pulling THWN wire through long conduit, which type to use, how difficult ?

[RustyShackleford]

I'm planning to install an EVSE (electric car charger). It'll be a 20 amp unit, on a 25-amp breaker (in an under-utilized sub-panel that's much closer to the parking area than the main panel). It's still a good 70 ft though, 20 feet up and 50 feet horizontally. I'll need three strands of #10 THWN wire (ground plus two hots, no neutral needed); this handles the OCPD limit and provides reasonably-small voltage drop (#10 stranded is about 1 ohm per 1000ft).

I'm wondering about the pros and cons of using rigid PVC conduit versus flexible non-metallic liquid-tight conduit, as well as what size to use. The tables in the NEC say that the 1/2" size of either type can handle 6 strands of THWN. But I've read that pulling through 1/2" over that distance and with a right-angle bend, is going to be really tough, so I'm planning to use 3/4". But I'm still unsure which to use.

I'm thinking pulling the wire will be easier with the rigid PVC, because the inside is smoother and I can put a conduit body at the right-angle turn. On the other hand, I could run the wire through the liquid-tight BEFORE I install it, at my leisure and with it more or less straight; but this means that I must either determine and cut the exact length of liquid-tight beforehand, or else manage to cut it to length as I'm installing it, without damaging the wire that's already in it. A final factor is that this will all be about 25ft off the ground - coming up the 20ft and then laterally 50ft along the bottom of a catwalk that leads to the parking area. Fortunately I'm a climber, so can do this on an extension ladder, with a belay off the many deck and catwalk supports that are available. Under these conditions, I think the liquid-tight with pre-installed wire would be easier to work with.

I welcome your thoughts on this. I never pulled wire through anywhere near this length of conduit, and I'm just not sure how tough it is.

 

[peakbagger]

I have always used PVC for underground with the lengths of extra heavy coming out of the ground along with lots and lots of pulling lube since I seem to end up doing these pulls solo.

 

[RustyShackleford]

Of course, I'm not doing underground at all. I'm pretty confused about the different kinds of liquid-tight conduit. I understand the blue stuff isn't appropriate. But for the others, the price varies radically. Even the Southwire website doesn't really explain the difference.

https://www.supplyhouse.com/Conduit-Cable-11786000

The cheapest one (that's a 100ft roll of 3/4") is cheaper than the rigid PVC stuff: https://www.supplyhouse.com/Southwi...t-Flexible-Non-Metallic-Conduit-100-Foot-Coil

 

[EbS-P]

I'm planning to install an EVSE (electric car charger). It'll be a 20 amp unit, on a 25-amp breaker (in an under-utilized sub-panel that's much closer to the parking area than the main panel). It's still a good 70 ft though, 20 feet up and 50 feet horizontally. I'll need three strands of #10 THWN wire (ground plus two hots, no neutral needed); this handles the OCPD limit and provides reasonably-small voltage drop (#10 stranded is about 1 ohm per 1000ft).

I'm wondering about the pros and cons of using rigid PVC conduit versus flexible non-metallic liquid-tight conduit, as well as what size to use. The tables in the NEC say that the 1/2" size of either type can handle 6 strands of THWN. But I've read that pulling through 1/2" over that distance and with a right-angle bend, is going to be really tough, so I'm planning to use 3/4". But I'm still unsure which to use.

I'm thinking pulling the wire will be easier with the rigid PVC, because the inside is smoother and I can put a conduit body at the right-angle turn. On the other hand, I could run the wire through the liquid-tight BEFORE I install it, at my leisure and with it more or less straight; but this means that I must either determine and cut the exact length of liquid-tight beforehand, or else manage to cut it to length as I'm installing it, without damaging the wire that's already in it. A final factor is that this will all be about 25ft off the ground - coming up the 20ft and then laterally 50ft along the bottom of a catwalk that leads to the parking area. Fortunately I'm a climber, so can do this on an extension ladder, with a belay off the many deck and catwalk supports that are available. Under these conditions, I think the liquid-tight with pre-installed wire would be easier to work with.

I welcome your thoughts on this. I never pulled wire through anywhere near this length of conduit, and I'm just not sure how tough it is.

I’d be using pvc. I’d probably go 3/4”. If you wanted add a #8 or even 6 in the future you could easily pull it. Realize that nothing is moisture proof and do you best to seal it. Don’t forget expansion slip joints. I forget what the spec is but it’s way more than I imagined it would be.

 

[RustyShackleford]

I’d be using pvc. I’d probably go 3/4”. If you wanted add a #8 or even 6 in the future you could easily pull it.

