# THHN loose wire thru buried conduit?



## amakarevic (Apr 12, 2007)

i am running 4 loose wires with 50A through 35 ft of buried conduit, from my basement to the shed. i know that XHHW is rated for direct burial but since this is not direct burial (using conduit), i was wondering if i can use THHN. it is cheaper and skinnier, i.e. should be easier to pull.

thanks


----------



## Jackofall1 (Dec 5, 2010)

Yes you can use THHN conductors, but they must be in a Rigid metal conduit, or nonmetallic conduit encased in not less than 3 inches of concrete.

Mark


----------



## amakarevic (Apr 12, 2007)

oh, i have PVC conduit but it is buried under concrete the whole way, except one 2 ft section


----------



## Jim Port (Sep 21, 2007)

Jackofall1 said:


> Yes you can use THHN conductors, but they must be in a Rigid metal conduit, or nonmetallic conduit encased in not less than 3 inches of concrete.
> 
> Mark


Could you please provide a code article that limits the OP to just these two choices? Why does the PVC need 3" of concrete?

Also the conductor insulation would need to have a W in the rating like THWN for the wet environment. It could not be just THHN.


----------



## nap (Dec 4, 2007)

Jackofall1 said:


> Yes you can use THHN conductors, but they must be in a Rigid metal conduit, or nonmetallic conduit encased in not less than 3 inches of concrete.
> 
> Mark


Huh? You can bury conduit without concrete. IMC is also rated for burial and strangely enough, so is EMT although I would never suggest it as such.

Burial depth varies based on location and type of conduit.

and NO you cannot use THHN in underground conduit. While most THHN is also dual rated as THWN, not all of it is. You must have that W in there for it to be rated for wet conditions, which underground conduit is.

edit; and Jim beat me to the punch


----------



## Jim Port (Sep 21, 2007)

But just by 2 minutes. It took you longer to type the longer answer.


----------



## Jackofall1 (Dec 5, 2010)

Jim Port said:


> Could you please provide a code article that limits the OP to just these two choices? Why does the PVC need 3" of concrete?
> 
> Also the conductor insulation would need to have a W in the rating like THWN for the wet environment. It could not be just THHN.


You are correct THHN without the W is not acceptable, but most THHN wire produced is also rated THWN, as for the conduit I may have been looking under the wrong section, 300.50 Underground Installations (2) Other Nonsheilded Cables.

Mark


----------



## nap (Dec 4, 2007)

Jackofall1 said:


> You are correct THHN without the W is not acceptable, but most THHN wire produced is also rated THWN, as for the conduit I may have been looking under the wrong section, 300.50 Underground Installations (2) Other Nonsheilded Cables.
> 
> Mark


You need to look to the regulation of the specific type of conduit to determine it's acceptable uses and limitations.


----------



## AliceT (Mar 17, 2011)

I agree with Nap on that


----------



## amakarevic (Apr 12, 2007)

so before i start pulling the 4 wires through, what's the best technique? should i keep them as straight as possible to ease the pull (i have 3 90 deg turns over about 30ish ft and the conduit is 1") or is it better to intertwine them or braid them? i did pull my ADT security system wire thru today but that was a cakewalk because it was really skinny and the conduit was 0.5".


----------



## nap (Dec 4, 2007)

NO do not braid or twist them. 

For 35 feet you can possibly just push them in but I wouldn't bet on it. You need to use a pull rope and attach the wires to the rope.

especially since this is PVC conduit, use wire lubricant, and plenty of it.


and of course, it takes 2 people.


----------



## bob22 (May 28, 2008)

For pulling, I used a mason's line with a bit of plastic bag tied to one end of the conduit. Had my son start shop vac at other end; air draft pulled string end with a bit of a plastic bag tied to the string (sort of acts like parachute to capture air)and done. This was about 40' with 2 elbows. I was amazed it worked.


----------



## tpolk (Nov 7, 2009)

no interference problem with electric and security in same pipe?


----------



## Jim Port (Sep 21, 2007)

tpolk said:


> no interference problem with electric and security in same pipe?


Two conduits.



> i did pull my ADT security system wire thru today but that was a cakewalk because it was really skinny and the conduit was 0.5".


Can't fit the #6s in the 1/2" conduit.


----------



## Jackofall1 (Dec 5, 2010)

Post #10 OP has 1" buried


----------



## J. V. (Jun 1, 2007)

bob22 said:


> For pulling, I used a mason's line with a bit of plastic bag tied to one end of the conduit. Had my son start shop vac at other end; air draft pulled string end with a bit of a plastic bag tied to the string (sort of acts like parachute to capture air)and done. This was about 40' with 2 elbows. I was amazed it worked.


Thats exactly how I would do it for wires this size. When you get to bigger wire you will need rope. Same method except use the string to pull the rope in.
They make special foam plugs that can be used instead of the plastic bag that can be a pain sometimes. You suck them through just like the bag. The foam plugs are sold for the conduit size and called a "mouse" by electricians. 





