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Separating and isolating neutrals in sub panels


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Good morning everyone,

I had an inspection on a house the other day that is pushing 50 yrs old. The house was wired with a three wire system and has a main service disconnect on the exterior wall with a sub-panel about fifty feet away in the center of the home. The neutrals and grounds are sharing the same lug bars and in some instances, the same lug. I recommended separating and isolating the neutrals in the sub-panel. The listing agent had an electrician look at it and said that separation was not necessary. Would anyone care to elaborate on this topic?

Thanks,

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250.24(A)(5);

A grounded conductor shall not be connected to normally non-current-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.

Marc

EDIT: I couldn't find any building codes enacted by the state. It might be county enacted/enforced. Which county are you in?

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Mark,

Thanks for the feedback. Yes you are correct, there are no state requirements. Only seven or eight conties in the whole state have any type of code enforcment laws enacted. The county that the house is located in is one of the counties thave have code inforcement. Pearl River Co. enacted code inforcment back in 06 after Katrina. They follow the 06 addition of the IRC. The county said that is how it was done before they enacted the code. They said that unless they have a reason to inspect a home such as:

A.) Any alteration of service.

B.) More than 50% of the house is under construction.

C.) If the house has been unoccupied.

That it should be considered grandfathered in. I was always under the impression that it has never been allowed. Where is your refrence pulled from?

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08' NEC.

Since you're a home inspector, you can still argue that the dual bonding of the grounding conductor to the neutral causes the neutral current to be divided between the two rather than carried by just the neutral. A poor connection involving any portion of the neutral that is parallel to the grounding conductor could result in most if not all of the neutral current being conducted through the grounding conductor instead. That ground wire is much smaller than the neutral. There's no breaker on it. It'll just heat up until temperatures reach ignition values or the wire melts.

Forget the sparky and code official. It's unsafe. Use my argument neighbor.

Marc

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Good morning everyone,

I had an inspection on a house the other day that is pushing 50 yrs old. The house was wired with a three wire system and has a main service disconnect on the exterior wall with a sub-panel about fifty feet away in the center of the home. The neutrals and grounds are sharing the same lug bars and in some instances, the same lug. I recommended separating and isolating the neutrals in the sub-panel. The listing agent had an electrician look at it and said that separation was not necessary. Would anyone care to elaborate on this topic?

Thanks,

In the world of real estate transactions, people often forget that there's a big difference between, "this thing is wrong and should be corrected," and, "the seller must correct this thing." Agents, buyers, and sellers always want us to help them with the second thing, but we can really only help with the first.

Regarding the first thing:

* It wasn't allowed 50 years ago and it's not allowed today.

* It was done *all the time*.

* Someone should probably fix it.

Regarding the second thing:

* If the seller doesn't want to fix it, he should just say so. Heck, I would. Most sellers are "out of the house" long before they're out of the house. The last thing that they want to do is fix up the house for someone else.

If I were the seller, I'd just say, "Yeah, too bad about that. Well, have fun fixing it. I'm outta here."

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In the world of real estate transactions, people often forget that there's a big difference between, "this thing is wrong and should be corrected," and, "the seller must correct this thing." Agents, buyers, and sellers always want us to help them with the second thing, but we can really only help with the first.

Regarding the first thing:

* It wasn't allowed 50 years ago and it's not allowed today.

* It was done *all the time*.

* Someone should probably fix it.

Regarding the second thing:

* If the seller doesn't want to fix it, he should just say so. Heck, I would. Most sellers are "out of the house" long before they're out of the house. The last thing that they want to do is fix up the house for someone else.

If I were the seller, I'd just say, "Yeah, too bad about that. Well, have fun fixing it. I'm outta here."

Jim,

From the words you wrote, it sounds like you were party to this happening. The seller originally agreed to have it fixed and the electrician started to balk saying, "that's just how they have done things around here" and preceeded to tell me that he would have to run a whole new wire from the main panel in order to accomplish what I was requesting. I got tired of arguing with him and told him to write a letter of safety clearance and attach his licence number so I could move on. I knew I was right, my mistake was just not forcing the issue. That will never happen again.

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Jim,

From the words you wrote, it sounds like you were party to this happening. The seller originally agreed to have it fixed and the electrician started to balk saying, "that's just how they have done things around here" and preceeded to tell me that he would have to run a whole new wire from the main panel in order to accomplish what I was requesting. I got tired of arguing with him and told him to write a letter of safety clearance and attach his licence number so I could move on. I knew I was right, my mistake was just not forcing the issue. That will never happen again.

The electrician is right about having to run a whole new cable (or wires, if they're in conduit). There's no way around that.

In these kinds of discussions, I try to keep the "this thing is wrong" discussion separate from the "seller should fix this thing" discussion. When I make that distinction, the tradesman & I usually agree pretty readily about the first part. Most of the time, his objection is that he thinks that it's unfair that the seller should have to pay for the repairs. I try to gently remind him that it's not his call and that the issue has already been negotiated and agreed to.

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Jim,

From the words you wrote, it sounds like you were party to this happening. The seller originally agreed to have it fixed and the electrician started to balk saying, "that's just how they have done things around here" and preceeded to tell me that he would have to run a whole new wire from the main panel in order to accomplish what I was requesting. I got tired of arguing with him and told him to write a letter of safety clearance and attach his licence number so I could move on. I knew I was right, my mistake was just not forcing the issue. That will never happen again.

