Detached garage sub panel question

Situation is: A residential home with a detached garage has a sub panel which is serviced from a 50A breaker located in the main breaker box. This service feed is approximately 20'. The house has a meter pan/disconnect where the 200A service enters the house. The breaker box is approximately 30' from the meter pan. There is a grounding rod, earthed at the meter pan entrance which goes to the breaker panel. The water lines are bonded. My main question is should the sub panel in the garage be earthed or do I use the ground wire from the main to act as my safety ground like to carry currents from a lightning strike to the original earthed point all the way across the house by the meter pan.

Since the garage is detached, wouldn't I want to provide a path for lightning to the closest point?

Any advice will be appreciated. :-) Thank you

Reply to
Ed B
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If the feeder to the garage is 4 wire, the grounds and neutrals at the garage should be on separate busses, and a ground rod or two should be driven at the garage and attached to the grounding detail. If there is only three conductors in the feeder from the house, the neutral and ground busses should be bonded together in the garage panel, and a ground rod or two should be driven and attached to the neutral - ground detail

Reply to
RBM

The 2008 code eliminated the 3 wire feeder entirely. You have to go the 4 wire route described above.

Reply to
gfretwell

Yep, rule is if he touches it then it needs to be up to current code. It should have 4 wires. The ground and neutral miust be on isolated form each other on different buss bars. There needs to be 2 ground rods.

On the other hand if all he has is a 3 wire setup already installed with no ground at the building and he's just looking to make it safer then he could add a ground rod or two at the garage. But don't get it inspected.

Reply to
jamesgangnc

This is not a new installation. It's existing, and the op doesn't say if it's 3 or 4 wire. He didn't ask how a new installation should be done.

Reply to
RBM

My bad, sorry. You are right about the rod.

Reply to
gfretwell

Don't get me wrong I'm not against just adding a rod. But I thought if you work on an area of your system that it then needs to be brought up to current code?

Reply to
jamesgangnc

You may add any supplemental grounding your heart desires. The rule is that the grounded conductor may only be grounded at one location. The grounded conductor is often mislabeled as the neutral, but it is always the "white" wire and is bonded to ground at the service entrance. This is the only location that it is allowed to be bonded. (your meter)

As long as you do not connect the "neutral" (grounded conductor) with the grounding conductor, in this location, any new grounding is okay.

However, lightning protection is generally anecdotal. Essentially, you can't win if it wants you to lose.

Reply to
MIB

No that is not the rule unless the authority having jurisdiction is abusing her/his authority. Once that feeder is installed and accepted by the AHJ it is good for the life of the structure unless more then a certain percentage of the structure is remodeled under a single permit. A Grounding Electrode System has always been required at detached structures so if yours does not have one then it should not have passed it's initial inspection.

To answer the original posters question if there is not already a Grounding Electrode System at the detached structure it would be a very good idea to install one.

-- Tom Horne

Reply to
Tom Horne

As Tom wrote, there should have been a grounding electrode in the initial installation.

As RBM wrote, the practice with a 3 wire feeder was to bond the neutral and ground at the garage. As greg wrote, starting the 2008 NEC 3 wire feeders are not allowed for new wiring.

A lightning strike to the garage requires lightning rods for protection.

A lightning strike coming from the house (from the service wires) on the feeder may result in the feeder wires at very different potential than the earth at the garage. Ground rods wouldn't help equalize the potential much. Bonding to the mesh/rebar in the floor at installation time would be nice. A suppressor at the feeder panel in the garage would help protect equipment in the garage.

Reply to
bud--

Thanks to all who responded, your advice is greatly appreciated

It is existing, using a three wire feed. I am installing additional electrical circuits off of this sub in the garage need to get it inspected. Once the inspector opens the panel I am afraid he will make me comply with the 2008 rule change. I am not sure if it is grand-fathered.

Reply to
Ed B

Understood, well put :-)

Reply to
Ed B

If it was done legally to begin with, it should have had ground rods already . There is no reason the inspector should have a problem with it since it was done before the code change.

Reply to
RBM

ered.- Hide quoted text -

Best solution is to cal him now and explain what you have. Ask him what he'll accept. It should not have passed inspection before but that's not your fault. How's the wire run between the house and garage now, overhead? Or buried? If it's buried maybe you should ask him out to look at it and that might help your case if he sees it will be a pain to change.

Reply to
jamesgangnc

grand-fathered.- Hide quoted text -

Boy things must work differently where some of you are from. My experience has been that as a homeowner you can get an inspector to answer some questions, but even then, it better be a direct code related question, not an open ended, what;s the best way to do this one. And as for a field visit, forget that without a permit and then only for inspection.

Reply to
trader4

fathered.- Hide quoted text -

That might be. If he's not willing to come out then take a few pictures and go visit him. He's eventually going to have to inspect it. It's actually in his interest for you to ask enough questions so that what you do satisfies him. Otherwise he's just going to have to make repeat visits and possibly going to piss you off. While you're not likely to win any actual concessions from his management they still do not like to hear from complaining citizens. At the end of the day they do work for you. I don't see a downside to trying to work with the guy up front to avoid problems later. If he blows you off and then decides he has problems with your job you really do have a valid complain then.

Reply to
jamesgangnc

Why shouldn't it have passed?

If it is because it was 3 wire with no ground wire, as several people have already said that was allowed prior to the 2008 NEC.

And it is explicitly grandfathered in the 2008 NEC: "250.32-B-Exception: For existing premises wiring systems only, the grounded conductor [neutral] run with the supply to the building or structure shall be permitted to 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 where all the requirements of (1), (2) and (3) are met:" (1) there is no ground wire from the source (2) there are no metallic paths bonded to the grounding system [like metal gas pipe] (3) ground fault protection is not installed at the source of the feeders And there are requirements on the size of the neutral - if it is the same size as the hot conductors it complies. end 250.32

There should have been a grounding electrode in the original installation (these days typically 2 ground rods, in the good old days I think you could use 1).

Reply to
bud--

That might be. If he's not willing to come out then take a few pictures and go visit him. He's eventually going to have to inspect it. It's actually in his interest for you to ask enough questions so that what you do satisfies him. Otherwise he's just going to have to make repeat visits and possibly going to piss you off. While you're not likely to win any actual concessions from his management they still do not like to hear from complaining citizens. At the end of the day they do work for you. I don't see a downside to trying to work with the guy up front to avoid problems later. If he blows you off and then decides he has problems with your job you really do have a valid complain then.

Clearly electrical inspection is different by location. In downstate NY, inspection is done by private certified electrical inspection companies. The only helpful information they'd be likely to give a homeowner is to call a licensed electrician. Many are unlikely to give licensed electricians any advice other than regarding subjective gray areas, and they could care less how many trips they have to make to a job, as we have to pay them for each one

Reply to
RBM

The OP hasn't specified, but since he seems sure that there are no rods, I wonder if the feeder isn't in metallic pipe.

Reply to
RBM

It is not allowed, and for some time, to re-bond the grounded conductor unless a "new" service is established. At no time is it allowed for the grounding conductor to carry current. Period, end of damned story.

Correct. The electrical grounding of the system is its "own" system. Lightning protection is a separate system with strange results.

Reply to
MIB

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