National Electrical Installation Standards

Standards as High as Your Own

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Monday, July 29, 2019

Question:

What happen to Monday's answer? Jimmy; Question of the day has no answer. Patrick Cook The answer to Monday July 22nd question was not published on Tuesday so we are repeating it here.

What is the length of run in a 2" PVC Conduit before it needs an expansion coupling?

Glenn Masters
A

Answer:

Hey Glen thanks for your question. It depends on the amount of temperature change the PVC conduit will be exposed to. If the conduit length in a straight run changes 1/4 inch or more between securely mounted items, an expansion fitting is necessary as stated in 352.44. For example using a 65 degree F temperature change (such as for 30 to 95 degrees) in the center column of Table 352.44 gives us 2.64 inches of change in 100 feet or .264 in 10 ft which is a little more than 1/4 in (.25). Follow the manufacturer's instructions when setting the position of the expansion based on the temperature at the time of installation. For example, if the fitting is "bottomed out" while the temperature is not at the maximum the conduit will buckle or the items at the end will be damaged or move as the conduit expands when the temperature rises.

A free publication about expansion fittings is available from NEMA at:

https://www.nema.org/Standards/Pages/Expansion-Fittings-for-Polyvinyl-Chloride-Rigid-Nonmetallic-Conduit.aspx

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