When am I required to use PVC expansion couplings...do I need them for the service I described in the PVC Service thread? I always use them at residential services on poles, but here I have block buildings and the 4" conduits come out of well compacted asphalt over gravel parking lot.
By the way, yes, I do have a code book...but you guys are just so darn accomodating.(LOL) Thanks for the input!
In Maine you definitely need to be concerned about ground movement due to frost heave. 300.5(J) is the reference and you will need to use one of several approved methods. Of course this is for conduit that is coming up from under the grade. Read the FPN following this section.
Re: Expansion couplings for PVC service#53547 06/28/0511:41 PM06/28/0511:41 PM
Fascinating! I never thought about frost heave. I am lucky to live where the winters are somewhat milder than they are in the "rust belt," and our ground doesn't have much moisture in it to freeze- so it's not an issue here. (Of course, the downside is you almost need dynamite to place a ground rod!)