Bonding EMT on both ends

[K8MHZ]

On a new 100 amp service for a residential garage / storage building, the inspector wants both ends of the EMT going from the bottom of the meter socket to the bottom of the panel to be bonded with a bonding bushing. There already is a bonding bushing on the end inside the panel. In addition to that, he wants another one on the end inside the meter socket (property of the POCO) bonded to the neutral passing through the meter socket.

I have never heard of an inspector making such a requirement. The inspector in question is in the county next to mine and the service belongs to a friend, so this is an inspector I have never dealt with before, and it's not really my gig.

Adding a bonding bushing is no big deal. My concern is 'a', the inspector is trying to enforce a 'shirt pocket' rule, and 'b' doesn't that create an additional grounded to grounding conductor connection?

My other concern is making a connection that is not accessible, as it is inside a locked meter socket, and if the POCO even allows such a connection. I have a call into the POCO's site engineer to clear that up.

If adding the extra bonding connection is not a code violation nor is it a safety issue, I feel it is best to just make the correction and be done with it.

Is adding the extra bonding connection either of the above? My friend owns a farm and is getting a little antsy about the inspector holding up calling the POCO for a turn on, but did give him a 'pass' sticker.

I don't feel comfortable with recommending adding a bond that in my 18 years of being in the trade I have never seen done.

 

[ActionDave]

You are correct. Only need a bond bushing on one side of the EMT. With a standard meter socket it is impossible for the neutral not to be bonded.

He is just plain wrong. I would argue this one, the inspector needs to be educated or humbled.

 

[infinity]

As Dave said it's not required. A service raceway only requires bonding at one end because it is not being used as part of the fault current path.

 

[Smart $]

This inspector may not going by a shirt-pocket rule... but would be overly exuberant about enforcing the letter of the Code.

In short, service raceways are required to be connected to the grounded system conductor [250.80]. If the bonding jumper on the panel end is connected to the ground bus rather than the neutral bus, he may be thinking that technically does not comply with Code.

Another potential issue is his interpretation of bonding to ensure continuity. See definition of bonding jumper under 250.2 and associate with 250.4(A)(3) and 250.92. When you couple all that with some interpretations of ensuring a ground fault path, taking it to the degree that you could literally take the neutral conductor completely out between bond points and not experience any degradation in normal system performance... which exemplifies that a ground fault path has been ensured should that neutral conductor become compromised.

BTW, the immediately preceding concept is the other side of the debate that neutral current on normally non-current-carrying metals parts of the service is objectionable current.

 

[K8MHZ]

This inspector may not going by a shirt-pocket rule... but would be overly exuberant about enforcing the letter of the Code.

In short, service raceways are required to be connected to the grounded system conductor [250.80]. If the bonding jumper on the panel end is connected to the ground bus rather than the neutral bus, he may be thinking that technically does not comply with Code.

Another potential issue is his interpretation of bonding to ensure continuity. See definition of bonding jumper under 250.2 and associate with 250.4(A)(3) and 250.92. When you couple all that with some interpretations of ensuring a ground fault path, taking it to the degree that you could literally take the neutral conductor completely out between bond points and not experience any degradation in normal system performance... which exemplifies that a ground fault path has been ensured should that neutral conductor become compromised.

BTW, the immediately preceding concept is the other side of the debate that neutral current on normally non-current-carrying metals parts of the service is objectionable current.

The ground bus and neutral bus are one and the same in the panel. It's a SqD 100 amp Homeline. Green grounding screw properly used. If the panel was to have the grounding and grounded bus separate, an additional grounding bar would be required, which is not present. Neutral conductor and grounding conductors for branch circuits will be intermingled as usual on the grounded/ grounding bus.

It was also my contention that bonding as the inspector required would split the neutral current between conductors and bonded exposed EMT, thus creating an objectionable current.

 

[K8MHZ]

So am I correct that so far we have three 'no's and no 'yeses' as far as the inspector's performance is concerned?

