Splicing in a meter bank

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sketchy

Senior Member
Location
MN
First of all, it is my understanding that the wireway section of a meter bank is considered a panelboard. Based on this, is it OK to splice the SER cable inside the wireway? We've got a 40 unit apartment building and each unit is getting a 1.5 kw PV system. Each unit is metered separately with its own 125 amp breaker. I want to tap each apartment units main breaker to feed the PV. I'm doing this instead of backfeeding a breaker in each apartment because of voltage drop and monitoring concerns. I plan on doing this with Polaris lugs. Does anyone see any cause for concern? I'm working on getting the fill calculations right now to show the inspector.
 

kwired

Electron manager
Location
NE Nebraska
Whether this "wire way" is part of a panelboard or is actually a wire way - the fill limit is same 20% for conductors and 75% where there are conductors and splices/taps.

Are you going to hit an overcurrent device within applicable distance of whichever feeder tap rule applies? AFAIK anything you tie to this is a feeder tap unless it has same ampacity as the feeder it is tapped to, even if it goes to a source instead of load. If something malfunctions and faults you will have current originating from utility side feeding into the fault just like you would with a feeder tap/branch circuit situation.
 

sketchy

Senior Member
Location
MN
Yes, each tap will terminate in a fused disconnect next to the meters. So if I understand 376.22(A) and 376.56(A) right, I can't go over 75% fill with my polaris lugs but it drops to 20% if there are no splices. Is cross sectional area calculated by drawing an imaginary horizontal line and taking depth x width along that line?
 

Carultch

Senior Member
Location
Massachusetts
First of all, it is my understanding that the wireway section of a meter bank is considered a panelboard. Based on this, is it OK to splice the SER cable inside the wireway? We've got a 40 unit apartment building and each unit is getting a 1.5 kw PV system. Each unit is metered separately with its own 125 amp breaker. I want to tap each apartment units main breaker to feed the PV. I'm doing this instead of backfeeding a breaker in each apartment because of voltage drop and monitoring concerns. I plan on doing this with Polaris lugs. Does anyone see any cause for concern? I'm working on getting the fill calculations right now to show the inspector.


Be aware that the wiring space of a meter enclosure, whether it be a meterbank or for a single meter, can often be subject to the rules of the utility company, and it is possible that they may not allow splicing inside.

National Grid has this rule in 4.1.6 of the following document:
https://www9.nationalgridus.com/non_html/shared_construction_greenbk.pdf


If it is a meter that doesn't serve any utility service purposes, then there is no NEC issue with splicing in such an enclosure, provided that you meet the same space requirements for splicing in a panelboard or disconnect.
 

david

Senior Member
Location
Pennsylvania
I’m picturing something like a service with 3phase 120/208 with a 1500 amp main with 40ea 125 amp feeder breakers. Each feeder taped. Say 10 amps total 400 amps.

I’m actually curious of what this actually looks like, what is the main and main buss for the service?
 

iwire

Moderator
Staff member
Location
Massachusetts
First of all, it is my understanding that the wireway section of a meter bank is considered a panelboard.

A meter bank is not a panelboard per the definitions in article 100.

To the NEC this is a panelboard which the rules for are found in article 408


Eaton-CUTPRL1A3225X42A-38480_ZM.jpg


A panelboard is installed in a cabinet which the rules for are found in article 312.
 

sketchy

Senior Member
Location
MN
The meter bank will be a Siemens WMM52125RJB. The entire bank is fed from a 1200 or 1600 amp main, not sure which. The section that contains the meter is all factory buss bar, no field connections are allowed. I showed a different inspector a cut sheet and he told me that the section where we bring in the SER cable would be considered a panelboard, that was his interpretation.
 

kwired

Electron manager
Location
NE Nebraska
The meter bank will be a Siemens WMM52125RJB. The entire bank is fed from a 1200 or 1600 amp main, not sure which. The section that contains the meter is all factory buss bar, no field connections are allowed. I showed a different inspector a cut sheet and he told me that the section where we bring in the SER cable would be considered a panelboard, that was his interpretation.
As said the panelboard would be the assembly mounted inside the cabinet that contains bus, breakers, etc. The wiring space is just extra space within the cabinet, but the conductor fill rules of that space are same as for a aux gutter or wireway, so for your fill question it sort of doesn't matter which one of those it actually is.

