Subpanel wire run

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ninjaryder1st
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Subpanel wire run

Post by ninjaryder1st » Mon Mar 16, 2015 6:45 am

I am hoping Aaron follows me here as well, as he was a tremendous help in initial wiring, circuits, making up boxes, and breakers in sub panel.

I now need to run my cable from main breaker, 200 amps, GE, to the basement sub panel, 50 amp breaker within the main.

(Note, I will not be hooking up this breaker w/o an electrician friend assisting me, so no worries for safety here).

I just meausured about a 50 foot run down the side of the house through conduit, into the house, across a crawlspace and into the sub panel service room.

Things to consider:
1) cable type, SER or THHN wire. I can get 6 guage Cerrowire THHN from local big box store
2) Size of wire: thinking about size 6 over 8 copper for 50 amp feed
3) brand or type and size of flexible conduit to run along side/under the already existing conduit/run for the AC.
4) A plastic conduit housing box for home entry above foundation, size?
5) I have a 50 amp GE breaker already for main panel when its time.
6) knock out wire clamps to hold the feeds at both panels, with plastic inserts to protect cable.
7) size and type of wire hanging brackets for support on side of house, and subfloor run.

Anything else to consider that I failed to mention?

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Aaron
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Re: Subpanel wire run

Post by Aaron » Mon Mar 16, 2015 2:47 pm

Individual THHN conductors must be run in conduit--either metallic or non-metallic, flexible or rigid. You could probably use SER instead, as long as it's sheathed and contains four conductors: one for Leg A, Leg B, neutral, and ground.

Honestly, you'd probably be fine with #8 conductors, especially if your panel isn't too far from the main panel. #8 90ºC cable is rated to support up to a 55A load, and again, it's probably not likely you'd ever meet or exceed that load in your basement.

Just be sure your ground and neutral terminal strips are isolated in the sub-panel, and that your ground and neutral conductors of branch circuits are wired separately on their respective terminal strips.

Honestly, I'm not sure if the 50A breaker in your main panel to feed to your subpanel must be AFCI or not, since it's in-home wiring that you're doing. You will want to research this.

ninjaryder1st
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Re: Subpanel wire run

Post by ninjaryder1st » Mon Mar 16, 2015 11:09 pm

That's what Im doing, is gathering my intel of which calbe to run, what size for the 50 amp feed, and cost based on THHN vs SER cable.

Its only a 50 ft run, so not too far.
The electrican I had giving me pointers had no issue locally with non arc fault breaker from the main feed, but I will double check on that as well.

Is there a big difference between the THHN, 3 individual 8 guage and a ground being run vs the SER?
Both are weather proof, and will be run in flexible conduit with staples/hangers every 4 feet, and run through conduit near 90 degrees at the home/subfloor entry, then can be out of conduit within the crawl space to my knowledge. (also w/in poured foundation walls, above ground) and hung w/ staples every 4 ft from floor joices above crawl space.

I have no issue running conduit inside as well, if you feel its safer.

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Re: Subpanel wire run

Post by ninjaryder1st » Mon Mar 16, 2015 11:11 pm

And I did confirm the neutral strip is isolated over plastic in the sub panel, and isolated from the ground bar. The ground bar is connected to the box, not isloated from box.

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Shannon
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Re: Subpanel wire run

Post by Shannon » Tue Mar 17, 2015 6:16 am

My 2 cents is I would run it in the conduit right from panel to panel. I'm sure it should be anyways by code. And i'm sure a standard 50 amp breaker is fine to feed the sub.
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ninjaryder1st
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Re: Subpanel wire run

Post by ninjaryder1st » Tue Mar 17, 2015 6:34 am

actually a pretty good idea Shannon, as that will protect it a bit from ever being damaged in the event someone goes into the crawl space and stands up into it.

Do you have a preference, or recommnedation of THHN over SER, and which size SER?
I think I've been talked out of aluminum though it costs a bunch less.

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Aaron
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Re: Subpanel wire run

Post by Aaron » Tue Mar 17, 2015 8:15 am

If you use conduit, use THHN conductors. Get 50 feet each of #8 black, red, white, and green. You'll probably need at least 1" conduit for those conductors.

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Re: Subpanel wire run

Post by ninjaryder1st » Tue Mar 17, 2015 12:48 pm

THHN sounds good. I'm not concerned about the cost as Im saving a bit running the cable myself. Will stick to copper, rather than cheaper aluminum.

I read that 8 guage wire is only good up to 40 amps,and 55-50 would need 6, so I'm right in the middle. Any issue on 8 guage w/ some inspectors or code?

any other 2014 NEC code restrictions for side of house/conduit placement for cable entry? not within so many feet of other cable/openings, AC etc?
I had an issue of 3 ft with a bath fan exhaust that I had to get around.

Couldn't find specfics in the NEC 2014 review which is what my county requires for code.

