what size pipe for 100 amp subpanel?

[d33pt]

I am trenching for a pipe to run a line to a future subpanel in a detached garage. I will be using gray PVC buried 18". A slab is going into this area, so I'm just getting the pipe installed for the future. The run will be about 50 feet, and only 10 feet or so is underground.

What gauge wire will i need, and how big of a pipe do I need to bury? I'm just going to bury the pipe, put the elbows on it, and bring it above ground then cap off for now. Anything else I need to think of doing?

 

[Norcal]

Bare minimum is 1 1/4" but if 2" is used it will be easier to pull then a smaller size w/ a limited increase in cost. As for wire size, #3 AWG copper or #1 AWG aluminum.

 

[d33pt]

Thank you. Then I will go with 2 1/2" as it's not much more expensive at all, with such a short run. I didn't think even that was big enough for #3 wire, so I wanted to make sure. Bigger is better because I may want to put something else in there down the line.

 

[contactme_11]

Thank you. Then I will go with 2 1/2" as it's not much more expensive at all, with such a short run. I didn't think even that was big enough for #3 wire, so I wanted to make sure. Bigger is better because I may want to put something else in there down the line.

You can't run other stuff in the same conduit as a service line. If you want to run other stuff later then you should just bury one or two extra 1 1/4 conduits in you trench for futures.

 

[Norcal]

Thank you. Then I will go with 2 1/2" as it's not much more expensive at all, with such a short run. I didn't think even that was big enough for #3 wire, so I wanted to make sure. Bigger is better because I may want to put something else in there down the line.

2 1/2" is a bad idea 2" will be fine, run extra conduits for telephone/data & a spare for other uses. 1 1/4" should be fine or even overkill for those spares.

 

[1Garageman]

2 1/2" is a bad idea 2" will be fine, run extra conduits for telephone/data & a spare for other uses. 1 1/4" should be fine or even overkill for those spares.

ya you might want to run a cat5/cat6 later, phone line, who knows. Go ahead and run an extra pipe or two!

 

[KENLUDE97]

I just ran 1-1/2" but i would go with at least 2" for ease.

I didn't bother to run Cat5-6 wire as i have wireless internet, and i didn't bother to run phone line as i have a Cell... But i did run TV Cable. Just some of my thoughts.


I ran #2 Aluminum.

From Home Depot

 

[d33pt]

2 1/2" is a bad idea 2" will be fine, run extra conduits for telephone/data & a spare for other uses. 1 1/4" should be fine or even overkill for those spares.

Curious why 2 1/2 would be a bad idea? I will run an extra 1 1/4 for the other stuff then, to keep it separate. Might have some cat5 or rg6, who knows.

 

[contactme_11]

Curious why 2 1/2 would be a bad idea? I will run an extra 1 1/4 for the other stuff then, to keep it separate. Might have some cat5 or rg6, who knows.

I think he just figured it was overkill. Just a thought though, I'm not sure if most 100amp boxes could fit a locknut and antishort bushing for 2 1/2 adapter?

 

[KENLUDE97]

My GE box easily took a 2" pipe. I would think that it would take a 2-1/2"... But not likely much bigger than 2-1/2"

 

[Norcal]

I just ran 1-1/2" but i would go with at least 2" for ease.

I didn't bother to run Cat5-6 wire as i have wireless internet, and i didn't bother to run phone line as i have a Cell... But i did run TV Cable. Just some of my thoughts.


I ran #2 Aluminum.

From Home Depot
http://i6.photobucket.com/albums/y205/KENLUDE97/amps.jpg[IMG][/QUOTE]

#2 AL is not suitable for 100A.:mad::mad::mad::mad::mad::mad::mad::mad::mad::mad::mad::mad::mad:

 

[Gooch]

I just ran 1-1/2" but i would go with at least 2" for ease.

I didn't bother to run Cat5-6 wire as i have wireless internet, and i didn't bother to run phone line as i have a Cell... But i did run TV Cable. Just some of my thoughts.


I ran #2 Aluminum.

From Home Depot

I'd ask that you remove that table as there are many issues with it.

 

[Norcal]

I'd ask that you remove that table as there are many issues with it.

