I have run into this on occasion over the years that AC, MC and Flexible Metal Conduit (FMC aka Greenfield) type cables get confused by many people including myself. MC has conductors preinstalled while Greenfield does not. For someone like me who usually gets supplies at Home Depot for a specific project, its easier to keep the empty conduit in stock at home and then buy the wires of the size I need to length. In this case it was a Solar DC home run. It has been awhile but think it was a 40 foot run of a couple of #10s and grounding conductor. FMC is cheap so I bought a 50 foot box of 3/4" (maybe 1") which is still kicking around and then bought wire to length adn pulled it in. Its also handy for when I need to run additional conductors.
pulling THWN wire through long conduit, which type to use, how difficult ?
- Thread starter RustyShackleford
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Ashful
Minister of Fire
No confusion in this case, just always thought it was easier to buy and install MC, than pulling my own wire thru FMC. None of it was expensive enough for cost or waste to be a real consideration, at least back when I was buying this stuff more frequently, until you got to the real large stuff.
On a related note, I just ordered 15 feet of AWG-2/3+G NM-B to rewire a subpanel feed. Ouch!
On a related note, I just ordered 15 feet of AWG-2/3+G NM-B to rewire a subpanel feed. Ouch!
semipro
Minister of Fire
Yeah, I noticed as I walked through Lowes yesterday that they have all their wire secured behind bars now -- pretty sad the cost and that theft is such a problem.
EbS-P
Minister of Fire
The bulk price kinda gets me mad. $0.56 per foot for 250 ft and $1.55 per ft for 50 ft. You can tell who they are making the profit on.
Ashful
Minister of Fire
Sometimes it can feel that way, but the reality is there's a ton of extra cost involved in smaller volume sales, from processing to packaging, and everything in-between. I price high power electrical components every day, and folks are always surprised that something which costs $1k/ea at 100 pieces costs more than $60k when they're buying just one unit.
With good reason too. I recall seeing the pvc conduit writhe on a commercial rooftop HVAC install back in the 1980s which had me wondering why PVC was used. That was the early days and there were no expansion couplings in the long conduit run.
I'm talking about putting three strands of #10 thru 1" liquid-tight (I'll call it "LT"). And I plan to do it BEFORE I bend and clamp the LT. And I'll use a fish-tape if I need to. My plan is:
1. Run the (rigid) PVC conduit, with a female adapter solvent-welded to end where LT will attach.
2. Pull the wire thru the PVC conduit, with 10ft or so hanging out the end where LT will attach.
3. Run the wire thru the LT (using fish-tape if necessary).
4. Attach the LT to the PVC (male screw-on fitting on LT into female adapter on PVC).
5. Bend and clamp the LT.
1. Run the (rigid) PVC conduit, with a female adapter solvent-welded to end where LT will attach.
2. Pull the wire thru the PVC conduit, with 10ft or so hanging out the end where LT will attach.
3. Run the wire thru the LT (using fish-tape if necessary).
4. Attach the LT to the PVC (male screw-on fitting on LT into female adapter on PVC).
5. Bend and clamp the LT.
definitely use string or rope or something. don't try to stuff the wires thru you'll use four letter words 😁
Ashful
Minister of Fire
- Push fish thru the rig
- Thread one AWG-10 conductor thru eye on end of fish, fold at least an inch at the end back onto the wire and tape with electrical tape.
- Bundle all wires together, and tape the first foot using a corkscrew pattern with the tape.
- Pull bundle bag thru the conduit rig
I am expert with those though.
Good advice on taping technique, thanks.
I don't have a 100ft fish-tape, so I'll still do it in stages as I described. For the PVC stage, I'll pull a string through using one of those foam "pistons" or "mouse" and a vacuum cleaner; hope that works. And fish tape for the LT.
EbS-P
Minister of Fire
I don’t understand why. But yeah…. I just bought 100’ of 14-2 and I’m going to need another 25. It’s all expensive. I just paid 120$ a ton for driveway rock. You don’t want to know how many tons.
brenndatomu
Minister of Fire
Can get a 36" - radius elbow pretty cheap on ebay. Wonder if that'd make it more forgiving (of temperature changes ? Definitely gonna put one expansion coupling in the horizontal, but if I only get 2" of movement (100 degrees over 50ft) that should be enough. Would prefer to avoid one on the vertical though.
brenndatomu
Minister of Fire
You can make your own sweep elbows with a heat gun (any shape you want actually)
You can also just use a length of sealtite in the corners instead of expansion joints...it works. (not in every situation, but from what I understand about what's going on here I think it would work)
You can also just use a length of sealtite in the corners instead of expansion joints...it works. (not in every situation, but from what I understand about what's going on here I think it would work)
By sealtite you mean liquid-tight conduit ?
