NM/Romex vs BX vs Aluminum Clad Cable

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Old 07-26-06, 04:30 PM
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NM/Romex vs BX vs Aluminum Clad Cable

I'd like to replace some flourescents in my basement with hi-Hats. The existing wiring is mostly BX/Armored Cable 14G/2 - No seperate Ground. The existing junction box from which these lights are supplied is basically fed from the breaker box by BX Cable & then at the junction box is spliced to supply 4 other cables - three of which are the same BX type, the other one is NM cable. Does it matter if I was to run cable to supply the new Hi Hats what kind of cable I use? I'd have to replace one of the BX cables that currently supply the existing flourescents. The easiest to work with is the NM cable followed by the Aluminum Clad & finally the BX/Armored. Does it matter "splicing" NM or Aluminum Clad to BX?
Part 2 - Both the NM & Aluminum Clad have a seperate Green Ground, The BX does not (Am I correct in believing the armored sheathing acts as its ground?) If I were to splice the NM or aluminum clad to the existing BX what's the best way to handle the green ground since the BX does not have a seperate ground to splice to?
Part 3 - I never saw the Aluminum clad before in Home Depot ("Metal lite"). What is its track record? I've used both NM & BX before, How does this aluminum clad stack up?

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Old 07-27-06, 01:45 AM
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The third type of cable you are talking about is called type MC. It stands for metal clad. BX is one brand name for type AC armor cable.

In most cases where either type AC or MC cable was used in a home, it was because of a local code issue. AC cable was often required by the city or county building dept. Now the IMHO better type MC cable has taken its place.

As for picking up a ground. IF a transition to NM (romex) or MC is allowed by local code, then you would bond the equpment ground wire from the cable to the metal box that the AC cable feeds. The clamp for the AC cable (yes these are special rated connectors) carries the ground from the cable armor to the box. A ground screw is needed from the box on.

Most often in cases like this the old small boxes that were used are not big enough to just add more wires to them. You may need to learn about box fill, and buy bigger junction boxes.
 
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Old 07-27-06, 03:38 PM
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Assuming I go with either NM or the Aluminum Clad - What are the pros & cons of each? I used NM many times before as well as AC/(BX type) but never aluminum clad. Thanks
 
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Old 07-29-06, 01:04 AM
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Type MC cable has greater protection from physical damage but is harder to work with.

I would use the NM if your local AHJ will allow it.
 
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