Correct wire terminology

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Old 05-13-16, 06:13 AM
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Correct wire terminology

I have a sub panel in a detached building. It is fed with a 240v feed coming from the house. Cable is 2 AWG aluminum, direct burial, no conduit. Coming into the sub panel are two hots, one neutral and a bare ground, which is also connected to a grounding rod. The insulated cables come out of the ground in a conduit as three separate cables.

The current shed is being replaced by a new barn. This will require moving the panel. The service feed wires will need to be extended by 10-12 feet.

Looking at my options, it seems that Polaris blue connectors will allow for an underground splice. I would have preferred an above ground splice, but don't think it will work for this situation.

Main question is, what is the "name" of the cable I need to extend the current one?

URD is direct burial. So far so good.

Then there is 2-2-4, 4/0 4/0 4/0 2/0. Etc. I know what I need, just not what to call it. I thought I could simply buy what I need by the foot, but it seems the choices are more involved.
 
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Old 05-13-16, 06:32 AM
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Can you read any identify and thing on the existing cable insulation,check out Southwire web site for direct burial (RHH,RHW,USE 2)
 

Last edited by Geochurchi; 05-13-16 at 06:35 AM. Reason: Couldn't down load a link
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Old 05-13-16, 07:56 AM
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Your comment about the ground being bare is concerning. The bare ground best not be aluminum because exposed to moisture it will turn to mush and fail over time. Also if you can't see any identifying marks on the wire how do you know it's direct bury approved wire. Direct bury wire will be listed as URD which carries a USE-2 only rating and cannot be installed inside. Mobile Home Feeder (MHF) is another and carries RHH,RHW,USE-2 ratings and can be installed inside. You do not want to see SER or SEU cable installed below ground in conduit because it's not allowed by code.
 
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Old 05-13-16, 01:06 PM
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Re the bare ground... That one is copper. I should have made that clear. I thought that wire is supposed to be bare as it need to connect to the bare ground rod. The three insulated cables are aluminum.

Aluminum cables are marked:

2 AWG XLPE 600v USE-2 SUN-RES

They exit the conduit as three separate wires. I do not know how they enter the condit at the end of the trench... Haven't made it to that part of the project yet.

The reason I am sure they are approved direct burial is that they were installed by a trusted electrician. The local building inspector approved the installation. If something is that wrong, I have bigger problems as those are the electrician/inspector who wired/approved my entire home.

There is a chance that the entire run is in conduit, but I doubt it. It's about 600'. If direct burial was possible, that's how they likely did it.
 
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Old 05-13-16, 03:20 PM
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The wire being marked USE-2 is correct wire for direct bury. But on the other hand being only USE-2 rated it is not allowed to enter the structure and is to be terminated on the outside. The feeder needs to transition to an approved wire/cable for interior installation. In other words there needs to be a junction box on the outside of the structure where a splice is done changing to something like SER for the entry into the structure and on to the service panel.
 
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Old 05-13-16, 04:40 PM
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Hi Pattenp, just curious what code article states that URD can not be installed inside,Oh never mind I found what I was looking for,as long as it has an NEC listing i.e. RHW , USE 2 etc. he is good to go.
 

Last edited by Geochurchi; 05-13-16 at 04:59 PM. Reason: Answered the question myself
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Old 05-13-16, 06:19 PM
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Ok, so then I need to splice the outside cable to make it longer. Then I run that to an outside junction box and splice again to something like SER to make the 6" run through the outside wall and into the panel on the other side of the wall. I'm surprised the inspector never caught that cable comin through the wall into the panel.


Original question remains. I understand the rating I need for the additional underground run. The retailers don't list it that way... They call it names like 2-2-4 or 4/0 4/0 4/0 2/0. What do I look for n the necessary rating?
 
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Old 05-13-16, 07:32 PM
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The problem I see is that you only have 3 wires feeding the subpanel. The copper ground wire isn't the 4th wire because you need it to run to the ground rod anyway. You are missing the EGC (ground) from the house. The feeder from the house should be 4 wires; 2 hots, 1 neutral and 1 ground. This feeder could be old enough that it could be grandfathered were it not for the fact that you now want to extend it. In my opinion you need to replace the feeder.
 
