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Old 10-07-2013, 02:46 PM   #1
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detached garage sub-panel??


A couple of questions regarding sub-panels in a detached garage....

A few years ago, when I bought my house c1915, I had an electrician upgrade me to a 200amp service with a sub-panel in the basement and one in my detached garage. Fast forward....neighbor down the street whom I later met has a sub panel in his detached garage. The difference is his was installed about 15-20yrs ago and does NOT have an isolated neutral. Of course mine does and I've been telling him for years he should probably fix that. Being as he does have GFI's on about every circuit, how important is it that he fix that? The problem is he doesn't have the separate neutral wire, just two hots and a ground coming in.

My understanding is that without the isolated neutral, he runs the risk of getting shocked if a neutral strays.... I also question if a detached building should have a separate ground. My garage does not have a grounding rod and apparently passed inspection without, but he added a 2nd garage and they made him put in a grounding rod, in case he ever added service to the 2nd garage. Of course he has now combined the two garages...should he run a ground wire to the rod in the garage?

I hope this all makes sense....it's been weighing on us both for some time!

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Old 10-07-2013, 02:57 PM   #2
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detached garage sub-panel??


Your confusing me with your terms of ground and ground rods. They are not the same and serve 2 totally different purposes.

He has a neutral not a ground.

Prior to the 2008 code is was allowed to run 3 wire feeders to detached structures as long as there wasn't any metallic paths between the two, ex. cable tv, water line, etc.

I say as long as something met the code at installation, it's fine but, it never hurts to go above code minimum.

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Old 10-07-2013, 04:09 PM   #3
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detached garage sub-panel??


Quote:
Originally Posted by wirenut1110 View Post
Your confusing me with your terms of ground and ground rods. They are not the same and serve 2 totally different purposes.

He has a neutral not a ground.

Prior to the 2008 code is was allowed to run 3 wire feeders to detached structures as long as there wasn't any metallic paths between the two, ex. cable tv, water line, etc.

I say as long as something met the code at installation, it's fine but, it never hurts to go above code minimum.
Sorry for the confusion! I'll try to clarify...

He has 3 wires, two hots and a bare (aluminum?/silver) wire feeding the sub-panel. I took that 3rd, silver wire, to be a ground wire...am I correct you are saying it is instead a neutral? Does that mean he doesn't have a true ground?

When I asked about needing a separate ground and grounding rod, I meant, should he run a separate, bare copper wire to the grounding rod, that they had him install in the 2nd garage when he had the foundation poured. The sub-panel is installed in garage #1, but it has since been attached to garage #2. Neither are attached to the house.

He does have water lines running to the garage, but they are PVC. He also does have cable tv and I believe a phone line running into the garage from the house.

If he does run a bare copper wire to the buried grounding rod, should he then install another isolated bus bar in the panel? I would assume the bare copper wire would attach to the bus bar attached to the panel with all the ground wires going to it and the neutral wires attached to the isolated bus bar attached to the silver(aluminum?) wire???
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Old 10-07-2013, 04:21 PM   #4
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detached garage sub-panel??


Is this (1), a garage with a couple of bare bulbs, a circular saw and a $10 radio? Or, is this (2), a man cave with wet bar, intercom and $20,000 of electronics?

Three wire feed or four wire feed(isolated neutral)

For (1), it's not worth it to upgrade.

For (2), from the house to the garage, any little piddly TV cable or wire can fry, or worse, degrade reception. Large stuff like water pipes can energize and kill people. (Good for mother-in-law suites.)

Grounding Electrode System

For (1), if you get lots of lightning, one or two ground rods may save the garage from burning down one day.

For (2), the better your ground the better your surge protectors will work. So skip the crappy 8 foot rod and get something professional and decent. And one surge protector in the panel box in addition to the ones at the equipment.
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Old 10-07-2013, 04:22 PM   #5
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detached garage sub-panel??


Is the feed to the garage overhead or underground?

The panel should have a ground rod.
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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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Old 10-07-2013, 04:25 PM   #6
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Dang I type slow! Wait up, I'll answer those questions.
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Old 10-07-2013, 04:32 PM   #7
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Quote:
Originally Posted by Master Brian View Post
"...am I correct you are saying it is instead a neutral? Does that mean he doesn't have a true ground?
It's a combined neutral/ground just like the three wire service from the power company. It works fine.

