Sub Panel Ground Question

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  #1  
Old 08-01-05, 01:36 PM
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Sub Panel Ground Question

I'm trying to make right what a previous homeowner started.
I have 3- #6 wires(no ground) running from my house to my garage which is unattached. I've been reading some previous posts about this and I'm pretty sure that I need to:
1. Use a ground rod at the garage since it is unattached and I'm not running supply wire with a ground.

2. I am going to use a subpanel with a main disconnect.

Now I have two questions.
1. There is a phone line and a gas line that run from the house to the garage. How does this affect the grounding situation?

2. I'm still a little unclear about the ground bar inside the sub panel. Do I treat this as a new supply since I will be using a ground rod and a main disconnect on the sub panel?

I'm a decent do-it-yourselfer but I want to make sure that this is done correctly. Thanks for any advice.
 
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  #2  
Old 08-01-05, 01:55 PM
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Use a ground rod at the garage since it is unattached and I'm not running supply wire with a ground
You need the grounding rod because it is detached, and whether or not you run a grounding conductor between buildings.

There is a phone line and a gas line that run from the house to the garage. How does this affect the grounding situation?
You must add a grounding conductor between buildings, and it must be in the same conduit as the other three wires. You can use a #10 bare grounding wire.

Do I treat this as a new supply since I will be using a ground rod and a main disconnect on the sub panel?
Because of the phone and gas line, this option is not available to you. You must keep the neutrals and grounding wires isolated.
 
  #3  
Old 08-02-05, 04:15 PM
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I know there's enough room for the ground in the conduit but isn't it going to be impossible to pull it through. It's probably about 25 feet from the house to the garage. Please tell me I'm not going to be digging all of this up and redoing it.

What about this. Does it change the grounding requirements if I disconnect the phone line (don't really need it) and use a poly type gas line in the garage? The gas line comes out of the ground next to the garage and I could make the switch to poly before it enters the garage. Would this change anything?
 
  #4  
Old 08-02-05, 06:31 PM
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The requirements for grounding a subpanel in a detached structure give two options: you can run an equipment ground conductor with the feeder, and wire as an ordinary subpanel, _or_ _IF THERE ARE NO CONTINUOUS METALLIC PATHWAYS BETWEEN THE TWO STRUCTURES_ you can run a feeder without an equipment ground conductor, and then wire the subpanel as though it were a main service entrance. In both cases you need to add grounding electrodes at the detached structure.

Having a metal pipe going from one structure to the other, converted to plastic right before the second structure, with the plastic entering the second structure, strikes me as still leaving the continuous metallic structure between the buildings, but this would really be a call for the local inspector. IMHO this is a bad idea, because it leaves most of the ground loop path present, with only a small break.

IMHO a better solution is to pull the #6 conductors out of the conduit, and then re-feed them with the #10. What size conduit is it, and what kind (PVC, EMT, ...)?

-Jon
 
  #5  
Old 08-04-05, 01:28 PM
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Thanks Jon. I guess pulling the wires back out and refeeding them is probably the way to go.
 
  #6  
Old 08-04-05, 04:15 PM
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Even digging up isnt that big of deal,, ask my helper who has dug hundreds of feet recently,, ha. We bite the bullet and dig when we have to, re-dig if it makes more sense, 25 ft isnt that big of deal and I would want the 4 wire system. When using 3 wire it is so easy to throw it out of compliance, it happens all the time and people dont realize it, run the wire,, whatever it takes and be done with it.
 
  #7  
Old 08-04-05, 07:15 PM
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When you pull the wires out put a conduit pulling string on one of the wires and pull it thru behind the wires. Then when you pull the 4 wires back, tie to the pulling string and use it to pull the wires back in.
 
  #8  
Old 08-05-05, 09:54 PM
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Thanks guys.
 
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