letsdoitright

[letsdoitright]

hole house generator with auto transfer switch in basement. unit sitting out side next to service meter. we used the same ground rod as the service for the generator putting the bare copper under ground 4 ft back to the rod. inspector
failed it said it had to have its own rod. and that the generator ground should not be tie to the water line. can some one explain this to me.

 

[electricalperson]

if the generator is not a seperatly derived system (switches neutral conductor) then all it needs is an equipment ground and doesnt require a ground rod of its own. you can drive a ground rod if you want but no where in the NEC does it say you need a ground rod for an optional standby generator

 

[augie47]

adding my 2 cents to electricalpersons post.

On a few installations, I hae seen where the gen mfg. asks for a ground rod (this would be in addition to the EGC ep mentioned).

I know of no Code limitation on using the same ground rod, as you did.

No idea where the "water line" comment comes from. Unless some one here shows you (us), I'd ask for a Code Refreence.

I'm not sure I've ever seen a residential gen. set-up wityh a switched neutral. If this happens to be one, then you would need to traet it a a SDS (250.30(A)(3).

 

[electricalperson]

adding my 2 cents to electricalpersons post.

On a few installations, I hae seen where the gen mfg. asks for a ground rod (this would be in addition to the EGC ep mentioned).

I know of no Code limitation on using the same ground rod, as you did.

No idea where the "water line" comment comes from. Unless some one here shows you (us), I'd ask for a Code Refreence.

I'm not sure I've ever seen a residential gen. set-up wityh a switched neutral. If this happens to be one, then you would need to traet it a a SDS (250.30(A)(3).

then if the manufacturer wants a ground rod thats where 110.3B might come into play.

 

[AKwiring]

Should the two ground rods be bonded or kept completely separate?

 

[electricalperson]

Should the two ground rods be bonded or kept completely separate?

250.54 talks about auxillary ground rods. you only need one and there not required to be bonded to the system ground

 

[augie47]

AK, thats a really good question.
250.50 would lead me to say yes, but 250.54 leads me the other way.
My opinion, and it's only that, would be if it's an electrode added per mfg (110.3) you would not need to bond the two together. If it's a SDS electrode, you would.
I'll be interested to other, more learned, persons comments.

sorry ep, I was typing as you answered

for a "newbie" he asked a good question, didn't he?

 

[electricalperson]

AK, thats a really good question.
250.50 would lead me to say yes, but 250.54 leads me the other way.
My opinion, and it's only that, would be if it's an electrode added per mfg (110.3) you would not need to bond the two together. If it's a SDS electrode, you would.
I'll be interested to other, more learned, persons comments.

sorry ep, I was typing as you answered

for a "newbie" he asked a good question, didn't he?

all questions are good if the person doesnt understand something. never be afraid to ask questions. i ask them all the time :grin: i was a little confused about generators when i started wiring them. they all come with lugs on the side of them but the ones i hook up dont mention anything about ground rods. probably just a personal preference or if an engineer or something specs it but its not an NEC to put ground rods on standard generators for houses

 

[letsdoitright]

if the generator is not a seperatly derived system (switches neutral conductor) then all it needs is an equipment ground and doesnt require a ground rod of its own. you can drive a ground rod if you want but no where in the NEC does it say you need a ground rod for an optional standby generator

it dose not switch the neutral or the ground

 

[eprice]

it dose not switch the neutral or the ground

In that case, it is not a separatly derived system. Section 250.30 does not apply. A separate grounding electrode for the generator is not required (unless the manufacturer requires it). If a separate ground rod is driven, either because you want to, or the manufacturer requires it, then it would be a supplementary grounding electrode covered under 250.54. It is not required to be bonded to the grounding electrodes used for the service and it may not be connected to the grounded conductor at the generator or a violation of 250.24(A)(5) will result.

The inspector may not understand the differance between a generator that is a separately derived system and one that is not. Ask him for a code reference requiring the additional rod. If he cites 250.32, refer him to the definition of "Separately Derived System" and point out that the non-switched grounded conductor (neutral) specificaly makes your installation not a separately derived system.

