armored cable

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  #1  
Old 03-04-14, 06:21 AM
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armored cable

Is flexible metal conduit rated to be grounded?
What fitting is best to connect to metal box?
Do I use bushings?

Intend to use 1/2" flex to junction box for can lights. The flex would be 3ft length?
 
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Old 03-04-14, 07:15 AM
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Is flexible metal conduit rated to be grounded?
What fitting is best to connect to metal box?
Do I use bushings?
Yes, the metallic flex must be grounded, but it isn't approved to carry the circuit ground, you still have to pull a ground wire through it. The grounding is accomplished through the metal squeeze connector connecting to the grounded metal box. The most common connector is the squeeze type connector, that's what I would use. I prefer using a plastic insulating bushing on the flex connectors unless they have an insulated throat. You can buy these in straight or 90 degree types.

https://www.google.com/search?q=flex...w=1024&bih=685
 
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Old 03-04-14, 07:27 AM
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Just to clarify, I have emt/conduit system. So if I branch off one box to a switch box, I have to run a separate ground as well or does the mechanical ground between the boxes and connector suffice?
 
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Old 03-04-14, 07:32 AM
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So if I branch off one box to a switch box, I have to run a separate ground as well or does the mechanical ground between the boxes and connector suffice?
Flexible metallic conduit is not rated to be the mechanical circuit ground and must have a ground wire pulled through it to the device box. If you are using armored cable, there will be a green grounding conductor in it from the factory. Flexible conduit will automatically be grounded when it is connected to the grounded metal box.

Flexible metal conduit and armored cable are two different things.
 
  #5  
Old 03-04-14, 07:44 AM
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Flexible metallic conduit is not rated to be the mechanical circuit ground
Flexible conduit will automatically be grounded when it is connected to the grounded metal box.
So which is it? Do I need to run a ground wire between the two boxes to achieve my mechanical ground? What material should I use here flexible metal or AC?
 
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Old 03-04-14, 07:56 AM
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So which is it? Do I need to run a ground wire between the two boxes to achieve my mechanical ground?
See Post #4

Flexible metallic conduit is not rated to be the mechanical circuit ground and must have a ground wire pulled through it to the device box.


What material should I use here flexible metal or AC?
It's your choice.
 
  #7  
Old 03-04-14, 10:15 AM
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I thought that you could go 6' using FMC as the grounding conductor?
 
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Old 03-04-14, 11:19 AM
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Fmc

I thought that you could go 6' using FMC as the grounding conductor?
Where flexibility is not required after installation of the FMC, a grounding conductor is not required and the armor of the flex can serve as the equipment ground if the conductors are protected by an overcurrent device not over 20 Amps and the flex is not over 6ft long. 250.118 2008 NEC
 
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Old 03-04-14, 12:07 PM
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Where flexibility is not required after installation of the FMC, a grounding conductor is not required and...
Pretty much the same rule still. 250.118(5), 2011 NEC:

(5) Listed flexible metal conduit meeting all the following
conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are
protected by overcurrent devices rated at 20 amperes
or less.
c. The combined length of flexible metal conduit and
flexible metallic tubing and liquidtight flexible metal
conduit in the same ground-fault current path does
not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is necessary
to minimize the transmission of vibration from
equipment or to provide flexibility for equipment that
requires movement after installation, an equipment
grounding conductor shall be installed.
 
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Old 03-04-14, 06:51 PM
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I have to say That's a new one on me, I've never seen it done that way.

I always recommend pulling a separate ground wire and not rely on the conduit ground so I think I'll just keep making that recommendation.
 
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Old 03-04-14, 08:06 PM
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Is there a reason you can't use NM cable? Just because it is metal now doesn't mean you have to follow as long as you connect the ground wire to the metal box.
 
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