Replacing meter bank and worrying about shared neutrals

Tainted

Tainted

Senior Member
Location
New York
Occupation
Engineer (PE)
We are thinking about removing the old meter banks shown picture below and replacing it with new Siemens modern meter bank in the same spot. (click here to see cutsheet of the new meter bank to be installed)

The new meter bank will allow apartments to upgrade in the future when needed.

After installing the new meter bank and removing the old meter bank, we would have to refeed all the existing wiring above the existing meter bank and I am worried about shared apartment neutrals when refeeding existing apartment feeders to the new meter bank.

Do the arrangements of the meters matter if the existing apartments have shared neutrals? Must the meters be in the same arrangement as the existing?


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The EC that wins the project should know what to do.
 
Tainted said:
Do the arrangements of the meters matter if the existing apartments have shared neutrals? Must the meters be in the same arrangement as the existing?
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Are you referring to a single neutral for 3 apartments as in 215.4?


215.4 Feeders with Common Neutral Conductor.
215.4(A) Feeders with Common Neutral.
Up to three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders shall be permitted to utilize a common neutral.
215.4(B) In Metal Raceway or Enclosure.
Where installed in a metal raceway or other metal enclosure, all conductors of all feeders using a common neutral conductor shall be enclosed within the same raceway or other enclosure as required in 300.20.
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I'd guess OP is concerned there may be improper mixing of neutral conductors down stream of this. At very least I'd probably identify which phase each outgoing ungrounded conductor is connected to and make sure they end up going back to the same. Then at least you don't create any new problems.

If you happen to be converting from single to three phase supply, or vice versa, then you need more thorough evaluation of what is downstream regardless as it will be easier to create new issues in either of those situations.
 
kwired said:
guess OP is concerned there may be improper mixing of neutral conductors down stream of this.
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If each apartment feeder had it own neutral I don't see an issue as long as all of the conductors of that feeder are terminated in the same meter bank. If the feeder neutral is shared with three apartments then it can be more complex because you will need to ensure that all three apartment feeders sharing a single neutral end up in the same meter bank.
 
infinity said:
If each apartment feeder had it own neutral I don't see an issue as long as all of the conductors of that feeder are terminated in the same meter bank. If the feeder neutral is shared with three apartments then it can be more complex because you will need to ensure that all three apartment feeders sharing a single neutral end up in the same meter bank.
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This older setup may have a neutral bus located in a common section and depending on arrangement may be more difficult to determine which neutral goes with which outgoing feeder where most modern meter centers likely have a neutral terminal in each tenant section and would be nice to land the neutral associated with the feeder in the same tenant section? Can still be done just involves more work to be put into identifying what you have to work with.
 
infinity said:
If each apartment feeder had it own neutral I don't see an issue as long as all of the conductors of that feeder are terminated in the same meter bank. If the feeder neutral is shared with three apartments then it can be more complex because you will need to ensure that all three apartment feeders sharing a single neutral end up in the same meter bank.
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neutral must land in same meter bank or same meter stack section? I believe each Siemens meter stack section has their own neutral terminals.

I want to clarify my concern:

Let's say I have apartment A, B and C share a neutral. They will be circuited to the same meter bank, but must they be in the same exact meter stack section?
 
Tainted said:
Let's say I have apartment A, B and C share a neutral. They will be circuited to the same meter bank, but must they be in the same exact meter stack section?
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Each separate meter bank will have a neutral bar for the feeders exiting that meter bank. As long as the three feeders with that shared neutral are all connected within that same meter bank you're good.
 
infinity said:
Each separate meter bank will have a neutral bar for the feeders exiting that meter bank. As long as the three feeders with that shared neutral are all connected within that same meter bank you're good.
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Ok I see. Just want to be a little more clear:

Let's say I have apartments A, B, C and D sharing the same neutral.

I have 2 meter bank sections.

I circuit apartment A and B in section 1

and I circuit apartment C and D on section 2.

How does the neutral get wired in this scenario when it has to leave the meter bank and connect to the existing shared neutral? Where would I take the neutral? Do I have to take it from section 1, section 2 or both?
 
