75 years of excellence NEMA RV 3 Application & Installation Guidelines For Flexible & Liquid Tight...
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Transcript of 75 years of excellence NEMA RV 3 Application & Installation Guidelines For Flexible & Liquid Tight...
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75 years of excellence
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