I'm looking for ideas on installing a 100 amp sub panel feeder wire to a dettached garage. It will be an undergound feeder to the panel. I plan on installing it in PVC SCH 80. Has anyone used Al XHHW as a feeder? If so, does #1 AL sound right? Or does anyone have any better suggestions? Thanks for your help.
Sub Panel underground feeder installation
- Thread starter chris1971
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Rewire
Senior Member
- Location
- Lake of the Ozarks
2-2-2 URD and a #6 thhn ground pulls nicely in 1 1/4 pvc
dwellselectric
Inactive, Email Never Verified
- Location
- Cape Cod, Massachusetts
Why sch. 80? Are you going under a driveway?
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
You can't use 310.15(B)(6) since a garage is not a dwelling, so table 310.16 would require 1-1-1-6 for Aluminum.
I done many and never had a problem, but here I install a double lug meter and just come off the meter and go right back in the ground and hit a main breaker in the out building, this way they are still considered service entrance conductors and you only need 1-1-1 no 6 grounding conductor, bonding and grounding at the garage panel will be done just like a service, it can save money sometimes, since your not required to have a disconnect at the house, you also don't load any more current on the house panel.
But check with your AHJ as some will freak out not having a disconnect at the house.
The NEC only requires a disconnect where service conductors "enter" a building, not where they exit a meter base and go right back into the Earth.
ksmith846
Senior Member
- Location
- Port St Lucie, Florida
How far away is the garage and what is the connected load on the new panel. May have to consider VD and use 1/0 AL.
Do not forget that the detached garage will require a Main disconnect outside and it will also require to you treat it as a new service. Ground rod and building steel tied into the main Disco.
Do not forget that the detached garage will require a Main disconnect outside and it will also require to you treat it as a new service. Ground rod and building steel tied into the main Disco.
my 2 cents
my 2 cents
this is going to be a good one!!!....7 posts so far and 5 different ideas...i am not saying right or wrong, legal or illegal.... i am saying the most common application i have seen in my years is #2/2/2/4 URD leaving a house panel on a 100 amp breaker going underground (no PVC) to a 100 amp MB panel. no grd rods, disconnects etc...only one time was told by an inspector that the the breaker in the garage could not be a 100 amp it had to be a 90 amp or less.
my 2 cents
this is going to be a good one!!!....7 posts so far and 5 different ideas...i am not saying right or wrong, legal or illegal.... i am saying the most common application i have seen in my years is #2/2/2/4 URD leaving a house panel on a 100 amp breaker going underground (no PVC) to a 100 amp MB panel. no grd rods, disconnects etc...only one time was told by an inspector that the the breaker in the garage could not be a 100 amp it had to be a 90 amp or less.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It does not matter what an inspector told you because that doesn't always mean it is correct. #2 alum at 75C is only good for 90 amps and there is no way art. 310.15(B)(2) enters into this. If it is copper than #2 would be fine.
Personally I pipe everything I can simply because I have seen too much UG DB wire fail around here. I would use UF before I would use a USE cable or wire.
Personally I pipe everything I can simply because I have seen too much UG DB wire fail around here. I would use UF before I would use a USE cable or wire.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
I'd run 1.5-2" pvc and pull individual 1/0 AL USE or XHHW conductors.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
May have to consider VD and run 500 - or if load is small 14 may be OK (for VD purposes)
Copper or aluminum? Aluminum should cost less. What is your calculated load? Do you need 100 amps or is it just what is desired. (You can't get a new Cadillac for the price of a Buick) I have connected many residential garages with only a 60 amp feed and even most of those probably would have calculated less than that. Calculate VD based on your calculated load and not necessarily 100 amps.
Install it as a service if possible and not a feeder - you will save on cost of equipment ground conductor with the feeder - Everything else will be just about the same.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
What does this mean? It is a feeder and if the OP is under the 2008 NEC then there is no choice. FWIW, even if the OP is under the '05 I would still run an egc.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
If it originates at the meter and not the house service panel or any point ahead of the service disconnect and has no overcurrent protection then it is a service and not a feeder no matter what code is in force.
If a service running, an EGC only makes a parallel neutral unless you can get around not having a main bonding jumper at the load end.
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Gotcha, I have never really run into an install like that. I thought you were getting at the difference between the '05 & '08 on this.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Better pour concrete in the trench too, in case it is a tractor powered post hole digger:roll:
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
I think I'd lay burial tape before I ever put sch. 80 in a ditch.......
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