Help with insulation for knob and tubing

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  #1  
Old 11-10-04, 09:47 PM
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Help with insulation for knob and tubing

Hi friends

I would apreciate some help finding some kind of thermal and electrical insulation to protect Knob and tubing wiring running very close to heating ducts. The original instalation had asbestos insulation[ about 1/8' thick] wedged between the wiring and round heating ducts [about 6 feet length running through three joist in the basement] that i just had removed by a lisenced abatement contractor] I need to find some kind of tube of insulating material to slide over the wires for there is no space between wires and metal ducts actually they touch in several places .It is geting cold and i cant turn the furnace on untill this problem is solved.the other option i see is to cut those wires and splicethem with NM running a good distance from the heating ducts but i think the splicing job would be too time consuming
HELP MUCH APPRECIATED THANK YOU
 
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  #2  
Old 11-11-04, 04:53 AM
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I would replace the knob and tube for this short run. If you don;t feel comfortable doing this, then hire a licensed electrician to do it.
 

Last edited by racraft; 11-11-04 at 07:04 AM.
  #3  
Old 11-11-04, 06:35 AM
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Tough problem. You know that knob and tube has to go eventually, but I'm guessing you don't want to freeze in the meantime. The only thing I can think of that might be safe is fiberglass pipe insulation. It comes in a roll, about 2 inches wide, and you can attach the faced side of it to the duct along where the wire runs. It's available at most big box (orange, blue...)home improvement stores. I wouldn't wrap it around the wire. Knob and tube was meant to be left open.

Doug M.
 
  #4  
Old 11-11-04, 08:43 AM
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Thankyou,if replasing the short run of K-T is the only way what is the proper way to splise it with NM?
METAL BOX[GROUNDED?]
ONE WIRE PER OPENING?
CAN THE KNOB AND T AND NM ENTER THE BOX FROM OPPOSITE SIDES OR DOES IT MATTER HOW THEY ARE RUN TO THE BOX?[INDUCTION HEAT]
IS THERE SOME MODERN LOOM AVAILABLE?
AM I FORGETING ANYTHING?
THANKS A MILLION
 
  #5  
Old 11-11-04, 11:30 AM
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Find an old piece of cement type siding and stick it in there. Well maybe a new piece. The old piece might contain asbestos.

Or maybe some fiberglass cloth like used for boat or car repairs. The boat stuff is available quite thick.

Another brainstorm just hit me. Muffler tape.
 
  #6  
Old 11-11-04, 12:39 PM
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papi,

I think that you will be wasting a good bunch of your time trying to reuse any part of this knob and tube circuit. But you seem to have a good grasp of the issues (insulating the individual wires, induction, etc). Please understand that what I am about to say is _not_ well supported; you really should do some more research. If this were my project, I would simply replace the entire circuit from the panelboard.

Because of induction issues, you are pretty well forced to use non-metallic boxes. One wire should enter per hole. I do not know what the clamping requirements are for single conductors entering a box.

Modern 'loom' insulation is available. Check www.mcmaster.car and search for 'Coated Fiberglass Sleeving'. You will need to get sizes larger than suggested, because the sleeving is sized for bare wire. I would suggest pulling the sleeving on over the current insulation. I have used this sleeving to protect wire with crumbly insulation in old BX cables; beautiful stuff.

Once inside the box, splice normally.

Best of luck
Jon
 
  #7  
Old 11-13-04, 07:52 PM
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Thank you my friends for concerns and replys much appreciated.
I think im going to post another call for help about how to splice the K and T and NM from the panel board
Regards papi
 
  #8  
Old 11-25-04, 08:09 PM
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I cant say how to safely repair your house wiring.
Just things to Note.

You need to see how you can replace the wire.

you cant put fiberglass sleeving over wire that has bad insulation like K & T. if the wire gets wet the current will go thru the pores of most fiberglass very Dangerous! and if it has metal contact, can electrify the metal or anyone.

this is something I ran into when I was working on an oven.
you need to know what temperature your wire will be exposed to ?

Teflon wire maybe something to look into. Teflon is hi temperature (don't know if its legal for repairing K & T).
Teflon wire with some fiberglass sleeving placed over the wire.

Or try your local appliance parts store for help on some 12ga wire (or the size you need) that is used in ovens.
ask some one if its water proof.

one thing about wire, it will move when you put power thru it. so keep your wire clamped snug and away from anything that will rub or saw thru it over time.
one reason they stopped using aluminum wire inside the walls of houses, the movement created breaks.
 
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