Meter Socket Neutral Bond

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This is one of those things you have done for years and one day you step back and go "what's wrong with this picture".
In my area the local utility requires the use of certain manufacturers meter sockets (to ensure their meters will operated correctly). Specifically I am talking about "line voltage" meter sockets. All of these have the neutral bar (lugs) mounted directly to the can. The issue, in question, occurs when there is a "multiple service" that has one main disconnect and that feeds a trough where multiple services (meter socket and overcurrent protection) are then tapped off. As you know the first disconnect means is the only place where you can have the neutral and the grounds together but all these meter sockets violate this by their design.
So my questions are:
1. Has anyone seen a line voltage meter socket that comes with an isolated neutral bar and if so does it come with a bonding screw (like a panel does) that could be installed if required?
2. Has anyone else come across this issue before and have an easy explanation or solution for me?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Take a look at Exception No. 2 to 250.142(B).

Chris

and if your sitaution does not meet all the requirements of Exception 2, they do, in fact, manufacturer meter sockets with isolated neutral blocks.
 
Roger -I am referring to 250.24(B), ("first disconnect means" is the term used in 250.30(1) and was inadvertently used in place of the "service-disconnect enclosure" used in 250.2(B)). The connection I am referring to is actually the Main Bonding Jumper. In panels and safety switches this is normally the bonding screw that comes loose inside, in transformers this is generally a manufactured "strap" of thin buss like material.
It is my understanding that you can only have the Grounded Conductors (Neutrals) and the Equipment Grounding Conductors (Grounds) connected together at one point in the electrical system. This is so there is only one ground reference. This connection is normally made at the service-disconnect enclosure (first disconnect means) which is normally after the meter socket. The meter socket is generally where the Grounding Electrode Conductor is connected to the Grounded Conductor (Neutral).
My question is strictly about the Equipment Grounding Conductor and Grounded Conductor (Neutral). On the line side of a service there generally is no "equipment grounds" so this is not an issue when the meter socket is ahead of the service disconnect.
In the scenario I am asking these questions in regards to is when the meter socket is after the first disconnect means (in this case the Grounding Electrode Conductor is connected to the Grounded Conductor inside the Service Disconnect, not in each of the more than six meters sockets. In this scenario I now have the Grounded Conductor connected to the Equipment Ground Conductor not only in the service disconnect but also in every meter socket.
Augie47 - Thanks, I learned something new today (that's why I love this job). That is the one way that would make the most sense.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Roger -I am referring to 250.24(B), ("first disconnect means" is the term used in 250.30(1) and was inadvertently used in place of the "service-disconnect enclosure" used in 250.2(B)). The connection I am referring to is actually the Main Bonding Jumper. In panels and safety switches this is normally the bonding screw that comes loose inside, in transformers this is generally a manufactured "strap" of thin buss like material.
It is my understanding that you can only have the Grounded Conductors (Neutrals) and the Equipment Grounding Conductors (Grounds) connected together at one point in the electrical system. This is so there is only one ground reference. This connection is normally made at the service-disconnect enclosure (first disconnect means) which is normally after the meter socket. The meter socket is generally where the Grounding Electrode Conductor is connected to the Grounded Conductor (Neutral).
My question is strictly about the Equipment Grounding Conductor and Grounded Conductor (Neutral). On the line side of a service there generally is no "equipment grounds" so this is not an issue when the meter socket is ahead of the service disconnect.
In the scenario I am asking these questions in regards to is when the meter socket is after the first disconnect means (in this case the Grounding Electrode Conductor is connected to the Grounded Conductor inside the Service Disconnect, not in each of the more than six meters sockets. In this scenario I now have the Grounded Conductor connected to the Equipment Ground Conductor not only in the service disconnect but also in every meter socket.
Augie47 - Thanks, I learned something new today (that's why I love this job). That is the one way that would make the most sense.

Did you check out exception No. 2 to 250.142(B)?

This exception permits the grounded conductor to be used to ground meters on the load side of the service disconnecting means provided that there is no service ground fault protection and the meters are installed immediately adjacent to the service disconnecting means.

Chris
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Yes - That is what I was going by. I inadvertently thanked Augie for the info but now see he was quoting you. So thank You raider1 also.

Your welcome, I wasn't worry about getting kudos or anything. I just wanted to be sure that you knew there was a way to install meters with bonded neutrals after the service disconnecting means.

Chris
 

Volta

Senior Member
Location
Columbus, Ohio
. . . The connection I am referring to is actually the Main Bonding Jumper. In panels and safety switches this is normally the bonding screw that comes loose inside, in transformers this is generally a manufactured "strap" of thin buss like material.

I believe that as Pierre C. Belarge metioned here:
http://forums.mikeholt.com/showthread.php?t=109186, post #3,
the strap you refer to in a transformer is simply to ground the enclosure,
and may not be sized properly to be the sytem bonding jumper, which would be sized based on the derived phase conductors. 250.30(A)(1).
 
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