320 Amp Service Bonding

H

HuntNJ

Member
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?
Click to expand...
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.
Click to expand...
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.
 
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