Quote:
Originally Posted by Master Brian View Post
If he does run a bare copper wire to the buried grounding rod, should he then install another isolated bus bar in the panel?
No! The isolated neutral is only for a four wire feed
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Old 10-07-2013, 04:47 PM   #8
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Quote:
Originally Posted by Master Brian View Post
I would assume the bare copper wire would attach to the bus bar attached to the panel with all the ground wires going to it and the neutral wires attached to the isolated bus bar attached to the silver(aluminum?) wire???
That's a really good way to kill people and screw up a lot of electronics. Like surge protectors and GFCI's. It may mess with your cable reception, too.

Quote:
Originally Posted by Master Brian View Post
He also does have cable tv and I believe a phone line running into the garage from the house.
So, get a quote to run a four wire feed or new cable and phone lines. Then decide how many times you can replace the cable and phone lines before you get pissed off enough to pay for the new feed.(By "you" I mean him or whoever.)

Last edited by Glennsparky; 10-07-2013 at 05:11 PM.
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Old 10-07-2013, 05:13 PM   #9
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detached garage sub-panel??


Quote:
Originally Posted by Glennsparky View Post
Is this (1), a garage with a couple of bare bulbs, a circular saw and a $10 radio? Or, is this (2), a man cave with wet bar, intercom and $20,000 of electronics?

Three wire feed or four wire feed(isolated neutral)

For (1), it's not worth it to upgrade.

For (2), from the house to the garage, any little piddly TV cable or wire can fry, or worse, degrade reception. Large stuff like water pipes can energize and kill people. (Good for mother-in-law suites.)

Grounding Electrode System

For (1), if you get lots of lightning, one or two ground rods may save the garage from burning down one day.

For (2), the better your ground the better your surge protectors will work. So skip the crappy 8 foot rod and get something professional and decent. And one surge protector in the panel box in addition to the ones at the equipment.
It is a little of both. He converted the original garage into a mancave and he does have a 47" flatscreen in there, but not $20k worth of electronics. In total he has a full size fridge for the beer and two coffin freezers for his game. He also has a 220v water heater and a 220v wall heater in the larger garage and of course various power tools, etc.

We are in South Central Kansas and do get a fair amount of lightening.
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Old 10-07-2013, 05:14 PM   #10
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Is the feed to the garage overhead or underground?

The panel should have a ground rod.
I am pretty sure the feed is underground, but I'll have to double check that.

The panel isn't hooked to a grounding rod and neither is mine. Not to get off course, but should I add a grounding rod for my garage panel?
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Old 10-07-2013, 05:18 PM   #11
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detached garage sub-panel??


Quote:
Originally Posted by Glennsparky View Post
That's a really good way to kill people and screw up a lot of electronics. Like surge protectors and GFCI's. It may mess with your cable reception, too.


So, get a quote to run a four wire feed or new cable and phone lines. Then decide how many times you can replace the cable and phone lines before you get pissed off enough to pay for the new feed.(By "you" I mean him or whoever.)

The phone and cable are overhead, so easy to replace if you are saying the 3 wire feed can hurt them. But I'm guessing leave it all alone and as is, UNLESS he wants to pay for the cost of running 4 wire feed.

I am also guessing, it won't hurt anything to tie into the ground rod they, the city, made him put in when he poured the foundation to the new garage!
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Old 10-07-2013, 05:20 PM   #12
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detached garage sub-panel??


Quote:
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The panel isn't hooked to a grounding rod and neither is mine. Not to get off course, but should I add a grounding rod for my garage panel?
Yeah, you can add ground rods.

I'm curious as to why there's bare aluminum if it's underground
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Old 10-07-2013, 05:23 PM   #13
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detached garage sub-panel??


Also, I see Kansas is under "local adoption" Do you know what code cycle your area is on?

Last edited by wirenut1110; 10-07-2013 at 05:25 PM.
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Old 10-07-2013, 05:32 PM   #14
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This is from the original post.

Quote:
Originally Posted by Master Brian View Post
My garage does not have a grounding rod and apparently passed inspection without...
Your garage probably does have a Grounding Electrode System, but it can take many forms. Like,

Since around '08 ground rods have been used much less. They have been replaced with a wire to the rebar in the concrete footer.(Concrete Encased Electrode/Ufer Ground) The wire may be hidden inside the wall or under siding.

To find out, open the garage sub panel door and remove the front cover. Now look, don't touch. Is there a fat wire on the ground bar that leaves the panel by itself? By that, I mean it doesn't leave the panel in a cable or pipe bundled with black or white wires. Find that wire and you probably have a GES.
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Old 10-07-2013, 05:42 PM   #15
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detached garage sub-panel??


I got this from ET but, maybe the mod's can add this as a sticky to help us figure out code cycles in the event the OP doesn't know.
http://www.nema.org/Technical/FieldR...on-Map-PDF.pdf

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