The following is from the 18th Edition of the hand book:
Subrule (8). As you should note from Diagrams 1 and 2, all the receptacles are required to have a grounding pin. Although this has been a CE Code, Part I, requirement since the mid 1950s, many older electrical installations still have ungrounded receptacles. When an ungrounded receptacle becomes defective, it has to be replaced with the grounded type, since the others are no longer available. If the grounding terminal is not effectively connected to ground, it creates a false sense of security. After all, some portable equipment is grounded for safety reasons, and if the grounding terminal is not bonded to ground, the safety feature is lost. Normally, a bonding conductor is run with the circuit conductors, but in situations such as this it is allowed to to be connnected to a local ground. We intend that the grounding terminal of the receptacle be bonded to ground by one of the following methods: (a) connection to a grounded metal raceway or metal cable sheath; or (b) a separate bonding conductor, sized by Table 16, and connected to the system ground; or (c) bonding to an adjacent grounded metal cold water pipe. Subrule (9). In existing residential occupancies, when an ungrounded receptacle has to be replaced, we intend to allow, under specific conditions, grounding type receptacles without a bonding conductor to be used where there is no grounding means in the existing receptacle's enclosure. The conditions are as follows: (a) the receptacle replacing the ungrounded receptacle is a ground fault circuit interrupter type receptacle of the Class A type; or (b) the receptacle being replaced is supplied by a receptacle containing a ground fault circuit interrupter of the Class A type; or (c) the receptacle being replaced is supplied by a circuit protected by a ground fault circuit interrupter of the Class A type.
The way I interpret that info from the handbook it seems as if it would be ok to use the armour as a bond in your situation. I would verify that the armour is actually grounded.
Edited to correct spelling
[This message has been edited by bigrockk (edited 02-24-2006).]
So are you saying that you think that when it refers to the metal cable sheath this means that they are talking about the armour on the bx? If so why do they use the term sheath and not "armour" like they do everywhere else in the code?
[This message has been edited by RobbieD (edited 02-25-2006).]
Just out of curiosity what other cable is sold today or in the past has a metal sheath?And the Armour must be grounded regardless 12-608. This type of installation falls to the inspector to decide on the rational.I have to say Ive seen gfci recepts replace two prong plugs without a ground wire and pass.Rational was that the gfci samples leakage the neutral not the ground wire.The only metal sheath cable i see in res is the old smooth bx.I blew the disk out of L3 three weeks ago and have been on a steady diet of cyclobenzeprine and oxycodone but i can't be that stoned,or can i?Anyhow i think the rational is that the bx must be grounded at the same potential as the rest of the system.So with a plasic box you need to slap a grounding ring on the bx connector.Hope i'm making some sort of sense here. cheers
[This message has been edited by frank (edited 03-02-2006).]
My impression was flex, or what is being referred to as armour, is not a suitable bonding method. Since the quoted rule 8(a) talks about a metal sheath, and not armour I dont think this applies. The metal sheath could be pyro, or the old alu-sheath cable that had the aluminum sheath. Has anyone out there been able to use flex as the bonding conductor? In any case, in old houses you never know how secure the lockrings are upstream of where you are working, better to assume it is not properly bonded and install the GFCI as per code.
I mean to say that the armour must be grounded if it is there.I really don't think a ground wire is required if a gfci is used.Do they use pyro/MI cable in res?The old bx had a strip that was originally intended for grounding(no longer accepted ).I'm almost positive if a gfci is used no ground wire is required as it samples for leakage to the neutral.Sheath is a general term and doesn't describe a specific type/design of material.Had an inspector tell me to fill in the ground prong hole on existing fixture mounted receptacles once to avoid a false sense of security.It,s probable a little different from province to province so...