Dry rotted insulation.

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  #1  
Old 02-21-11, 05:14 PM
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Dry rotted insulation.

I started changing a light fixture in my kitchen and the fabric-like insulation on the wires is so brittle it seems a risk to leave it. Even the slightest move causes chunks to fall off leaving exposed wire.

I believe I need to go outside the box, cut the Romex (with dremel?), maybe I'll get some wire in better shape. I will then have to add new wire to replace the cut off portion.

The house is from the 1930's, has 2 prong outlets, and I'm not looking forward to seeing what condition the other wire is in.

Does "splicing" a couple feet of new wire at the light fixtures sound better than using the dry rotted stuff (dumb question)? Do I have to use a junction box? Cut Romex with a dremel? Or should I buy/rent a special cutting tool?
 
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Old 02-21-11, 05:50 PM
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Your plan would be good if the NM had a ground but code prevents changes in ungrounded circuits. If your inspector would consider this a change I can't say. The splices would need to be made in a Jbox.

Cut Romex with a dremel? Or should I buy/rent a special cutting tool?
You can use a cable cutter or bolt cuter. The pros here may groan but I normally use a bolt cutter but only on non-metalic cable.. This is coth covered cable isn't it? The age and mention of a Dremel to cut it almost make me wonder if it is metal covered.
 

Last edited by ray2047; 02-21-11 at 06:41 PM. Reason: to add iformation.
  #3  
Old 02-21-11, 06:00 PM
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Originally Posted by ray2047 View Post
Your plan would be good if the NM had a ground but code prevents changes in ungrounded circuits. If your inspector woyld consider this a change I can't say. The splices would need to be made in a Jbox.

You can use a cable cutter or bolt cuter. The pros here may groan but I normally use a bolt cutter. This is coth covered cable isn't it? The age and mention of a Dremel to cut it almost make me wonder if it is metal covered.
Yes it is metal coated. I need to strip metal coat. Will bolt cutter cut only jacket and not cloth coated wires inside.

I will just call inspector.
 
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Old 02-21-11, 06:05 PM
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There is a tool called a Roto-split that will cut the netal sheath. You can also carefully use a fine tooth hacksaw blade to cut diagonally.
 
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Old 02-21-11, 07:08 PM
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The Insulation is probably just dried out from overlamping and the sheath is probably lead.
 
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Old 02-21-11, 11:17 PM
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Thank you very much for your replies. I dread this project a lot less now. I was hesitant about asking for advice but glad I did. Hopefully the wiring is not so dried out a couple feet from the light fixture box and all will go well. If not, I will be back with some new questions eventually. It's kind of urgent now that I have the wiring trimmed about ten inches and the circuit is off. At ten inches the "undersheathing" is still pretty brittle. Will go a couple of feet and it better get better or I'm not sure what I will do if it's still brittle. Maybe the attic runs are more abused from the high temps.

By the way, that metal sheathing is very hard to remove with pliers. Can't be much lead in it. Will have to buy either a hacksaw or a dremmel abrasive cut off wheel or borrow a saw from the neighbor. Seems the hacksaw will be the best for just 2 cuts.
 
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Old 02-22-11, 09:44 AM
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You can split the sheath with a hacksaw if you're careful. You make a small cut through it sort of at a diagonal and then unscrew the sheath off the cable.

I wouldn't use the Dremel. You don't want the hot sparks from the cutting wheel getting into the already fragile wire insulation.

However, remember you are dealing with wires potentially 80 years old. There is a good chance that any disturbance to the wire is going to crack the insulation off and make this cable unusable.

By the way the cable you have is not Romex. You have "armored cable" (AC). It went by the brand name "BX Cable" from the era yours was installed.
 
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Old 02-22-11, 10:20 AM
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After cutting partway you snap the cable but with rotted insulation you may damage the insulation. The roto-split recommended first by PCBoss is a safer way to do it.
 
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Old 02-22-11, 01:11 PM
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Unhappy

Originally Posted by ibpooks View Post
You can split the sheath with a hacksaw if you're careful. You make a small cut through it sort of at a diagonal and then unscrew the sheath off the cable.

I wouldn't use the Dremel. You don't want the hot sparks from the cutting wheel getting into the already fragile wire insulation.

However, remember you are dealing with wires potentially 80 years old. There is a good chance that any disturbance to the wire is going to crack the insulation off and make this cable unusable.
Yes, my feelings exactly, thank you. Hopefully the stuff is better upstream of the "overlamped" area. But I will still execute careful operation lol. I plan to wrap some elec tape around wires at exit of the "armor cable" to protect against sharp edges...there WAS a petrified piece of rubber cone assuming these arent too easy to find.
BTW, armor is commonly used on commercial, right?

Is the insulation really cloth? What happens if the roof leaks a couple drips into the armor and saturates the cloth, provided the water can actually seep through the armor...things that make me go hmmm.
 

Last edited by ibpooks; 02-22-11 at 03:20 PM. Reason: fixed formatting
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Old 02-22-11, 01:46 PM
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I HAD the stuff in my garage. If you even moved the stuff the insulation cracked off. There was a layer of rubber before the cotton braid. It was made by halex. The Stuff used In commercial has Polyvinylchloride Insulation. :hooray:
 
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Old 02-22-11, 03:19 PM
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Originally Posted by Mr Obvious View Post
I plan to wrap some elec tape around wires at exit of the "armor cable" to protect against sharp edges
You can get a little plastic insert called an "antishort bushing" in the electrical aisle that you stuff into the cut end of the cable to protect the wires.

BTW, armor is commonly used on commercial, right?
Yes, but it was common in residential long ago. Some cities like Chicago and NYC still require it.

Is the insulation really cloth? What happens if the roof leaks a couple drips into the armor and saturates the cloth, provided the water can actually seep through the armor...things that make me go hmmm.
The insulation is natural rubber and cloth; water can damage it, especially as the rubber breaks down. Modern wire is made with synthetics.
 
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Old 02-22-11, 04:12 PM
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Just a note all splices must be made in a metal box. You must use armored cable clamps for the BX. If you use NM-b for your whip the ground wire must be fastened to the metal box.
 
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