 

[RUWired]

It could be that the generator pad is considered a structure and an electrode would be required.This would only be tied into the frame and the ground wire.
Rick

 

[electricalperson]

It could be that the generator pad is considered a structure and an electrode would be required.This would only be tied into the frame and the ground wire.
Rick

around here i rarely put a generator pad for residental. i just dig a little grass out, put down that black paper to stop weeds and fill it with gravel. the generators usually come with a plastic pad built on them. the larger generators might need a pad. usually we install 16kva and under. i got a 10kva at my house

 

[SegDog]

last generator grounded/grounding/bonded/bonding thread

last generator grounded/grounding/bonded/bonding thread

As I am trying to get my mind around (small as it may be) the entire business of generator grounded (neutral) and GES issues, I am making a list of points:

1. if the generator is wired (plugs) into a premises (dwelling) grounded (neutral), then only in ONE place can the grounded (neutral) and grounding system be connected. Usually at the first disconnect (circuit breaker panel) ONLY ONE - check

2. if the generator transfer switch switches the grounded (neutral) and the generator powers selected premises (dwelling) circuits, then it is a Separately Derived System (SDS) and attention should be paid to insure that the grounded (neutral) and grounding system is connected in one place, on-board the generator. ONLY ONE - check

Here's the rub -

3. the generator is in close proximity to a building, premises (dwelling); why not use the existing GES (grounding electrode system) to ground the generator and generator chassis??? If an argument is made that the existing GES is connected to the existing premises (dwelling ) wiring, and a separate electrode should be installed to insure a completely isolated set-up, I still can't see it (equipotential-wise), but I can understand the possibility of creating a loop.

4. in the case where the generator doesn't involve the premises (dwelling) wiring, and the generator is just used to power one or two pieces of equipment, e.g. - refrigerator, beer-meister, and is using an extension-cord set-up, I can buy the argument of no rod, unless the manufacturer requires. (no connection to existing electrode) But does it not create a problem with equipotential still, and does it hurt to bond-on to the existing GES???

5. I am intentionally staying away from non-building situations, for now; i.e. RV, motorhome, carnival.

I'm starting to get loopy now, so I'm letting this fly.

THANKS in advance

 

[stretch12]

does the genny switch or break the grounded conductor?

 

[SegDog]

better wording...

better wording...

I should have started by saying that the connections and switching are properly executed. There is no argument or confusion about "single-point, grounded and grounding connection".

Whether a SDS or non-switched (solid) grounded (neutral) is a better way-to-go is academic, in my view, as long as you can determine what you have and know what to do next.

Grounded (neutral) switching?
1. no
2. yes
3. optional
4. not applicable

 

[winnie]

It is not required to be bonded to the grounding electrodes used for the service and it may not be connected to the grounded conductor at the generator or a violation of 250.24(A)(5) will result.

Could you clarify for me: when you say that this electrode is 'not required to be bonded', you mean that it doesn't require a separate bonding jumper. I presume that this electrode must be tied to the EGC that is part of the generator circuit, and thus does end up bonded to the grounding electrode system. Or am I misunderstanding the code in this case?

-Jon

 

[K8MHZ]

hole house generator with auto transfer switch in basement. unit sitting out side next to service meter. we used the same ground rod as the service for the generator putting the bare copper under ground 4 ft back to the rod. inspector
failed it said it had to have its own rod. and that the generator ground should not be tie to the water line. can some one explain this to me.

You may have misunderstood the inspector. He may be telling you that you can't use the water line as the grounding electrode as you have to use a grounding rod (or two) instead.

All grounding electrodes on a premises should be bonded together for equipotentiality but in some cases it is not practical.

I just talked to an inspector about a fixed generator that I was going to do some work on. He said that the metal on the generator should have a ground rod, a three wire feed could be run to the house and the ground / neutral connection should be made at the panel, not in the generator. He did not require the electrodes to be bonded in this case (the generator is over 100 feet from the house).

The requirement for the neutral to be switched has been an issue on some jobs where a portable generator was used and the generator had been bonded internally by the manufacturer. The requirement was so that if the generator was connected but not used there still would only exist one bonding point.

As more and more people use generators, I wish the NEC would be easier to understand. The requirements for generators seem to vary and the differences between requirements for fixed, portable and vehicle mounted generators should be made clearer, IMHO, and not rely on bouncing from chapter to chapter in the book.

 

[eprice]

Could you clarify for me: when you say that this electrode is 'not required to be bonded', you mean that it doesn't require a separate bonding jumper. I presume that this electrode must be tied to the EGC that is part of the generator circuit, and thus does end up bonded to the grounding electrode system. Or am I misunderstanding the code in this case?

-Jon

I think that the electrode in this case would fall under 250.54 as a supplementary grounding electrode. That section specifically exempts it from the requirement in 250.50 that it be bonded to the other electrodes in the grounding electrode system. It will be connected to the EGC, so it will end up being bonded to the grounding electrode system indirectly.