Agreed, it is a bullsh*t chart, very misleading to a novice. Plus a photo like that needs to be downsized, WAAAAAAAY to large.

 

[KENLUDE97]

removed...

im just trying to help.

one thing that i ask is that you "correct" the chart not just shoot it down. thanks

 

[Falcon67]

removed...

im just trying to help.

one thing that i ask is that you "correct" the chart not just shoot it down. thanks

I'm not the NEC guy, but there are many "charts" and wire size is impacted by load, distance, wire type, insulation type, how it's run (conduit/free air), where used, etc, etc. So one "chart" doesn't get it, or even gets close. You look at the total installation and its context, then go to the appropriate table and start looking. So they are not trying to be mean, just to get you away from a misleading set of information.

 

[KENLUDE97]

That did have the NEC callout on the pic (table 310-16 NEC 1999). That is why I posted it, not just some chart that i made up. Im NOT trying to spread false info, the internet is FULL of it.

Yes i understand that you need to take into account the distance and such.

 

[Falcon67]

What I think they are saying is that even though the table has an NEC callout, it is half-assed. It's generic, and maybe too generic. It was probably put together based on what HD stocks. And having bought wire from HD, what they say they stock on the big chart may not be what's on that big rack.

http://www.elliottelectric.com/References/Allowable_Ampacities.aspx
http://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm
http://www.houwire.com/products/technical/article310_16.html

 

[Gooch]

That did have the NEC callout on the pic (table 310-16 NEC 1999). That is why I posted it, not just some chart that i made up. Im NOT trying to spread false info, the internet is FULL of it.

Yes i understand that you need to take into account the distance and such.

I'd be happy to post a table if there was one to post, but unfortunatly, there are about 3 or 4 more tables that possibly would be refered too. NEC 1999 was 5 code cycles ago.

 

[Charles (in GA)]

That did have the NEC callout on the pic (table 310-16 NEC 1999). That is why I posted it, not just some chart that i made up. Im NOT trying to spread false info, the internet is FULL of it.

Yes i understand that you need to take into account the distance and such.

The table is correct, however it uses RHH and THHN types (and from the 90C column) to arrive at the 100 amps. Problem is, "mobile home" feeder, quadplex or triplex, is not either of those, and that is what everyone buys to run to an outbuilding or detached garage. And you are not allowed to use the 90C column to size the wire. It is there for derating purposes. You normally will not find terminal ends, lugs, switches, etc, that are rated at 90C, generally, the common everyday stuff everyone uses is rated 60C/75C.

Basically, its accurate, but not information anyone can use.

Charles

 

[Cobra6]

I ran a 2" PVC for my power subpanel,
and ran a 1.5" PVC for my coax, Cat 5, SHTF, etc.

 

[d33pt]

i should leave some room between the two pipes right? also should space them out a bit from the wall?

 

[Cobra6]

I left 3 or 4 inches between mine -
Mine come up inside the wall so I can mount the panel flush on the wall
If you are using 16" spacing on your studs, measure to make sure they don't come up where your studs will be. I will try to find a better pic of mine. You can see the gray PVC pipes in this pic.

Are you pouring your own concrete?
If you are contracting your concrete, they should be able to help you - all you need is the pipe and elbows or sweeps to go with them

 

[BLUBAYOU]

I did two runs of 2 1/2" and another of 1" or 1 1/2" (which I already had on hand). Better too much than not enough!

I also took the time to figure out the eventual placement of the CMUs in that area of the garage pre-pour. All 3 runs of conduit come right through the voids in the CMUs and within the same stud cavity in the wall. A little planning goes a long way to make things tidy!

Power came through the first run of 2 1/2" to a 125 amp panel, data will go through the smaller run and I've actually used the vacant 2 1/2" on occasion to run an air line from the 60 gallon in the garage into my basement when doing finishing work in the house. Comes in handy and the nailer is quiet enough that I can work while our kids sleep upstairs since there's no compressor noise.

 

[oleguy]

what is a CMU?

 

[Aceman]

cinder block

 

[Norcal]

what is a CMU?

Concrete Masonry Unit / concrete block / cinder block.