The subpanel is 40 amps (fed with #8 NM-B) and already has a 20 amp load on it (minisplit), so I don't imagine I'd ever be running heavier wire to the EVSE.

Realize that nothing is moisture proof and do you best to seal it.

I'll use THWN wire.

Don’t forget expansion slip joints.

Oh yeah, thanks for the reminder. I guess one advantage of liquid-tight is not having to worry about that.

 

[tlc1976]

I always used rigid PVC conduit. Nice because I didn’t have to pull a huge length of wire. I first laid out the wire, and then assembled the sections over the wire and cemented them one by one. Especially when I did my satellite cabling, I doubt that thin wire would have held up to the tension of being pulled 120 feet. Same when I did my network cable to the barn which was like 70 or 80 feet. Last thing I wanted was to strain it and damage it and have to start all over.

 

[gthomas785]

I can tell you for sure the hard PVC will be easier to pull through than flexible liquid tight. A single 90 degree bend with 70ft straight is no problem. Use stranded conductors.

The only time you should use flex is if you've got some really impossible shape to follow.

and Do Not assemble the conduit with the wire inside! Not only do you damage the wire insulation by doing that, but you may inadvertently create an un-pullable conduit that is impossible to work on later. Code says the conduit must be fully assembled before pulling the wire in, and that's for a reason.

Edit: if you're really worried about pulling around the 90 degree bend, you can consider replacing it with an LR or LL conduit body and do 2 pulls.

 

[RustyShackleford]

Thanks guys, rigid PVC seems to be the consensus.

FWIW, I've read it's ok to get conduit cement on wire insulation. But I think I'll assemble the conduit over a pulling string instead. So don't need to get a 50ft fish-tape, but don't push my luck with the cement. I also read about this thing called a "mouse", that you use to get a pulling string through the conduit using a shopvac - sounds pretty slick.

Definitely will put a conduit body at the bend, which would make things lots easier, except ... it'll be on the underside of a catwalk about 25ft above grade ! Maybe I can temporarily remove a decking board from the catwalk.

 

[gthomas785]

Yep you can even use a piece of a plastic shopping bag as a mouse. Use that with a shop vac to pull in a lightweight string or fishing line, then use that to pull a heavier rope in, then use the rope to pull the conductors.

 

[tlc1976]

Good to know if I was to ever do any conduit with actual household voltage. I did take measures to keep the connection clean and protect the wire from the solvent. Also I only applied cement to the male end, so any excess would end up only on the outside. I read that pros actually do this for that reason. And of course rotating the parts thoroughly during assembly to spread the cement well through the connection.

 

[begreen]

Will the 90º turn be above ground? If so, instead of using a 90º sweep elbow you could use an LB fitting with a gasketed cover. That allows the pull to be straight.

Cantex 1/2 in. Type LB Conduit Body R5133663 - The Home Depot

The Type LB Conduit Body is used for a change of direction of the conduit run with the back hub usually exiting through a wall. It is a rectangular shaped conduit body with a removable cover and a foam

www.homedepot.com

 

[RustyShackleford]

Will the 90º turn be above ground? If so, instead of using a 90º sweep elbow you could use an LB fitting with a gasketed cover. That allows the pull to be straight.

Cantex 1/2 in. Type LB Conduit Body R5133663 - The Home Depot

The Type LB Conduit Body is used for a change of direction of the conduit run with the back hub usually exiting through a wall. It is a rectangular shaped conduit body with a removable cover and a foam

www.homedepot.com

The whole thing is above ground. Up vertically 20ft from an externally-mounted sub-panel, to a 50ft-long catwalk that leads to the parking area. Definitely plan to use a conduit body.

 

[begreen]

The whole thing is above ground. Up vertically 20ft from an externally-mounted sub-panel, to a 50ft-long catwalk that leads to the parking area. Definitely plan to use a conduit body.

Then the pull might not be too bad with the proper snake. Use a wire-pulling lube if concerned. Also, check to see if a #12 ground wire is ok.

https://www.lowes.com/pd/IDEAL-32-oz-Clear-Wire-Pulling-Lubricant/1017915

 

[brenndatomu]

I always pull a string in with my wires...makes it easier in the future if you want/need another conductor or 2 for some reason.
I like to go a size bigger than I think I'll need on the conduit too...makes the pull easier, and better future expansion possibility's...never say you'll never need that.
If you are buying wire on rolls, mount them on a rod or pipe so they just come straight off the spool as you pull...and keep them tight so that the wires go in the conduit nice and straight, side x side/on top of each other...if you try to pull the wire out across the yard first, good luck keeping them from getting tangled up as you pull, you'll invent some new 4 letter words, even with an assistant...and even if you actually are successful at getting them in like that, they can be wrapped around each other in the conduit, and be very hard to pull 1 or 2 wires back out, if you ever need to for some reason.
Don't cheap out on the wire lube...the cheap stuff dries sticky sometimes...the good stuff just evaporates. Sticky wires are very difficult to impossible to pull anything in or out in the future.
I have some 3" conduits at work that were pulled way too full (too many oversized wires, with extra heavy insulation (for no reason) right from the beginning, and they used the cheap lube...so now nothing can be pulled out, or put in...so if I have a wire fail, I get to run another conduit for new conductor(s)...already had to do it once...ugh!

