New Wire In Old Cable? - Electrical - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical


Thread Tools Display Modes
Old 06-24-2008, 09:13 PM   #1
Join Date: Jul 2007
Posts: 308
Rewards Points: 250

New wire in old cable?

Has anyone had any luck with pulling new THNN wires through an old BX?
It would be a way to avoid having to open walls/ceilings to replace the cable itself.
The existing BX is #14. I would try to pull three (black, white, green) THNN wires for the lights in the ceilings where access from upstairs is not possible.

I would imagine that this could work if there are no sharp (RA) bends in the cable. I often see RA BX clamps at the boxes, so these would be very difficult unless I can get the old box out.
Then, if I can get the box out, I might as well pull a whole new cable, right?



fw2007 is offline   Reply With Quote
Old 06-24-2008, 09:34 PM   #2
Power Gen/RS Engineer
Join Date: Jun 2006
Location: Oak Park, Illinois
Posts: 785
Rewards Points: 566

Good luck. I've never before heard of anyone trying this so I wouldn't even know where to look in the NEC regarding its legality. You would have hells own time removing the old wires (esp. if they are cloth covered). It can be difficult to fish wires through a piece of 1/2" greenfield (which has a considerably larger ID) with a few bends in it. I think that you're better bet would be to try connecting new MC cable to the old BX (splicing the wires together) and using the BX to pull in the new armored cable. There is no way in "H" that this will work if there is even one strap on the old stuff though.

Best bet is to bite the bullet and pull in/fish new MC cable. If you have attic/basement access, this can be rather easy actually.

Take care,


Well, now, there's what's right and what's right and never the twain shall meet.
BigJimmy is offline   Reply With Quote
Old 06-24-2008, 09:49 PM   #3
You talking to me?
nap's Avatar
Join Date: Dec 2007
Location: sw mi
Posts: 7,551
Rewards Points: 6,290

it's not legal. BX is made as a cable and it is not legal to alter it. Altering it would make it not BX anymore.

On top of that, what you essentially are doing is using the metal sheath as flexible metallic conduit, which is not allowed in sizes under 1/2 except in a very few applications.
nap is offline   Reply With Quote
Old 06-25-2008, 07:18 AM   #4
Join Date: Jul 2007
Posts: 308
Rewards Points: 250

Thanks for your advice. I read about doing this somewhere, and was interested to find whether anyone had actually done it. I'm not really surprised that it's not legal.
I'll have to find where I read it, and send a comment to the author.

fw2007 is offline   Reply With Quote
Old 06-25-2008, 10:24 AM   #5
Join Date: Jun 2007
Posts: 3,772
Rewards Points: 204

Follow naps instructions and warnings. He is absolutely correct.
J. V. is online now   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Dryer Grounding??? Traci_howdyadothat Electrical 7 05-27-2008 01:14 PM
Installing Fluorescents in Garage rzrbkpk Electrical 26 04-08-2008 09:00 PM
Stranded wire on screw connections BigJimmy Electrical 7 01-19-2008 02:42 PM
Coaxial Cable Question bahaisamurai Home Theater 9 08-08-2007 02:54 PM
I really need help! POOK Electrical 34 04-20-2007 07:01 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1