(Sorry, AGT junkie.....)

 

[K8MHZ]

I just got off the phone with the POCO engineer and he said if his linesmen saw a bonding busing connected to their neutral in their socket they would not connect the service.

So the inspector is going to get a call from the POCO engineer to try to figure out what he is thinking.

Now, this is a rural county and the inspectors don't work there every day, so this may drag on for days. The inspector won't allow connection without the bond and the POCO won't connect it with the bond.

To make things worse, every time my friend has to use his phone he has to climb a pole as the phone is on top of the pole.

Not really....but the area does remind me of Hooterville, Pixley and Crabwell Corners.

 

[jap]

The inspector won't allow connection without the bond and the POCO won't connect it with the bond.

If that's the final stance, just let your friend know he's probably the only resident in the county that will need to survive without electricity.

JAP>

 

[Smart $]

The ground bus and neutral bus are one and the same in the panel. It's a SqD 100 amp Homeline. Green grounding screw properly used. If the panel was to have the grounding and grounded bus separate, an additional grounding bar would be required, which is not present. Neutral conductor and grounding conductors for branch circuits will be intermingled as usual on the grounded/ grounding bus.

It was also my contention that bonding as the inspector required would split the neutral current between conductors and bonded exposed EMT, thus creating an objectionable current.

Okay, so the EMT is bonded to the grounded neutral conductor at the panel end... and why I eluded to the second possibility. Lacking a formal concise definition, no one can truly say neutral current on exposed metal parts of service equipment is non-compliant.

 

[cowboyjwc]

Is there a concentric knock out at the bottom of the meter socket?

 

[K8MHZ]

Is there a concentric knock out at the bottom of the meter socket?

Yes .

 

[Smart $]

Is there a concentric knock out at the bottom of the meter socket?

Yes .

I see where you're going with this, but I don't believe there is any requirement that the bonding jumper be connected directly to the grounded conductor in that enclosure. You could just connect the jumper from fitting to the enclosure. The requirement of 250.90(B) first sentence just says "around impaired connections"... and the impaired connection is conduit to enclosure.

 

[K8MHZ]

I see where you're going with this, but I don't believe there is any requirement that the bonding jumper be connected directly to the grounded conductor in that enclosure. You could just connect the jumper from fitting to the enclosure. The requirement of 250.90(B) first sentence just says "around impaired connections"... and the impaired connection is conduit to enclosure.

The meter socket is solidly bonded to the POCO neutral.

The panel is bonded to the POCO neutral.

The EMT is bonded to the POCO neutral in the panel.

An inspector friend of mine told me that adding the second bonding bushing would create parallel neutrals of unequal construction which was a violation of the NEC. He said he would call me back when he gets to a code book with the article #.

Despite that, the Hooterville inspector called me and said he talked to the POCO engineer and they decided it would be OK to install the second bonding bushing and once that is done, the call to re-connect will be made.

So for the moment, the plan is to add the second bonding bushing.

Has anyone a clue as to any hazard that may be posed by such a parallel neutral? I know we don't like current on a raceway, but how, exactly, would this be a hazard? The owner is a friend of mine and I would like to assure him that adding the second bond is going to be safe.

Thanks!

 

[david]

The meter socket is solidly bonded to the POCO neutral.

The panel is bonded to the POCO neutral.

The EMT is bonded to the POCO neutral in the panel.

An inspector friend of mine told me that adding the second bonding bushing would create parallel neutrals of unequal construction which was a violation of the NEC. He said he would call me back when he gets to a code book with the article #.

Despite that, the Hooterville inspector called me and said he talked to the POCO engineer and they decided it would be OK to install the second bonding bushing and once that is done, the call to re-connect will be made.

So for the moment, the plan is to add the second bonding bushing.

