Replacing armor with romex

Hi:
We have a 65-year-old home with the original BX, armor-cable wiring. The wiring is without a ground, and the wire insulation is cloth and very brittle. I'm thinking of replacing the old wiring with new. How likely is it that I'll be able pull Romex through the armor cable? From what I'm able to tell, often a ceiling box is used as a junction to outlets within a room. I was thinking I could disconnect the wires from one of the outlets, tape the Romex to the old wire and pull the wire at the ceiling box, along with the Romex.

Has anyone tried this? Do you think I'll get hung up mid-run?

Would I have better luck pulling three separate wire?

Thanks.

 

You will need to replace the ENTIRE cable.

Reusing the old armor is a bad idea all-around, and is impossible if you havn't tried yet. Just so you know, the newer 'smooth' insulation of wires will allow them to slide as a bundle inside MC cable, but only in short pieces (for the concept). The old cloth stuff has to much friction, leaves junk in the armor, and the grounding is another issue. You would need to pull a green conductor, and that add another wire. Most importantly, the cable was listed in ~1940 as it is. The new cables are the same deal, listed for use in specific manner(s). Also By code , Romex may not be installed inside armor af any type for the application you want to.

I wanted to provide you with some details, rather than give you a short flat answer stating that you idea is no good, etc.
If you had/have conduit, new wiring could be pulled through in some instances. (EMT, IMC, RMC, PVC, ENT, etc.)
Another issue that must be considered is the volume of the boxes and their cubic capacity. Each wire entering the box has a box fill value. A 12AWG wire is 2.25 cu.in. A 4" octagon has minimal room. The old boxes were filled until stuffed, and was dangerous. The current standard is a minimum of 6" of each conductor from its entry point.
Unfortunately, I have given you a picture of a larger project than you were intending, based upon the idea of pulling new conductors through the old armor.
Feel free to ask additional questions about what steps to take next, obviously the old wiring is in need of replacement if the insulation is crumbling.

gj

 

Hi:
Thanks for the reply.

I want to make sure I understand the response.

I'm clear on the workbox volume issue.

I'm still unclear on the new wire within the exiting conduit. I understand that pulling Romex through the conduit is against code. What about pulling 3 separate wires? To this do-it-yourselfer, it seems this method would just replace what's there. Would this meet code?

Thanks again for the help.

 

In general, it is not against code to pull Romex through conduit. I'm not quite sure to what GJ is referring, but he put several qualifiers on his statement.

 

BX/armour cable is a cable. It is not a conduit system. You need to forget about the idea of pulling NM cable though the old BX. Just fish the new NM cable to where it needs to be. The old BX will stapled down so just abandon it in place.