Article 350 Liquidtight Flexible Metal Conduit: Type LFMC

Exception No. 1: Where LFMC is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical.

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Exception No. 2: Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following:

1. 900 mm (3 ft) for metric designators 16 through 35 (trade sizes (1/2 through 11/4)
2. mm (4 ft) for metric designators 41 through 53 (trade sizes 11/2 through 2)
3. mm (5 ft) for metric designators 63 (trade size 21/2) and larger

Exception No. 3: Lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap conductors to luminaires , as permitted in 410.117(C)

Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to luminaire (s) or other equipment

For the purposes of the exceptions, listed LFMC fittings shall be permitted as a means of securement and support.

LFMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet conduit body , or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (4ft). Where used, cable ties shall be listed and be identified for securement and support.

The exception only applies for connections within an accessible ceiling to a luminaires or other equipment.

Code Change Summary: Code language was added to address the use of flexible metal conduit fittings as a means of support.

Most of the time, lay in luminaires installed into a suspended grid ceiling are wired to a junction box above ceiling with the factory made 18 AWG fixture whips that come with the luminaire. Sometimes, MC or AC cable is used instead. Once in a great while an electrician might use flexible metal conduit (FMC).

The general rule for securing and supporting FMC is to fasten it within 12 inches of the box and secure it no further than every 4.5 feet. If the FMC is installed above an accessible ceiling, exception 4 allows the support spacing to be increased to 6 feet &#;from the last point where the raceway is securely fastened&#;. The question has been, what is considered &#;the last point where the raceway is securely fastened&#;?

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In the NEC®, that question has been answered by a code change to exception 4. According to the new code language, for the purposes of this exception, listed flexible metal conduit fittings shall be permitted as a means of support. This means that a 6-foot length of FMC installed with listed fittings above an accessible ceiling between a junction box and a luminaire &#;or other equipment&#; can go without any additional strapping or supporting at all.

The new code language aligns with similar existing code language for MC and AC cables. A similar change occurred for liquidtight flexible metal conduit (LFMC) at 350.30(A), Ex. No. and for liquidtight flexible nonmetallic conduit (LFNC) at 356.30(4).

Below is a preview of the NEC®.  See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the &#;free access&#; tab and select the applicable year of NFPA 70 (National Electrical code).

Code language:

348.30(A) Securely Fastened. FMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (4 ½ ft).

Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment.

Code Language:

348.30(A) Securely Fastened. FMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (4 ½ ft).

Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment. For the purposes of this exception, listed flexible metal conduit fittings shall be permitted as a means of support.

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