Has anyone a clue as to any hazard that may be posed by such a parallel neutral? I know we don't like current on a raceway, but how, exactly, would this be a hazard? The owner is a friend of mine and I would like to assure him that adding the second bond is going to be safe.

Thanks!

Did the inspector ever say he wanted the bushing connected to anywhere other than the meter enclosure?

If it is metal conduit how does adding the bushing change the neutral current path when you said the neutral is solidly bonded to the enclosure.
All the inspector seems to be asking is for the knock outs to have a bonding bushing for fault current

 

[Smart $]

The meter socket is solidly bonded to the POCO neutral.

The panel is bonded to the POCO neutral.

The EMT is bonded to the POCO neutral in the panel.

An inspector friend of mine told me that adding the second bonding bushing would create parallel neutrals of unequal construction which was a violation of the NEC. He said he would call me back when he gets to a code book with the article #.

Despite that, the Hooterville inspector called me and said he talked to the POCO engineer and they decided it would be OK to install the second bonding bushing and once that is done, the call to re-connect will be made.

So for the moment, the plan is to add the second bonding bushing.

Has anyone a clue as to any hazard that may be posed by such a parallel neutral? I know we don't like current on a raceway, but how, exactly, would this be a hazard? The owner is a friend of mine and I would like to assure him that adding the second bond is going to be safe.

Thanks!

I understand all that. Taking the view that you only need to bond one end of the EMT is not the only view. Some adhere to the rationale that bonding must be double ended with in- between equipment. In other words, if the particular piece under review were to be cut in half with sides electrically isolated from each other, fault current on either half has a fault pathway. While two connections do not preclude half having no path and the other half still having two, there is a substantially lower probability than the piece only having one connection...

As to your inspector friend, he may be referring to 310.10(H). If so, the general statement limits the parallel requirements to aluminum, copper-clad aluminum, and copper.

The hazard is minimal... typically. Atypical instances would be quite rare IMO, so unless there's a need, will not elaborate further.

 

[K8MHZ]

Did the inspector ever say he wanted the bushing connected to anywhere other than the meter enclosure?

If it is metal conduit how does adding the bushing change the neutral current path when you said the neutral is solidly bonded to the enclosure.
All the inspector seems to be asking is for the knock outs to have a bonding bushing for fault current

The connection is to be made from the neutral lug to the bonding bushing.

I understand what he is asking. So it's your take that adding a second bond creates no hazard, and separately, is not an NEC violation?

 

[K8MHZ]

I understand all that. Taking the view that you only need to bond one end of the EMT is not the only view. Some adhere to the rationale that bonding must be double ended with in- between equipment. In other words, if the particular piece under review were to be cut in half with sides electrically isolated from each other, fault current on either half has a fault pathway. While two connections do not preclude half having no path and the other half still having two, there is a substantially lower probability than the piece only having one connection...

As to your inspector friend, he may be referring to 310.10(H). If so, the general statement limits the parallel requirements to aluminum, copper-clad aluminum, and copper.

The hazard is minimal... typically. Atypical instances would be quite rare IMO, so unless there's a need, will not elaborate further.

Thanks!

 

[cowboyjwc]

Well I probably wouldn't take it from the boding bushing to the neutral lug.

 

[al hildenbrand]

The connection is to be made from the neutral lug to the bonding bushing.

Is the neutral lug capable of landing the neutral AND the bonding jumper? That is, are there actually two separate lugs?

 

[david]

So it's your take that adding a second bond creates no hazard, and separately, is not an NEC violation?

It is my take that adding the bonding bushing adds no additional hazard, and eccentric and concentric knockout bonding ensures an effective fault clearing path

250.92 Services. Bonding jumpers meeting the other requirements of this article shall be used around concentric or eccentric knockouts that are punched or otherwise formed so as to impair the electrical connection to ground. Standard locknuts or bushings shall not be the sole means for the bonding required by this section.

A lot of class 200 meter sockets have an additional terminal that will accept a conductor up to #4 AWG that can be used for this purpose