Bonding EMT on both ends

[shortcircuit2]

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!

The fact the neutral is bonded to the meter enclosure makes the enclosure part of the neutral return path to the transformer. Whether the EMT is bonded at one end or both ends...it too is part of the return path for neutral current to the transformer. Bonding bushings at both ends will cost the contractor more, that's all.

I can't think of any hazard other than if the meter enclosure or the EMT were NOT bonded and it was to become live by an ungrounded conductor.

 

[al hildenbrand]

Given the description of this being out beyond the boonies, I could easily imagine the PoCo's allowed 100 Amp approved meter base list including models that have, simply, one load side neutral lug, and that the inspector's requirement will create a 110.3 violation and ultimately lead to an open neutral, at minimum, years down the line.
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[K8MHZ]

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

They aren't separate lugs, they are single lugs with 2 ports. No problem with the lugs and the conductor. There are 2 large hex bolts for the neutral and a smaller straight blade screw for a bonding connection. You can see it on the right.

Like this:

 

[K8MHZ]

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

This one has it as well. It's a 200 amp Milbank.

 

[K8MHZ]

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

It's that or no connection.

 

[K8MHZ]

The fact the neutral is bonded to the meter enclosure makes the enclosure part of the neutral return path to the transformer. Whether the EMT is bonded at one end or both ends...it too is part of the return path for neutral current to the transformer. Bonding bushings at both ends will cost the contractor more, that's all.

I can't think of any hazard other than if the meter enclosure or the EMT were NOT bonded and it was to become live by an ungrounded conductor.

No additional cost. I had a bonding bushing in my part drawer and plenty of wire. I just gave it to him. It's done, now.

 

[al hildenbrand]

Heh! Well then, I salute this inspector for creating the contradiction to those who cite "objectionable current".

While I agree that the NEC minimum is exceeded by the double bond, it ultimately only lowers the neutral impedance and increases the neutral path redundancy.
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[K8MHZ]

Given the description of this being out beyond the boonies, I could easily imagine the PoCo's allowed 100 Amp approved meter base list including models that have, simply, one load side neutral lug, and that the inspector's requirement will create a 110.3 violation and ultimately lead to an open neutral, at minimum, years down the line. Sent from my RM-893_nam_tmous_201 using Tapatalk

This is a 200 amp Milbank. The POCO allows them for 100 amp services and they have more room. I don't see any 110.3 violation. I think the 100 amp Milbanks have the 'double' lug for the neutral, too. Next time I see one, I will check.

 

[K8MHZ]

Heh! Well then, I salute this inspector for creating the contradiction to those who cite "objectionable current".

While I agree that the NEC minimum is exceeded by the double bond, it ultimately only lowers the neutral impedance and increases the neutral path redundancy.
Sent from my RM-893_nam_tmous_201 using Tapatalk

I agree and so does my inspector friend in my county. The inspector in the other county is the one mandating a possible objectionable current problem.

When the power is connected, I will take some measurements to see just how much current is flowing through the conduit and bonding jumpers. It seems to me the current should be just about equal on both the insulated neutral and the exposed EMT. If so, that means the EMT could be carrying 50 amps or so under a full load, which will likely never be reached. But 15 - 20 may happen.

 

[cowboyjwc]

So we don't do it like that out here, but is the meter considered the point of service? Do you bond the grounds and the neutrals anywhere beyond that point?

 

[K8MHZ]

So we don't do it like that out here, but is the meter considered the point of service? Do you bond the grounds and the neutrals anywhere beyond that point?

Sure do. In the panel where the main breaker is located. Here, the meter is not considered the point of service. The 'bullseye' is always in the panel. On the other side of the state, if the bond is in the meter, then none is done on the panel side. We call that 'Detroit' style.

 

[texie]

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.

I agree. (250.92(B) And concentric KO is irrelevant as standard lock nuts are not allowed. There is no requirement for a bonding jumper to connect directly to the neutral. That would only apply to a GEC.
As for the OP per his description of the install it is compliant if the meter can has a bonded neutral.

Note that many current Milbank meter sockets (and others) do not have a permanently bonded neutral in order to accommodate other applications. Some give you a bond screw or jumper that is up to the installer to use if required. If, say, the installer lost the jumper he could use bushings at both ends of the nipple since the service disconnect is required to have a neutral bond in any case and that would effectively bond the nipple and the meter socket. This is done with CT cans all the time as they usually don't have factory bonded neutrals.

Or you could do like the clever guys and use a PVC nipple between the meter socket and the disconnect...just use a bonded neutral meter can and bond the disco neutral and you are good to go.

 

[K8MHZ]

I agree. (250.92(B) And concentric KO is irrelevant as standard lock nuts are not allowed. There is no requirement for a bonding jumper to connect directly to the neutral. That would only apply to a GEC.
As for the OP per his description of the install it is compliant if the meter can has a bonded neutral.

Note that many current Milbank meter sockets (and others) do not have a permanently bonded neutral in order to accommodate other applications. Some give you a bond screw or jumper that is up to the installer to use if required. If, say, the installer lost the jumper he could use bushings at both ends of the nipple since the service disconnect is required to have a neutral bond in any case and that would effectively bond the nipple and the meter socket. This is done with CT cans all the time as they usually don't have factory bonded neutrals.

Or you could do like the clever guys and use a PVC nipple between the meter socket and the disconnect...just use a bonded neutral meter can and bond the disco neutral and you are good to go.

Somewhere in my collection I have a pic of a 4" PVC service entrance run that was smashed in by a snow plow. The correction was, and still is to this day, to split some white plumbing PVC and use it to protect/hide the damage to the PVC conduit. That is not the first time I have seen PVC of large diameter meet it's demise in the depths of winter when battered by a snow plow wielding Ram Hemi.

As such, and being a Michigander for nearly 6 decades, I use PVC conduit outdoors with some trepidation.

Maybe I should run only 2 inch conduit from the socket to the panel. That way there would be no knock out issues to mitigate.

 

[Smart $]

...

Maybe I should run only 2 inch conduit from the socket to the panel. That way there would be no knock out issues to mitigate.

...and renders the objectionable current issue moot. :happyyes:

 

[david]

...and renders the objectionable current issue moot. :happyyes:

He didn?t say 2 in PVC, He said 2 in conduit so that the knock out bonding issue goes away

 

[Smart $]

He didn?t say 2 in PVC, He said 2 in conduit so that the knock out bonding issue goes away

:slaphead:

 

[zbang]

There's also a remote possibility that the PoCo engineer tells his lineman "If you see this jumper, just remove it and close the box."

 

[K8MHZ]

There's also a remote possibility that the PoCo engineer tells his lineman "If you see this jumper, just remove it and close the box."

We may never know.

 

[paul]

Next time use PVC and the issue is moot.

 

[dhalleron]

Around here in Louisville KY about 30 years ago we used to bond the bushing to the neutral in the meter base of the many 100 amp services I built. This was even when there was not a separate lug for the bond. We just put it under the same lug with the neutral. Later we had meters with a separate lug that we used.

Sometime in the last 20 or so years the POCO started not allowing a bond from the grounding bushing in their meter base. Now we just use a plastic bushing.