grounding of generator

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ccha9219

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My local inspector says I don't need a ground rod a the generator.
To my way of thinking when the ATS goes into emergency power, the generator "Separately derived source"
At the ATS the?normal power grounded elect. is not broken by the switch, and the equipment ground is common to the gen set equipment ground,
This could possible set up a ground loop with the power co.
The grounds and Nutls. should be kept separate and a ground rod installed at the gen set.
Is my thinking right? :confused:
 
Re: grounding of generator

Is your generator SDS? SDS is determined by the ATS. If the neutral is not switched, then your generator is not SDS.

Read 250.34 completely.

[ February 23, 2004, 05:42 PM: Message edited by: dereckbc ]
 
Re: grounding of generator

Your the guy doing the airport right?

I would imagine what they want is clearly spelled out.

I would install it as specified by the engineers.

JMO
 
Re: grounding of generator

If the neutral is not switched in the ATS, there is no need to re-ground it at the generator.

The equipment bonding (EGC) connections (green in sketch) are more important.

The generator neutral should not be bonded to the generator frame.

Ed

Gen10.gif
 
Re: grounding of generator

Originally posted by iwire:
Your the guy doing the airport right?

I would imagine what they want is clearly spelled out.

I would install it as specified by the engineers.

JMO
Click to expand...
Yes that's me
The engineer only supplied tech specs for gen set,
breaker size, settings,, ect..
On the drawings he shows 2 parallel runs of 350 going to the transfer switch.
 
Re: grounding of generator

Originally posted by Ed MacLaren:
If the neutral is not switched in the ATS, there is no need to re-ground it at the generator.

The equipment bonding (EGC) connections (green in sketch) are more important.

The generator neutral should not be bonded to the generator frame.

Ed

Gen10.gif
Click to expand...
My concern is more of setting up a ground loop with the utillity company and also once the gen set starts where is my earth ground for that source, It would be like haveing you grounded conductor originate from a different source than your feeders
your am I making a mountian out of a mole hill?
 
Re: grounding of generator

ccha9219,
once the gen set starts where is my earth ground for that source
Click to expand...
Refer to my sketch A, of a non-SDS, above.
If you trace the neutral from the generator, through the ATS, and back to the service equipment, you will see that it is already grounded.

My concern is more of setting up a ground loop
Click to expand...
A "ground loop" is created when the neutral conductor is connected to grounding electrodes in two locations.

If you used an SDS configuration, in other words, a transfer switch that opened the neutral, this would isolate the generator neutral from the service grounding electrde, and then you would be required to ground the generator neutral, and bond it to the frame. (Sketch B below)

Ed

Gen9.gif
 
Re: grounding of generator

It is a non sds transfer switch,
I have spoke to both the city and electrical engineer and both have assured me that a ground rod is not necessary. The lightning protection co. is going to bond the gen set to the counterpoise. I still feel there is a potential for a problem, I am not so arrogant as to think I know it all...
thanks for all the input. but it seems this one has been taken off my hands
 
Re: grounding of generator

Originally posted by ccha9219:
It is a non sds transfer switch,
I have spoke to both the city and electrical engineer and both have assured me that a ground rod is not necessary.
Click to expand...
That means the neutral is not switched, and the neutral in the generator is NOT bonded to the frame. Refer to Ed's first drawing.

However you can install a rod, lightning counterpoise, or any type of GES at the generator, no harm done, as long as you do not bond the neutral of the generator to the frame. Good luck

[ February 24, 2004, 02:52 PM: Message edited by: dereckbc ]
 
Re: grounding of generator

To any Elctrical Engineers out there...
how do you feel when a feild electrician where to question your work?
I get the feeling this one is tried of my RFI's already.
 
Re: grounding of generator

I have no problem with RFI's, as long as the answer is not obvious.
I had one two days ago;
Q: "Is LFMC required when connecting to the MCC?"
A: "Review Specification Section 16100 (Raceways) which requires RMC".
The installer just didn't want to look it up.
My favorite is an intelligent question that shows the guy is thinking.

[ February 24, 2004, 08:39 PM: Message edited by: ron ]
 
Re: grounding of generator

Ron and others. this is like the old saying that it is not always easy inside looking out as it is outside looking in. and to us it might seem like an easy question but to others who haven't gone through the schooling and years of experience, it could be rocket science to them. I kid around allot but there is never a dumb question. we all at one time or another probably ask these same questions. They only seem like RFI now.
 
Re: grounding of generator

Originally posted by hurk27:
Ok now I got a dumb question what in the heck does RFI stand for? I know your not talking about radio frequency interference? LOL :D
Click to expand...
Not a dumb question if you have not used them before.

An RFI is official paper work for documenting you asked a question of an Architect. GC Engineer, etc.

A C.Y.A document. :D

Request For Information.

We write, keep a copy send it to the GC keeps a copy and sends it on to the appropriate person.

The person answers it and it comes back to us via the GC so any changes are well documented. :cool:

[ February 25, 2004, 08:55 AM: Message edited by: iwire ]
 
Re: grounding of generator

Originally posted by ron:
I have no problem with RFI's, as long as the answer is not obvious.
I had one two days ago;
Q: "Is LFMC required when connecting to the MCC?"
A: "Review Specification Section 16100 (Raceways) which requires RMC".
The installer just didn't want to look it up.
My favorite is an intelligent question that shows the guy is thinking.
Click to expand...
Some times the shoe is on the other foot.
I recently sent an RFI to an enginner as follows:
Q: I dont' have a conduit at the gen set from "EQ: panel. I do however have one from "DL".Can I take ckt 2,4,6, out of panel "EQ" and feed them from Panel "DL"?
A: NO You can not have "EQ" ckts in "DL" panel :mad: It took 6 RFIs and three phone callls to get an answer
 
Re: grounding of generator

Originally posted by hurk27:
Ok now I got a dumb question what in the heck does RFI stand for? I know your not talking about radio frequency interference? LOL :D
Click to expand...
The only dumb question is one not asked. We keep two pads on the job RFIs and feild change orders
it helps to solve probles quicker and also lets the GC know how much & who pays, and keeps us from getting stuck :cool:
 
Re: grounding of generator

Wayne, RFI, Request For Information.

I echo Ron's comments, I do not mind them at all unless the info is contained in the spec's and not in error. I do not get a lot of them as I have had the privilage of working with the same contractors from job-to-job. So these guys know my designs and have saved my butt a few times.
 
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