Service bonding question

[Strathead]

OK maybe this has been asked. I was looking for a Mike Holt picture (I thought I saw once) that covered this installation and I can only find similar so here goes:

• Overhead service in RMC to the meter enclosure.
• Grounding electrode conductor brought to the meter and bonded to neutral which is in turn factory bonded to the meter enclosure.
• conductors now must leave the meter enclosure and travel to the Service Disconnect.
• Unless this is wrong, the grounded conductor and the service enclosure and hence the "ground bus" must be bonded together in the service enclosure per 250.24 (B) regardless of where the along the service conductors the grounding electrode connection is made.

And my multipart question.

1. Does there need to be a grounding equipment conductor between the meter enclosure and the service enclosure?
2. If yes, then why is such a big deal made out of "parallel ground paths" when this one is OK?
3. I can see by many MH examples that the parallel paths is OK because he shows metal conduit between the items. So my real question is whether a 3 conductor SE cable or PVC conduit is OK between the meter enclosure and the service enclosure since there is a fault path between them via the grounded conductor bonded at both devices?

We are going around and around about this and the code really chases you back and forth. Please try to reference code that clears this up if you can.

 

[HackElectric]

My local PoCo helps clear this up by not allowing any grounding in the meter pan. We bring the GEC from the ground rods and/or ISBB inside to the main disconnect.

 

[GoldDigger]

There are several places that the bond which is required at (or near) the service disconnect can be made. One of them is at the meter enclosure.
If the required bond is made at the meter enclosure and a non-metallic raceway (not usable as EGC) joins the meter enclosure to the disconnect enclosure, then you can, I believe, either run an EGC between the two and isolate the neutral from ground at the service disconnect or add an additional bond at the service disconnect.
If the two enclosures are joined by a metallic raceway that can serve as an EGC, then no redundant bond is allowed at the service enclosure.

JMO, of course.

 

[Strathead]

There are several places that the bond which is required at (or near) the service disconnect can be made. One of them is at the meter enclosure.
If the required bond is made at the meter enclosure and a non-metallic raceway (not usable as EGC) joins the meter enclosure to the disconnect enclosure, then you can, I believe, either run an EGC between the two and isolate the neutral from ground at the service disconnect or add an additional bond at the service disconnect.
If the two enclosures are joined by a metallic raceway that can serve as an EGC, then no redundant bond is allowed at the service enclosure.

JMO, of course.

My interpretation of 250.24 (B) is that you actually can't separate the neutrals and the grounds at the service disconnect, because it states that there will be a bonding jumper in the enclosure and in a separate section it states that the ground conductor must be bond metal that may become energized to the grounding system. As such the neutral and the ground will always be at the same potential in the service disconnect.

Anyone please enlighten me if I am wrong.

 

[Smart $]

1. I think you got the words of the terminology out of order. No EGC required between meter and disconnect. FWIW, there is never an EGC on the line side of service equipment. If there is a grounding conductor, it would be an equipment bonding jumper (EBJ).

2. N/A per answer to #1

3. For a grounded system, no [extra] grounding conductor is required, regardless of the wiring method. All non-current-carrying metal is bonded to the grounded conductor. Only ungrounded systems require a bonding jumper on the line side of the service disconnecting means, which for obvious reasons is electrically isolated from all circuit conductors.

Refer to 250.92

 

[HackElectric]

There are several places that the bond which is required at (or near) the service disconnect can be made. One of them is at the meter enclosure.
If the required bond is made at the meter enclosure and a non-metallic raceway (not usable as EGC) joins the meter enclosure to the disconnect enclosure, then you can, I believe, either run an EGC between the two and isolate the neutral from ground at the service disconnect or add an additional bond at the service disconnect.
If the two enclosures are joined by a metallic raceway that can serve as an EGC, then no redundant bond is allowed at the service enclosure.

JMO, of course.

I've noticed that in the territory below where I normally work, the PoCo allows grounding in the meter pan unlike my PoCo.