Thing is, you guys have been telling me how hard it is to get wires thru liquid-tight, so the last thing I'd want to do is to put some of it in the middle of my 70ft conduit run, right ? Of course, I will have introduced a string thru the run using one of those foam "mouse" or "piston" things, so maybe it's ok; except the male screw-on fittings I'd have to put at each end of the section of liquid-tight do slightly decrease the I.D. (sort of like pex crimp fittings do).
My vertical run is only 20ft. So expansion/contraction is an inch or less. Doesn't seem like it'd be hard to allow for that if I simply don't clamp the elbow super-tight, so the elbow end of the 50ft run can move 1/2" or so up and down (as the vertical run expands and contracts).
Last edited:
Ashful
Minister of Fire
I was thinking of you an hour ago, Rusty. I'm setting up to pull two new circuits from my boiler room out to my back yard, and had been planning to use a buried 2" PVC conduit that's been installed but unused since 1995. Then I noticed I still have some capacity in an existing 1.5" conduit running parallel to it. So... pull the existing bundle out and re-pull with the added wiring, or just use the unused 2"? Both options come with other chores (eg. setting up a junction box in basement on 2" to transition from NM to THHN, versus using or upgrading existing box on 1.5").
I spent 14 hours in my boiler room on Saturday, missing gorgeous weather, while replacing a breaker panel. Hot room, zero air flow, and a low ceiling that wouldn't allow me to stand up straight. I actually found that kneeling on the concrete floor was more comfortable than trying to stand, most of the time.
I spent 14 hours in my boiler room on Saturday, missing gorgeous weather, while replacing a breaker panel. Hot room, zero air flow, and a low ceiling that wouldn't allow me to stand up straight. I actually found that kneeling on the concrete floor was more comfortable than trying to stand, most of the time.
brenndatomu
Minister of Fire
Meant to ask for followup on this: is there a simpler/cheaper way to connect liquid-tight to PVC conduit, than to solvent-weld a female adapter to the end of the PVC, put a terminal onto the end of the liquid-tight, and screw 'em together ?
Also, when you bring PVC conduit into a box or device with a male adapter and metal locknut, how to you make it water-resistant ? The liquid-tight terminals have rubber washers on them, and it seems like those would do the job nicely, but I never see 'em for sale separately. I've just smeared RTV silicon around it ...
brenndatomu
Minister of Fire
Ashful
Minister of Fire
This is exactly how I've always done it. Not sure if there's a simpler way, but this works and is easily repairable or accessible, if you want to break apart for any reason.
The liquid tight adapters should have an o-ring, but it's usually pretty useless against a sloppy knockout hole. Notice that outdoor panels always have the knockouts either in the bottom or the lower sides, below all electrical connections, for this reason. They're rain and splash resistant, not submersible.
If you need to enter the top of the panel with PVC, get a hub like this (which seals to the box with a gasket) and thread the male adapter into that.
I've actually finished this, but have some concern about protection. Most of the 1" PVC conduit is pretty inaccessible (up the side of the house, starting 5ft or so above grade, and then along the underneath side of the catwalk. But the last 3ft, that comes up the side of the 6x6 at the end of the catwalk into the EVSE, is pretty exposed - not kosher for Sch40 PVC. I'm not getting this inspected, but I still want to follow code. (Check out the photo in post #26, page 2, if this is confusing).
Schedule 80 PVC is impossible to get around here, and I'd hate to pay $30+ for a 10ft stick and use 3ft of it. I guess I could come down from the EVSE with EMT, but not sure how to transition that to the PVC or the liquid-tight underneath the catwalk. Simplest might be to just add some physical protection, wood of an outer layer of some kind of other pipe, but not sure what.
Schedule 80 PVC is impossible to get around here, and I'd hate to pay $30+ for a 10ft stick and use 3ft of it. I guess I could come down from the EVSE with EMT, but not sure how to transition that to the PVC or the liquid-tight underneath the catwalk. Simplest might be to just add some physical protection, wood of an outer layer of some kind of other pipe, but not sure what.
brenndatomu
Minister of Fire
Why not...you used conduit, right? That is sunlight rated.
Couple the liqi tight fitting to an EMT box connector with a female x female conduit coupler
Ashful
Minister of Fire
I had the same concern on a recent install for an outdoor breaker panel for a pool. Spoke with a few contractors, and they all basically said sch.80 is spec, but no one actually uses it. Same reason you cite, it's nearly impossible to find.
For my concrete patio penetrations, I went to threaded adapters on the PVC conduit below the slab, with stainless pipe penetrating the slab. That way, nothing will ever break off at slab, leaving me in an un-repairable situation. The breaker panel which is set on posts in a garden is plumbed with two sch.40 conduits (1.5" and 1") and two liquid tights (3/4" and 1/2") zip-tied to those conduits. I don't love it, but it appears to be standard practice.
Similar threads
