Running Service to Barn - 100 amp

12259 Views 20 Replies 11 Participants Last post by Injun, Oct 14, 2014

AndrewF

Discussion Starter · Jun 4, 2009

3

I will be trenching and running conduit to my polebarn in the next week.

I bought #2 copper THWN-2 for this project.

Total length will be around 180'

Am I correct in that I can use 2" SCH 40 PVC for this project?

I plan on running 4 runs and installing two grounding rods at the sub-panel in the barn and not bonding the neutral and GEC. Do I really need grounding rods for this install?

Second question, all four wires will be black, is it ok for me to utilize colored electrical tape to mark each one (red, white, green, black)?

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1 - 20 of 21 Posts

robertmee

· #2 · Jun 4, 2009

Don't take my word for it and hopefully the more seasoned pro's will chime in, but I believe 4 #2's w/ 40% fill would be allowable in an 1 1/4" pipe. I just ran 2-2-2-4 in 1 1/2" over 250 feet and it was an easy pull.

ScottR

· #3 · Jun 4, 2009 (Edited)

AndrewF said:
Am I correct in that I can use 2" SCH 40 PVC for this project?

Yep. Like robertmee pointed out, it might be overkill, but not a bad thing.

AndrewF said:
Do I really need grounding rods for this install?

Yep.

On a separate note, you could use #8 or #6 Cu for the EGC and save yourself some bucks on the #2.

AndrewF said:
Second question, all four wires will be black, is it ok for me to utilize colored electrical tape to mark each one (red, white, green, black)?

OK as they're larger than #6. AFAIK the EGC has to be marked anywhere it's accessible, even if not the cable termination. Probably not an issue for your run.

Disclaimer: This is from the 2008 NEC. Not sure if your area has different requirements. (And I'm not an electrician :no

.

micromind

· #4 · Jun 4, 2009

For 100 amp, a #8 is code minimum for the ground. You can go larger, but there's no need to. The #2s are about right for the hots and neutral though. You can use colored tape on anything larger than #6, according to code. Almost all of my work is inspected, and I can't even count the number of #6s and #8s I've used colored tape on, and have never had a problem.

2" is plenty for this run. If there are only two 90s, it'll be an easy pull. If there are 4, it'll still be fairly easy.

If it were me, I'd install a 1" in the trench while it is open. Just stub it up somewhere, you might want a phone or something else out there someday.

You'll need at least one ground rod to be legal, two if your soil doesn't conduct well. There's no requirement for more than two though. Around here, one rod will give about 5-10 ohms. 25 is the code maximum. #6 is the code minimum for the ground rod wire.

Rob

theatretch85

· #5 · Jun 4, 2009

micromind said:
#6 is the code minimum for the ground rod wire.

Rob

Actually I thought the code said something like the wire to the ground rods is not required to be any larger than #6. Water pipe bond is sized to the service and may be bigger than #6.

AndrewF

Discussion Starter · #6 · Jun 4, 2009

I used 1 1/4" for the sub-panel to the basement, that was around 80-90 feet, and was a PITA to pull. Had 4 90s though...

The cost difference to jump to 2" isn't really that bad.

Yes, I'll be running a separate 1 1/4" conduit for future need as well as I am burying a few inches up in the same trench, several RG6 lines and direct burial rated Cat5 cable.

Definitely a lot easier now than later.

I figured #2 was bigger than I needed, but since I bought a 1000' spool to run the 100 amp subpanel to the basement and the barn, I wanted to ensure I never had a voltage drop problem.

micromind said:
For 100 amp, a #8 is code minimum for the ground. You can go larger, but there's no need to. The #2s are about right for the hots and neutral though. You can use colored tape on anything larger than #6, according to code. Almost all of my work is inspected, and I can't even count the number of #6s and #8s I've used colored tape on, and have never had a problem.

2" is plenty for this run. If there are only two 90s, it'll be an easy pull. If there are 4, it'll still be fairly easy.

If it were me, I'd install a 1" in the trench while it is open. Just stub it up somewhere, you might want a phone or something else out there someday.

