320 Amp Service Bonding

H

HuntNJ

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Location
NJ
Occupation
Electrician
I’m installing a 320A residential service with a meter and (2) 200A service disconnects, feeding (2) 200A subpanels inside the house.

My initial approach is to size the water bonding conductor per NEC 250.102(C) and run the bonding conductor back to each disconnect, similar to how I handle a standard 200A residential service.

However, NEC 250.104(A)(3) references “Buildings or structures supplied by feeders.” That has me second-guessing my approach.

Since the interior panels are being fed from the outdoor disconnects, would this be considered a structure supplied by a feeder? If so, can I size the water bonding conductor based on the feeder (e.g., 4/0 aluminum) instead of sizing it based on the service conductors (which would require 600 kcmil aluminum)?

Also, if this is the case. Can I install the water bond in the sub panels as well?
 
Is the water pipe an electrode? What size conductors are feeding the meter?
 
The water pipe is not an electrode and the conductors feeding the meter are 600 aluminum
 
What Code cycle is enforced ? (Requirements varied from 250-.66 to 250.102)
 
If you have 2- 200 amp service panels then you bonding conductor size would be #2 copper. I always take that back to the meter base. Not sure NJ's power company will allow it.
 
Dennis Alwon said:
If you have 2- 200 amp service panels then you bonding conductor size would be #2 copper. I always take that back to the meter base. Not sure NJ's power company will allow it.
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Technically he has two 200 amp sub-panels. The service disconnects are adjacent to the meter. The metallic water piping system is not a grounding electrode but it is required to be bonded. So his questions are:
1) How does he size the water pipe bonding conductor.
2) Can if be connected at the sub-panel.
 
is your 2 - 200a disconnects attached to the outside of the structure of the dwelling unit? or is it on a separate structure like a pole or meter rack?

if attached, that is your service disconnect, and grounding electrode system must be taken back to those.

if they are separate structure, and not the dwelling, then you are fed by feeders, and will need to meet 250.32 grounding electrode system requirements.
 
Master Nater said:
is your 2 - 200a disconnects attached to the outside of the structure of the dwelling unit? or is it on a separate structure like a pole or meter rack?

if attached, that is your service disconnect, and grounding electrode system must be taken back to those.

if they are separate structure, and not the dwelling, then you are fed by feeders, and will need to meet 250.32 grounding electrode system requirements.
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He's asking about bonding the water pipe which is not an electrode not the GES.
 
infinity said:
He's asking about bonding the water pipe which is not an electrode not the GES.
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The water pipe bonding is the same size as the grounding electrode conductor until you get to larger services. Table 250.102(C)(1) I don't believe it can be connected to a sub panel.

250.104 Bonding of Piping Systems and Exposed Structural Metal

(A) Metal Water Piping.

The metal water piping system shall be bonded as required in 250.104(A)(1), (A)(2), or (A)(3).
(1) General.

Metal water piping system(s) installed in or attached to a building or structure shall be bonded to any of the following:
  • (1)
    Service equipment enclosure
  • (2)
    Grounded conductor at the service
  • (3)
    Grounding electrode conductor, if of sufficient size
  • (4)
    One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size

The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible. The bonding jumper(s) shall be sized in accordance with Table 250.102(C)(1) except that it shall not be required to be larger than 3/0 copper or 250 kcmil aluminum or copper-clad aluminum and except as permitted in 250.104(A)(2) and (A)(3).
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the meter and (2) 200 amp disconnects are attached to the house and the (2) 200 amp sub panels are on the adjacent interior walls.
 
HuntNJ said:
I’m installing a 320A residential service with a meter and (2) 200A service disconnects, feeding (2) 200A subpanels inside the house.

My initial approach is to size the water bonding conductor per NEC 250.102(C) and run the bonding conductor back to each disconnect, similar to how I handle a standard 200A residential service.

NEC 250.104(A)(3) references “Buildings or structuHowever, res supplied by feeders.” That has me second-guessing my approach.

Since the interior panels are being fed from the outdoor disconnects, would this be considered a structure supplied by a feeder? If so, can I size the water bonding conductor based on the feeder (e.g., 4/0 aluminum) instead of sizing it based on the service conductors (which would require 600 kcmil aluminum)?

Also, if this is the case. Can I install the water bond in the sub panels as well?
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Answer here based on 2023 NEC.


NEC 250.104(A)(3) references “Buildings or structuHowever, res supplied by feeders.” That has me second-guessing my approach.
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250.104(D) is for separately derived systems, which I don't think is what you have. 250.104(A) is what you should be following, and the correct way to follow that is you first need to determine is the structure service supplied or feeder supplied as there is some differences each way.

If the service disconnect is on the building in question then it must be connected to the service equipment and sized per 250.102(C)(1)
If building is supplied by a feeder it still needs to connect to the building main disconnecting means but is installed per 250.102(D) which says to size per 250.122.

The main difference in why it is different - the building supplied by a feeder has an overcurrent device upstream somewhere so you size this like you do an equipment grounding conductor.
 
kwired said:
If the service disconnect is on the building in question then it must be connected to the service equipment and sized per 250.102(C)(1)
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In this case the service disconnects are on the building so the connection is required to be as Dennis outlined in post #12 and the conductor sized according to 250.102(C)(1). Does he use 600 kcmil to determine the bonding conductor size or #4/0?
 
What makes the metal water piping not an electrode? As far as I've always understood it, if the water service is metallic (i.e. copper), its an electrode and the GEC is sized based on 250.66 for the total service size along with supplemental ground rods or UFER.
 
going_commando said:
What makes the metal water piping not an electrode? As far as I've always understood it, if the water service is metallic (i.e. copper), its an electrode and the GEC is sized based on 250.66 for the total service size along with supplemental ground rods or UFER.
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In post #3 it was stated that the water pipe is not an electrode. Im guessing that the part of the water pipe that is buried in the ground is non-metallic so it would not be an electrode.
 
infinity said:
In post #3 it was stated that the water pipe is not an electrode. Im guessing that the part of the water pipe that is buried in the ground is non-metallic so it would not be an electrode.
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Interesting. I've never come across a water system that comes in as plastic and is distributed as copper. If it's not all metal, including the water service, does it count as a metal water piping system? I've never run across this so I am quite perplexed.
 
going_commando said:
Interesting. I've never come across a water system that comes in as plastic and is distributed as copper. If it's not all metal, including the water service, does it count as a metal water piping system? I've never run across this so I am quite perplexed.
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It does seem somewhat strange. Could be the original metallic water pipe was replaced with plastic.
 
going_commando said:
Interesting. I've never come across a water system that comes in as plastic and is distributed as copper. If it's not all metal, including the water service, does it count as a metal water piping system? I've never run across this so I am quite perplexed.
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Back in the 80's and 90-'s the water from a well came in plastic but copper was the desired plumbing method. Now, of course, plastic piping is the preferred way to plumb a home.

The water pipe in the house still must be bonded to the service, IMO so I am not sure what the issue is... Often the power company ran a smaller wire then we did so with 4/0 conductors we only needed #2 for 2- 200 amp panels. A meter main panel at 400 amps would require 1/0. Why the difference I don't know but it calculates out that way.

Now if the service conductors are larger coming from the power company (600 kcm)then, imo, the bond must be based on the larger size conductors, thus 1/0 copper or 3/0 aluminum
 
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