Yes, I think they should be used, and in my case they are required by local amendment. Plus they make it easy to finish the run.Should these be used for risers from buried conduit? Not talking about a stub into the ground and then direct burial cable with no conduit but where there is a 90 at the bottom and a horizontal buried conduit. We get freezing to 30" max here as I recall.
Should these be used for risers from buried conduit? Not talking about a stub into the ground and then direct burial cable with no conduit but where there is a 90 at the bottom and a horizontal buried conduit. We get freezing to 30" max here as I recall.
300.5(J) Earth Movement. Where direct-buried conductors,
raceways, or cables are subject to movement by settlement
or frost, direct-buried conductors, raceways, or cables shall
be arranged so as to prevent damage to the enclosed conductors
or to equipment connected to the raceways.
Informational Note: This section recognizes “S” loops in
underground direct burial to raceway transitions, expansion
fittings in raceway risers to fixed equipment, and, generally,
the provision of flexible connections to equipment subject
to settlement or frost heaves.
Thanks. Does that mean I should loosen the straps to allow for expansion ? Not sure how long the generator (at my installation) has been in place but there doesn't seem to be much movement or warping of that PVC from what I saw.Will you pass inspection? Depends on how savvy the inspector is.
Yes, you have to anticipate the expansion or contraction, which is dependent on temperature when installed. Many overlook this requirement when the run doesn't seem worthy of consideration. However, the length of a outdoor straight run between secured points requiring an expansion fitting is surprisingly short. Where there is a 100°F temperature swing, that length is about 6' 2"... and it varies inversely with respect to temperature swing.
You can support with strut and straps, but the straps must allow longitudinal movement (i.e. permit the conduit to slide lengthwise).
Loosened straps also allow easier side movement. Not ideal, but time will tell whether it suffices. The best way is to use straps designed for longitudinal slip.Thanks. Does that mean I should loosen the straps to allow for expansion ? Not sure how long the generator (at my installation) has been in place but there doesn't seem to be much movement or warping of that PVC from what I saw.
Not because the ends are free to move...Whether expansion fittings are needed or not depends on amount of length change to be expected which is directly related to amount of ambient temp change to be expected. Also depends on whether or not the ends of the run in question are secured or if they are allowed to move.
A run with a fixed box on each end needs to have an expansion fitting if expected movement is more then 1/4 inch according to NEC.
A run of the same length with an elbow on each end may not need an expansion fitting at all because the ends are free to move.
...
Ok, that is basically what I was thinking I just didn't provide as much details. Be careful some people don't like it when you give too many details and make the post too long, apparently they can't keep awake long enough to read all those details.Not because the ends are free to move...
Don't forget that enclosures, boxes, and such are required to be securely fastened (unmovable). The run with the elbow may not need an expansion fitting because the run between terminations is not straight... and requirement to "be fastened so that movement from thermal expansion or contraction is permitted" should allow the elbow to move... but if the elbow is supported too rigidly and close to its tangent points, it may not allow enough movement and one, perhaps two expansion fittings may be required.
No worries there. I try to keep my posts as succinct as possible. Not for those you mention, but simply because I don't want to be typing up an essay to explain a simple concept. hmy:Ok, that is basically what I was thinking I just didn't provide as much details. Be careful some people don't like it when you give too many details and make the post too long, apparently they can't keep awake long enough to read all those details.
Well sometimes I don't chew things up enough before swallowing I guessNo worries there. I try to keep my posts as succinct as possible. Not for those you mention, but simply because I don't want to be typing up an essay to explain a simple concept. hmy:
Continuing the analogy, I think it depends on the "food". But either way is fine as long as your "health" don't suffer. But please, please do not "regurgitate".Well sometimes I don't chew things up enough before swallowing I guess
Add: Then again maybe it's the other way around, I chew too much and should swallow sooner.