# generators



## elec 1 (Dec 31, 2010)

I had an inspector look at a generator we installed on a project. He said that sinse we did not ground at the gen.,we should have sized the ground cond. per grnd. electrode.The xfer sw. is three pole (solid neutral).He was not real sure about it so he asked me to research and he will do the same.Can you clarify


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## 480sparky (Sep 20, 2007)

Say what??!?! The inspector wants you to do his job for him? :001_huh:


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## McClary’s Electrical (Feb 21, 2009)

elec 1 said:


> I had an inspector look at a generator we installed on a project. He said that sinse we did not ground at the gen.,we should have sized the ground cond. per grnd. electrode.The xfer sw. is three pole (solid neutral).He was not real sure about it so he asked me to research and he will do the same.Can you clarify


 
What do you mean "did not ground at the genny"

Do you mean you did not drive a ground rod?


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## Rap2 (Dec 17, 2010)

our inspectors insist on a unbroken ground from any generator including PV inverters directly to the GEC. However on this last job I did we were permitted to split bolt other PV inverters to that same unbroken run... which makes no sense to me....


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## jwjrw (Jan 14, 2010)

So you are saying this is not a separately derived system?


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## william1978 (Sep 21, 2008)

jwjrw said:


> Are you saying the neutral is not switched?


 Yes, a 3 pole transfer switch doesn't switch the neutral. A 4 pole is switching the neutral.


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## jwjrw (Jan 14, 2010)

william1978 said:


> Yes, a 3 pole transfer switch doesn't switch the neutral. A 4 pole is switching the neutral.



I thought he said 3 phase....:no:.....are you gonna answer his question William or what?


What code cycle are you on?


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## william1978 (Sep 21, 2008)

jwjrw said:


> I thought he said 3 phase....:no:.....are you gonna answer his question William or what?
> 
> 
> What code cycle are you on?


 What are you talking about? He did say 3 phase. 

2008 if that matters.


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## jwjrw (Jan 14, 2010)

william1978 said:


> What are you talking about? He did say 3 phase.
> 
> 2008 if that matters.



I'm saying when I originally read the thread I thought he said 3 phase genny not 3 pole transfer switch.
Speed reading strikes again.

And then I was asking the OP what code cycle he was on.


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## McClary’s Electrical (Feb 21, 2009)

elec 1 said:


> (solid neutral)





jwjrw said:


> So you are saying this is not a separately derived system?


 


He answered that


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## jwjrw (Jan 14, 2010)

mcclary's electrical said:


> He answered that



I was making sure that is what he meant by "solid neutral". I know what I think he is asking but it is not clear in his OP.


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## jwjrw (Jan 14, 2010)

mcclary's electrical said:


> What do you mean "did not ground at the genny"
> 
> Do you mean you did not drive a ground rod?



This is what I was talking about. He is not clear in his OP what he is talking about.


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## McClary’s Electrical (Feb 21, 2009)

jwjrw said:


> I was making sure that is what he meant by "solid neutral". I know what I think he is asking but it is not clear in his OP.


 

I was just being a smart azz:laughing:


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## jwjrw (Jan 14, 2010)

mcclary's electrical said:


> I was just being a smart azz:laughing:




I'm so dumb I can't be a smart azz anymore.:laughing:


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## elec 1 (Dec 31, 2010)

yes, what I meant was we did not drive ground rod. and yes it is not a seperately derived syst. in retrospect, what we did does seem wrong because we have a neutral and a ground conductor from the gen. to xfer sw. and at the gen. they are attached to the same neutral bus. I believe the right answer is to drive a ground rod and attach to neutral at gen. but my knowledge of gen. is limited


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## jwjrw (Jan 14, 2010)

elec 1 said:


> yes, what I meant was we did not drive ground rod. and yes it is not a seperately derived syst. in retrospect, what we did does seem wrong because we have a neutral and a ground conductor from the gen. to xfer sw. and at the gen. they are attached to the same neutral bus. I believe the right answer is to drive a ground rod and attach to neutral at gen. but my knowledge of gen. is limited



What code cycle you on?


Last one I did I ran a #4 bare from GES of service to frame of genny I believe. It's been a while. I just went and looked at some pics of the last one we did. It was a SDS as the neutral was switched in transfer switch.


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## McClary’s Electrical (Feb 21, 2009)

elec 1 said:


> yes, what I meant was we did not drive ground rod. and yes it is not a seperately derived syst. in retrospect, what we did does seem wrong because we have a neutral and a ground conductor from the gen. to xfer sw. and at the gen. they are attached to the same neutral bus. I believe the right answer is to drive a ground rod and attach to neutral at gen. but my knowledge of gen. is limited


 
The ground rod, and generator frame should be together on the grounding conductor. The grounded conductor should be isolated IMO

I drive a ground rod because I consider a GEN a seperate structure, not because I consider it a seperately derived system.


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## jwjrw (Jan 14, 2010)

mcclary's electrical said:


> The ground rod, and generator frame should be together on the ground wire. The grounded conductor should be isolated IMO
> 
> I drive a ground rod because I consider a GEN a seperate structure, not because I consider it a seperately derived system.




Most of the gennys we do are for sewer lift pump stations. We usually have one heck of a GES with all the concrete rebar and unistrut that the equipment is mounted to so we just attach to that. A rod is never a bad idea.


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## brian john (Mar 11, 2007)

william1978 said:


> What are you talking about? He did say 3 phase.
> 
> 2008 if that matters.


Actually he said 3 POLE SOLID NEUTRAL and most REASONABLE electricians would assume 3 phase...BUT who knows without a clarification form the OP!


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## elec 1 (Dec 31, 2010)

Thanks for all the input guys. Let me clarify some things. What I've got is a 150 KVA gen set to back up Panel "EM" 120/208 3 phase service with a 3 pole xfer sw. meaning it breaks the three phase conductors but not the neutral or grounded conductor.I believe the issue is when there is a ground fault, where is the fault current flowing to ground. If it is through the neutral, then there is the risk of back feeding to power co xfrmr through xfer sw


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