knob and tube found in attic

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  #1  
Old 08-05-13, 12:50 AM
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knob and tube found in attic

Hello,

Bought a house recently (which is why I'm just now finding the knob and tube), crawled up into the attic to re-route an electrical line for a ceiling fan and found it is all knob and tube. not to thrilled right now. i haven't tracked it back to see where it ties into the breaker box as there's a lot of insulation to move. i noticed all the knob and tube wiring is insulated in this older material, none of which I see in the breaker box. that said, i suspect someone at some point brought up a new line from the breaker box and then re-supplied the knob and tube (I'm hoping this was done in a junction box). there is no other knob in tube in the house, unless of course the switches in the rooms that service the lights in the ceilings are knob and tube (not sure how that works, can anyone explain?). second question, what do I do about this - should I have it all replaced? I had plans to remove, add, and reposition a lot of lights in the house. Below is a picture of the line that branches off of the two knob and tube lines and up to an existing ceiling fan.



Thanks for the help!
 
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  #2  
Old 08-05-13, 08:16 AM
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Knob and tube wiring is okay undisturbed usually. It can not be extended. Your big problem is it can not be burried in insulation as it is in your attic.
 
  #3  
Old 08-05-13, 09:49 AM
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Knob and Tube refers to an older ungrounded wiring method. The knobs were nailed to the sides of framing and the conductors were secured to them. Tubes were used where the wiring ran through the framing.

You best course of action is to run new grounded wiring. Abandon the old knob and tube after the new wiring is installed. As Ray already said, the NEC does not permit K&T to be used in insulation. Also extending ungrounded circuits is prohibited.

After the K&T is decommisioned or removed you can insulate and save yourself money on heating and cooling costs.
 
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Old 08-05-13, 10:42 AM
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Welcome to the forums!

Bought a house recently (which is why I'm just now finding the knob and tube), crawled up into the attic to re-route an electrical line for a ceiling fan and found it is all knob and tube. not to thrilled right now. what do I do about this - should I have it all replaced?
It sounds like you're worried about what you don't know. As Ray said, K&T wiring can be left in place and in service if it's in its original condition. I deliberately left some sections when I renovated a slightly younger (1908) house for our family. Some of that was because I didn't want to open perfectly good plaster walls and ceilings to replace it in some places and part of it was to tease my inspector.

That said, leaving it involves a bit of work to make sure it is, and will remain, safe.

i haven't tracked it back to see where it ties into the breaker box as there's a lot of insulation to move.
As Ray also said, K&T wiring cannot be buried in insulation. It relies on dry air as part of its insulation. If you have to move insulation to trace the wiring, you need to replace it. There are also restrictions on how many modern cables can be bundled into one run through, or across, wall insulation, but we can advise you about that.

should I have it all replaced?
If you the money to pay for the electrical work and the wall and ceiling repair right now, you can do that. Or you can spend one Saturday assessing and recording what you have now and deciding what you want to wind up with, what you need to replace, and the best way to get from here to there. The actual wiring is something you may be able to do yourself. We can advise you.

Right now I only see a few concerns. One is the implication that some of this wiring is hidden under attic insulation. The insulation needs to be moved off the wiring and left off the wiring. Another is that you haven't yet seen the splices where the K&T is presumably connected to newer wiring.

I also noticed, in your picture, that one leg of the original wiring has been pulled off the knobs and draped across the insulation. In fact, I don't see the knobs for it. Maybe they're on the side of the joist to the left, which would make sense. The two conductors should have been run on on the opposite sides of the framing bay, following best practice at the time. As it is now it appears that the loose conductor is lying on - touching - the conductor for a different potential. That creates a potential hazard, and is something you should correct pretty soon.

Tell us a bit about your house and your electrical system. Do you have more than one story, so that some wiring is between a finished floor and a finished ceiling? Was the original lighting in your house dual fuel (gas and electric)? Where is your main distribution panel, how big is your service, what company made your main panel, how many breaker spaces does it have and how full is it? Do you know whether a full bond to ground exists at your electrical service entrance?
 
  #5  
Old 08-05-13, 11:21 AM
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i noticed all the knob and tube wiring is insulated in this older material, none of which I see in the breaker box.
This interests me. My logic suggests that you either; 1) have knob and tube directly connected before the breaker box (not likely) or 2) have new wiring going to a junction box where it connects with knob and tube.

If it's just a few fixtures and receptacles to junction boxes, it might not be too hard or expensive to replace.

Do the fixtures/receptacles with the k&t work? I have a bit of knob and tube still in my place, but none of it goes anywhere; it was simply left hanging in the attic when the new wire was installed and one closet light that was never rewired, so it just has k&t that is cut off after two feet..
 
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Old 08-05-13, 01:37 PM
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there is no other knob in tube in the house, unless of course the switches in the rooms that service the lights in the ceilings are knob and tube (not sure how that works, can anyone explain?).
Can anyone explain what? Switching in the era of K&T wiring?

With a K&T system, the conductors for lighting were basically run straight to the ceiling outlet. Switching was basically done at the fixture with a built-in switch that might be a pull chain or a turn button built into the lampholder, or a pull chain mounted in the canopy. The canopy-mounted ones sometimes look like they were added on site, and I've wondered sometimes if they were done when the fixture was installed or were added later to replace one at the lampholder.

When a wall switch was wanted, one of the conductors would be routed to it before going to the ceiling outlet. Notice that I said "one of the conductors." Since opening either the hot or the neutral conductor will turn the light off, it is not uncommon to find that it's the neutral that was taken through the switch, and that there's one wire at the ceiling outlet that is always hot unless the fuse is removed or the breaker is switched off. Just something to keep in mind when you're working on one of these old systems. This is one instance when a non-contact voltage detector can be a useful tool to have in your pocket.

