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

2. Application Guidelines for FMC
Construction of FMC
Grounding and Bonding
Uses Permitted and Not Permitted

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

4. Picture Example for FMC

5. Diagram Example for FMC
Cross-section view illustrating interlocking construction

6. 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. 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. FMC Marking Example

9. 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

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

11. 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. Reference Articles Reference UL 1 and NEC
NEMA RV – National Electric Code
NEMA RV – Related NEC Articles
NEMA RV – UL Standards
Guide information page:
White book “Guide Information for Electrical Equipment”

13. Application Guidelines for LFMC
Construction of LFMC
Grounding and Bonding
Marking
Uses Permitted and Not Permitted

14. 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. 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. Picture example for LFMC
Cut-away view of Liquidtight Flexible Metal Conduit to illustrate construction

17. Diagram Example for LFMC
Cross-section view illustrating interlocking construction

18. 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. 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. 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. 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. 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. Reference Articles for LFMC
NEMA RV – National Electric Code
NEMA RV – Related NEC Articles
NEMA RV – UL Standards
Guide information page:
White book “Guide Information for Electrical Equipment”

24. Installation Guidelines
Installation Considerations
Securing & Supporting FMC & LFMC
Terminating FMC

25. 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. 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
15.5
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
25.2
25.3
25.6
25.9
26.2
27.2
28.3 30
30.0
30.1
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

27. 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. 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

29. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Fitting Example

40. 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