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75 years of excellence www.nema.org NEMA RV 3 Application & Installation Guidelines For Flexible & Liquid Tight Flexible Metal Conduits.

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Presentation on theme: "75 years of excellence www.nema.org NEMA RV 3 Application & Installation Guidelines For Flexible & Liquid Tight Flexible Metal Conduits."— Presentation transcript:

1 75 years of excellence NEMA RV 3 Application & Installation Guidelines For Flexible & Liquid Tight Flexible Metal Conduits

2 75 years of excellence Application Guidelines for FMC Construction of FMC Grounding and Bonding Uses Permitted and Not Permitted

3 75 years of excellence Construction for FMC Constructed in accordance with NEC Complies with safety requirements of UL1 Interlocked corrosion resistant steel or Aluminum strip

4 75 years of excellence Picture Example for FMC

5 75 years of excellence Diagram Example for FMC Cross-section view illustrating interlocking construction

6 75 years of excellence 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 (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…

7 75 years of excellence Product Marking for FMC Manufacturer’s designation UL Logo Conduit type  Reduced wall (RW)  Extra reduced wall (XRW) Material type  Aluminum (AL)  Steel (No Mark Required)

8 75 years of excellence FMC Marking Example

9 75 years of excellence Uses Permitted for FMC Exposed and concealed locations – NEC Dry locations only Branch circuits and feeders Ducts or plenums for environmental air  (B) limits to 4’ length  (C) no length limit Under raised floors for computer rooms Lighting whips and motor leads These uses are not all inclusive, but serve as guidelines

10 75 years of excellence Uses Not Permitted for FMC NEC Wet locations  2008 NEC removed exceptions Hoistways except as permitted in (A)(1) Storage battery rooms

11 75 years of excellence Uses Not Permitted – cont. for FMC Hazardous locations except (B) and Where conductors are exposed to deteriorating material Underground or in concrete Where subject to physical damage

12 75 years of excellence Reference Articles Reference UL 1 and NEC NEMA RV – National Electric Code NEMA RV – Related NEC Articles NEMA RV – UL Standards Guide information page: bin/XYV/template/LISEXT/1FRAME/index.htm White book “Guide Information for Electrical Equipment”

13 75 years of excellence Application Guidelines for LFMC Construction of LFMC Grounding and Bonding Marking Uses Permitted and Not Permitted

14 75 years of excellence Construction for LFMC In accordance with NEC Complies with safety requirements of UL360 Interlocked zinc-coated corrosion resistant steel Trades sizes are 3/8” through 4” Sizes 3/8” – 1 ¼” have bonding strip enclosed by convolution

15 75 years of excellence Construction – cont. for LFMC Jacket material is liquid-tight, non metallic Jacket specifications governed by UL 360 Fittings for LFMC are constructed to UL 514B

16 75 years of excellence Picture example for LFMC Cut-away view of Liquidtight Flexible Metal Conduit to illustrate construction

17 75 years of excellence Diagram Example for LFMC Cross-section view illustrating interlocking construction

18 75 years of excellence 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

19 75 years of excellence Surface Print for LFMC Manufacturer’s name or location Trade size Temperature rating Burial rating (when applicable) Flame rating (when applicable) Current rating (for equipment bonding according to NEC article 250)

20 75 years of excellence Uses Permitted for LFMC Exposed and concealed locations as follows:  When flexibility or protection from liquids, vapors or solids are required  As permitted by (B), , and  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:

21 75 years of excellence Uses Permitted –cont. for LFMC Outside branch circuits and feeders Under raised floors for computer rooms Lighting whips and motor leads These uses are not all inclusive, but serve as guidelines References throughout the NEC Code:

22 75 years of excellence Uses Not Permitted for LFMC Where subject to physical damage Where operating conditions cause temperatures to exceed material ratings See NEC for prohibited uses

23 75 years of excellence Reference Articles for LFMC NEMA RV – National Electric Code NEMA RV – Related NEC Articles NEMA RV – UL Standards Guide information page: bin/XYV/template/LISEXT/1FRAME/index.htm bin/XYV/template/LISEXT/1FRAME/index.htm White book “Guide Information for Electrical Equipment”

24 75 years of excellence Installation Guidelines Installation Considerations Securing & Supporting FMC & LFMC Terminating FMC

25 75 years of excellence 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)

26 75 years of excellence Lateral Offsets Use tables for length Lateral offset Example below

27 75 years of excellence 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

28 75 years of excellence 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

29 75 years of excellence Securing & Supporting FMC & LFMC According to NEC &  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

30 75 years of excellence 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’

31 75 years of excellence 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)

32 75 years of excellence Conduit Preparation for FMC & LFMC Square the cut end of the metal conduit Insert conduit flush with fitting end stop Ensure seating of clamp on conduit before torquing Be careful torquing the securement screw Always follow the manufacturer's instructions Follow recommendations from NEMA FB 2.20, “Selection and Installation guidelines for Fittings for use with Flexible Conduit and Cable”

33 75 years of excellence Cutting Conduit for FMC Rotary armor cutters Hacksaw  Cut one convolution at a 60 degree angle Diagonal wire cutters  Brake the conduit or twist open  Then cut with the cutters

34 75 years of excellence 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

35 75 years of excellence 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

36 75 years of excellence 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 instructions Follow recommendations from NEMA FB 2.20, “Selection and Installation guidelines for Fittings for use with Flexible Conduit and Cable”

37 75 years of excellence Fitting Attachment for LFMC Squared end must be fully inserted into ferrule Assembly methods vary for LFMC fittings, follow manufacturer's instructions Table 2 in NEMA RV 3 show standard torque values for LFMC fittings

38 75 years of excellence Unthreaded Entries Hand tighten the threaded portion of fitting to secured box using a locknut Assemble nut, gland and ferrule onto conduit After securely tightening the gland nut to the threaded body, finish tightening the locknut ¼ turn

39 75 years of excellence Fitting Example

40 75 years of excellence 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


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