As I understand it, they are pretty much the same except that MC has a ground and BX relies on the jacket as the ground. Any other differences? Either harder to use?
How do you use the ground on BX, at the breaker box and junction box? Does it simply go through the mechanical connection at the box, or is there a wire to attach?
If did a google search, but didn't come up with much.
In Canada, BX or armoured cable with the aluminum sheath now has a separate ground wire, while a number of years ago it relied on the sheath to act as ground.
You might have better luck with your search if you used type AC instead of BX, which was a brand name. The original product from Bronx cable (BX) was steel wound armor. It is referred to in the NEC as Type AC. A bonding strip was added later. This has a paper inner wrapper and is dry location only. It requires an insulating bushing (AKA Read Head) where it enters the box. It can be aluminum or steel armor Type MC is a newer product using a similar armor, aluminum or steel. The inner wrapper is plastic and newer versions can be listed for use in wet locations. The insulation bushing is not necessary when used with the proper connector. Traditionally the armor of type MC was not listed for grounding and it came with an insulated green wire grounding conductor, This is about to change. The newest version has a large uninsulated bonding conductor in continuous contact with the armor that will allow the armor to be the ground. It is not necessary to terminate this bonding conductor and it is cut off flush with the armor when you use the new bonding connector at the box. Either MC or AC can have additional grounding conductors for applications like hospitals.
I can buy BX (AC...) for $0.60/ft and MC for $1.10/ft. I don't care about wet applications. I don't know anything about their construction; it is internet and they don't give any specs.
Any reason not to use the BX? The vendor is Dale Electric. If you can suggest an alternative... I also need a Murray 30/50 quad breaker for the project.
There is nothing wrong with AC cable. Just be sure you use the right connectors and make them up well since this is your grounding path. I imagine the difference in price is the grounding conductor in MC. Dale has been OK to me but I usually try to patronize my local suppliers when I can.
I seem to recall some types of metal armoured cable that had a flat aluminum tape conductor running through in addition to the copper conductors to be connected and form the ground.
That was presumably in those jurisdictions where it became unacceptable to depend on the ground being through the metal cable connectors and the metal sheath?
I also recall some very old (1938 installed? steel sheathed cabling that did depend on the sheath being the ground conductor.
On this news group IIRC there have been more recent statements that electrical code in many jurisdictions requires the use of specific 'ground' conductor of correct gauge withing the sheath in addition to the current carrying conductors. In other words the sheath now is merely for mechanical protection; not grounding?
When we rewired our hot water tank; with two wire #10 AWG recently, we also provided a third ground conductor and slid it all through an approximately 3 foot length of armoured mechanically protecting it from the wall box to the hot water tank itself.
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