We are installing a new oil filled transformer and will be penetrating the oil pit liner. The drawings indicate the conduit immediately turning up to a field termination cabinet. The conduit is 4" sch 40 PVC, the cable will be 3-1/C 350kcmil. The engineer says the conduit needs to penetrate the liner at a right angle and to use a 90 degree LB fitting to turn up as we don't have room for a sweep. As this will later be filled with stone, is it acceptable to use an LB fitting that will be below grade? I've never done this before, but am drawing a blank if it's permissible. Thanks for any input. Greg

Not Permitted. You must retain access to that LB when installation is complete, just as if it were a junction box.

Invariably, someone at this point will say "but we can remove the stones later." They might even find code language that would allow, say, minor amounts of leaf mulch to conceal outdoor lighting fittings. Nice try; we might as well just eliminate any restrictions on accessibility if we're going to stretch that loophole that far.

You'd be better using another code provision that might let you re-examine 'conduit fill,' and make a sweep using a conduit barely large enough for the cable to enter. Or, for that matter, use a cable that's rated for direct burial.

Renosteinke, thanks for the quick response. That's what I thought, treat the LB like a junction box, you need to retain access. I told the engineer, and he agreed to look for a different solution. I appreciate the quick input. Best regards, Greg

You may consider a 'Quazite' box adjacent to the pit; punch thru the sidewall of the box into the pit and exit at 90 degrees either right or left side & up.

The LB would be a red tag.

John, I'm having a hard time picturing your solution. I guess I'm missing something in the translation. Could you further explain? We've put this on hold so I have some time to complete.
Thanks, Greg

OK, I'll try...
A 4" nipple out of the side of the pit, and into the side of a 'quazite' box of suitable depth and bending spaces for your conductors.

Basically think like a j-box adjacent to the tranny pit. Then exit the 'box' from either side to your cabinet.

Another bit of code trivia:

The accessibility requirement for the LB would also apply to a 90 degree fitting for "Flex" or "Sealtite." The requirement does not apply, however, to MC. "MC" is best described as flex that is sold with the wires already in it.

Whether there is a rated MC and fitting for your application is another question.

I've seen MC that was suitable for under slab and concrete encasement, it had/has a PVC exterior jacket, and special connectors.

There could be an issue with bend radius.

This may be an idea, but...availability?? minimum length??
Is it 'made to order', or warehouse stock?

I only saw it on one job, at least 5-8 years back.

Southwire's current price sheet lists it's PVC coated MC cable at $79.80 a foot for 3-350kcm with a ground

Thanks Electure, this may help the OP.

100' minimum????? $7980.00 plus any tax???

Curious

Oh, ok John. Thanks for the clarification. Got it now.
Greg