3 pole transfer switch

[SmithAndrewR]

I have 2 generators feeding 120/208 loads going thru a 3 pole transfer switch. My company engineers provide new drawings on how this should be wired about every 6 months. Sometimes bonded at the MDP sometimes at the generators. Sometimes 4 wire sometimes 5 wire and combinations of both. IMO there is no truly safe way to do this any thoughts.

 

[ron]

Is there any ground fault protection on the output of the gens? Is the neutral and ground bonded at either generator?

 

[SmithAndrewR]

The Generators do not have Ground fault protection. And as for bonding at the generator not when we use a 4 wire from the gens to the MDP but yes when we run a 5 wire. As I see it either way by using a 3 pole TS you still have a paralell path for the neutral. The gens are usually 5-6 feet apart.

 

[iwire]

The Generators do not have Ground fault protection. And as for bonding at the generator not when we use a 4 wire from the gens to the MDP but yes

But do the buildings have GFP ahead of the transfer switch?

 

[ron]

The Generators do not have Ground fault protection. And as for bonding at the generator not when we use a 4 wire from the gens to the MDP but yes when we run a 5 wire. As I see it either way by using a 3 pole TS you still have a paralell path for the neutral. The gens are usually 5-6 feet apart.

You can do it either way with 3 pole or 4 pole. That then decides whether you bond the N-G at one of the generators or both. If you have phase to neutral loads, then you need three phase conductors, one neutral and an EGC. The EGC conductor can be an approve raceway system or an EGC as an actual conductor in the raceway.

 

[Strathead]

You can do it either way with 3 pole or 4 pole. That then decides whether you bond the N-G at one of the generators or both. If you have phase to neutral loads, then you need three phase conductors, one neutral and an EGC. The EGC conductor can be an approve raceway system or an EGC as an actual conductor in the raceway.

Ron beat me to it. I would just like to add a couple of clarifications. "3 pole or 4 pole" Ron means "when the neutral (grounded) wire is switched along with the hots. In a simgle phase system, this would be a 3 pole 120/240 volt single phase transfer switch, for example.

Second, when the neutral is switched that makes it a "separately derived system". That is what actually decides whetehr you bond the N-G.

Ron I hope you are not offended, I understood perfectly what you wrote, but thought it might be better to clarify it a little for less code savy readers.

 

[ron]

Ron beat me to it. I would just like to add a couple of clarifications. "3 pole or 4 pole" Ron means "when the neutral (grounded) wire is switched along with the hots. In a simgle phase system, this would be a 3 pole 120/240 volt single phase transfer switch, for example.

Second, when the neutral is switched that makes it a "separately derived system". That is what actually decides whetehr you bond the N-G.

Ron I hope you are not offended, I understood perfectly what you wrote, but thought it might be better to clarify it a little for less code savy readers.

I can use as much help as I can get.