ECN Forum Forums Photo Discussion Forums Photos for General Discussion Is an expansion fitting required here?

Photo submitted by Joe Tedesco

The answer to this is easier to find in the '99 NEC than the '96. The table for the expansion of PVC has been moved to Article 347 from an obscure spot in Chapter 9.
­ If that conduit is 4' long, and the temperature change is 130°, the answer would be no. (5.3"X.04=.212", which is less than 1/4")
However, if it's 5' long, with a 130° change in temp,5.3"X.05=.265", one would be required.

Temperatures not withstanding, if frost heave is a problem, then an expansion fitting would be required. Look in the misc. section of the code, 300-5(j)

Tom

I wouldn't expect frost to be a problem if the conduit extends below the frost line.

The temperature change of the portion below ground is narrower.

Frost can heave inches in certain soils. A simple expansion joint won't solve that problem.

Thanks, I never thought about that, being from So.CA. That's one thing that's so good about the BB, is that I'm able to learn about circumstances and reasons for other locations. (Is this what you guys were calling a "frosty"?) I just thought of the 130° as being a pretty extreme variance

With the last code review our AHJ decided that all transitions from above or below grade must have expansion fittings. I have had to pull a direct buried service lateral and install a expansion joint when the pipe ended 18" below grade.

I agree that the expansion joint is a good idea when running continuos conduit.....but when direct burial is used, it's ridiculous

GJ