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Electrical Wiring

Schedule 40 expansion joints

14 years ago

I am replacing a service entrance cable and putting the new cable in 1 1/4" schedule 40 conduit. It goes from the meter on the pole down and then 18' underground and back up on the side of the house. Is it code now to use an expansion joint and if so do you need one on both vertical sections? This is in Minnesota. Thank you in advance for your input.

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Comments (7)

texasredhead
14 years ago
If you are using 3, 2/0 conductors, I would suggest 2" conduit. 18' or 18"?
terribletom
14 years ago
Assuming that 18' is the run length, Red's (implied) question about burial depth is still relevant.

In much of the country, expansion fittings are not necessary for relatively short direct-burial runs because the temperature 18" below ground (the usual minimum depth for burying conduit) is fairly constant. However, in very cold areas, it may be necessary to bury the conduit below the frost line. If you make the run above the frost line, you can get buckling in the conduit even with an expansion fitting.

I'd imagine that the frost line is pretty darn deep in your area of Minnesota, no?

As an aside, you might want to check with your AHJ to determine whether they'll require Schedule 80 conduit for the segment running from the meter pan to grade. I believe that this depends on whether your area interprets that part of the run as being subject to physical damage (crushing or impact) of the sort that requires Schedule 80. I've heard annecdotally that some do and some don't.

Here is a link that might be useful: One manufacturer's discussion about expansion fittings
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christophersprks
14 years ago
TT is correct schedule 80 from meter pan to grade is a must. you can switch to 40 below grade.
Don't forget to use the primer before gluing.
oleycow
Original Author
14 years ago
Thanks for your replies. The manufacturer's discussion link was very helpful. The run is 18 feet long. Minnesota code is to bury 18 inches down and that is what I will do but the frost depth is at least 4 feet. Water lines are buried at 6 foot. Most buried cables are put in conduit to help prevent gophers chewing through the wire. I'll check on the schedule 80 use above ground.
hexus
14 years ago
"Don't forget to use the primer before gluing"

what?

this isn't plumbing. I've never seen a two stage glue for PVC conduit and I've been doing this a long time.....
hexus
14 years ago
The National Electrical Code (NECÂ®) does not require primer to be used in the
joining of PVC conduit. However, under some conditions, primer can aid in the
ease of assembly and enhance the quality of the joints."

*shrugs*
I never have and doubt I ever will. Just get a good all weather glue from you local shop.
lbpod
14 years ago
All of the issues I have seen requiring slip joints is
because of the settling of the trench and pulling the
conduit down with it and many times pulling the meter box
off of the building. As much extra wire as possible
must be left in boxes at both ends.

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