Tainted said:
I have 2 meter bank sections.

I circuit apartment A and B in section 1

and I circuit apartment C and D on section 2.
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You cannot have 4 apartments sharing a neutral so in your scenario do you have feeders A & B+N and feeders C & D+N? In that case the neutral for A & B would go to compartment A, C & D to compartment B unless the meter bank is designed so that all of the neutrals land on a single neutral bus. For example your meter bank has one set of service conductors feeding three sections with a single neutral bus within the three sections.
 
infinity said:
You cannot have 4 apartments sharing a neutral so in your scenario do you have feeders A & B+N and feeders C & D+N? In that case the neutral for A & B would go to compartment A, C & D to compartment B unless the meter bank is designed so that all of the neutrals land on a single neutral bus. For example your meter bank has one set of service conductors feeding three sections with a single neutral bus within the three sections.
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Must all the apartments that have shared neutrals be in the same section? Below I am showing a single section. I circled in red the neutral.

How about this example using the meter bank below. Apartments A, B, and C share the same existing neutral. I put A and B on section 1 of the meter bank and C on section 2. Can I use neutral on section 1 to feed A, B and C? Or must the neutral come from both sections?

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Tainted said:
neutral must land in same meter bank or same meter stack section?
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I don't know of any requirement to do so, but if there is a neutral lug within a meter compartment it kind of doesn't make sense to land a neutral conductor from a different feeder there.
 
kwired said:
I don't know of any requirement to do so, but if there is a neutral lug within a meter compartment it kind of doesn't make sense to land a neutral conductor from a different feeder there.
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You see in my picture above, I circled neutral terminal. Must this neutral terminal (circled in red) be dedicated for the meters on the single section only? When you have shared apartment neutrals and you want to refeed them, it can get hairy so that's why I ask
 
Tainted said:
You see in my picture above, I circled neutral terminal. Must this neutral terminal (circled in red) be dedicated for the meters on the single section only? When you have shared apartment neutrals and you want to refeed them, it can get hairy so that's why I ask
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I can see your dilemma. You have 3 feeders sharing a neutral but each section of the new meter bank is 4 meters so the neutral for one meter will end up in another section with the two other shared neutral feeders. Electrically It won't really matter where the common neutral is located. One might expect that all of the neutrals in the section belong only in that section but I cannot think of a code section that would require it to be done that way.
 
infinity said:
I can see your dilemma. You have 3 feeders sharing a neutral but each section of the new meter bank is 4 meters so the neutral for one meter will end up in another section with the two other shared neutral feeders. Electrically It won't really matter where the common neutral is located. One might expect that all of the neutrals in the section belong only in that section but I cannot think of a code section that would require it to be done that way.
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Yes this is exactly my concern.

As an example

Section 1 will have apartments A,B,C,D
Section 2 Will have apartments E,F,G,H

A,B,C share a neutral
D,E,F share a neutral
G,H share a neutral

D,E,F is where the problem is because they share a neutral but are at different sections. The neutral for D,E,F will have to either come from section 1 or section 2. But is this against code?

I thought this was not allowed because the associated ungrounded conductors must be in the same raceway and enclosure as the grounded conductors.

Isn't this like taking a neutral from another random panel?
 
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infinity said:
Are you referring to a single neutral for 3 apartments as in 215.4?
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2023 NEC TX
I think you're just asking for future trouble shooting, could be expensive, too.
What is your neutral load now, before any changes are made?
Are the apartments wired now for all electric, dryers, cooking?

TX+MASTER#4544
 
TX+ MASTER#4544 said:
2023 NEC TX
I think you're just asking for future trouble shooting, could be expensive, too.
What is your neutral load now, before any changes are made?
Are the apartments wired now for all electric, dryers, cooking?

TX+MASTER#4544
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We are not changing any load, just replacing the meter bank with higher capacity for future upgrades and reconnecting existing wiring. In the future everyone will have a dedicated neutral and not shared.
 
If there is one bus for all neutral terminals, I'd say that it doesn't matter, metallic-conduit issues aside.
 
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