What I have seen many times is a grounding conductor attached to the lug in the meter pan, then run thru a bonding bushing on the rigid pipe service raceway, and then brought thru the service raceway into the main panel where it lands on the ground/neutral bar. There is also the neutral running thru the service raceway which means there are 3 parallel paths.

 

[Smart $]

I've noticed that in the territory below where I normally work, the PoCo allows grounding in the meter pan unlike my PoCo.

What I have seen many times is a grounding conductor attached to the lug in the meter pan, then run thru a bonding bushing on the rigid pipe service raceway, and then brought thru the service raceway into the main panel where it lands on the ground/neutral bar. There is also the neutral running thru the service raceway which means there are 3 parallel paths.

It's amazing how many electricians do not know how to properly bond service equipment, or get influenced by what other electricians do... :happyyes:

 

[HackElectric]

It's amazing how many electricians do not know how to properly bond service equipment, or get influenced by what other electricians do... :happyyes:

It's more amazing that electrician do what the PoCo wants so that they connect the customer's house to the grid.

Every house that I have seen with the setup I mentioned in my last post has been inspected by both the municipal inspector and a JCP&L wiring inspector.

 

[Smart $]

It's more amazing that electrician do what the PoCo wants so that they connect the customer's house to the grid.

Every house that I have seen with the setup I mentioned in my last post has been inspected by both the municipal inspector and a JCP&L wiring inspector.

I've never run into a situation where the POCO requires something non-compliant with the NEC... so cannot fathom this aspect of non-compliance. When I hear of such, I think it is because the electricians (and AHJ) don't challenge the POCO.

 

[mwm1752]

If your meter grounded conductor is bonded to the frame by the grounded conductor terminal (as in most cases) then;
1- use a non metallic raceway & bond the grounded conductor to the electrode conductor to the disconnect enclosure or
2- your EC is bonded to the meter enclosure, with a metallic raceway, bond raceway to enclosure but do not bond grounded conductor or
3- your EC is bonded to the meter enclosure with a non metallic raceway, bond raceway with EGC to enclosure but do not bond grounded conductor or
4- use a metallic raceway, bond raceway to EC & enclosure but do not bond grounded conductor.

if EC is bonded to the meter enclosure,it is non compliant with 250.64(D)(3)(only states to connect the EC on load side of main)

 

[GoldDigger]

...if EC is bonded to the meter enclosure,it is non compliant with 250.64(D)(3)(only states to connect the EC on load side of main)

If the grounded conductor is bonded to earth on the POCO side of service point, that is a POCO and NESC issue and in general they can bond it as many times as they want in as many places as they want.
NEC picks up at the service demarcation point, which may or may not be the same as the service disconnect.

 

[Strathead]

1. I think you got the words of the terminology out of order. No EGC required between meter and disconnect. FWIW, there is never an EGC on the line side of service equipment. If there is a grounding conductor, it would be an equipment bonding jumper (EBJ).

2. N/A per answer to #1

3. For a grounded system, no [extra] grounding conductor is required, regardless of the wiring method. All non-current-carrying metal is bonded to the grounded conductor. Only ungrounded systems require a bonding jumper on the line side of the service disconnecting means, which for obvious reasons is electrically isolated from all circuit conductors.

Refer to 250.92

For #1, somewhat intentionally I used that word because the entire purpose would be that stated in the definition of and EGC and definitely not the definition of the EBJ in article 100

Anyway, splitting hairs am I correct to assume that you say my above scenario with PVC conduit with 2 hots and a grounded conductor between meter and service disconnect is OK?

