flex conduit

[infantryldr]

How far can I run flex? I was told five feet, I was also told all the way back to the box providing there is two grounded conductors. Please advise. Thanks

[jbwhite]

by flex, do you mean FMC. as long as you want. no more than 360 deg in total bends. art 348

i dont know why you would need two grounded conductors unless you have an isolated ground circuit.

most job specs limit flex to other lenghs. this is a job spec, not a code issue.

[roger]

Are you talking about Equipment Grounding Conductors or Grounded Conductors?

Roger

[infantryldr]

Roger, Green equipmet conductors.

[roger]

JB is right, there would be no need for (2) Equipment Grounding Conductors unless an Isolated ground was called for, and if 250.118(5) is met it would still only require (1).

The maximum length allowed by 348.20 is for 3/8" FMC.

Roger

[infantryldr]

ok, but does the 6 ft rule per 348.20 apply to an outlet or just lights and hardwired equipment. I should have clarified my question better. We run FMC outlet to box in existing construction, I was told that was ok only if you have a ground with the FMC run. Thanks

[roger]

Infantryldr, if the FMC is longer than 6' in any size it will need one EGC. It doesn't matter what it is connecting to.

Below is a graphic and accompanying commentary form Mike Holts Training material.

http://www.mikeholt.com/onlinetraining/page_images/1100206760_2.jpg

Part VI. Equipment Grounding (Bonding) and Equipment Grounding (Bonding) Conductors

New text specifies when an equipment (bonding) conductor is required for flexible metal conduit and liquidtight flexible metal conduit.

(5) Listed Flexible Metal Conduit meeting all of the following conditions [348.60]. Figure 250-29
a. The flexible metallic conduit terminates in fittings listed for grounding (bonding).
b. The circuit conductors are protected by overcurrent devices rated 20A or less.
c. The combined length of the flexible metal conduit used as an equipment grounding conductor in the same fault return path doesn’t exceed 6 ft. Figure 250-30
d. Where flexibility is necessary, an equipment grounding (bonding) conductor must be installed in accordance with 250.102(E) regardless of the circuit rating or the length of the flexible metal conduit.

(6) Listed Liquidtight Flexible Metal Conduit meeting all of the following conditions [350.60]. Figure 250-31
a. The liquidtight flexible metal conduit terminates in fittings listed for grounding (bonding).
b. For 3/8 through 1/2 in., the circuit conductors are protected by overcurrent devices rated 20A or less.
c. For 3/4 through 11/4 in., the circuit conductors are protected by overcurrent devices rated 60A or less.
d. The combined length of the liquidtight flexible metal conduit in the same ground return path doesn’t exceed 6 ft.
e. Where flexibility is necessary, an equipment grounding (bonding) conductor must be installed in accordance with 250.102(E) regardless of the circuit rating or the length of the flexible metal conduit.

[ December 09, 2005, 04:08 PM: Message edited by: roger ]

[roger]

[ December 09, 2005, 04:10 PM: Message edited by: roger ]

[roger]

Oooops! :(

Roger

[infantryldr]

got it

[infinity]

Originally posted by infantryldr:
ok, but does the 6 ft rule per 348.20 apply to an outlet or just lights and hardwired equipment. I should have clarified my question better. We run FMC outlet to box in existing construction, I was told that was ok only if you have a ground with the FMC run. Thanks You still can't use 3/8 FMC in a length greater than 6'. Look at 348.20(A)(2). You would need to go up to 1/2" or larger, then your length would be unlimited. As Roger said after 6' you'll need a EGC.