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Splicing main service wire (aluminum)

Posted by localhero (My Page) on
Tue, Nov 30, 10 at 14:52

I'm wanting to make a change in my house that would mean moving the breaker box about 6' further from the meter. I'd like to avoid running a whole new service wire and I was told that it's legal to splice them. This is a 1960 era house and the splice would take place in an accessible attic.

While I've done a fair amount of wiring (for a carpenter) and I understand wiring basics, I've never spliced aluminum wire or any wire this big before.

I'm just starting to research the proper method and am asking for advice/direction here. I've been reading about parallel groove connectors and sealants, etc....

Thanks for all help,
John


Follow-Up Postings:

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RE: Splicing main service wire (aluminum)

Find a list means and follow the instructions for doing it. It must be in a suitable enclosure which will be pretty big with this size stuff.

However, you better talk to the inspector before you get started. If the panel you're moving is the service disconnect, running the wires up to a splice box in the attic and then back down again may run afoul of the definition of "inside nearest the point of entrance."

Frankly, other options are:

Move the meter/service entrance.
Run the service conductors from the meter to the disconnect via a more direct means either through the walls or exterior to the building.
Install a proper disconnect out near the meter.


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RE: Splicing main service wire (aluminum)

Sorry but I don't understand your first sentence. As for the rest, I figured it would take a large junction box of some kind but that's ok.

The current service simply runs thru the attic and turns thru the top plate and into the breaker box. It seems to my admittedly inexperienced self that I can just pull the wires back up into the attic, junction them in an appropriate box and extend the 6' or so with like wire down into a new box of same amp capacity.

If that is workable it seems it would be far easier/cheaper than running a whole new wire or moving the meter/service entrance, right?
Thanks,
John


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RE: Splicing main service wire (aluminum)

That should have read "listed" means.

If that's the way things are now, you might get away with it. Are you saying the wires go from the meter to the the service disconnect by way of the attic now? That would be extremely unusual. Usually, they have a very short path from the meter into the panel.


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RE: Splicing main service wire (aluminum)

Well I had an unexpected opportunity to have an electrician take a look at my situation. It's not exactly what I thought...
Yes the service wire goes from the meter to the breaker box which is in the middle of the house. Probably 25-30ft run. Although the box is a 125Amp box (an old federal pacific)the service wire connects to a 70amp breaker. The wire is not-so-big and the electrician thought it is probably only rated for 70 amps. We didn't measure it.
Now I'm thinking the whole service wire needs replacing anyway.
I apologize for not looking closer at the box myself before I started asking questions here. I had only looked at the box's rating and assumed that the wire was rated the same.
Back to the drawing board for me.

Thanks for the help,
John


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RE: Splicing main service wire (aluminum)

In addition to the size of the main breaker and the size of the wiring you need to determine what the size of the "service" that is delivered to your house if you plan on increasing things.


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RE: Splicing main service wire (aluminum)

Got it.


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RE: Splicing main service wire (aluminum)

Is there a disconnect at the meter? If not there will need to be one. You will not be permitted to run 25-30 feet of unfused feeder cable inside your house.


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RE: Splicing main service wire (aluminum)

I intend to consult an electrician from here on but in the meantime I'm not familiar with the idea of a disconnect at the meter. Why would there need to be a disconnect for a 30' run but not for, say a 10' run?


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RE: Splicing main service wire (aluminum)

"Is there a disconnect at the meter? If not there will need to be one. You will not be permitted to run 25-30 feet of unfused feeder cable inside your house."

Not required unless the AHJ wants to be hard nosed about how close the main is to the meter pan and what wiring method is used.

Most seem satisfied with rigid conduit for longer runs.


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RE: Splicing main service wire (aluminum)

"Why would there need to be a disconnect for a 30' run but not for, say a 10' run?"

For safety's sake. If you were in the attic working on something and knicked the service conductors going to the panel with a tool or other metal object. There is no fuse or breaker between you and the utility transformer on the pole outside to protect you. If however, you put a fused, service rated disconnect beside the meter, anything that might happen to the conductors crossing your attic would be protected by the fuses and not take out the whole neighborhood...... along with the person that became part of the circuit in the attic. Thus the rigid conduit some will require to prevent such accidents.


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RE: Splicing main service wire (aluminum)

That makes sense. What is the disconnect like? Is it just a flip switch such as is found next to an AC unit or is it actually breaker/fuse protected?
On a 150 amp service wouldn't you have to have a 150 amp breaker?

Also, what is AHJ?

Thanks,
John


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RE: Splicing main service wire (aluminum)

The disconnect will resemble the ones located next to the A/C units. The ratings on the box are for the maximum allowed amperage for said box, which is why you see 150Amps coming into a 200A service. AHJ = Authority Having Jurisdiction. He's the one with the final say.


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RE: Splicing main service wire (aluminum)

"The disconnect will resemble the ones located next to the A/C units. The ratings on the box are for the maximum allowed amperage for said box, which is why you see 150Amps coming into a 200A service. AHJ = Authority Having Jurisdiction. He's the one with the final say."

So if you have a 200A service but a 150A box, your service would really be 150A wouldn't it? Not that it's likely we'd actually be pulling 200A thru the service at once, but it seems odd that you would ever put a lower capacity link in a higher capacity run.

I figured AHJ meant (for me)building inspector, but I couldn't figure out the words...

Thanks.


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RE: Splicing main service wire (aluminum)

Why would there need to be a disconnect for a 30' run but not for, say a 10' run?

Actually you need a fused disconnect. Because code requires the disconnect it to be as close as possible to the point where the feeder enters the building. That is commonly understood to be not more than 5'. Some AHJs want even less. If you run the feeder around the outside of the house and then enter, that usually is acceptable.
You need to realize that until your first fused disconnect(usually the main breaker) the wires have no fuse and will continue to burn, arc, melt, etc. until the fuse that supplies you whole neighbourhood trips out.


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RE: Splicing main service wire (aluminum)

"You need to realize that until your first fused disconnect(usually the main breaker) the wires have no fuse and will continue to burn, arc, melt, etc. until the fuse that supplies you whole neighbourhood trips out."

This.

The fuse is on the high side of the local transformer (7.2 kV is about as low as distribution usually goes).

The current available for a short circuit are very large, thus the interrupt ratings of breakers (and fuses) of 10,000+ amps at 120 V.


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