When are expansion fittings required per 352.44?

[infinity]

Admittedly, -3/16" to 3/16" deformation is going to be less stressful than 0 to 3/8" deformation.

I agree and that was my point, the NEC allows up to 1/4" but the methodology for calculating it is flawed.

 

[oldsparky52]

For example, if the temperature was at the minimum of range, you would fully collapse the coupling, if at max temp, you would fully extend it. Most likely, you’re somewhere in the middle.

Isn't that backwards? If the ambient temperature is near the low range, the conduit would shrink and the expansion coupling would expand. If the conduit is near the max range then the conduit would be expanded and the expansion coupling would shrink.

 

[electrofelon]

Isn't that backwards? If the ambient temperature is near the low range, the conduit would shrink and the expansion coupling would expand. If the conduit is near the max range then the conduit would be expanded and the expansion coupling would shrink.

I think by "you would" he means during installation.

 

[kwired]

Isn't that backwards? If the ambient temperature is near the low range, the conduit would shrink and the expansion coupling would expand. If the conduit is near the max range then the conduit would be expanded and the expansion coupling would shrink.

Yes, you need to factor in where ambient is at time of installation to determine how far to install pipe into the expansion fitting.

If at lowest expected ambient at time of install - the pipe doesn't go in as far - it will expand when temp rises.

If at highest expected ambient at time of install - the pipe goes in (maybe all the way even) - it will contract when temp falls. If you not in far enough you could pull apart if it contracts enough to do so.

They also make long and short styles of expansion fittings. If you have longer expansion/contraction lengths involved you may prefer a long fitting over a short fitting. If you have long enough run you may even need more than one expansion fitting in the run.

Elbows are not necessarily " secured or fixed", though they can be. Same with conduit bodies. Boxes - Don't think you will find many if any that are not intended to be secured in PVC material. Unlike the malleable iron FS type boxes that can be raceway supported.