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normbac

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upgraded a main metered panel on detached garage.
guest house has water pipe grounded at entrance from main panel, main house has a 125amp panel which is also grounded at water pipe entrance the water pipe is continuous metal pipe between the two detached structures no pvc (guest & main house) should I remove the ecg to the water pipe at the main house? am concerned about this being a problem. TIA
 
I don't think you have a choice -- you must bond or ground those water pipes. What is more important is how many wires were run from the garage to the guest house and main house, three or four each? Does that water pipe run to the garage as well?

I'm not so sure the code addresses this particular install regarding undesirable currents unless the pipes also go to the garage. But each building has a partial parallel path back to the main panel via the pipe. A 4 wire feeder to each building is the solution.
 
The only problem that may exist is if the grounded conductor is re-grounded after the service. As in a 3 wire feeder. The water pipe would then carry neutral current, As stated by suemarkp

The ground rod is required also. 250.53(D)(2)

If the feed is 3 wire, then 1 foot section of pvc in the water pipe between the buildings is an option.

(Also stated by suemarkp -- a 4 wire feed to each building is the solution. )

The best & safest solution.
 
Last edited:
SG-1 said:
The only problem that may exist is if the grounded conductor is re-grounded after the service. As in a 3 wire feeder. The water pipe would then carry neutral current, As stated by suemarkp

The ground rod is required also. 250.53(D)(2)

If the feed is 3 wire, then 1 foot section of pvc in the water pipe between the buildings is an option.

(Also stated by suemarkp -- a 4 wire feed to each building is the solution. )

The best & safest solution.
Click to expand...
ok there is no water at garage and it is a 4 wire to main house so I guess all is good just wasnt sure about both panels bonding to cold water when there is continuous pipe
 
normbac said:
ok there is no water at garage and it is a 4 wire to main house so I guess all is good just wasnt sure about both panels bonding to cold water when there is continuous pipe
Click to expand...

The continuous pipe will supplement the EGC during a fault. There should be no current there otherwise. You can use a clamp-on ammeter to prove all is well when a line to neutral load is present.
 
normbac said:
ok there is no water at garage and it is a 4 wire to main house so I guess all is good just wasnt sure about both panels bonding to cold water when there is continuous pipe
Click to expand...

in many towns even if it were a separate run to the street it would still be electrically continuous through the main in the street ,. very common
 
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