... 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"
Hear-say (from the photo discussion area on ECN , 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.