Sizing conduit for long pull - Page 3 - Electrician Talk - Professional Electrical Contractors Forum

RIVETER · 11-11-2009, 04:12 PM

Quote:

Originally Posted by David Channell

I should not tell you this because you have a bad attitude, but I will anyway because I don't want to have a bad attitude. See Art 250.80 and you will see that all metal raceways including metal sweeps connected to pvc, unless buried 18" deep and isolated from possible contact must be grounded. It is inforced here in Calif. and has been for at least 20 years.
David Channell SSE

I am totally in agreement, here. The steel sleeves ARE.....are they not, a part of the electrical system? What if a phase conductor gets cut and ends up being in contact with the metal at the sleeve? If the sleeve is not bonded to ground does it just remain as an electrode forever until the poor ditchdigger finds it just before his funeral. By the way, it's not my attitude...is it?

sparks134 · 11-11-2009, 04:18 PM

here's a solution: stay consistant and put it all in PVC,or Rigid.

220/221 · 11-11-2009, 05:27 PM

Metal sweeps are stupid.

Pre lube the conduit/string/rope and there will be no burning of the PVC.

I've pulled some pretty heavy pulls with things other than a tugger. A trencher works nicely because it has more feel/control than a truck. If you can plan your pull properly you may be able to leave off the end 90 and pull straight out. Yeah...I know...article number blah blah blah, section blah.blah says blah blah complete conduit system blah blah

Old Spark · 11-11-2009, 05:32 PM

I like PVC conduit, but I know of at least two reasons to install steel 90's at times. 1. if you have a long hard pull, the rope can cut thru the 90, 2. is in hazardous locations, such as gas stations. We are required to install at least 2' of run plus your riser in steel in order to make it explosion proof. If it gets a conduit seal, then it get steel at the ends. A few years ago we had to use steel end to end and still some we sometime required to install pvc coated steel instead of galv. rigid or IMC. Talk about costly, price out a 1" stick of pvc coated galv. rigid conduit, plus the expense of buying special cutting dyes that will fit over the coating. Then you have the explosion proof unions, ey's, LBY's and so on. Sorry I got carried away.
David Channell SSE

LJSMITH1 · 11-11-2009, 06:16 PM

From the 2008 NEC...

Quote:

Exhibit 250.34
An application if 250.80, Exception, which permits the metal elbow to be ungrounded, provided it is isolated from contact by a minimum cover of 18 inches to any part of the elbow.

Seems to me that using the metal sweeps are ok to be un-bonded provided they meet the minimum cover requirement...

sparky105 · 11-11-2009, 06:43 PM

Quote:

Originally Posted by bharbwyr

I'm gearing up to pull almost 500' of 250kcmil aluminum through pvc conduit. Other than the steel sweeps at both ends the path is pretty straight, dipping down in the middle and gently sweeping across the driveway to the house. Can anybody out there recommend, based on their experience, the minimum conduit diameter that should keep me out of trouble? I'm hoping to be able to do it with manpower alone, maybe 3 or 4 guys. Is that ridiculous?
The cable will be 250,250,3/0 URD,USE and a #2 XHHW EGC

http://www.alanwire.com/awscripts/ma...cgi?ntype=THHN herer is th e wieght chart for copper single conductors your going to need 4 boys the size of the mountains to pull that in rent a tugger

nitro71 · 11-11-2009, 07:01 PM

If I was using rigid for the sweeps I'd bring them up in rigid and bond accordingly depending on what I was taking them to.

For the OP, don't pull a woven wire assembly 500'. It adds a lot of drag to the pull. If you break off 250' in you are going to be hating life. Get cut to length conductors on their own spool. You're going to need a tugger or something else to pull with. Fork lift, truck, back hoe.. Go nice and slow and lube the heck out of it. Have your sweeps buried really good as there is going to be a lot of presure pulling upward with your tugger.

wildleg · 11-11-2009, 07:07 PM

that pull is a cakewalk. lube it up, make a good basket on the head, tie the rope to your truck, one helper at the reel, one mechanic at the pull end, 3 walkie talkies, go for it.

bharbwyr · 11-18-2009, 09:15 AM

someone mentioned prelubing the conduit. sounds like a good idea but how? I could see maybe tying wads of rag onto the rope ahead of the cable and loading them up with lube...

minibdr · 11-18-2009, 11:28 AM

He didn`t say that. Wow

JayH · 11-18-2009, 01:07 PM

David is correct about using the rigid elbows, at least here in California. I cannot speak for jurisdictions outside of California.

Using the steel sweeps was a wise decision in a run that long. A rope will burn through the inside elbow of PVC as you pull (ask me how I know.) Basic physics at work here.

Pre-lubing a rope is a bad idea if you are using a tugger. The rope will begin to slip as the load increases.

I work primarily on institutional projects and they ALL, without fail, specify rigid sweeps and risers.