Copper Pipe bonding sizing

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Bama_Electrical

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Alabama
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Electrician
I have a house that I am close to wrapping up the rough-in and I am waiting on the plumbers to wrap up their rough-in. Part of the hold up is all copper water lines in the attic. I know I need to bond it, but have a question on the sizing. #4 good? (NEC 250.66 - largest conductor is 3/0 copper, but not sure what the POCO is bringing to the can) House is a 400/320 AMP service. Going to bond it and jump over to the gas line (AHJ requires gas line bonding) at the tankless water heater. Planning to use #4 for bonding, if ok, but will it need to be bonded in both service disconnects or is 1 sufficient? There is also 2 tankless water heater units and pretty sure the AHJ will require both to be bonded, so will probably be doing this twice.
 
Based on 250.66 (or 250.102 if bonding) a #4 would be fine IF you are installing a GEC from each panel but IF you are installing a common GEC it would likely need to be a 1/0.
 
If the water supply from the city is plastic, then the interior copper the water piping system need to be bonded. @augie47 , I don't think #4 is "required" the OP can do smaller bonding based on the size of the circuit likely to energize the water piping system.
Which also applies to the bomding between H/C/G at the water heater.

Did I interpret the code incorrectly?
 
edward said:
If the water supply from the city is plastic, then the interior copper the water piping system need to be bonded. @augie47 , I don't think #4 is "required" the OP can do smaller bonding based on the size of the circuit likely to energize the water piping system.
Which also applies to the bomding between H/C/G at the water heater.

Did I interpret the code incorrectly?
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In this particular case, it is well water with plastic supply pipe, but everything else is copper pipe. Based on 250.104 it must be bonded. Will the wire size be determined based on what the POCO brings in for 400/320 or the 200amps for the main service for the house?
 
tom baker said:
Wouldn’t the GEC size be based on the conductors from meter to service disconnect?
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Agree for the GEC. How about bonding of the interior water piping system when the supply is plastic?

IMO, we treat that according to the largest circuit that may energize the piping.
 
edward said:
IMO, we treat that according to the largest circuit that may energize the piping.
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I think the way the code reads is if its a regular domestic water pipe the bonding conductor must be sized per table Table 250.102(C)(1) otherwise its ok for it to be largest circuit that may energize the piping 250.104(B).
 
tortuga said:
I think the way the code reads is if its a regular domestic water pipe the bonding conductor must be sized per table Table 250.102(C)(1) otherwise its ok for it to be largest circuit that may energize the piping 250.104(B).
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I respectfully disagree..
250.104 on bonding metal water piping systems states:
The bonding jumper(s) shall be sized in accordance with Table 250.102(C)(1) except as permitted in 250.104(A)(2) and 250.104(A)(3).
Which, for all intent and purposes, sizes it as a GEC (up to 1100kcmil service).
Makes little sense to me as other piping is as you describe but interior water pipe bonding requires full size.
 
But, I say, ... ANYONE that starts out with "I respectfully disagree"... gets a ton of respect from me.

As opposed to "no, you are wrong"!
:)
Carry on...
:)
 
In general, what size the poco runs is not relevant. They usually run conductors smaller than the NEC too.

Does this house have multiple main disconnects or just one 200A panel? If there are two 200A disconnects, you need to add the two sets of 3/0 together to determine the water pipe bond wire size. Would be 1/0 if two sets of 3/0 service entrance conductors.
 
suemarkp said:
In general, what size the poco runs is not relevant. They usually run conductors smaller than the NEC too.

Does this house have multiple main disconnects or just one 200A panel? If there are two 200A disconnects, you need to add the two sets of 3/0 together to determine the water pipe bond wire size. Would be 1/0 if two sets of 3/0 service entrance conductors.
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167800+167800= 335600
? Would that not make it a #2 cu
 
I think so. Was remembering my last 400A service, but it had 400kcmil up the mast which was larger than the two 3/0 swts to the disconnects. So it crossed crossed over into 1/0 territory.
 
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