You'll need at least one ground rod to be legal, two if your soil doesn't conduct well. There's no requirement for more than two though. Around here, one rod will give about 5-10 ohms. 25 is the code maximum. #6 is the code minimum for the ground rod wire.

Rob

ScottR

· #7 · Jun 4, 2009

I figured #2 was bigger than I needed, but since I bought a 1000' spool to run the 100 amp subpanel to the basement and the barn, I wanted to ensure I never had a voltage drop problem.

#2 75C is good for 115A if you don't need to derate (I'm looking at table 310.16).

But if you resize the EGC down to #8 (a lot of people say they'd use #6 even though #8 is the min. requirement), you won't have any voltage drop on your supply. It'll be an easier pull, and you can sell that extra #2 or keep it for the next project.. (Obviously no harm done if you oversize).

J. V.

· #8 · Jun 5, 2009 (Edited)

To second Robs comment. Your wire size is fine and your conduit is more than fine. An extra conduit is a great idea. You never know. I have to buy wireless speakers for my gazebo because I did not think about an extra conduit.
You can use a #6 for the ground wire (EGC). Mark the neutral with white tape and the ground with green. As you can see on the wire it says THHN/THWN. The "W" is the keyword for wet locations. Have fun.

ScottR

· #9 · Jun 5, 2009

J. V. said:
You can use all #6 if you have enough wire. For the ground too.

I'm looking at table 310.16, NEC 2008 -- where are you getting 100A as an allowed ampacity of #6?

AndrewF

Discussion Starter · #10 · Jun 15, 2009

Per the recommendation here, I dropped in 1 1/2" pvc. Total length, 130'.

I trenched it down 24-32", even though only 18" is required around here.

J. V.

· #11 · Jun 15, 2009

ScottR said:
I'm looking at table 310.16, NEC 2008 -- where are you getting 100A as an allowed ampacity of #6?

Sorry Scott and the OP. I meant for the EGC. He is using #2cu for the CCC's.

Stubbie

· #12 · Jun 15, 2009

theatretch85 said:
Actually I thought the code said something like the wire to the ground rods is not required to be any larger than #6. Water pipe bond is sized to the service and may be bigger than #6.

Actually it really is a minimum...the gec to the electrode if it is a rod must be at least 6 awg copper but can be larger if you want.....

Stubbie

· #13 · Jun 15, 2009

I'm surprised that no one brought up NEC 250.122(B)....

220/221

· #14 · Jun 16, 2009

Should have stuck with 2".

Bigger is generally better.:thumbup:

J. V.

· #15 · Jun 16, 2009

Stubbie said:
I'm surprised that no one brought up NEC 250.122(B)....

Stubbie,
I am not sure what this section has to do with the thread.

250.122(B) Switches.
No automatic cutout or switch shall be
placed in the equipment grounding conductor of a premises
wiring system unless the opening of the cutout or switch
disconnects all sources of energy.

jimmy21

· #16 · Jun 16, 2009

220/221 said:
Should have stuck with 2".

Bigger is generally better.:thumbup:

I disagree. 1 1/2 Is already plenty overkill. Spend the money saved on a couple 1 inches

AndrewF

Discussion Starter · #17 · Aug 17, 2009

6

I ran 1 1/2" for a total distance of 145' including two 90s. The pull was too hard to do manually, especially considering I didnt have any help.

I ran 3 #2s, 1 #6, and 5 #12s.

Here are a few photos of my pull.

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Injun

· #18 · Oct 14, 2014

Something I read said when I run a 100A circuit to the barn I need to keep the neutrals and grounds separate in the panel. My NEC book is old and I just moved so don't know where it is anyway but am curious why the neutrals and grounds need to be kept separate.

ritelec

· #19 · Oct 14, 2014

objectionable current

\http://www.youtube.com/watch?v=M3lX4XtlYXk

Injun

· #20 · Oct 14, 2014

Ok I have found information stating the neutral and ground must be separated in the subpanel. So I use a ground rod there and attach it to the ground bar and all should be good.

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