expansion fittings for rigid

[don_resqcapt19]

Where you are installing expansion fittings for long runs of rigid conduit do you need to use support straps that permit the conduit to move? It seems like this should be a requirement, but I am not aware of such a rule in the NEC for rigid. There is one in 352.30 for PVC.

 

[Carultch]

Where you are installing expansion fittings for long runs of rigid conduit do you need to use support straps that permit the conduit to move? It seems like this should be a requirement, but I am not aware of such a rule in the NEC for rigid. There is one in 352.30 for PVC.

By omission, the NEC doesn't specify you have to use them. Common sense would dictate that you do, otherwise the expansion fitting serves no purpose (outside of those that cross building expansion joints). Good luck finding them in anything other than zinc-plated steel, which isn't enough corrosion protection for most outdoor environments. If mounted on durablocks that are free to slide, I wouldn't see the concern for having to have straps that allow axial movement.

A similar issue arises for PV rail systems, where they are rigidly fastened to the building at intervals of just a few feet, and still require an expansion joint after typically 50 ft of length. It makes me wonder if the expansion joint is actually effective.

 

[don_resqcapt19]

By omission, the NEC doesn't specify you have to use them. Common sense would dictate that you do, otherwise the expansion fitting serves no purpose (outside of those that cross building expansion joints). Good luck finding them in anything other than zinc-plated steel, which isn't enough corrosion protection for most outdoor environments. If mounted on durablocks that are free to slide, I wouldn't see the concern for having to have straps that allow axial movement.

A similar issue arises for PV rail systems, where they are rigidly fastened to the building at intervals of just a few feet, and still require an expansion joint after typically 50 ft of length. It makes me wonder if the expansion joint is actually effective.

This will be a horizontal rack on a right angle support from the outside of a building. The right angle bracket will be supported from vertical strut that will be attached to the building purlins. I guess I could use over sized u-bolts through the right angle bracket to secure the conduit and also permit movement along the length of the conduit.

We have often used zinc plated strut straps outside with no real corrosion issue.

 

[don_resqcapt19]

It looks like B-Line has a clamp for this purpose. I have never used it before, but looks like it should work well for an expansion application.