Transcript Application Guidelines for FMC

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NEMA RV 3
Application & Installation Guidelines For Flexible & Liquid Tight Flexible Metal Conduits
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Application Guidelines for FMC
Construction of FMC
Grounding and Bonding
Uses Permitted and Not Permitted
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Construction for FMC
Constructed in accordance with NEC
Complies with safety requirements of UL1
Interlocked 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 designation
UL Logo
Conduit 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 348.10
Dry locations only
Branch circuits and feeders
Ducts or plenums for environmental air
 300.22(B) limits to 4’ length
 300.22(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
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Uses Not Permitted for FMC
NEC 348.12
Wet locations
 2008 NEC removed exceptions
Hoistways 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 504.20
Where conductors are exposed to deteriorating material
Underground or in concrete
Where subject to physical damage
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Reference Articles
Reference UL 1 and NEC
NEMA RV 3 1.4.1 – National Electric Code
NEMA RV 3 1.4.2 – Related NEC Articles
NEMA RV 3 1.4.3 – UL Standards
Guide information page: http://database.ul.com/cgibin/XYV/template/LISEXT/1FRAME/index.htm
White book “Guide Information for Electrical Equipment”
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Application Guidelines for LFMC
Construction of LFMC
Grounding and Bonding
Marking
Uses Permitted and Not Permitted
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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
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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
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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 location
Trade size
Temperature rating
Burial 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 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:
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Uses Not Permitted for LFMC
Where subject to physical damage
Where operating conditions cause temperatures to
exceed material ratings
See NEC 350.12 for prohibited uses
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Reference Articles for LFMC
NEMA RV 3 2.4.1 – National Electric Code
NEMA RV 3 2.4.2 – Related NEC Articles
NEMA RV 3 2.4.3 – UL Standards
Guide information page:
http://database.ul.com/cgibin/XYV/template/LISEXT/1FRAME/index.htm
White book “Guide Information for Electrical
Equipment”
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Installation Guidelines
Installation Considerations
Securing & Supporting FMC & LFMC
Terminating 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
Overall Length of Conduit for Given Offset and Lateral Distance
"B" (in.)
Lateral Dist.
"R" Offset Distance (in.)
1.0
1.5
2
2.5
3.0
4.0
5.0
6.0
8.0
10.0
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
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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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Installation Considerations – cont. for
FMC & LFMC
Fittings should be tightened properly
 Section 3.3, tables 1 and 2 of NEMA guidelines for
proper torquing values
 Closely follow manufacturer's instructions
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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 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”
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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
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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 instructions
Follow 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 ferrule
Assembly methods vary for LFMC fittings, follow
manufacturer's instructions
Table 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 conduit
After 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
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