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#57727 10/18/05 11:21 PM
Joined: Dec 2003
Posts: 524
Member
... We're doing a 300 amp. underground service for a residence,and I know that I need to insert an expansion coupling,..but where?? on the line side schedule 80 pvc,just before the meter,or in the trench,...and do I also need one on the load side before entering the basement through the foundation??

I realize it depends on the length of run and the expected change in ambient temperature, but I'm a little fuzzy on where to place it...(don't be funny, I know what you're about to say..)
Russ


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#57728 10/19/05 12:07 AM
Joined: Jun 2004
Posts: 1,273
T
Member
Fully buried PVC is not prone to expansion issues.

The expansion joint would be needed if the length of exposed run is more than stubbing out to a panel/ meter pan.

Buried runs usually do not have expansion joints since the ground greatly moderates their temperature swings.


Tesla
#57729 10/19/05 07:38 AM
Joined: Sep 2003
Posts: 650
W
Member
Hear-say (from the photo discussion area on ECN [Linked Image], rather than personal experience: for a short stub of pvc from underground to the meter pan, the thermal expansion will not be enough to matter. Thermal expansion and contraction shows up as a percentage change in length, so the shorter the 'nominal' length, the smaller the change produced by thermal effects.

However the expansion joint will also nicely accommodate things like the soil settling after construction, or the earth moving for other reasons. If you search in the Photos Submitted for Discussion area, I'm sure you will find pictures of residential service stubs ripped out of meter pans by the ground settling.

-Jon

#57730 10/19/05 09:53 PM
Joined: Nov 2000
Posts: 2,148
R
Member
As Jon stated, ground movement is a problem that can be solved by using an expansion fitting and is one method of compliance with 300.5(J).
Don


Don(resqcapt19)
#57731 10/20/05 07:39 PM
Joined: Apr 2002
Posts: 7,333
Likes: 7
Member
Rat:

IF you run pvc from meter pan (at house) to pole, & up the obligatory 10'; you need an expansion joint between the ma at the meter pan, and the dirt.

IF you only have to 'leave' a short pvc piece, with the bell/bushing; for BUD direct burial by utility; you do NOT need an exp. joint.

As Jon & Don said....ground heaving, not expansion in this case.

(From another Jersey Guy)

John


John

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