I have a project where the documents currently call for 3-800A feeders each from an 800A c.b. in some outdoor swtichgear the plan shows them going undergrouond for about 6-8' then up the exterior of the building into a "LB" thru the wall into the ceiling space of the adjacent space running about a additional 75' into the mcc / switchboards they are serving. my question is after pulling from the swbd down over up to the "LB" can you install 500's in a 4" "LB"? will the contractor be able to fit the cover back on after bending the cable almost 90 degrees? I suggested a pull box for each conduit 6"w x 12" high? I am looking for some contractors opinions as I am not a contractor and have never installed anything this size before? Thanks in advance for your input.
Conduit / Cable instalaltion Pull
- Thread starter Mike01
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Many manufacturers of the LB will state what is the largest size wire allowed in their LB. I would check with the manufacturer.
I don't have one of the tables Dennis references handy, but in the event you do install LB's for this I would strongly suggest ones with "split bodies" such as Appleton's LBD series. Pricey, but the ability to pull either direction with no "opposing wall" is fabulous.
peter d
Senior Member
- Location
- New England
I recently did a pull on a service installation that was 4-600's THHN/THWN copper in 4" conduit. The conduit turned up and went into a buidling, so a pull point was needed. The installer who came before changed over to a 5" rigid LB rather than use a 4". It made the install a lot easier but it was still difficult nonetheless. I haven't checked to see if it was compliant.
I think most LB's are installed in a non-compliant manner.
I think most LB's are installed in a non-compliant manner.
- Location
- Illinois
- Occupation
- retired electrician
A standard LB will not be suitable....it will have to be an LBD or mogual fitting and even some of them many not be suitable for that size wire. Remember that the rule in 314.28(A)(2) applies to LBs unless the LB is marked per 314.28(A)(3).
Don
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I just checked Kraloy Manufacturer of PVC LB's and the dimension they give from the top of the LB to the center of the bottom hole is 12.75 inches. The entire LB is 15" so it may be a tight fit.
I don't believe I would attempt this with an LB, although I (fortunately) have never had to pull 500 MCM cables. A JB certainly seems easier if you have the space.
I believe a conduit body would fall under art. 314.28 and specifically 314.28(A)(3). This brings us back to whether it is listed for the size conductors you want to use.
I don't believe I would attempt this with an LB, although I (fortunately) have never had to pull 500 MCM cables. A JB certainly seems easier if you have the space.
I believe a conduit body would fall under art. 314.28 and specifically 314.28(A)(3). This brings us back to whether it is listed for the size conductors you want to use.
- Location
- Illinois
- Occupation
- retired electrician
Dennis,
Don
The fitting in question and 314.28(A)(2) requires 24" between the two conduit entries.
Don
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
don_resqcapt19 said:
I read that and knew it requires 24" but art. 314.28(A)(3) appears to allow smaller if the unit is listed for it. That is why my first post states to check with the LB manufacturer. Am I wrong here?
mdshunk
Senior Member
- Location
- Right here.
When you're up into conductors that big, conduit bodies are normally out of the question for more practical reasons. A pull box is the way to fly on this, and if sized appropriately, one pull box will replace the whole line of LB's you had planned. The materials price will be about the same also, except you won't have bloody knuckles and an inflamed temper.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
don_resqcapt19 said:
I agree. I checked OZ/Gedney's website and they do not list the largest permitted conductors on a 4" LB. Therefore you would be required to use the 6X formula as Don has pointed out. Unless of course you could try to find a manufacturer that does make a 4" LB listed for X number of 500 kcmil conductors.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Smart $ said:
Good point, that's why I was thinking that there may be a manufacturer that makes an LB that will be code compliant. He could use the Red Dot LB if he has 3-500 kcmil conductors.
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