Detached garage sub panel

[monkey]

The home inspector tagged a customer for a 3 wire sub panel in a detached garage. There are no water or gas pipes between the garage and the house, but there is a phone line. I believe if I remove the phone line, the 3 wire feed will be legal. (The panel was installed in 1982). Would a grounding electrode (rod) have been required in 1982?

 

[iMuse97]

Because it is a sub panel, it needs a separate equipment grounding conductor. I don't know of any way around it. The ground rod serves only to make it as if it is a separately derived system, which it is not.

About the 1982 thing, I don't know.

I do know that on the farm where I grew up (midwest), the farm was there way before electricity, and they (the people who owned it) added their own electrical systems as time and money allowed. They've got such a mishmash of stuff, I've had to completely rework most of it so as to create a reasonable equipment grounding system for personnel and animel safety.

 

[monkey]

Karl,
I was under the impression that prior to the 08 NEC a detached building with no other metallic paths could be supplied with a 3 wire feed.

Are you near Crystal Lake?

 

[iMuse97]

Karl,
I was under the impression that prior to the 08 NEC a detached building with no other metallic paths could be supplied with a 3 wire feed.

Are you near Crystal Lake?

Actually, near Cedar Lake (IN). Two miles from the state line and 40 mins. to the Loop. :smile:

You are correct. I just checked the 1999 book and it permits the configuration you describe, exactly as you pointed out, if there are no other metallic paths between the buildings. 250-32(b)(2)

As I read the 1999 code you need a ground rod and that Ground rod and any structural or plumbing metal in the building should be bonded to the grounded conductor (ie. neutral).

 

[Twoskinsoneman]

Karl,
I was under the impression that prior to the 08 NEC a detached building with no other metallic paths could be supplied with a 3 wire feed.

Are you near Crystal Lake?

You right. This is from the 05

(2) Grounded Conductor​

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Where (1) an equipment​

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grounding conductor is not run with the supply to the building or structure, (2) there are no continuous metallic paths
bonded to the grounding system in each building or structure
involved, and (3) ground-fault protection of equipment has not been installed on the supply side of the feeder(s), the
grounded conductor run with the supply to the building or
structure shall be connected to the building or structure
disconnecting means and to the grounding electrode(s) and
shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.​

 

[iMuse97]

Karl,
I was under the impression that prior to the 08 NEC a detached building with no other metallic paths could be supplied with a 3 wire feed.

Are you near Crystal Lake?

You from around here at one time?

 

[monkey]

I spent the first 13 years of my life in Crystal Lake.

Twoskins, I wonder if the grounding electrode(s) were required to be there, or just required to be bonded to the grounded conductor IF PRESENT. I am talking 1982.

I will just bid it with rods anyway.

 

[iMuse97]

You right. This is from the 05

(2) Grounded Conductor​

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Where (1) an equipment​

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grounding conductor is not run with the supply to the building or structure, (2) there are no continuous metallic paths
bonded to the grounding system in each building or structure
involved, and (3) ground-fault protection of equipment has not been installed on the supply side of the feeder(s), [COLOR="MediumTurquoise"]the
grounded conductor run with the supply to the building or
structure shall be connected to the building or structure
disconnecting means and to the grounding electrode(s) and
shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded[/COLOR].​

Arizona, I'm sure you have a grounded conductor (its the third wire of your three-wire system) and you do need to bond it to your building and your ground rod, which itself is a supplemental ground only.

 

[Twoskinsoneman]

I spent the first 13 years of my life in Crystal Lake.

Twoskins, I wonder if the grounding electrode(s) were required to be there, or just required to be bonded to the grounded conductor IF PRESENT. I am talking 1982.

I will just bid it with rods anyway.

I imagine rods are there but I don't have any codes before '05.

480sparky is a good one to ask about rods from 1982. He always seems to have references to old code. You should PM him.

 

[infinity]

In the 1987 NEC, the oldest I have, 250-24 requires a grounding electrode at a separate building. Not sure what the 1981 NEC said.

 

[iwire]

Arizona, I'm sure you have a grounded conductor (its the third wire of your three-wire system) and you do need to bond it to your building and your ground rod, which itself is a supplemental ground only.

The ground rods at a separate building or structure are not supplemental. They are just regular grounding electrodes and make up the grounding electrode system required at separate buildings and structures by 250.32(A).

250.32(A) requires a grounding electrode system to be installed at separate buildings or structures following the rules in 250.50

 

[monkey]

Arizona, I'm sure you have a grounded conductor (its the third wire of your three-wire system) and you do need to bond it to your building and your ground rod, which itself is a supplemental ground only.

Sorry what I meant was if the electrode was present, not the grounded conductor.

 

[charlie b]

I believe if I remove the phone line, the 3 wire feed will be legal.

I don't think you need to do that. The phone wires are not bonded to the grounding systems at both ends. See the article quoted in post #5.

 

[M. D.]

I don't think you need to do that. The phone wires are not bonded to the grounding systems at both ends. See the article quoted in post #5.

Iwould say it depends on the cable and or wiring method used to get it there... article 800.93 ,.I think?

 

[iwire]

The phone wires are not bonded to the grounding systems at both ends.

I bet your right and they are not, but they are likely required to be. 800.90 and / or 800.93.

 

[tom baker]

Because it is a sub panel, it needs a separate equipment grounding conductor. I don't know of any way around it. The ground rod serves only to make it as if it is a separately derived system, which it is not.
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Why do you say this could be a separately derived system with a ground rod?