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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
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Figure 01
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Figure 01
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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
Note: The answers to these questions are based on the 2020 NEC.
Q1: What are the conditions LFMC can be used and installed?
A1: 350.10 Uses Permitted
Listed LFMC is permitted, either exposed or concealed, at any of the following locations:‚
(1) If flexibility or protection from machine oils, liquids, vapors, or solids is required.
(2) In hazardous (classified) locations as permitted in Chapter 5.
(3) For direct burial if listed and marked for this purpose.‚Figure 01
(4) Conductors or cables rated at a temperature higher than the listed temperature rating of LFMC conduit may be installed in LFMC, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the LFMC per 110.14(C).
Q2: Under what conditions can LFMC not be used and installed?
A2: 350.12 Uses Not Permitted
LFMC must not be used where subject to physical damage.‚
Q3: What is the minimum and maximum LFMC trade size permitted?
A3: 350.20 Trade Size
(A) Minimum. LFMC smaller than trade size ½ is not permitted to be used.
Ex: LFMC can be smaller than trade size ½ if installed in accordance with 348.20(A).
(B) Maximum. LFMC larger than trade size 4 is not permitted to be used.
Q4: What are the requirements for securing and supporting LFMC?
A4: 350.30 Securing and Supporting
LFMC must be securely fastened in place and supported in accordance with (A) and (B).
(A) Securely Fastened. LFMC must be securely fastened by a means approved by the authority having jurisdiction within 1 ft of termination and must be secured and supported at intervals not exceeding 4½ ft.‚
Where cable ties are used for securing LFMC they must be listed and identified for securement and support.
Ex 1: LFMC is not required to be securely fastened or supported where fished between access points through concealed spaces and supporting is impractical.
Ex 2: If flexibility is necessary after installation, unsecured lengths from the last point where the raceway is securely fastened are not permitted to 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
Ex 4: Lengths not exceeding 6 ft from the last point where the raceway is securely fastened can be unsecured within an accessible ceiling for a luminaire(s) or other equipment. Listed fittings are considered a means of securement and support.‚
For the purposes of these exceptions, listed LFMC fittings are permitted as a means of securement and support.
Author's Comment:
â–ºThis last sentence following the four exceptions means that the use of LFMC fittings as the means of securing and supporting only applies to installations made using one of the four exceptions. It should not be interpreted as permission to use these fittings to secure and support LFMC in all applications.
(B) Horizontal Runs. LFMC 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 termination.
Q5: What are the conditions PVC can be used and installed?
A5: 352.10 Uses Permitted
Type PVC conduit is permitted in the following applications:
Note: In extreme cold, PVC conduit can become brittle and is more susceptible to physical damage.
(A) Concealed. PVC conduit can be concealed within walls, floors, or ceilings.‚
(B) Corrosive Influences. PVC conduit is permitted in areas subject to severe corrosion for which the material is specifically approved by the authority having jurisdiction.
(D) Wet Locations. PVC conduit is permitted in wet locations such as dairies, laundries, canneries, car washes, and other areas frequently washed. It is also permitted in outdoor locations. Support fittings such as straps, screws, and bolts must be made of corrosion-resistant materials or must be protected with a corrosion-resistant coating in accordance with 300.6(A).
(E) Dry and Damp Locations. PVC conduit is permitted in dry and damp locations except where limited in 352.12.
(F) Exposed. Schedule 40 PVC conduit is permitted for exposed locations where not subject to physical damage. If the conduit is exposed to physical damage, the raceway must be identified for the application.‚
Note: PVC Schedule 80 conduit is identified for use in areas subject to physical damage.‚
(G) Underground. PVC conduit is permitted to be installed underground and in concrete and must comply with the burial requirements of 300.5.
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