bx and romex

I am in the process of rewiring my kitchen. I have come across one box where I will have three switches. Two of them are wired with bx (old) which are three way switches. One of them is with romex(new) on a dimmer. The problem is -- that I dont want to tear into that wall, and I cant find a metal old-work box. How does one go about connecting all of the various grounding sources, romex is straight forward. But do I have to connect the bx to the box, to the other ground wires, or the switches, or all of them? Would it be ok to use a plastic box, and connect the ground wires to the bx with a clamp?? or is it not necessary?
Thanks

 

The metal casing of the cable can be considered a ground. When it is connected properly with an approved connector to a metal box then a path is set. The Romex is then tied together and to the box so the system has a good ground. So a plastic box is out if you wish to keep those cables. What do you mean a metal-old work box? If you require a box that will take a L16 connector you should be able to purchase one at any electrical supplier.

 

I mean a metal box with clips that, when screwed in, the clips fold out and the box is tightened down to the inside of the drywall. There is no way to connect the romex to the bx cable?

 

Newgy:

There are a few types of metal old-work boxes. HD carries them. My local hardware does too.

One type has a U-shaped bracket going around the sides and back of the box. It has a screw in the middle of the box, attached to the bracket. You put it in the hole, the bracket springs open to touch the backside of the sheetrock, you tighten the screw and it clamps on.

The other type has two screws, one on each side of the box. They are pretty long and go thru a strap flush with the side of the box. You push the box in and tighten the screws, alternating from side to side. The straps bend as you tighten and they clamp to the backside of the sheetrock.

I know at HD they aren't displayed very prominently, the plastic ones being more popular, but they should have them. Failing that, try an electrical supply, as gard suggested.

 

A comment was made that the armor making up the BX can be considered as the ground. That is only correct if the BX is the newer style with a metal strip run within the cable. In AC cable (BX), it is a combination of the metal strip and armor that makes it acceptable for use as a ground.

 

This does have the metal strip. but it doesnt seem to have enough substance to connect it to the copper ground of the romex?!?

 

You state--"I can't find a metal "old-work" box."----There are 2 types of metal "gem"-boxes, "new-work" and "old-work". Individual gem-boxes can be assembeled into any number of "gangs", one "gang" for each device.-----I am in complete dis-agreement with the concept that "old" armored cable without a bonding-strip cannot be used as an Equiptment Grounding Conductor, which is applying the NEC "retro-actively" This is often cited on the issue of replacing non-grounding (2-prong) receptacles with ground-type (3-prong) receptacles. Using "old" armored-cable as the Equiptment Grounding Conductor when replacing non-grounding receptacles is practicaly SOP for contractors doing residential work. Art. 404.12 of the NEC reads----"Metal enclosures for switches shall be Grounded----."-----If we were to apply the NEC uniformly, then it would be a Code violation to replace old switches mounted on metal boxes clamped to "old" armored cable if one believes the "old" AC does not effectively Ground the metal box.

 

"Standard SOP does not a code make". If you perform work on a circuit, that aspect of it must be brought to the current code. I believe that the replacement of a light switch (with a similar fuction) would be considered maintenance, and not a new installation.
For example, the replacement of a two prong recept. has many options. If the replacement is with another two prong, then no other changes are required, it is somewhat grandfathered. But if you change to a three prong, you have other responsibilities to perform to bring it to the current code.
The design of AC cable was forced to change due to the high impedance of the armor without the metal bonding strip.

 

disregard and stop arguing. I have ripped up the wall and installed all new romex. up to the point that it enters the ceiling fan. from that point, there is two more bx cables coming out of that. with the ceiling fan being a "wiggly" fixture, I am now wondering about the safety of leaving that bx up there!!!the wires look fine, not brittle or anything. What do you think. I know that it may never stop, as far as wanting to replace wire, but now I would have to rip up the entire dining room!!

 

If you belive it's correct to apply the "Construction Speciifications" of the present Code "retro-actively", then to be consistent you must apply Art.320.104,Conductors, which requires conductors "of a type listed in Table 310.1", " which have a "moisture-resistant covering". Obviously,the conductors in "old" AC do not comply with the present Code requirements for conductors used in AC.I do not belive that it's the intent of the Code that the bonding-strip requirement means that "older" AC without the stip does not comply with Art. 320.108 which requires the AC to "provide an adequate path for (Grounding)".

 

that almost answers my question!?!?

 

Definity leave the BX. It sounds to be in good condition.
The discussion regarding the use of BX as a grounding means is a valid one, and has been discussed for many years in different jursidictions.
If you change the function of a circuit, or the application, then the current code must apply. If you are performing maintenance, then generally the circuit is grandfathered into the code cycle it was installed. Again consider the regulations regarding the replacmeent of a two prong recept.

Different jursidictions handle renovations/new work/maintenance in different ways as to application of the current code. Check your local code official to see how they apply the codes to your type of work.

 

For those interested in the old bx - new bx discussion, go to the search tab, then type the words grounding armor cable
then look for the thread dated 8/7/01.

 

If it has the bonding strip it is NOT BX, but A/C. You do not connect the bonding strip to anything. Cut it off even with the end of the armor. Intall the anti-short bushing. Use an A/C cable clamp (internal or external) and tighten the locknut (external) or screw (internal) and the set screw to hold the armor. You are done. Connect a pigtail with a green screw in the 10-32 hole in the back of the box. Connect all the NM ('romex') grounds to the pigtail with a wirenut. In newer boxes the 10-32 hole is already threaded. I have found many old installations with A/C (the bond wire is there) that do not have a threaded hole for a ground. Most have a hole the right size, just not threaded. I just taop them and go on. AHJ thinks all is fine.