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Aaron
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Re: Subpanel wire run

Post by Aaron » Tue Mar 17, 2015 9:38 pm

THHN sounds good. I'm not concerned about the cost as Im saving a bit running the cable myself. Will stick to copper, rather than cheaper aluminum.
You could certainly use aluminum, you'd just need to get one gauge bigger (#6 instead of #8). But bigger wire is harder to pull and fish through conduit, but aluminum is less expensive than copper. So whatever works for you. Aluminum tends to be only SER-type as well, and probably hard to find in 4-conductor configurations, and you also need to treat the stripped ends of the cable with anti-ox paste.
I read that 8 guage wire is only good up to 40 amps,and 55-50 would need 6, so I'm right in the middle. Any issue on 8 guage w/ some inspectors or code?
This is the ampacity chart on Cerro Wire's website:

http://www.cerrowire.com/ampacity-charts

The copper #8 THHN you get should have a 90ºC heat rating, which allows a continuous 55A load.
any other 2014 NEC code restrictions for side of house/conduit placement for cable entry? not within so many feet of other cable/openings, AC etc? I had an issue of 3 ft with a bath fan exhaust that I had to get around. Couldn't find specifics in the NEC 2014 review which is what my county requires for code.
Are you running the conduit outside your house? If so, will it take any unusual path?

The primary rule with conduit is you can't make more than 270 degrees of bends, otherwise it gets very difficult to fish wires through it. To get around this, you can install junction boxes at various points after a few bends to serve as a intermediate points were you can have an opening so you can re-fish the line. There are outside-corner fittings that have a pill-shaped access cover that accomplishes this also.

Other than than, there shouldn't be any other real restrictions for outdoor conduit other than it should be strapped every 4 feet, and must be liquid tight. I recommend gray PVC conduit with bell ends that you solvent weld with PVC primer and cement. For the penetrations through the exterior of your house, you use duct seal putty around where the conduit meets the siding of your home. (Shannon might have additional suggestions for better weather-tightness; I actually have not done this before.)

Make sure your subpanel is not under a bathtub or near any water pipes. Some jurisdictions might allow water plumbing above a breaker panel if there's a drip pan below the plumbing, but if you're doing new construction it's best to avoid compromising.

You also need 36 inches of clearance around any breaker panel in case you don't know that. They also can't be in bathrooms or any potentially wet location.

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Re: Subpanel wire run

Post by ninjaryder1st » Tue Mar 17, 2015 10:27 pm

Very helpful tips Aaron.
I did double check and the THHN 8 guage alllows up to 55 amps, so I went with that, and a size smaller ground at 10 ga.
The big box store associate was actually very helpful, and recommended less expensive 1" gray PVC conduit for outdoor use, and glue for joints. I only need one 90 degree curve coming out of main panel, with a straight shot 20 feet to entry point, with 4 foot hanging braces.

Then I enter home with the standard 90 degree mounting conduit box, and I have some left over conduit to run into crawlspace for 8-10 feet, before exiting it and using reducer down to 3/4 inch flexible metal conduit to make my slight 45 degree jog over about 15 ft to interior wall pass through to end up over sub panel.

I do have 3 ft of room in front of the panel at eye level for me, 5'6" tall.
Location is a utility room with furnace and water heater 3 ft away. Inspector didn't say anything bad about location at last visit.
Also got my panel wired up as well w/ proper AFCI and GFCI breakers for GE as you suggested.
I left a clear path for top panel entry for the neutral over to bus bar. I do have 2 circuit grounds running across from left to right in back of box behind the area where feed will enter.
Do you recommend the plastic inserts for the collar to protect the wire? I think I forgot to buy them, but can return for them at $1.56 a bag.

The only water pipe near by would be a sold copper pipe without any joints near by, and there are not drain pipes to worry about.
For sealing the house hole in wall, I just have some outdoor spray foam in a can, that works similar to fire blocking foam. I also need to re-treat the air conditioner entry pt that is below my planned entry, as that old foam cracked and shriveled up over 14 years.

Total cost for all fittings, and 60 ft run of cable (times 4) was $150 bucks. Not bad.

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Shannon
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Re: Subpanel wire run

Post by Shannon » Tue Mar 17, 2015 11:14 pm

ninjaryder1st wrote: For sealing the house hole in wall, I just have some outdoor spray foam in a can, that works similar to fire blocking foam. I also need to re-treat the air conditioner entry pt that is below my planned entry, as that old foam cracked and shriveled up over 14 years.

