Detached Structure

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SCountry

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South Carolina
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Electrician
My father-in-law used to have a wooden garage that was severly damaged from a hurricane. The building was torn down and he purchased a new metal garage. He has a home built in the 60s with a three wire service to his main panel. The garage was also fed by three wire. I wired his garage, and the panel he purchased only has a neutral bus. I supplied a ground rod and installed a ground bus for it. The neutral bus is not bonded to the ground. His friend who is an electrician stopped by and told him the ground and neutral have to be bonded and stated things I’ve only found legal in 2005 nec.

I’m a commercial electrician so I don’t deal with dwellings ever. I just want to know who’s right? Should they be isolated or boned? It’s not for sake of who’s right to me. I couldn’t care less. It’s not in my wheel house and I can’t find anything in 250.32 about metal detached structures that make me 100%. Anyone familiar I would appreciate your help.

I will say it’s not getting inspected but that’s not going to stop me from making right. Any input is greatly appreciated.

Edit: His friend’s claim was in the 80’s on a wood garage, he failed inspection because of this.
 
My view point with a metal structure is that if they were bonded… It would make a bad day for someone because the building itself isn’t grounded.
 
Welcome to the forum.

With a 3-wire feeder (back when it was compliant), the ground and neutral must be bonded together.

Without that bond, a hot-to-ground fault would energize the panel, the rod, and the building itself.

The ground must be solidly tied to the neutral at some (one) point in the system for it to function.
 
SCountry said:
The garage was also fed by three wire. I wired his garage, and the panel he purchased only has a neutral bus. I supplied a ground rod and installed a ground bus for it. The neutral bus is not bonded to the ground. His friend who is an electrician stopped by and told him the ground and neutral have to be bonded and stated things I’ve only found legal in 2005 nec.
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Your new structure must be fed by four wires: two hots, a neutral and a ground from the main panel where it comes from.

The panel in the new structure is a sub panel. I would use a main breaker panel to provide a disconnect for the building. The two hots from the feeder obviously go to the main breaker, the neutral to the neutral bar and the ground to the ground bar.

The neutral IS NOT bonded to the ground in a sub panel.

Additionally, you must drive two 8' ground rods at least 6 feet apart and bond them together from one to the other and then to the ground bar in the new panel with #6 copper.

I would also run #6 copper from the ground bar around the building either inside or outside and bond to the metal with lugs in several places, at least one on each side.

-Hal
 
Do what Larry said. The 3-wire feed used to be legal until about 2005 like you said, but it is unsafe without the neutral and ground bonded together.

Hal is correct that to bring it up to current code it would need a 4 wire feed and separated ground and neutral. But I doubt you're going to shut it down and re-install the feeder tomorrow. So do what Larry says, so that you have an effective ground fault current path, and the breakers in that panel actually trip if you have a hot-to-ground fault, including a hot to metal building fault. Do that tomorrow.
 
The building being metal doesn't change much and makes no difference to code. It just means the current situation is even somewhat more unsafe.
 
hbiss said:
Your new structure must be fed by four wires: two hots, a neutral and a ground from the main panel where it comes from.
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250.32(B)(1) Exception 1 starts off "For installations made in compliance with previous editions of this Code . . ." So that can plausibly be interpreted to mean that if the building is replaced, but the feeder to the building is existing and intact, the exception still applies.

Cheers, Wayne
 
Thank you for all the replies. I of course left details out. I already took care of the building not be grounded and I’m under the same impression as Wayne. Also I’m headed to work but some where in 250 I read that they shouldn’t be bonded if there’s any type of metal between the feeder panel and the sun panel. I may have interpreted this incorrectly.

Thanks for the input fellas
 
LarryFine said:
Welcome to the forum.

With a 3-wire feeder (back when it was compliant), the ground and neutral must be bonded together.

Without that bond, a hot-to-ground fault would energize the panel, the rod, and the building itself.

The ground must be solidly tied to the neutral at
hbiss said:
Your new structure must be fed by four wires: two hots, a neutral and a ground from the main panel where it comes from.

The panel in the new structure is a sub panel. I would use a main breaker panel to provide a disconnect for the building. The two hots from the feeder obviously go to the main breaker, the neutral to the neutral bar and the ground to the ground bar.

The neutral IS NOT bonded to the ground in a sub panel.

Additionally, you must drive two 8' ground rods at least 6 feet apart and bond them together from one to the other and then to the ground bar in the new panel with #6 copper.

I would also run #6 copper from the ground bar around the building either inside or outside and bond to the metal with lugs in several places, at least one on each side.

-Hal
Click to expand...
Click to expand...

Appreciate the reply. The panel has less than six circuits so a main breaker isn’t required. I suggested swapping his main lug for additional safety. He didn’t want to so I didn’t argue.
 
wwhitney said:
250.32(B)(1) Exception 1 starts off "For installations made in compliance with previous editions of this Code . . ." So that can plausibly be interpreted to mean that if the building is replaced, but the feeder to the building is existing and intact, the exception still applies.

Cheers, Wayne
Click to expand...

Was my thoughts, thanks for the advise,
 
SCountry said:
Thank you for all the replies. I of course left details out. I already took care of the building not be grounded and I’m under the same impression as Wayne. Also I’m headed to work but some where in 250 I read that they shouldn’t be bonded if there’s any type of metal between the feeder panel and the sun panel. I may have interpreted this incorrectly.
Click to expand...
Actually, the rule is that the 3-wire feeder was never legal if there was a metallic pathway like a water pipe.
 
I believe until 1996, or perhaps '99, a 3-wire feeder and separate GES bonded to the neutral was the way one was supposed to wire a detached building.
 
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