Jackofall1 said:


> Post #10 OP has 1" buried


Plenty big enough. :thumbsup:


----------



## amakarevic (Apr 12, 2007)

tpolk said:


> no interference problem with electric and security in same pipe?


like Jim said, i have two conduits, the electric pipe is 1", the security one is 0.5".


----------



## amakarevic (Apr 12, 2007)

also, i dunno about rope but i just used fishtape for the security wire and plan to do the same for the fat sucker.


----------



## nap (Dec 4, 2007)

bob22 said:


> For pulling, I used a mason's line with a bit of plastic bag tied to one end of the conduit. Had my son start shop vac at other end; air draft pulled string end with a bit of a plastic bag tied to the string (sort of acts like parachute to capture air)and done. This was about 40' with 2 elbows. I was amazed it worked.


then you would simply be ecstatic with some of the lines I have pulled. 3-400 feet isn't uncommon and a few longer than that. I know guys that have pulled much further than that.

and yes, using basically the same system as you have. I tend to stay away from masons line though. I prefer line intended for the purpose. In my hand, I have some "Duraline bonded nylon conduit fish line #9". It has a 98 pound break strength and is smaller than a masons line (at least what I see them typically use) Smaller means less weight and less surface area to cause friction (resistance)

I prefer to use a very lightweight bag such as the material used in Walmart bags. I take a piece about 3 times the diameter of the pipe (it can be square or irregular even). Pinch the center and let the plastic hang down from that point. Tie the string securely to this pinched point. When putting this into the pipe, use your finger and poke the center into the pipe with the string side facing you. That causes the plastic to act like a parachute like bob spoke of.

There are blowers and suckers available to use. A shop vac works fine for runs less than 100 feet, sometimes a bit further. For longer runs, a blower tends to work better and sometimes it takes both in combination.

once you get the line through, tie it to a larger rope (1/4" should be plenty large for this). the string WILL cut through the PVC as it tightens on a 90º turn so try to not pull to hard on the string. Once it cuts into the pipe, it makes things more difficult.



warning: if this line is underground and the ends are above the middle, there is likely water in the line. One of a journeyman's favorite things to do is have an apprentice watch one end of the conduit while using a blower on the other end. I have made fountains of solid water 10' tall (it was a 4" pipe and had better than 100 gallons of water in it and was using a compressed air system to blow it out) and the spray much higher. It usually only takes once for an apprentice to learn to not do that again.

The water isn't going to hurt anything but just be aware so you don't take a shower.

If you have the facilities to blow it out, you should. It makes it less messy and usually makes it a bit easier to pull the wire. You can even drag a swab through the line if there is dirt in the pipe (which happens more than one might think)

If there is water in the pipe, it makes blowing a line in more difficult.

PVC is sticky when trying to pull wire so wire lubricant helps a lot. 35' isn't very far but sometimes even that can be a PITA so lube would be a good idea.


----------



## nap (Dec 4, 2007)

amakarevic said:


> also, i dunno about rope but i just used fishtape for the security wire and plan to do the same for the fat sucker.


If you have a fishtape handy, that would work just fine and is a lot faster.

Run it in, tie a rag to the end and swab the pipe prior to pulling in the wire.


----------



## crankcase (Sep 21, 2010)

Reading this made me think of what I found the other day: 
At the old house we had the main service panel in the garage, then i had a 150'- 1.5" conduit run to a back shed to feed a sub panel. I removed the sub panel and feeder cables when we moved. Never capped the feeder line, just left it open. I went back the other day to do somethig with my air compressor and needed to pop a breaker in for compressor power. When I removed my main panel front I found allof the clay sealant from the main 200 amp feeder lines was chewed to bits and there was plenty of room for a mouse to enter the 2" main feeder line ! We are selling the house in a week and this is bad to say the least! I quickly found some pocket gopher poison and poured some down the conduit pipes. Then I capped off the 1.5" line in the main panel and left the front cover off in case he was in the 2" main feeder line and decided to crawl back out. In whch case he hopefully now can jump out, and run rampant in the garage. I returned 3 days later and no signs of mickey so I cleaned up the clay sealant and added some more to plug the incoming cables :whistling2: 



nap said:


> then you would simply be ecstatic with some of the lines I have pulled. 3-400 feet isn't uncommon and a few longer than that. I know guys that have pulled much further than that.
> 
> and yes, using basically the same system as you have. I tend to stay away from masons line though. I prefer line intended for the purpose. In my hand, I have some "Duraline bonded nylon conduit fish line #9". It has a 98 pound break strength and is smaller than a masons line (at least what I see them typically use) Smaller means less weight and less surface area to cause friction (resistance)
> 
> ...


----------



## nap (Dec 4, 2007)

crankcase said:


> Reading this made me think of what I found the other day:
> :


that is the kind of thing that gives me nightmares. Mice do chew insulation sometimes and it would obviously be where the wire was dry. If the pipe subsequently fills with water, you can end up with a short and the worst part; if it is a high resistance short, it may not trip a breaker. You could actually have energized water in the pipe. Running a metal fishtape down a pipe with those energized conductors could cause a very bad situation.


----------

