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#90482 - 11/22/04 05:19 PM flexibility-FMC  
Steve T  Offline
Joined: Feb 2001
Posts: 306
Oak Park, IL, USA
What is everyone's opinion on "installed for flexibility" when refering to an equipment grounding conductor being required?

Does this include a whip that is installed to facilitate installation and removal of such appliances as residential dishwashers or stoves?

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#90483 - 11/22/04 10:41 PM Re: flexibility-FMC  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,099
I worked around the computer biz for 30 years where flexible wiring methods were the standard. I think they all need a hard wire ground. I have seen far too many that have separated from the connectors.
Joe Tedesco may have some of my pictures. They were in the IAEI magazine a couple times

Greg Fretwell

#90484 - 11/24/04 05:53 PM Re: flexibility-FMC  
Steve T  Offline
Joined: Feb 2001
Posts: 306
Oak Park, IL, USA
So what about AC cable? Doesn't it come loose too?

#90485 - 11/24/04 06:32 PM Re: flexibility-FMC  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Greg: Remind me about the images and what was included in them. I think I still have some and one with about a size 12 boot with the underfloor in a computer room.

The reason for the "flexibility" rule calling for the EGC at all times is because CMP 9 went out into the field and found that most of the compressors on roofs were with loose connections, and the flexible metal conduit that was used was not secure in many instances.

I think that the they did this around the 1981 or 1984 NEC cycle. Maybe someone can check the TCR and TCD

Joe Tedesco, NEC Consultant

#90486 - 11/25/04 01:46 AM Re: flexibility-FMC  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,099
Steve I will say I don't see any difference between AC, FMC or LFMC in this regard. If it is not installed to 300.11 standards (secured next to the box) it should have a ground wire. Whenever you have a whip to something that can move around or where the whip can be moved around you are going to loosen a certain percentage of the connectors. At least one of the pictures I sent into IAEI shows a separated FMC connector under a computer room floor with about 4" of conductor exposed. Without a green wire ground that equipment was floating. The same can happen to T bar lights, pump motors, wall ovens or whatever you hang out on a whip. Fortunately I never had the fight when I was an inspector. Insulated EGCs were required in all state contracts, even in EMT, IMC or RMC.

Greg Fretwell

#90487 - 11/25/04 08:03 AM Re: flexibility-FMC  
shortcircuit  Offline
Joined: Jun 2004
Posts: 608
I have recently noticed that furnace manurfacturers that use FMC to connect between the controls on the unit now have a insulated EGC installed in their factory assembled units.I always wondered how they got away without the ECG in the flex.


#90488 - 11/25/04 11:37 AM Re: flexibility-FMC  
John Steinke  Offline
Joined: Apr 2001
Posts: 518
Reno,Nv., USA
I will have to agree with gfretwell; when the appliance is likely to be physically moved (as with a dishwaser), and not simply vibrating (like a transformer), I believe that it is wise to run a grounding wire.
his also applies when the flex is likely to be snagged, or tripped over, etc. I've just seen too many connectors -especially "jakes"- come loose. Indeed, I will often install liquid-tight for this reason; their connectors are more substantial.

#90489 - 11/25/04 11:54 AM Re: flexibility-FMC  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
None of these installations are allowed to transmit stress to the connectors.

Other than flexible whips to Luminaires all flexible cables and raceways require a support near the connector before and after the section that may be flexed. [Linked Image]


Manufacturers are not covered by the NEC and comparing their work against our work can only lead to frustration. [Linked Image]

The fact is manufacturers equipment gets tested by an NTL and must pass certain tests.

We do not test our grounding paths so the code has to make a blanket statements about what will be acceptable and what will not.

I always run a grounding conductor in flexible raceway it just makes me feel better. [Linked Image]


Bob Badger
Construction & Maintenance Electrician

#90490 - 11/26/04 08:00 AM Re: flexibility-FMC  
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
Bob- State of Michigan requires an EGC in all flex regardles of length. There are two exceptions: One is Flexible Metal Tubing and the other is for flex 6 feet or less when used in one and two family housing subject to the Michigan Residential Code (IRC). Most contractors pull in an EGC all the time in flex regardless. I would say one of the primary reasons electricians run flex is to avoid running EMT or Conduit. The vibration issue is secondary.

George Little

#90491 - 11/27/04 10:30 PM Re: flexibility-FMC  
electure  Offline

Joined: Dec 2000
Posts: 4,260
Fullerton, CA USA
I always put an EGC in all flex that I install, and make sure the fittings are tight.

Sadly, I can go up to probably 8 or 9 out of 10 flex installations I find, and take them apart barehanded, because that's the way they were installed.
The same holds true for the gland nuts on LTFlex connectors.
I don't like to see it that way, but it's a fact. [Linked Image]

[This message has been edited by electure (edited 11-27-2004).]

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