Application Guidelines for FMC

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NEMA RV 3Application & Installation Guidelines For Flexible & Liquid Tight Flexible Metal Conduits

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Application Guidelines for FMC

Construction of FMCGrounding and BondingUses Permitted and Not Permitted

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Construction for FMC

Constructed in accordance with NECComplies with safety requirements of UL1Interlocked corrosion resistant steel or Aluminum

strip

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Picture Example for FMC

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Diagram Example for FMC

Cross-section view illustrating interlocking construction

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Grounding and Bonding for FMC

Permitted for bonding When installed with listed fittings and; Flexibility is not required after installation and; When installed according to NEC Articles 348 and 250 and; Protected by overcurrent device rated 20 Amperes or less.

Limited to 6’ lengths when used for bonding (see NEC 250.118 (5))

Grounding conductor required if FMC installed for flexible equipment or when used in lengths greater than 6’.

Grounding and bonding continued in slide 7…

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Product Marking for FMC

Manufacturer’s designationUL LogoConduit type

Reduced wall (RW) Extra reduced wall (XRW)

Material type Aluminum (AL) Steel (No Mark Required)

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FMC Marking Example

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Uses Permitted for FMC

Exposed and concealed locations – NEC 348.10Dry locations onlyBranch circuits and feedersDucts or plenums for environmental air

300.22(B) limits to 4’ length 300.22(C) no length limit

Under raised floors for computer roomsLighting whips and motor leadsThese uses are not all inclusive, but serve as guidelines

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Uses Not Permitted for FMC

NEC 348.12Wet locations

2008 NEC removed exceptionsHoistways except as permitted in 620.21(A)(1)Storage battery rooms

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Uses Not Permitted – cont. for FMC

Hazardous locations except 501.10(B) and 504.20Where conductors are exposed to deteriorating materialUnderground or in concreteWhere subject to physical damage

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Reference ArticlesReference UL 1 and NEC

NEMA RV 3 1.4.1 – National Electric CodeNEMA RV 3 1.4.2 – Related NEC ArticlesNEMA RV 3 1.4.3 – UL StandardsGuide information page:

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.htm

White book “Guide Information for Electrical Equipment”

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Application Guidelines for LFMC

Construction of LFMCGrounding and BondingMarkingUses Permitted and Not Permitted

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Construction for LFMC

In accordance with NECComplies with safety requirements of UL360Interlocked zinc-coated corrosion resistant steelTrades sizes are 3/8” through 4”Sizes 3/8” – 1 ¼” have bonding strip enclosed by

convolution

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Construction – cont. for LFMC

Jacket material is liquid-tight, non metallicJacket specifications governed by UL 360Fittings for LFMC are constructed to UL 514B

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Picture example for LFMC

Cut-away view of Liquidtight Flexible Metal Conduit to illustrate construction

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Diagram Example for LFMC

Cross-section view illustrating interlocking construction

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Grounding and Bonding for LFMC

LFMC trade sizes 3/8” – 1 ¼” permitted for equipment bonding: When installed with listed fittings and; Flexibility is not required after installation and; When installed according to NEC Articles 350 and 250

and; Only in 6’ lengths or less

Sizes 3/8” – 4” may be installed in unlimited lengths provided: A separate grounding conductor is installed And installed according to NEC Articles 350 and 250

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Surface Print for LFMC

Manufacturer’s name or locationTrade sizeTemperature ratingBurial rating (when applicable)Flame rating (when applicable)Current rating (for equipment bonding according to NEC

article 250)

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Uses Permitted for LFMC

Exposed and concealed locations as follows: When flexibility or protection from liquids, vapors or

solids are required As permitted by 501.10(B), 502.10, 503.1 and 504.20 Other hazardous classified locations per 553.7(B) Direct burial where listed & marked for that purpose If LFMC is marked direct burial it is also suitable for use

in concrete or in poured concrete The following are references throughout the NEC code:

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Uses Permitted –cont. for LFMC

Outside branch circuits and feedersUnder raised floors for computer roomsLighting whips and motor leadsThese uses are not all inclusive, but serve as

guidelinesReferences throughout the NEC Code:

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Uses Not Permitted for LFMC

Where subject to physical damageWhere operating conditions cause temperatures to

exceed material ratingsSee NEC 350.12 for prohibited uses

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Reference Articles for LFMC

NEMA RV 3 2.4.1 – National Electric CodeNEMA RV 3 2.4.2 – Related NEC ArticlesNEMA RV 3 2.4.3 – UL StandardsGuide information page:

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.htm

White book “Guide Information for Electrical Equipment”

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Installation Guidelines

Installation ConsiderationsSecuring & Supporting FMC & LFMCTerminating FMC

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Installation Considerations for FMC & LFMC

Minimum centerline bend radius Table 2 chapter 9 NEC “Other bends” column

Maximum # of bends between pull points Not to exceed (4) - 90 degree bends Or a total of 360 degrees (any direction)

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Lateral Offsets•Use tables for length

•Lateral offset

•Example below

Offset Table 2

3/4" Trade Size 0.75

"B" (in.) "R" Offset Distance (in.)