And yes cross section would be the two dimensional area at any point of the width x the depth. Staggering splices sometimes is necessary so you don't over fill one point of the cross section.
 

david

Senior Member
Location
Pennsylvania
The meter bank will be a Siemens WMM52125RJB. The entire bank is fed from a 1200 or 1600 amp main, not sure which. The section that contains the meter is all factory buss bar, no field connections are allowed. I showed a different inspector a cut sheet and he told me that the section where we bring in the SER cable would be considered a panelboard, that was his interpretation.

your 40 Individual PV sources will be load side connected to 40 separate 125 amp mains on 1200 amp main buss to 1200 amp main over-current protection what is your PV source Out put and how do you calculate the 120% rule.

Roughly 200 amps from the right 20 feeders and roughly 200 amps from the left 20 feeders? 200 X 1.25

250 X 2 = 500

1200 x 1.2 = 1440
1440- 1200= 240


How do you calculate this?
 

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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The inspector sees it as back feeding each meter individually, not the system as a whole.
That is logically consistent and each connection would be a supply side tap if connected between each meter and it's associated service disconnect. And IMHO there would be no NEC rule applicable to the internal bussing.
 

david

Senior Member
Location
Pennsylvania
First of all, it is my understanding that the wireway section of a meter bank is considered a panelboard. Based on this, is it OK to splice the SER cable inside the wireway? We've got a 40 unit apartment building and each unit is getting a 1.5 kw PV system. Each unit is metered separately with its own 125 amp breaker. I want to tap each apartment units main breaker to feed the PV. I'm doing this instead of backfeeding a breaker in each apartment because of voltage drop and monitoring concerns. I plan on doing this with Polaris lugs. Does anyone see any cause for concern? I'm working on getting the fill calculations right now to show the inspector.

Is your meter bank outside? The last time i worked on a 72 unit apartment the service and metering was inside the apartment building.

is it OK to splice the SER cable inside the wireway


That is logically consistent and each connection would be a supply side tap if connected between each meter and it's associated service disconnect. And IMHO there would be no NEC rule applicable to the internal bussing.

He said the tap is to the SER which is a feeder and a load side tap in the MDP does that change the way you look at it
and if so how would you calculate this?
 
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david

Senior Member
Location
Pennsylvania
That is logically consistent and each connection would be a supply side tap if connected between each meter and it's associated service disconnect. And IMHO there would be no NEC rule applicable to the internal bussing.

ANd just for my own understanding are you saying that a tap on the load side of the 1200 amp service disconnect in this MDP is a supply side tap?
 

david

Senior Member
Location
Pennsylvania
The inspector sees it as back feeding each meter individually, not the system as a whole.

I was thinking an engineer might design something like this. Combine the PV and supply the gear through disconnects on each end of this gear
 

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iwire

Moderator
Staff member
Location
Massachusetts
I was thinking an engineer might design something like this. Combine the PV and supply the gear through disconnects on each end of this gear

They apparently want each PV system on each meter, your solution tosses that out the window.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
ANd just for my own understanding are you saying that a tap on the load side of the 1200 amp service disconnect in this MDP is a supply side tap?
I take my statement back. There is only one service and service point and all of the meters are downstream of it.
If there were only an unfused disconnect before the meters it would be different.
 

iwire

Moderator
Staff member
Location
Massachusetts
The inspector sees it as back feeding each meter individually, not the system as a whole.

It is as far as the feeder breaker for each unit but not for the single main ahead of them all.

I agree with David that there is a serious code issue you here and regardless of the inspector being OK with it, and even potentially signing off on it, you will always be liable for the violtion.
 

sketchy

Senior Member
Location
MN
I see both sides. The pv output is 7 amps. Would it be any different if each system was back fed at the panel in each apartment? I don't think it makes any difference.
 
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