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Old 09-24-2010, 03:03 AM   #1
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This is a bad thing?


My detached garage is supplied by a 240/30a breaker and a 10/3 no-ground circuit ... but the garage is wired up as two general light/appliance circuits with 12g wire. Is there any way this makes sense, or is this a 9-1-1 call waiting to happen? The garage used to be set up as an (illegal) apartment, and I'm guessing that the 240/30a circuit was feeding a subpanel.

To continue using the wiring in the garage, I assume that I need to (a) replace the 30a breaker with a 20a (GFCI) breaker and (b) run a ground from the main panel?

If the garage wiring ties into a water pipe for ground (haven't checked yet), do I disconnect it or leave it? I did notice that at the main panel, the ground conductor to the water pipe also bonds the water line supplying the garage. If the garage wiring is grounded to a water pipe in the garage (the other end of which is definitely bonded to the main panel) does that eliminate the need for a ground conductor run to the main panel?

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Old 09-24-2010, 07:17 AM   #2
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This is a bad thing?


Actually it has a ground, but no neutral. Either way, it needs a 4th wire(2 hot, 1 neutral, 1 gnd) to be split to 120, and to be safe as a 240 citcuit. The neutral should be isolated from the ground buss and panel, and the ground should have a ground earth rod.

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Old 09-24-2010, 09:07 AM   #3
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This is a bad thing?


A true 10-3 wire has 2 hots, neutral & a ground
What colors are the wire ?
Red black & white ?
In the past a 3 wire sub was allowed
If there weren't any other metal pathways between the buildings
The copper water pipe negates the exception
Not sure if it was ever allowed to be used as the sole means of ground
A detached structure needs ground rods
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Old 09-25-2010, 05:00 AM   #4
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This is a bad thing?


Quote:
Originally Posted by Scuba_Dave View Post
A true 10-3 wire has 2 hots, neutral & a ground
What colors are the wire ?
Red black & white ?
Individual conductors -- red/red/white, connecting to a two-pole breaker and the neutral bar, and up to a weatherhead and tied into the original overhead lines between the house and garage (originally the service entrance was to the garage, with an overhead run from garage to house (weatherhead to weatherhead) with 3 seperate conductors).
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Old 09-26-2010, 11:43 AM   #5
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This is a bad thing?


Quote:
Originally Posted by jeffeverde View Post
Individual conductors -- red/red/white, connecting to a two-pole breaker and the neutral bar, and up to a weatherhead and tied into the original overhead lines between the house and garage (originally the service entrance was to the garage, with an overhead run from garage to house (weatherhead to weatherhead) with 3 seperate conductors).
Is there a ground rod present at the unattached structure? Is the neutral and the ground rod wire (GEC) connected together? On the neutral bar, is the green ground screw installed so as to bond the neutral bar to the enclosure?
If this was installed prior to the 2008 code cycle your installation could be compliant.

Caution: With a three wire feeder to the structure as it is, there can be no other metallic paths to the structure. No water lines, phone or cable lines to the structure are strictly prohibited. Nothing but the 3 wire overhead feeder.
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Old 09-26-2010, 08:07 PM   #6
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This is a bad thing?


Add a fourth (overhead) conductor to be your ground.

A ground rod at the detached garage is still needed.
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Old 09-27-2010, 10:51 AM   #7
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This is a bad thing?


Quote:
Originally Posted by AllanJ View Post
Add a fourth (overhead) conductor to be your ground.

A ground rod at the detached garage is still needed.
Since he already has the 3 wire feeder he can use it as long as it was installed before the 2008 code cycle. Lets hope it was a permitted job?
There are literally thousands of feeders installed this way. I don't like it and the NEC doesn't like it either, but he can use what he has, as long as he has the ground rod, GEC connected to the neutral bus and the neutral bus bonded to the panel just like his service panel.
As said above, no other metallic paths are allowed to the structure from the main structure.

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