Stumped by the Code? Rules for Securing and Supporting Raceways

March 19, 2014
Your most pressing National Electrical Code (NEC) questions answered

All questions and answers are based on the 2011 NEC.

Q. What are the NEC rules for securing and supporting raceways? Specifically compare EMT, FMC, and PVC.

A. Electrical metallic tubing (EMT) must be installed as a complete system in accordance with 300.18 [300.10 and 300.12], and it must be securely fastened in place and supported in accordance with 358.30(A) and (B). In other words, EMT must generally be securely fastened within 3 ft of every box, cabinet, or termination fitting — and at intervals not exceeding 10 ft. Fastening is required within 3 ft of termination, not within 3 ft of a coupling.

Exception No. 1: When structural members don’t permit the raceway to be secured within 3 ft of a box or termination fitting, an unbroken raceway can be secured within 5 ft of a box or termination fitting. EMT 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.

FMC must be securely fastened by a means approved by the AHJ within 1 ft of termination, and it must be secured and supported at intervals not exceeding 4½ ft [348.30(A)].

Exception No. 1: Flexible metal conduit isn’t required to be securely fastened or supported where fished between access points through concealed spaces and supporting is impracticable.

Exception No. 2: If flexibility is necessary after installation, unsecured lengths from the last point the raceway is securely fastened must not exceed:

1) 3 ft for trade sizes ½ through 1¼

2) 4 ft for trade sizes 1½ through 2

3) 5 ft for trade sizes 2½ and larger

Exception No. 4: FMC to a luminaire or electrical equipment within an accessible ceiling is permitted to be unsupported for not more than 6 ft from the last point where the raceway is securely fastened.

FMC 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 1 ft of terminations [348.30(B)].

PVC conduit must be securely fastened and supported in accordance with 352.30(A) and (B):

• PVC conduit must be secured within 3 ft of every box, cabinet, or termination fitting, such as a conduit body [352.30(A)].

• 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 [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.

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 to compensate for thermal expansion and contraction of the raceway in accordance with Table 352.44, if the length change is determined to be ¼ in. or greater [352.44].

Table 352.44 in the NEC was created based on the following formula: Expansion/Contraction inches = raceway length ÷ 100 × [(temp change ÷ 100) × 4.00]

Q. What does the NEC require for coloring of device terminals to which grounded or equipment grounding conductors are to be attached?

A. Receptacles must have the terminal intended for connection to the grounded conductor identified by [200.10(B)]:

• A metal or metal coating that’s substantially white in color or marked by the word “white” or the letter “W.”

• If the terminal isn’t visible, the conductor entrance hole must be marked with the word “white” or the letter “W.”

Grounding-type receptacles, adapters, cord connections, and attachment plugs must have a means for connection of an equipment grounding conductor to the grounding pole. A terminal for connection to the grounding pole must be designated by one of the following [406.10(B)]:

• A green-colored hexagonal-headed or -shaped terminal screw or nut, not readily removable.

• A green-colored pressure wire connector body (a wire barrel).

• A similar green-colored connection device, in the case of adapters. The grounding terminal of a grounding adapter must be a green-colored rigid ear, lug, or similar device. The equipment grounding connection must be so designed that it cannot make contact with current-carrying parts of the receptacle, adapter, or attachment plug. The adapter must be polarized.

• If the terminal for the equipment grounding conductor is not visible, the conductor entrance hole must be marked with the word “green” or “ground,” the letters “G” or “GR,” a grounding symbol, or otherwise identified by a distinctive green color. If the terminal for the equipment grounding conductor is readily removable, the area adjacent to the terminal must be similarly marked.

Q. What is the Code rule regarding the location of switches for stairway lighting?

A. If the stairway between floor levels has six risers or more, a wall switch must be located at each floor level and at each landing level that includes an entryway to control the illumination for the stairway [210.70(A)(2)(c)]. Exception: Lighting outlets can be switched by a remote, central, or automatic control device.  

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.

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