Electrical code ? Wire type indoor vs buried

[C4Ranch]

Trying to figure out the wire type needed to run to a sub panel in barn.

Want to run 150' in attic (no conduit) of main house, come out by garage and then 50' under ground (in conduit).

Planning on 2/3 with #4 ground... 100amp

From what I can tell, cannot run URD in attic but could be an option from garage to barn if I put a j-box at garage.

What kind of wire can I run in the attic that requires no conduit? Can I run 2/3 SEU with a separate #4 copper ground wire the whole way and in the attic without conduit?

Thx!

 

[JPRambo]

SER service entrance cable. I'm guessing aluminum ( if copper that is awful large for 100 amp).



Here we can under size 1 size for residential. So 4/4/6/8 would work if you can find it.

 

[C4Ranch]

SER service entrance cable. I'm guessing aluminum ( if copper that is awful large for 100 amp).

Thx! Was thinking aluminum. So is SER acceptable to run in attic without conduit? When I go to running in ground from garage to barn in conduit, can I use same SER or do I need to go to SEU or URD?

 

[quicksandfarmer]

Multi-conductor cable is not meant to be run in conduit. Put a junction box where the conduit enters the house and switch to individual conductors. Or run conduit the whole length. At my Home Depot 150 feet of 1-1/4" PVC is about $65. You would more than make that up by using THHN instead of SEU through the attic.

 

[s219]

If you decided to use conduit in the attic, you could get XHHW-2 wire and use that the whole way. It can be used indoors, outdoors, or underground as long as it's in conduit. They make it in both copper and aluminum.

Otherwise, you could use SER in the attic with no conduit (in fact it should not be used in conduit) and then transition over to URD for the outdoor run. The SER is available with 3 conductors and smaller ground inside the bundle. I don't think you can run a separate ground wire in the attic, so I'd say get SER with the ground inside the bundle.

Technically, you can use 2-2-2-4 aluminum wire for a 100A service feeder to a panel (as a branch, it's limited to 90A). However, over 200', I'd say run the voltage drop calculation to see if you should upsize.

 

[s219]

Thx! Was thinking aluminum. So is SER acceptable to run in attic without conduit? When I go to running in ground from garage to barn in conduit, can I use same SER or do I need to go to SEU or URD?

You cannot run SER or SEU inside conduit except for short runs, say to get into a circuit panel, from meter to panel, etc.

Generally NEC looks at bundled jacketed wire as already being in a "raceway" (the jacket counts) and you cannot put a raceway (jacket) inside another raceway (conduit).

 

[grsthegreat]

If you decided to use conduit in the attic, you could get XHHW-2 wire and use that the whole way. It can be used indoors, outdoors, or underground as long as it's in conduit. They make it in both copper and aluminum.

Otherwise, you could use SER in the attic with no conduit (in fact it should not be used in conduit) and then transition over to URD for the outdoor run. The SER is available with 3 conductors and smaller ground inside the bundle. I don't think you can run a separate ground wire in the attic, so I'd say get SER with the ground inside the bundle.

Technically, you can use 2-2-2-4 aluminum wire for a 100A service feeder to a panel (as a branch, it's limited to 90A). However, over 200', I'd say run the voltage drop calculation to see if you should upsize.

What he said is 100% correct.

 

[Industrial Toys]

That's something I learned here. I used to put jacketed cable in conduit (for ug stuff) figuring I was doing a one better type of thing! Fortunately, usually the conduits were rather large.

Personally, I would not use aluminium for anything, except overhead or main underground service.

 

[buickanddeere]

What are the plans for over current protection and grounding ?

 

[LD1]

That's something I learned here. I used to put jacketed cable in conduit (for ug stuff) figuring I was doing a one better type of thing! Fortunately, usually the conduits were rather large.

Personally, I would not use aluminium for anything, except overhead or main underground service.

From a common sense standpoint, underground is a different thing. Not a NEC code guru, but the whole Idea of not having "cable" like SER inside conduit is to keep the wire from overheating. Allowable ampacities are all based on how much heat can the insulation sustain before breaking down. Thats why there are charts for the allowable number of current carrying conductors allowed, what gauge, and what size conduit. More wires and smaller conduit = more heat.