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Old 05-14-16, 05:11 AM
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So there need to be five wires? The four coming from the house and then a fifth, separate wire for the ground rod? Does the ground come into the sub panel first and then have to go out to the ground rod separately? Or can it connect to the ground rod as it comes in?

Can I not just extend the copper ground wire I already have from the house, or do I need to re-open the trench and replace all 600 feet of cable?

And when I try to order this cable, what exactly do I call it? Looking for "2 AWG XLPE 600v USE-2 " brings up several numbered options. And I am not sure what the "sun-res" means... It isn't listed in most descriptions. Just trying to match the cable.

At this rate, I am leaning towards candles as a better solution.
 
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Old 05-14-16, 06:17 AM
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Anyone of these
RHH or RHW-2 or USE-2 #8 AWG - 1,000kcmil Underground service entrance cable, for direct burial Abrasion, moisture, heat, and sunlight resistant black cross-linked polyethylene (XLP). 90C, wet or dry
 
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Old 05-14-16, 10:31 AM
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So there need to be five wires? The four coming from the house and then a fifth, separate wire for the ground rod? Does the ground come into the sub panel first and then have to go out to the ground rod separately? Or can it connect to the ground rod as it comes in?
This is the current requirement: 4 wires from house to feed the subpanel; 2 hots, 1 neutral and 1 ground. The neutral bus is isolated from ground and is not bonded to the panel box. The ground terminates on a separate ground bar. You need at least one ground rod with a #6 copper from the rod to the ground bar. In my opinion, since you want to extend the feeder it must be brought up to code. You should probably check with your AHJ and see if they will require this to meet current code or if they will continue to grandfather it under previous code.

If the AHJ will allow you to extend the 3-wire feeder, all you need to buy is three lengths of Type XHHW aluminum wire to match the sizes you currently have, they must be installed in conduit. The #6 copper ground wire will need to be replaced with a continuous length or ground wire OR spliced with an irreversible connection such as a HyPress connector or by cadwelding.
 
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Old 05-14-16, 11:05 AM
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Then I run that to an outside junction box and splice again to something like SER to make the 6" run through the outside wall and into the panel on the other side of the wall.
The letter of the code says USE is to be terminated on the outside but I see a lot of the time when USE enters directly into the back of the service panel and only has a distance of a foot or less to penetrate the wall it will be approved by an inspector. You just don't want several feet of USE running inside.
 
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Old 05-19-16, 01:09 PM
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I have reached out the original electrician and will involve the inspector once I have a better idea of what is going on and my available options.

Let's assume:
- There is only a 3-wire feed running to the building (no ground)
- No metallic connection between the two structures (confirmed)
- The AHJ allows the 3-wire to be grandfathered and doesn't require a full re-run of 4 wire.

Trying to better understand the advice given here

If the AHJ will allow you to extend the 3-wire feeder, all you need to buy is three lengths of Type XHHW aluminum wire to match the sizes you currently have, they must be installed in conduit. The #6 copper ground wire will need to be replaced with a continuous length or ground wire OR spliced with an irreversible connection such as a HyPress connector or by cad welding.
XHHW is okay for direct burial? How do I start a conduit between the current underground burial (USE-2) wire and the new XHHW wire?

What I was thinking is this...

Get a length of AL wire rated RHH or RHW-2 or USE-2 (I see that lowes carries this in the 2AWG size I need). Splice that to the current wire using Polaris Blue connectors (ISW-1, rated for submersible and direct bury). That will give me the extra few feet of length I need. This run is outside and underground. It cannot be moved indoors or above ground due to the new structure layout.

Relocate the PVC conduit coming out of the ground to the new location and continue that cable up to the entrance point. My understanding is this cable can be terminated inside the structure. (Either way, the local inspector does allow USE-2 to terminate inside as opposed to an exterior junction box).

To comply with code, the ground and neutral bus in the sub panel would be bonded.

I would also drive a new ground rod and relocate the current copper (continuous) wire to connect.

Does this make sense or is there a problem with this plan? I want to make it easy for the inspector to say yes.
 
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Old 05-19-16, 01:15 PM
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The plan sounds good to me.
 
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Old 05-19-16, 08:03 PM
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XHHW is okay for direct burial?
No, XHHW wire must be installed in conduit. You didn't state previously that the extension was to be direct buried.

I agree with ibpooks, your latest plan should work.
 
 

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