The electrician is right about having to run a whole new cable (or wires, if they're in conduit). There's no way around that.

In these kinds of discussions, I try to keep the "this thing is wrong" discussion separate from the "seller should fix this thing" discussion. When I make that distinction, the tradesman & I usually agree pretty readily about the first part. Most of the time, his objection is that he thinks that it's unfair that the seller should have to pay for the repairs. I try to gently remind him that it's not his call and that the issue has already been negotiated and agreed to.

Very well put.

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  • 2 weeks later...

This was a change in the 2008 NEC 250.32, if it was installed before this code went into effect it would be grandfathered.

Also correct a (4) wire would have to be run to the panel or there will be nothing to carry the fault current.

Read it again. This is a subpanel in the house, not a separate garage.

What you just posted is wrong, AFAIK.

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This was a change in the 2008 NEC 250.32, if it was installed before this code went into effect it would be grandfathered.

Also correct a (4) wire would have to be run to the panel or there will be nothing to carry the fault current.

Read it again. This is a subpanel in the house, not a separate garage.

What you just posted is wrong, AFAIK.

Does not matter, answer applies to a feeder(sub) panel, or a separate structure. In the 2008 NEC it does not allow to re-bond after the service( 1st over current device).

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This was a change in the 2008 NEC 250.32, if it was installed before this code went into effect it would be grandfathered.

Also correct a (4) wire would have to be run to the panel or there will be nothing to carry the fault current.

Read it again. This is a subpanel in the house, not a separate garage.

What you just posted is wrong, AFAIK.

Does not matter, answer applies to a feeder(sub) panel, or a separate structure. In the 2008 NEC it does not allow to re-bond after the service( 1st over current device).

I think you are misunderstanding my point. I am saying this rule was code long before 2008 and I am not even in the USA. There is no rule to grandfather bonding the neutral at the sub. The electrician is wrong to say it is OK, or that it was OK before.
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This was a change in the 2008 NEC 250.32, if it was installed before this code went into effect it would be grandfathered.

Also correct a (4) wire would have to be run to the panel or there will be nothing to carry the fault current.

Read it again. This is a subpanel in the house, not a separate garage.

What you just posted is wrong, AFAIK.

Does not matter, answer applies to a feeder(sub) panel, or a separate structure. In the 2008 NEC it does not allow to re-bond after the service( 1st over current device).

Exactly where, in the 2005 and earlier editions, do you think it says that it's ok to bond the neutral to the ground in a subpanel in the same house?

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There is no where it says its OK to do it, there was no where that said you can't do it prior to 2008.

250.32 Buildings or Structures Supplied by a

Feeder(s) or Branch Circuit(s)

(B) Grounded Systems.

(1) Supplied by a Feeder or Branch Circuit. An equipment

grounding conductor, as described in 250.118, shall be

run with the supply conductors and be connected to the

building or structure disconnecting means and to the grounding

electrode(s). The equipment grounding conductor shall

be used for grounding or bonding of equipment, structures,

or frames required to be grounded or bonded. The equipment

grounding conductor shall be sized in accordance with

250.122. Any installed grounded conductor shall not be connected

to the equipment grounding conductor or to the

grounding electrode(s).

Exception: For installations made in compliance with previous

editions of this Code that permitted such connection,

the grounded conductor run with the supply to the building

or structure shall be permitted to serve as the ground-fault

return path if all of the following requirements continue to

be met:

(1) An equipment grounding conductor is not run with the

supply to the building or structure.

(2) There are no continuous metallic paths bonded to the

grounding system in each building or structure involved.

(3) Ground-fault protection of equipment has not been installed

on the supply side of the feeder(s).

Section 250.32(B) requires the installation of an equipment

grounding conductor with all feeders and branch circuits

that supply a building or structure. Using the grounded conductor

to ground equipment, in lieu of installing a separate

equipment grounding conductor, creates parallel paths for

normal neutral current along metal raceways, metal piping,

metal cable sheaths or shields, and other metal structures

such as ductwork. Installing an equipment grounding conductor

with the supply circuit conductors helps ensure that

normal circuit current is not imposed on continuous metal

paths other than the insulated grounded or neutral conductor.

At a building or structure supplied by a feeder or branch circuit,

the equipment grounding conductor is connected to the

grounding electrode system [unless the installation complies

with 250.32(A), Exception] in the equipment supplied by

the feeder or branch circuit. Where installed, the grounded

or neutral conductor is electrically isolated from the equipment

grounding conductor and any grounding electrodes at

the building or structure supplied by the feeder or branch

circuit as illustrated in Exhibit 250.19.

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Sounds like someone has just realized he's been screwing up for a while and now he's trying to rationalize his mistake by working overtime to create implied exceptions to the code.

Just sayin'

ONE TEAM - ONE FIGHT!!!

Mike

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There is no where it says its OK to do it, there was no where that said you can't do it prior to 2008.. . .

Actually there is. Check 250.24(A)(5), which says, "Except as permitted in 250.30(A)(1) and 250.32(B), a grounded circuit conductor shall not be used for grounding non-current-carrying metal parts of equipment on the load side of the service disconnecting means or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.

The exceptions listed in the section and the exceptions that follow it have nothing to do with sub panels in the same building.

This prohibition, by the way, goes back at least as far as 1923.

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