Rigid foam and spray foam deteriorate when exposed to sunlight so I would use a good quality chalking over it on the actual exterior of the hole.
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Aaron
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Re: Subpanel wire run

Post by Aaron » Wed Mar 18, 2015 12:29 am

Very helpful tips Aaron. I did double check and the THHN 8 guage alllows up to 55 amps, so I went with that, and a size smaller ground at 10 ga. The big box store associate was actually very helpful, and recommended less expensive 1" gray PVC conduit for outdoor use, and glue for joints. I only need one 90 degree curve coming out of main panel, with a straight shot 20 feet to entry point, with 4 foot hanging braces.
Yeah 1" is good, 3/4" is minimum for four #8s. It might be helpful to use a synthetic dielectric grease to lube wires for easier pulling through the conduit. You want the conduit completely installed before you pull wires through, with the necessary access points (junctions) as needed. Also, when you pull the four wires through, I recommend that you also pull an additional piece of string (as long as your wires) so that it can be used to pull another wire in the future. You never know and string is cheap. Either you'll thank yourself or someone will thank you later.
Then I enter home with the standard 90 degree mounting conduit box, and I have some left over conduit to run into crawlspace for 8-10 feet, before exiting it and using reducer down to 3/4 inch flexible metal conduit to make my slight 45 degree jog over about 15 ft to interior wall pass through to end up over sub panel.
That could work, but it might be easier to keep 1" diameter for the whole run. But whatever you are able to make work is fine.
I do have 3 ft of room in front of the panel at eye level for me, 5'6" tall. Location is a utility room with furnace and water heater 3 ft away. Inspector didn't say anything bad about location at last visit.
Yeah that sounds like an appropriate place for a breaker panel. Just make sure it's accessible with the 36" clearance all around. (Don't end up putting a shelf in front of it.)
Also got my panel wired up as well w/ proper AFCI and GFCI breakers for GE as you suggested.
Good. That's important.
I left a clear path for top panel entry for the neutral over to bus bar. I do have 2 circuit grounds running across from left to right in back of box behind the area where feed will enter.
Do you recommend the plastic inserts for the collar to protect the wire? I think I forgot to buy them, but can return for them at $1.56 a bag.
You'll want the entrance for the feeder at the closest possible knockout on the panel for a good path to the bus lugs. Yes, you'll need those plastic bushings to protect the conductors from chafing on the opening of the threaded fitting--on both ends. As you probably know, these bushings are not necessary for 1/2" fittings for branch circuits because with non-metallic cable (NM-B or NMD90) the sheath must always extend into a box or enclosure 1/4" for its clamp to protect the conductors, regardless of the type of fitting, clamp, or its material.

When you start knocking out the 1/2" holes for your branch circuits, always start with the rear holes and work your way to the front of the box. This way the wiring you're doing inside the panel will always be in front the work that was done before, making it much easier to organize the wire inside.
The only water pipe near by would be a sold copper pipe without any joints near by, and there are not drain pipes to worry about. For sealing the house hole in wall, I just have some outdoor spray foam in a can, that works similar to fire blocking foam. I also need to re-treat the air conditioner entry pt that is below my planned entry, as that old foam cracked and shriveled up over 14 years.
Yeah the duct seal putty is fairly resilient to UV very unlike expanding foam is. You can find "blocks" of that duct seal in the electrical aisle, it's usually a dark gray and wrapped in plastic. You basically break off a piece of it roll out a small rope of the stuff, wrap it around the pipe and push it into where the pipe meets the house. You could use this for your A/C lines too.
Total cost for all fittings, and 60 ft run of cable (times 4) was $150 bucks. Not bad.
That's not bad at all, I'm very surprised it was that cheap. I wonder if copper prices are coming down. I was thinking you were going to spend north of $300 for all that material.

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Re: Subpanel wire run

Post by ninjaryder1st » Thu Mar 19, 2015 1:23 pm

I was planning on $250-$300 as well, according to my electrician guy I talked about, but I saved $0.25 per linear foot just dropping from 6 g to 8 g, so that helped over 60 ft times (4). $60 bucks right there.

I did end up going from PVC conduit from 1" to 3/4" flex conduit w/ reducer once in the crawl space. Worked out well. I didn't see your note about the string, but If I had to run another wire (not sure why) I'd likely need to increased to 1 " flex conduit and re-do that anyway. Good news is that its onloy 25 ft of conduit, and I can separate it from the PVC inside, and re-run that section of wire if I had too, and then push into outside jxn box w/ access pt, and its only 20 ft of PVC outside to get a 5th wire through, so not horrible.

I passed inspection today, and want to say a HUGE thank you to both Aaron and Shannon for the help and availability of this site, and Shannon's you tube video. I'm fairly mechannicaly inclined, but couldn't have done all the planning and avoid pit-falls w/o your help. THANKS AGAIN!

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Shannon
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Re: Subpanel wire run

Post by Shannon » Thu Mar 19, 2015 10:36 pm

Glad all went well at inspection time!
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Aaron
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Re: Subpanel wire run

Post by Aaron » Thu Mar 19, 2015 11:22 pm

Glad it all worked out. Congratulations.

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