 

[oleguy]

Concrete Masonry Unit / concrete block / cinder block.

thanks...thats why i hate accronims...lol.

 

[zmaxmotorsports]

You can't run other stuff in the same conduit as a service line. If you want to run other stuff later then you should just bury one or two extra 1 1/4 conduits in you trench for futures.

 

[zmaxmotorsports]

I left 3 or 4 inches between mine -
Mine come up inside the wall so I can mount the panel flush on the wall
If you are using 16" spacing on your studs, measure to make sure they don't come up where your studs will be. I will try to find a better pic of mine. You can see the gray PVC pipes in this pic.

Are you pouring your own concrete?
If you are contracting your concrete, they should be able to help you - all you need is the pipe and elbows or sweeps to go with them

If youre bring the pipe up through a concrete floor wrap it with sill seal in the area the concrete will be covering.

 

[Notgrownup]

I am gonna use 2"' It seems plenty big an I will run a separate smaller for RG cable in case.

 

[Notgrownup]

I told my concrete guy to put my electrical pipes in the corner, I said around there so it will miss the studs... He put them in THE CORNER.....I mean the very corner so now I think I will cut them and come from the outside with a LB fitting...

 

[sberry]

2 1/2 is an odd size, for all this 2 inch is plenty and much easier to work with. I used some 1 1/2 and wish I would have went with 2 especially if it has more than 2 turns.

I told my concrete guy to put my electrical pipes in the corner

This should be a good lesson learned. Never leave placement of critical pieces to others, it has hurt more than one job,,, I bet I have hears a hundred times thru tears,,, well I told the laborers etc.

I remember a while back my pluma bud did this,,, he "told" someone and didn't want to drive the hour each way to insure it was done so he got to hire a couple men for a couple days to tear out a stairway and replace framing to get a tub unit to the second floor.

 

[Justanoldguy]

If youre bring the pipe up through a concrete floor wrap it with sill seal in the area the concrete will be covering.

I think after 3 1/2 years, he may have it sorted.

 

[Notgrownup]

2 1/2 is an odd size, for all this 2 inch is plenty and much easier to work with. I used some 1 1/2 and wish I would have went with 2 especially if it has more than 2 turns.

This should be a good lesson learned. Never leave placement of critical pieces to others, it has hurt more than one job,,, I bet I have hears a hundred times thru tears,,, well I told the laborers etc.

I remember a while back my pluma bud did this,,, he "told" someone and didn't want to drive the hour each way to insure it was done so he got to hire a couple men for a couple days to tear out a stairway and replace framing to get a tub unit to the second floor.

Shoulda never left him alone but such is life.

 

[dledinger]

You can't run other stuff in the same conduit as a service line.

This OP is installing a feeder, not a service.

 

[d33pt]

I actually just got this done recently. Never got around to it 3 years ago. Ended up going with two 1 1/4" pipes. 60A panel with #6 copper in one and cat5 in the other. Thanks for the advice.

 

[alfredeneuman]

This OP is installing a feeder, not a service.

It is a detached garage so only 1 circuit (or multiwire circuit in the case of a subpanel) is allowed to serve the garage.

It would be a violation to put other circuits in it

 

[wyliesdiesels]

That did have the NEC callout on the pic (table 310-16 NEC 1999). That is why I posted it, not just some chart that i made up. Im NOT trying to spread false info, the internet is FULL of it.

Yes i understand that you need to take into account the distance and such.

That table is old as of 2011. The new table is 310.15(b)(16)

This OP is installing a feeder, not a service.

Doesn't matter. Telecom wire should not be in the same conduit as main service or branch feeders because telecom wire isn't rated for 300v or 600v. Also, telecom wire such as phone is also suseptable to 60hz power line buzzing! I've fixed countless voice runs that had buzzing on the phone because the wire was run next to electrical wire.

It is a detached garage so only 1 circuit (or multiwire circuit in the case of a subpanel) is allowed to serve the garage.

It would be a violation to put other circuits in it

This subject all started with someone saying to run telecom cable in the same conduit as electrical wire...they weren't talking about running multiple circuits to a detached garage!