I am not too familiar with residential service installations and was looking at some

[Mike01]

I am not too familiar with residential service installations and was looking at some installation standards provided by the local utility when reading the grounding and bonding it has a diagram that indicates a typical service to the meter 2-phase conductors and a neutral the neutral connect to a set of lugs in the center of the meter and continues to show the load side with the conductors to the main panelboard and the neutral and ground bonded at that point, I understand the bonding at the main thing but here is my question:
The "neutral" to the meter and then to the panelboard is typically bare similar to a concentric neutral on service entrance cabling, but why is the meter itself not grounded? I think of my installation at home where multiple single family homes are served from a single pad mounted xfmr. (in the neighbors back yard) and tapped to serve multiple homes, but what happens to a fault in the meter? The meter would be energized, there would be no OCPD only the wire? Just trying to figure this all out thanks.

 

[480sparky]

You typically bond in the panel instead of the meter socket because you'll have access to the terminations in the panel. Not so in the meter socket.

 

[Mike01]

utility side??

utility side??

So does this mean that the utitily runs a primary (H1,H2,H3&Grd.) and the secondary "XO" would not be connected to the xfmr. ground?

 

[augie47]

The Grounded conductor serves as your grounding conductor up to and including your service equipment. Most meter sockets have the neutral buss permanently bonded to the enclosure and your bonding jumper "grounds" your service equip met. Only after the service does the grounded and grounding need to be separated.

 

[480sparky]

So does this mean that the utitily runs a primary (H1,H2,H3&Grd.) and the secondary "XO" would not be connected to the xfmr. ground?

3-phase resi?

 

[Mike01]

1-ph

1-ph

sorry I mean 1-ph, I usually do not work with residential so the designations just got messed up so no not 3-ph but 1-ph.
Just curious because typically with a SDS there is still a "bonding" conductor if the first point of disc. is specified at the panelbaord, you would run your phase conductors, neutral and a equipment grounding conductor (or raceway as ground) but from what I see there is no ground bond between the meter and the utility xfmr secondary? unless they are using the neutral (correct me if I am wrong but the neutral is tied to the meter enclosure) so the fault current would go back on the neutral but then where?

 

[roger]

You typically bond in the panel instead of the meter socket because you'll have access to the terminations in the panel. Not so in the meter socket.

Why do you not think there is access to the terminations in a meter socket?

If the inside of meter can is inaccessible, why do the other terminations in a meter socket need not be accessible?

I would say a locked equipment room / electrical closet in a building is just as aggravating to gain access to as a meter is.

In the Southeast the meter socket is the norm for landing the GEC and bonding the neutral and IMO is the most logical.

Roger

 

[480sparky]

Why do you not think there is access to the terminations in a meter socket?


Roger

It a legal matter in some places. You cut a seal, you end up talking to law enforcement. Some POCOs don't take kindly to someone messin with their cash registers.

 

[roger]

It a legal matter in some places. You cut a seal, you end up talking to law enforcement. Some POCOs don't take kindly to someone messin with their cash registers.

I am not implying that anyone has to cut a seal. A lock or seal does not render the inside wiring inaccessible regardless of how long you may have to wait for it to be unlocked.

And once again, why do the other connections not have to be accessible?

Roger

 

[Mike01]

Location:

Location:

Below is the some image's out of the service planners guide, the neutral going thru to the panelboard. it appears that the neutral termination is not isolated from the enclosure?, I understand in the other sketch the reason for the parallel path but then the how is the meter enclosure grounded? and whats up with the 5th stab thing for 120/208 volt services?

 

[augie47]

Below is the some image's out of the service planners guide, the neutral going thru to the panelboard. it appears that the neutral termination is not isolated from the enclosure?, I understand in the other sketch the reason for the parallel path but then the how is the meter enclosure grounded? ?

by the grounded (neutral) conductor, which is allowed on the line side of the service disconnect

and whats up with the 5th stab thing for 120/208 volt services?

many POCO meters that are suitable for single phase 208/120 require the 5th jaw to operate correctly.

 

[Mike01]

stupid question??

stupid question??

if you have a fault in the enclosure what trips? the wire would be the fuse then right? the cabinet would be energized for that duration.

 

[Cold Fusion]

if you have a fault in the enclosure what trips? the wire would be the fuse then right? the cabinet would be energized for that duration.

I don't do much residential either. I never have liked the poor level of safety provided by the utilities.

I'd guess the xfm pole cutouts open or the service drop burns in two.

cf

 

[augie47]

Until you go thru your service disconnect any fault would be the same.
Thats why 250.66 calls for larger wire than 250.122

 

[Mike01]

true

true

yes that's true, however if you are served from a utility pad mounted transformer with multiple taps (no secondary OCPD) the utility in my area for underground runs like a 250al conductors min. so the fault would continue until the primary protection of the xfmr. opens. if that's the case there exist a shock hazard on the meter enclosure? I guess it depends on the size of the xmfr. and the TCC of the primary fuse.

 

[roger]

if you have a fault in the enclosure what trips? the wire would be the fuse then right? the cabinet would be energized for that duration.

It would be the same regardless of where the bonding is done.

Roger

 

[LarryFine]

so the fault would continue until the primary protection of the xfmr. opens. if that's the case there exist a shock hazard on the meter enclosure?

Yes, which exemplifies why we don't intentionally impose neutral currents on EGC's. The short circuit is expected to be a short-term event; the neutral current is not.

But, the answer to the OP is that every meter I recall ever seen had the neutral lugs bolted to a plate that was riveted to the enclosure. Same for CT cabinets, too, I think.

 

[Mike01]

return

return

so all the imbalanced loads (neutral and ground currents) would return to the xfmr via the neutral in the panel, the meter enclosure etc.

 

[augie47]

when it works as designed....

 

[philly]

Why do you not think there is access to the terminations in a meter socket?

If the inside of meter can is inaccessible, why do the other terminations in a meter socket need not be accessible?

I would say a locked equipment room / electrical closet in a building is just as aggravating to gain access to as a meter is.

In the Southeast the meter socket is the norm for landing the GEC and bonding the neutral and IMO is the most logical.

Roger

In the attached photo wouldnt the conducter to connect the grounded neutral to the grounding electrode be referred to as the system bonding jumper? Wouldn't the location of this jumper be determined by where the grounding electrode is located? I believe the system bonding jumper should only be installed at the location of the grounding electrode which in this case is the service disconnct, and not at the transformer secondary.

What if both the service disconnect and the transformer had a grounding electrode, do you still only install the system bonding jumper at one of these locations, but not both?