 

[RustyShackleford]

Don't cheap out on the wire lube...the cheap stuff dries sticky sometimes...the good stuff just evaporates.

How does this look ? https://www.idealind.com/eu/en/shop/aqua-gelr-ii.html

 

[brenndatomu]

How does this look ? https://www.idealind.com/eu/en/shop/aqua-gelr-ii.html

That'll work

 

[semipro]

I'd encourage you to go bigger than you think you'll need on the conduit. The increase in price is small in return for the future expansion capability you get. The wire and subpanel can be replaced with a larger one later if needed.
Electric vehicle chargers are quickly increasing in size as batteries and max charge rates grow.

 

[RustyShackleford]

I'd encourage you to go bigger than you think you'll need on the conduit. The increase in price is small in return for the future expansion capability you get. The wire and subpanel can be replaced with a larger one later if needed.
Electric vehicle chargers are quickly increasing in size as batteries and max charge rates grow.

I'd also have to go bigger with the previously installed #8-3 from main panel to subpanel. So if I did ever decide to go with bigger charger, I'd probably just bypass the subpanel and go straight to the main panel (and the conduit I install from charger to subpanel wouldn't be far out of the way). So yeah. I'm already up to 3/4" conduit, even though 1/2" can handle my three #10 conductors. But maybe I should go with 1" (cost me an extra $20 over 3/4").

 

[begreen]

I'd also have to go bigger with the previously installed #8-3 from main panel to subpanel. So if I did ever decide to go with bigger charger, I'd probably just bypass the subpanel and go straight to the main panel (and the conduit I install from charger to subpanel wouldn't be far out of the way). So yeah. I'm already up to 3/4" conduit, even though 1/2" can handle my three #10 conductors. But maybe I should go with 1" (cost me an extra $20 over 3/4").

I would if you intend to live there for a long while and have a long commute plus need to go a long distance for normal town runs. You won't need pulling lube for #8 in 1".

fbelec, @gthomas785 what is the ruling on the ground wire for a dedicated 220v circuit? Does the gnd wire gauge need to be the same as the hot legs?

 

[brenndatomu]

You won't need pulling lube for #8 in 1".

Good point...upsizing the conduit is almost paid for by not having to buy lube.

 

[Ashful]

Never heard of anyone using any PVC or flex conduit overhead, but I guess that doesn't mean much, there's a lot I haven't seen.

I have a good fraction of a mile of conduit buried in my back yard for receptacles, lighting, irrigation control, pool equipment, etc. In the last addition, we laid an extra seven conduits, 1" up thru 3" out to the back yard, and we're preparing to fill the last one with new pool electric and water supply this summer.

Word to the wise, always lay double the count and double the size you think you'll need. If you're always on projects (maybe just me?), you'll eventually need it for something.

But having said all of that:

1. Why wouldn't you just string up a steel cable and hang UV-resistant romex on that? Standard practice for overhead outdoor.

2. If you want conduit, why not just bury it? Much cleaner, no overhead obstacles, etc. Not that big a job, unless there are multiple driveway / parking area crossings. I'd bury 1" or 1.5", pull your 3+ ground THHN thru it, and be done.

 

[begreen]

Never heard of anyone using any PVC or flex conduit overhead, but I guess that doesn't mean much, there's a lot I haven't seen.

It's done all the time, even on commercial rooftops.

 

[Ashful]

It's done all the time, even on commercial rooftops.

Yeah, rooftop, for sure. But I got the impression Rusty was talking about a suspended job between buildings.

Like I said, there's a lot I haven't seen, but I've only ever seen metallic conduit used for that. Figured PVC would sag between suspension points, under the load of the wire it's carrying.

 

[begreen]

Agreed if it is free-air. I was assuming that it would be regularly fastened to the catwalk, but could be wrong.

 

[gthomas785]

The original post says "along the bottom of a catwalk" so I assume it would be supported by the catwalk. PVC conduit definitely would not be suitable for a 50' span in free air.