Neutral to Ground Connection Point ?

[davidaengelhart]

The meter enclosure is allowed to be bonded to the grounded conductor on the load side of the service disconnect per '11 NEC 250.142(B)exc#2, but this situation does not fit as the load side meter enclosure is not within close proximity of the main; GFP not specified in this thread.

 

[Pizza]

The meter enclosure is allowed to be bonded to the grounded conductor on the load side of the service disconnect per '11 NEC 250.142(B)exc#2, but this situation does not fit as the load side meter enclosure is not within close proximity of the main; GFP not specified in this thread.

And Technically its not a meter enclosure now. There is no meter in it.

 

[jaggedben]

If the neutral is lost, all the equipment grounding conductors become potential neutral paths.

Yes, but the objectionable current will flow on path of lowest impedance. If the neutral was lost between the new meter and the old meter base, the low impedance pathway for the objectionable current would be the conduit coming out of the top of the old meter base, not the 'nipple' to the panel. (Quotes because isn't actually a nipple).

The nipple between the panel and meter as shown may very well be attempting to carry 100% of neutral current.

This does not seem at all likely unless there is also a (code violating) neutral to ground bond in the panel. Otherwise if the neutral was lost downstream of the old meter base, you'd simply have an open neutral, which doesn't seem to be the case here.

Given what we already know about this site, I guess I would not be totally surprised to see some EGCs landed together with neutrals on a single busbar in the panel. That could also explain how current could be flowing on the 'nipple', without a ground-fault per se, and without the panel enclosure being directly bonded to the neutral.

It's also possible there could be another mysterious pathway back to ground through the panel, but we've no reason to believe that yet.

 

[kwired]

Yes, but the objectionable current will flow on path of lowest impedance. If the neutral was lost between the new meter and the old meter base, the low impedance pathway for the objectionable current would be the conduit coming out of the top of the old meter base, not the 'nipple' to the panel. (Quotes because isn't actually a nipple).



This does not seem at all likely unless there is also a (code violating) neutral to ground bond in the panel. Otherwise if the neutral was lost downstream of the old meter base, you'd simply have an open neutral, which doesn't seem to be the case here.

Given what we already know about this site, I guess I would not be totally surprised to see some EGCs landed together with neutrals on a single busbar in the panel. That could also explain how current could be flowing on the 'nipple', without a ground-fault per se, and without the panel enclosure being directly bonded to the neutral.

It's also possible there could be another mysterious pathway back to ground through the panel, but we've no reason to believe that yet.

You started answering some of my questions. We don't know what else there is that we can't see or have had described to us. Is the bonding screw in panel? As this install seems to be just because it is not supposed to be there we can't assume it is not installed. How about any other neutral to EGC connections on the premesis?

N-G connections are easy to get away with and never know they are there or that something is wrong - unless ground fault protection is involved then they can give you headaches if you are not aware of looking for N-G connections.

 

[mbrooke]

It is a false statement that objectionable current will flow on the path of lowest impedance. Objectionable current like any current will take all paths avalable more on the lower impedance one but none the less all. If the first were the case all lighting and equipment would shut off in your house when someone switches on your oven or dryer.

Any time a current carrying conductor such as the neutral is grounded at more than one point current will begin to flow between between the 2 ground points and everything conductive between them (ie soil, building steel, conduit)

This can be a fire hazard not only if the neutral opens like mentioned and cause resistive heating of conduit connections but because the current is running on all metal parts including adjacent conduit and building steel, magnetic fields can not completely cross cancel in the service conduit.

Example:, 100 amps phase A and B 200 amps on C phase, 33 amps on conduit, 33 on the neutral and another 33 amps are on anything else providing a path back to the source. The missing 33 amps from the service conduit cause inductive heating wich reduces the current carrying capacity of the conductors in the conduit. In a properly connected service the neutral current would be 100 amps and zero on all other metal objects.

 

[meternerd]

POCO opinion...

POCO opinion...

I, being a member of the power company folks, would not have allowed those bypass jumpers to be installed. They are not rated for continuous use. They are called "test bypass jumpers" for a reason. Their intended use is to provide power to the customer while the meter is removed and tested. I'm surprised any inspector would allow them. But everyone is right about the bonding. I, as a meter tech, would require the wires to be spliced and insulated before I'd heat up the new switchgear. As many times as you want AHEAD of the service disconnect, but only once after. The old meter panel is now nothing more than a splice box.

 

[meternerd]

Welll...that didn't make much sense!

Welll...that didn't make much sense!

I, being a member of the power company folks, would not have allowed those bypass jumpers to be installed. They are not rated for continuous use. They are called "test bypass jumpers" for a reason. Their intended use is to provide power to the customer while the meter is removed and tested. I'm surprised any inspector would allow them. But everyone is right about the bonding. I, as a meter tech, would require the wires to be spliced and insulated before I'd heat up the new switchgear. As many times as you want AHEAD of the service disconnect, but only once after. The old meter panel is now nothing more than a splice box.

I read this after I posted it. Not really what I meant to say. A meter socket that is abandoned and then fed from another service disconnect is not a good way to re-wire. No manufacturer will stand behind a meter socket that has test bypass jumpers installed long term. Reason being, that the UL testing is done when the equipment is used as designed. Any field modifications will violate the UL rating. When a meter is installed in the socket, the meter socket jaws only hold tension to allow rated current flow. The weight of the meter is held by the meter lock ring and cover. When jumpers are installed, there is no mechanical attacment to the meter enclosure, so any loosening of the jaw tension over time can result in the jumpers becoming loose and overheating. I deal with manufacturers on a regular basis, and this subject has come up more than once. The way it should have been done is to remove the socket and mounting bracket altogether and splice the wires as in any other junction box. That would have elimnated the grounded neutral termination. If I go to a new or modified service, the first thing I do is check that the neutral bus is grounded only in the service disconnect section of the meter panel. Any "downstream" grounds must be removed before we will energize the service. Even building inspectors miss things.

 

[jaggedben]

It is a false statement that objectionable current will flow on the path of lowest impedance. Objectionable current like any current will take all paths avalable more on the lower impedance one but none the less all. If the first were the case all lighting and equipment would shut off in your house when someone switches on your oven or dryer.

You are correct. What I meant to say is that current would not flow on the 'nipple' if it is not part of a pathway back to the either the utility grounded conductor or the ground.

 

[Pizza]

I read this after I posted it. Not really what I meant to say. A meter socket that is abandoned and then fed from another service disconnect is not a good way to re-wire. No manufacturer will stand behind a meter socket that has test bypass jumpers installed long term. Reason being, that the UL testing is done when the equipment is used as designed. Any field modifications will violate the UL rating. When a meter is installed in the socket, the meter socket jaws only hold tension to allow rated current flow. The weight of the meter is held by the meter lock ring and cover. When jumpers are installed, there is no mechanical attacment to the meter enclosure, so any loosening of the jaw tension over time can result in the jumpers becoming loose and overheating. I deal with manufacturers on a regular basis, and this subject has come up more than once. The way it should have been done is to remove the socket and mounting bracket altogether and splice the wires as in any other junction box. That would have elimnated the grounded neutral termination. If I go to a new or modified service, the first thing I do is check that the neutral bus is grounded only in the service disconnect section of the meter panel. Any "downstream" grounds must be removed before we will energize the service. Even building inspectors miss things.

And thats how I plan to fix it. I will remove the old meter socket, install a J-Box and splice in it.