I have a long run (1300') of PVC for some decorative lighting along a driveway. The lamps will be spaced about 130' apart. I'm wondering what the experience is regarding expansion/contraction of the PVC conduit. I know the temp down at 4' or so is pretty constant, but at 2' I'm not so sure it's constant. I certainly don't want any fittings to pull apart. Above ground, expansion fittings would be mandatory.
InspectorE, 300.5(J) ground movement, and 300.7(B) expansion fittings. I'm assuming that you are in a zone 3 or 4.(did a google on "frost zones") I personally probably would not bother with the expansion fittings if you can get down to 48"...like you said, it should stay a constant 55° anything less than 4', I would put one every 50-100'. 352.44(A) (let's say in the summer the earth is an even 55°, and in the winter it is 32°., so 1.01 inches per 100'.)
Re: Underground Long PVC Run#44385 11/03/0408:00 PM11/03/0408:00 PM
There will be lantern posts (5' high or so?) every 130'. Since it is underground, it has to be wet rated wire, so I'm not too concerned about any leakage/condensation inside the conduit. Stubs will have to be brought up to the posts, that's correct. Fortunately, the lamps are only 25 w or so, the voltage drop won't be a big factor.