7 7.6

8 8.3 8.7

9 9.2 9.5 9.8

10 10.2 10.4 10.6 11.0

11 11.1 11.3 11.5 11.8

12 12.1 12.2 12.4 12.7 13.0

13 13.1 13.2 13.4 13.6 13.8 14.4

14 14.1 14.2 14.3 14.5 14.7 15.3

15 15.1 15.2 15.3 15.5 15.6 16.1 16.7

20 20.0 20.1 20.2 20.3 20.4 20.7 21.2 21.7 22.9 24.4

25 25.0 25.1 25.1 25.2 25.3 25.6 25.9 26.2 27.2 28.3

30 30.0 30.1 30.1 30.2 30.2 30.4 30.7 31.0 31.7 32.7

Overall Length of Conduit for Given Offset and Lateral Distance

Lateral Dist. 1.0 1.5 2 2.5 3.0 4.0 5.0 6.0 8.0 10.0

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Vertical Loop–Vertical loop w/offset

–L=(8xTS)+(1.57xA) +T/2+F

•L = Overall length

•TS = Trade size

•A = Horizontal dist between fittings

•T = Travel distance

•F = Offset

–This accounts for suggested tangent length

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Fittings should be tightened properly Section 3.3, tables 1 and 2 of NEMA guidelines for

proper torquing values Closely follow manufacturer's instructions

Installation Considerations – cont. for FMC & LFMC

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Securing & Supporting FMC & LFMC

According to NEC 348.30 & 350.30 Both must be supported and secured every 4.5’ or less Must be secured within 12” of each termination

These support requirements are waived if needed for flexibility or for luminaries

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Securing & Supporting – cont. for FMC & LFMC

Both may be unsupported when: Conduit is fished between access points through concealed

spaces in finished buildings or structures and supporting is impractical

Flexibility is required• 3’ maximum for LFMC• 3’ maximum for FMC ½” through 1¼”• 4’ maximum for FMC 1½” through 2”• 5’ maximum for FMC 2½” and larger

Used on luminaries; 6’ maximum Run through non-vertical framing members with distances

not exceeding 4½’

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Terminating FMC

Fitting Selection requires knowing: Trade size or metric designator Type of FMC, (standard, reduced or extra-reduced

wall) Type of metal (steel or aluminum)

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Conduit Preparation for FMC & LFMC

Square the cut end of the metal conduitInsert conduit flush with fitting end stopEnsure seating of clamp on conduit before torquingBe careful torquing the securement screwAlways follow the manufacturer's instructionsFollow recommendations from NEMA FB 2.20, “Selection and

Installation guidelines for Fittings for use with Flexible Conduit and Cable”

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Cutting Conduit for FMC

Rotary armor cuttersHacksaw

Cut one convolution at a 60 degree angle

Diagonal wire cutters Brake the conduit or twist open Then cut with the cutters

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Cutting Conduit for LFMC

Hacksaw Blade should have 32 teeth per inch

Band saw with ½” X .025 Blade with 24 teeth per inch at 350 ft/min

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Fitting Attachment for FMC

Always make sure the conduit is inserted completely to the smooth end stop

When using a clamp type fitting, be sure the fitting seats between the convolutions

Hand tighten the fitting screws and slightly rotate the conduit in the fitting

If there are two screws, tighten alternately to provide even pressure.

Table 1 in NEMA RV 3 shows standard torque values for FMC fittings

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Terminating for LFMC

Fitting Selection requires knowing: Trade size or metric designator The environment of installation

Conduit preparation Square the end of the conduit Fully insert conduit to end stop Ensure jacketing is not cut or ripped

Always follow the manufacturers instructionsFollow recommendations from NEMA FB 2.20, “Selection and

Installation guidelines for Fittings for use with Flexible Conduit and Cable”

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Fitting Attachment for LFMC

Squared end must be fully inserted into ferruleAssembly methods vary for LFMC fittings, follow

manufacturer's instructionsTable 2 in NEMA RV 3 show standard torque

values for LFMC fittings

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Unthreaded Entries

Hand tighten the threaded portion of fitting to secured box using a locknut

Assemble nut, gland and ferrule onto conduitAfter securely tightening the gland nut to the

threaded body, finish tightening the locknut ¼ turn

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Fitting Example

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Verification of Installation

• Conduit shall be properly terminated at boxes• Conduit shall be properly secured and supported• Conduit shall not show evidence of damage or physical

abuse

Documents

Application Guidelines for FMC