 

[Strathead]

If your meter grounded conductor is bonded to the frame by the grounded conductor terminal (as in most cases) then;
1- use a non metallic raceway & bond the grounded conductor to the electrode conductor to the disconnect enclosure or
2- your EC is bonded to the meter enclosure, with a metallic raceway, bond raceway to enclosure but do not bond grounded conductor or
3- your EC is bonded to the meter enclosure with a non metallic raceway, bond raceway with EGC to enclosure but do not bond grounded conductor or
4- use a metallic raceway, bond raceway to EC & enclosure but do not bond grounded conductor.

if EC is bonded to the meter enclosure,it is non compliant with 250.64(D)(3)(only states to connect the EC on load side of main)

Very cryptic. I either don't understand or I don't agree with you. A couple points that I mean. Mike Holt clearly shows, bonded at or before the meter, with metal raceways, no ground conductor and the neutral and ground bonded in the service enclosure. Also as I stated before it is very clear to me that there must be a bonding jumper in the Service disconnect. It looks like you say no in item #4

BTW I have no idea what EC stands for. I thought it might be electrode conductor but I am not sure.

 

[mwm1752]

If the grounded conductor is bonded to earth on the POCO side of service point, that is a POCO and NESC issue and in general they can bond it as many times as they want in as many places as they want. transformer always but no EGC is run with the service lateral.
NEC picks up at the service demarcation point, which may or may not be the same as the service disconnect.

I have not experienced a utility that owned or recognized a demarcation point after the service disconnect and usually not after the unfused service enters a structure. I will correct myself as recognizing the meter base not being under NEC code as it is prior to the demarcation point.

 

[Smart $]

For #1, somewhat intentionally I used that word because the entire purpose would be that stated in the definition of and EGC and definitely not the definition of the EBJ in article 100

You are technically correct. It would simply be a bonding conductor or jumper. I tens to add the "equipment" on the front because that is all it would be doing for an ungrounded system.

Anyway, splitting hairs am I correct to assume that you say my above scenario with PVC conduit with 2 hots and a grounded conductor between meter and service disconnect is OK?

Yes. In fact it is the preferred method of those that take 250.6 literally.

 

[mwm1752]

Very cryptic. I either don't understand or I don't agree with you. A couple points that I mean. Mike Holt clearly shows, bonded at or before the meter, with metal raceways, no ground conductor and the neutral and ground bonded in the service enclosure. Also as I stated before it is very clear to me that there must be a bonding jumper in the Service disconnect. It looks like you say no in item #4

BTW I have no idea what EC stands for. I thought it might be electrode conductor yes but I am not sure.

If your meter grounded conductor is bonded to the frame by the grounded conductor terminal 2 thru 4 would creat a parallel path if the grounded conductor was bonded to the disconnect frame -- The older meter base grounded conductor lugs were attached directly to the housing of the meter. The newer ones with a bypass might be different not sure.
Funny thing about electrical installations is that there are many installation methods to meet the intent of the code, which would be no parallel paths

 

[Smart $]

I have not experienced a utility that owned or recognized a demarcation point after the service disconnect and usually not after the unfused service enters a structure. I will correct myself as recognizing the meter base not being under NEC code as it is prior to the demarcation point.

A meter is not always prior to the service demarcation (NEC refers to it as Service Point). A meter base on the consumer side of the service point is excluded from being considered as service equipment.

 

[mwm1752]

Just trying to relate to the OP not every circumstance like cold sequencing

 

[Strathead]

If your meter grounded conductor is bonded to the frame by the grounded conductor terminal 2 thru 4 would creat a parallel path if the grounded conductor was bonded to the disconnect frame -- The older meter base grounded conductor lugs were attached directly to the housing of the meter. The newer ones with a bypass might be different not sure.
Funny thing about electrical installations is that there are many installation methods to meet the intent of the code, which would be no parallel paths

But that is the thing is that there are definitely legal service bonds that create parallel paths. See the attached illustration by Mike Holt. It clearly shows bonding in the gutter, meter and disconnect while it also shows metal conduits connecting everything. That is part of the reason I asked this question.

 

[Hendrix]

Anyway, splitting hairs am I correct to assume that you say my above scenario with PVC conduit with 2 hots and a grounded conductor between meter and service disconnect is OK?

I have done it that way for 40 years. I sure hope that I don't have to back track and re-do them all :happysad: