Main Residence Service Wire Junction Box


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Old 07-17-13, 09:53 AM
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Main Residence Service Wire Junction Box

Hi,
I am in the process of building a new house, and have just run the main electric service wire from the meter to the back of our detached garage. From there, it runs to the back of the house. All of this is underground in 3" PVC conduit.

The detached garage is between the meter and the house, so it made good sense to run the service to the garage first. There will be a 125A panel in the garage and a 200A panel in the house. The service wire is AL 4/0-2 2/0-1 URD. That translates to aluminum wire with two hot and one ground wire. The hot wires are about 1/2" diameter aluminum with insulation, and the ground is a little smaller.

What I want to do is to put a junction box on the back of the garage. From a wiring standpoint, it would be just like a typical residential switch box where the hot wires are run in and spliced into a wire run to the next box, with two short pigtails run to the switch terminals. Since I am dealing with large service wire instead of 12-14 ga. house wiring, is there a standard way of making the connections in a large steel electrical box? It was suggested to me that I use 4/0 lugs, but I would need insulated lugs. Do those exist for this type of application?

I also dreamed up a box with the typical bus bars where I could connect the four hot wires (two from the meter, and two going out of the box to the house), and two more connections on the bus bar to run two hot wires into the garage for my 125A panel. There must be an easier way.

It would seem to me that I need some insulated 4/0 lugs. Anyone know if they exist, and if so, is this an appropriate method to meet my electrical goals? I have found copper 4/0 lugs with 1/2" bolt holes. They crimp onto the wire. I could put these onto the end of all of my wires and bolt the two sets of hot wires and pigtails together. Then, I would still need to insulate them from each other because of the bolts. Is there an electrical junction box with two places to bolt the wires, so designed that the two bolt bars are insulated from each other and the box?

Regards,
Chuck
 

Last edited by Factotum; 07-17-13 at 10:03 AM. Reason: Update
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Old 07-17-13, 10:36 AM
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Some solutions

To my surprise, I did find the following thread.

http://www.doityourself.com/forum/el...-panels.html#b

Evidently, there are various connectors out there to use in a box. Polaris is one. I will have to do some research on bugs, multi-taps, and other insulated wire connectors.

In my area, which is served by a rural electric company, the box below the meter has circuit breaker protection built in. Also, only 3-wire service is required, provided that the ground wire goes to a real ground rod into the earth. In my case the concrete guys put a 1/2" rebar through the footing into the earth for me to tie into.

Chuck
 
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Old 07-17-13, 10:38 AM
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For the splices at the garage, you can use Polaris connectors or the clear connectors from Morris.

The service wire is AL 4/0-2 2/0-1 URD. That translates to aluminum wire with two hot and one ground wire.
That's two hots and a neutral. You must establish and bond to a grounding electrode.
only 3-wire service is required, provided that the ground wire goes to a real ground rod into the earth. In my case the concrete guys put a 1/2" rebar through the footing into the earth for me to tie into.
That should be good. Check with your inspector.

Reading Wiring Simplified should help answer many of your questions.
 

Last edited by Nashkat1; 07-17-13 at 11:09 AM.
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Old 07-17-13, 11:01 AM
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the box below the meter has circuit breaker protection built in. Also, only 3-wire service is required, provided that the ground wire goes to a real ground rod into the earth.
In my opinion, the NEC requires you have 4 wires between the circuit breaker and the two subpanels at the garage and the house. I know codes are sometimes relaxed in rural areas, what code has been adopted there? Normally there is some version of the NEC that has been adopted, some may still go back to the 1999 NEC or earlier. Have any amendments to the NEC been adoipted? Not much sense trying to proceed till we know what code you have to follow.
 
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Old 07-17-13, 12:03 PM
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I agree about the need for 4 wire feeders. The buildings would also need a means of disconnect.

Also the wires are not big enough for both a 125 and 200 amp loads.
 
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Old 07-17-13, 02:20 PM
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Thanks to all who replied. I will get a copy of Wiring Simplified. I should have thought of that first.

I think that I am on the right track with the Polaris or Morris insulated connectors and a grey PVC junction box that has mounts in and out for my 3" PVC conduit.

I did speak with the local electrical inspector about 3 or 4 wire service feeds. He said that 3 wire are OK in our rural county, provided that that the neutral is properly grounded.

Chuck
 

Last edited by pcboss; 07-19-13 at 09:44 AM. Reason: formatting
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Old 07-17-13, 04:48 PM
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He said that 3 wire are OK in our rural county, provided that that the neutral is properly grounded.
What does that mean? Bonded to a grounded electrode conductor?
 
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Old 07-17-13, 07:10 PM
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For 3" conduits in and out you are required to have an 18" x 18" pull box if the pipes are on adjacent/same sides (U-pull), and 24" x XX" if the pipes are on opposite sides (straight pull), minimum.
 
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Old 07-19-13, 09:08 AM
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Where is the meter located , and where is the Service Dis-connecting means located?----Could you please decribe you plans for Grounding Electrodes , Grounding Electrode Conductors, and Equiptment Grounding Conductors?.
 
 

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