect 1, service disconnect 2, and the generator). The main bonding jumpers in building 1 and 2 are required. Since the grounded conductor in the ats in building 1 is not switched, the grounded conductor at the generator needs to be isolated to prevent the parallel path in building 1. To keep the grounded conductor and grounding conductor seperate in building 2, a switched neutral transfer switch is required. The ground fault path, if a fault in building 1 or 2 should occur while the generator is running will travel through the main bonding jumper in building 1. There are better mouse traps to use such as two 4-pole switches or by making a 3-wire feeder in the building 2, but the are no articles preventing the use of a 3-pole and 4-pole,

Rick

Sometimes reading a post like this one is not easy for me.

Question:
Are you saying that it is permitted to make the installation with the 2 different types of transfer switches (1-3pole and 1-4 pole)?

 

[RUWired]

Sometimes reading a post like this one is not easy for me.

Question:
Are you saying that it is permitted to make the installation with the 2 different types of transfer switches (1-3pole and 1-4 pole)?

Yes i am saying that.

 

[benaround]

my point exactly,Pierre,. how do we make it code correct?
seems like its quite the dilemma..:-?

Use two 4 pole ATS's.

 

[RUWired]

Use two 4 pole ATS's.

I agree that the use of two 4-pole switches is a better arrangement, but can you find an article preventing the use of a 3-pole and a 4-pole switch? I can't.

 

[benaround]

I agree that the use of two 4-pole switches is a better arrangement, but can you find an article preventing the use of a 3-pole and a 4-pole switch? I can't.

Rick,

If using a 4 pole switch, you need to bond the N/Gd at the generator, if using a 3 pole

switch the Neutral and Grd need to stay seperated at the generator, while no one section

of the NEC states that, using one 3-pole and one 4-pole would reground the neutral on its

load side and that would be the violation.

 

[RUWired]

Frank before we go any further, i'm refering to 2 seperate buildings and 1 gen set. It would be different if there were only one building involved.

Typically in a non sds gen set, the MBJ in the service equipment is allowed to be used for faults when the generator is running instead of requiring the generator to have its bonding jumper installed. If it's ok to use it in that application, then why not use it when there is another building involved.

I might add that the MBJ in the building with the gen set is only used while the generator is running.
Rick

 

[RUWired]

Atached is a sketch of two buildings with one generator.

View attachment 3675

 

[benaround]

Rick,

Nice drawing !! I was still refering to the OP's set-up, one transformer feeding both

services, one generator with two cb,s one for each ats, both neutrals would need to come

from generator then to ats's and this is where I see the problem.

On the other hand, I'll look at your set up agian, but, it looks like that set-up would work !

 

[benaround]

I ran out of edit time, In the drawing during normal operation the neutrals are regrounded.

 

[RUWired]

I ran out of edit time, In the drawing during normal operation the neutrals are regrounded.

In the normal operation the 4-pole switch prevents the regrounding. Everything is kept seperate through out in both normal and gen mode.