Hypothetical

[hurk27]

Re: Hypothetical

Bennie the reason the NEC require both end to be bonded is because someone can come along and change the water pipe to plastic and then there would be no bond. so they took another route to prevent objectionable current by running a separate grounding conductor that has no current on it. It's like bonding this water pipe and everything else in this separate building back to the main service without any voltage drop. If you use the neutral the voltage drop of the neutral would place current on this water pipe or any else that was common between the two buildings. Which would be bad news for very small wires like telephone, Doorbell, alarm wires, or even a remote garage door opener control wires. That could be a fire hazard.

 

[don_resqcapt19]

Re: Hypothetical

Bennie,
I don't think that 250.6 permits the removal of a bonding connection.
Don

 

[bennie]

Re: Hypothetical

Bonding the premises wiring system to the cold water pipe only has to be done once.

The premises wiring system will include a separate building.

 

[don_resqcapt19]

Re: Hypothetical

Bennie,
In my opinion 250.104(A)(3) requires the metal water piping system to be bonded at each building or structure even when fed from a common service.
Don

 

[bennie]

Re: Hypothetical

Don: You are likely correct, but we do agree there is a lot of ambiguity in some procedures.

 

[tgreif]

Re: Hypothetical

2002 EDITION, 250.32(A) exception allows the 2nd building to NOT have a ground electrode connection as long as the supply to the 2nd building is from a single branch circuit in the 1st building and a ground conductor is run with the supply (4-wire). I believe this goes against Don's opinion that bonding is required in both buildings. 250.32(B) lists two separate ways to treat the separate building, depending on whether there is a 3-wire or 4-wire supply (3-wire only allowed if there is no metallic path between the two).

 

[tom baker]

Re: Hypothetical

tgreif: The rule you cite is for a branch circuit. This dissussion is for a feeder, a feeder always requires a grounding electrode system and disconnect. 250.32B is for a feeder.

 

[bennie]

Re: Hypothetical

I don't understand two different grounding electrode systems on one service.

 

[don_resqcapt19]

Re: Hypothetical

tgreif,
I don't see anything in 250.32(A) that changes the bonding rule in 250.104(A)(3).
Don

 

[tgreif]

Re: Hypothetical

Tom, I see your point on the branch circuit exception. I stand corrected.