All questions and answers are based on the 2020 NEC.
Q. What is the NEC requirement for securing and supporting PVC conduit?
A. PVC conduit must be fastened and supported in accordance with Sec. 352.30(A) and (B), so movement from thermal expansion and contraction is permitted (Fig. 1).
Secured. PVC conduit must be secured within 3 ft of every box, cabinet, or termination fitting, such as a conduit body [Sec. 352.30(A)].
Supports. PVC conduit must be supported at intervals not exceeding the values in Table 352.30, and the raceway must be fastened in a manner that permits movement from thermal expansion or contraction [Sec. 352.30(B)].
PVC conduit installed horizontally in bored or punched holes in wood or metal framing members, or notches in wooden members, is considered supported, but the raceway must be secured within 3 ft of termination.
Q. What are the Code requirements for expansion fittings in PVC conduit runs?
A. If PVC conduit is installed in a straight run between securely mounted items, such as boxes, cabinets, elbows, or other conduit terminations, expansion fittings must be provided if the expansion or contraction length change, in accordance with Table 352.44, is expected to be ¼ in. or greater [Sec. 352.44] (Fig. 2).
When determining the number and setting of expansion fittings, you must pay close attention to the manufacturer’s documentation. For example, instructions for Carlon expansion fittings for PVC states, when the PVC has sunlight exposure, we must add 30°F to the high ambient temperature.
Q. What are the minimum and maximum trade sizes allowed by the Code for PVC conduit?
A. Type PVC conduit smaller than trade size ½ isn’t permitted to be used. Type PVC conduit larger than trade size 6 isn’t permitted to be used. [Sec. 352.20].
These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code.
