Grounding/Grounded Conductors From Generator

[electriciansnet]

We have been asked by our client to install a "more permanent" (better than stretching out wires across the ground) set off feeders from their client's generator. The inspector does not approve of this because the generator is on wheels.
Nevertheless, they've asked us to quote some underground feeders for them. I was escorted to the back of this government building to find the following scenario:
(2) New, 600A/208V/3PH/4W/N3R Disconnects (1 normal/ 1 generator with empty line-side lugs).
I could not see in the generator because my escort did not have the right key but was told that it had a 3P/500A Breaker

For the sake of the quote I will include (2) 2-1/2 Sch80 PVC, (4) 4/0cu -OR- (2) 3" Sch80 PVC, (4) 300 alu.

To what extent do I actually need to provide for neutral and ground in this situation? I realize the generator does not provide grounding but do I treat the generated source as if it was a utility transformer?

 

[ceb58]

We have been asked by our client to install a "more permanent" (better than stretching out wires across the ground) set off feeders from their client's generator. The inspector does not approve of this because the generator is on wheels.
Nevertheless, they've asked us to quote some underground feeders for them. I was escorted to the back of this government building to find the following scenario:
(2) New, 600A/208V/3PH/4W/N3R Disconnects (1 normal/ 1 generator with empty line-side lugs).
I could not see in the generator because my escort did not have the right key but was told that it had a 3P/500A Breaker

For the sake of the quote I will include (2) 2-1/2 Sch80 PVC, (4) 4/0cu -OR- (2) 3" Sch80 PVC, (4) 300 alu.

To what extent do I actually need to provide for neutral and ground in this situation? I realize the generator does not provide grounding but do I treat the generated source as if it was a utility transformer?

Is the neutral being switched in the DP switch? Look at 702.11 You will also want to see the breaker on the gen. Most state the use of copper conductors only so that would throw you for figuring using Al.

 

[electriciansnet]

Is the neutral being switched in the DP switch? Look at 702.11 You will also want to see the breaker on the gen. Most state the use of copper conductors only so that would throw you for figuring using Al.

Hello. Thank you for your reply.
No I don't believe i saw the neutral as being switched. I read 702.11 which only seems to indicate their 2nd disconnect would not be required but it is acting as a manual transfer switch.
(i.e. main switch goes off- generator gets started- generator switch goes on)
In a test environment the building neutral would be fine but, thinking practically, if they lost the entire primary set of feeders in a storm or disaster the absence of the neutral would case them to lose all their lighting loads and could potentially create a dangerous situation for a lineman with the unexpected load.

But what about the grounding conductor?

 

[ActionDave]

The generator has a neutral, or I should hope it has.

You either switch the hots and the neutral in the transfer switch and bond the neutral to the ground in the generator bond all the neutrals at the building and leave the neutral unbonded in the generator. Then you would need an equipment ground to the generator. Just like the wiring to a sub-panel.
There is no danger to linemen since it is only the neutral conductor that is common.

 

[electriciansnet]

The generator has a neutral, or I should hope it has.

You either switch the hots and the neutral in the transfer switch and bond the neutral to the ground in the generator bond all the neutrals at the building and leave the neutral unbonded in the generator. Then you would need an equipment ground to the generator. Just like the wiring to a sub-panel.
There is no danger to linemen since it is only the neutral conductor that is common.

Okay I think I got it. Thanks!

 

[jwelectric]

What about a transfer switch, wouldn't one be needed?

 

[electriciansnet]

What about a transfer switch, wouldn't one be needed?

I think the 1st switch just breaks the normal feed and the 2nd breaks the emergency.

 

[electriciansnet]

Not Our Doing

Not Our Doing

What about a transfer switch, wouldn't one be needed?

Keep in mind0 this system has been in place for about a year I'm guessing and was not installed by us. The only involvement we have in it is the conductors from the generator.

 

[jwelectric]

If it was not code compliant when it was installed it is not code compliant today. Depending on the code official you might be installing something that will have to be changed.

 

[ceb58]

I think the 1st switch just breaks the normal feed and the 2nd breaks the emergency.

[/QUOTE]

Keep in mind0 this system has been in place for about a year I'm guessing and was not installed by us. The only involvement we have in it is the conductors from the generator.

If it was not code compliant when it was installed it is not code compliant today. Depending on the code official you might be installing something that will have to be changed.

You need to heed what Mike is saying. I just went back and read the OP I thought you had a double pole manual transfer switch but by your OP you do not. The transfer equipment must meet

702.5 Transfer Equipment.​

Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of norma land alternate sources of supply in any operation of the transfer equipment. Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.Transfer equipment, located on the load side of branch circuit protection, shall be permitted to contain supplementalovercurrent protection having an interrupting rating sufficientfor the available fault current that the generator candeliver. The supplementary overcurrent protection devicesshall be part of a listed transfer equipment.Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric utility supply is either the normal or standby source.

Exception: Temporary connection of a portable generator without transfer equipment shall be permitted where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the normal supply is physically isolated by a lockable disconnecting means or by disconnection of the normal supply​

conductors.

The only strech would be the exception but that would be an inspectors call.

 

[jwelectric]

This reminds me of the HVAC guy that changed out a self-contained outside unit. When the inspector came to do the inspection it got turned down.
The HVAC man said, ?I replaced tic for tack so why is it wrong?? The inspector said, ?the unit can?t be under the service disconnect.? The HVAC man said, ?It was like that before.? The inspector said, ?But it won?t be tomorrow.?

 

[ActionDave]

What about a transfer switch, wouldn't one be needed?

Keep in mind0 this system has been in place for about a year I'm guessing and was not installed by us. The only involvement we have in it is the conductors from the generator.

Just went back and re-read. You need a transfer switch.

 

[Strathead]

Regarding the transfer switching, if it is more convenient for you, you can explore a "Kirk Key" Do a Google search. Otherwise I concur with other poster who quoted the code section. A transfer switch is not what is required, but a means to ensure that both sources can not be activated at the same time.