In reality, burrying SER in conduit in the GROUND, the wire will stay cool. Attic would worry me.

 

[techman]

The code does not disallow putting the cable in a raceway (conduit). You need to use the appropriate tabled for the insulation temperature rating to either derate the current (or use a larger gage size), or use a larger conduit diameter.

paul

 

[Industrial Toys]

Anything in an Attic worries me. Especially as far as mice are concerned. Any new wiring in my outbuildings is done in conduit or BX.

I am a little confused about all this temperature rating of insulation, I have seen in the last few decades. Is it really that critical? Do allowable ampacities for a given conductor size really create such heat?

 

[kcflhrc]

Just FYI, you can also ground locally at the remote structure, just remove the bonding at the remote panel and drive an 8' ground rod. That will save you a lot of money on ground wire.

 

[dickfoster]

SER service entrance cable. I'm guessing aluminum ( if copper that is awful large for 100 amp).



Here we can under size 1 size for residential. So 4/4/6/8 would work if you can find it.

If you use aluminum be sure to goop the connections otherwise it'll go bad, it cold flows, and you can end up burning your place to the ground. I hate aluminum and use copper for all of my wiring.
BTW copper is smaller than aluminum for the same current as copper is the better conductor, it's just a cost thing as aluminum is a lot cheaper.
After burning a lot of houses down they quit using Romex aluminum for standard home wiring so it's no longer code compatible however they still allow it for high amp runs to sub panels etc.. I just won't use it and will pay the extra for copper.
Just recently a bad aluminum connection to the breaker for a 100amp sub panel went bad and cooked the breaker. It had been gooped too. The breaker wasn't cheap to replace. When I recently redid the panel layout in my place no aluminum wiring was used for anything because I hate that stuff.

BTW you don't run Romex in conduit you are supposed to run THHN or THWN . You can run UFB for direct burial of low power circuits but conduit and THHN is the better way to go.

XHHW Wire - Sunlight Resistant Electrical Wire Similar To THHN THWN-2

The idiot previous owner of this place put standard indoor Romex about 3" under ground up to the RV shed so of course I found it with the tiller. I wouldn't even reconnect it, instead I disconnected the branch at the feed end. Talk about water logged. I'll trench and run conduit up to the shed this summer and install a proper sub panel. It scares the bejeebers out of me to think that this guy once made his living repairing commercial airliners. Little wonder I don't like to fly anymore.

 

[aczlan]

Just FYI, you can also ground locally at the remote structure, just remove the bonding at the remote panel and drive an 8' ground rod. That will save you a lot of money on ground wire.

Not if your municipality has adopted the newer version of the NEC (2012?). They now require that you run a neutral and a ground, not just a neutral.

Aaron Z

 

[C4Ranch]

Fantastic replies!!!

The aluminum fire thing got me thinking.

My biggest hesitation with conduit in attic is pulling it up there....

But maybe I just go metal clad the whole way and be done with it!!

Whatcha think? Can MC be direct buried?

MC 4/3 Metal Clad Cable | Electrical Wire | Mobile

 

[buickanddeere]

Just FYI, you can also ground locally at the remote structure, just remove the bonding at the remote panel and drive an 8' ground rod. That will save you a lot of money on ground wire.

Ground wire is supposed to run between the supply and the sub panel. The sub panel as stated needs the bond screw removed . There needs to be two ground rods driven or a plate burried at the sub panel.

 

[buickanddeere]

Why go through the attic ? Go underground from panel to panel.

 

[C4Ranch]

Why go through the attic ? Go underground from panel to panel.

That would be ideal route but I have main service electric line, pool, septic,gutter drains, sprinkler, phone in the way...

 

[joefromga]

Just FYI, you can also ground locally at the remote structure, just remove the bonding at the remote panel and drive an 8' ground rod. That will save you a lot of money on ground wire.

Just curious, can this be dine when retrofitting a house with 2 conductor outlets?

I've often wondered how one would go about it besides total rewiring of the home.