It was also typical to mount devices without electrical boxes at the time. You may need to add a box for a switch or receptacle or lighting fixture here and there as you go.
 
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Old 08-05-13, 02:48 PM
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I grew up in a house that was built in 1905 and was extensively remodeled in the early 1930s. I have no idea when the electrical was installed, it may have been original or it may have been during the remodel. It had knob and tube wiring throughout and it DID have switches (switch loops) and steel boxes. Some of the light fixtures did have pull chains but this was in addition to the wall switches and I suspect just the way the fixtures were made back then.

My parents bought this house in 1948. After going through one winter and having an oil bill for (as I recall my daddy saying) of about $250 my daddy had the entire house insulated and all the doors and windows fitted with interlocking metal weatherstripping. After that the oil bills dropped to about $50 a year up to the oil embargo of 1973. The insulation was a blown-in mineral fiber (made from steel mill slag) and filled all the exterior walls as well as the attic spaces to the level of the ceiling joists. Yes, the wiring was buried in the insulation. All of the k&t wiring was 14 gauge tinned copper with rubber and cotton insulation. There was also an overhead pair going to the garage that was an extension of the kitchen receptacle circuits.

Because he had power tools and my mother had an electric waffle maker and electric frying pan my daddy put 30 ampere fuses in the kitchen circuit to avoid blowing the fuses when he would start up his table saw. Yup, 30 ampere fuses on #14 wire! Eventually, as I entered my teen years I started to re-wire the house. I was a Justin. As time went by I rewired most of the original receptacles and added a few more. I used type NM 12-2 w/g for most of the work. We added a 200 ampere split-bus Murray circuit breaker panel but never upgraded the meter or service conductors from the original 60 ampere service. We did replace the wires to the garage with a 240/120 branch circuit using #8 copper type RH (rated at 70 amperes as single conductor in free air) running these conductors through the attic, down the wall and into the circuit breaker panel. Totally NON-CODE even back in those days but I was young and stupid at that time.

I continued to work on the rewiring well into the 1980s but there were some circuits that it would have been almost impossible to rewire such as the front hall light and the front porch light. Since the loads on these last remaining circuits was so low I figured the hazard was minimal. This also applied to the overhead lights in the bedrooms. During all this work the ONLY time I saw deteriorating insulation was where the original wiring went to an overhead fixture that had been severely overlamped. All of the wiring that had been buried in insulation for some thirty years was in as good of condition as the day it was installed.

None of this is meant to belittle the code admonishments towards knob and tube wiring but in my experience it just isn't the horrible hazard that it is often played up to be.
 
  #8  
Old 08-05-13, 04:30 PM
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Similar experiences, Furd. Espesially
During all this work the ONLY time I saw deteriorating insulation was where the original wiring went to an overhead fixture that had been severely overlamped. All of the wiring that had been buried in insulation for some thirty years was in as good of condition as the day it was installed.
I don't think I was as clear as I could have been earlier. The admonishment against (prohibition against) covering K&T wiring with insulation, everybody, especially on the floor of the attic, is in the requirement for dry air, but it's the dry part that's considered critical. The folks who update the NEC were concerned that the current could arc through the dampness if and when the insulation got wet. Probably from observation.

So long as the insulation your daddy had blown in stayed dry, Furd, there should have been no problem.

The other one was... yes, the bit about the damage from overlamping. My old house didn't have that problem because it had never had a flush fixture installed, only pendants. I've seen it more than once in rehab work, though.
 
  #9  
Old 08-12-13, 10:55 PM
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Hello everyone,

sorry for the delayed reply, notifications were going into my junk box and we've been in the process of moving into the new house.

we ended up going with an electrical bid of $1300.00, which I think is pretty cheap considering what they did. i did this because circuit "a" mentioned below first went to the basement then to the attic, it was simply too much for me to do in the midst of a move. They found two 15amp circuits that fed the attic k&t via a junction box. They re-wired:

circuit a 15amp, 7 fixtures, 148 watts
circuit b 15amp, 7 fixtures, 652 watts
  1. bedroom 1 with switch (circuit a) 3x 4w LED
  2. bedroom 2 with switch (circuit a) 1x 8w LED
  3. bathroom with switch (circuit a) 1x 4w LED sconce
  4. bathroom with switch (circuit a) 1x 8w LED, 1x 80w Fan
  5. added bedroom 1 closet w /switch (circuit a) 1x 4w LED
  6. rewired light 1 to basement (circuit a) 1x 16w CFL
  7. rewired light 2 to basement (circuit a) 1x 16w CFL
  1. kitchen with switch (circuit b) 8x 35w halogen track lighting
  2. entry with switch (circuit b) 1x 40w carbon
  3. porch with switch (circuit b) 1x 40w tungsten
  4. pantry with switch (circuit b) 2x 4w LED
  5. dining with switch (circuit b) 2x 8w LED
  6. living with switch (circuit b) 3x 60w tungsten, 1x 80w fan
  7. added hallway w/ switch (circuit b) 2x 4w LED
diy, i staged ceiling and switch boxes for anything added (not a lot, sorry...).
 
  #10  
Old 08-13-13, 04:50 AM
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Glad to hear you have it all fixed up.
One thing to keep in mind when sizing a circuit is that it must be done to the max rating of the fixture and not what you are actually running (assuming you are running under via LED or CFL).

I thing I should mention for yourself and anyone else that reads this, insurance companies in some (or all) areas don't like K & T, and will really make you pay for it. A co-worker of mine that bought an old (1905) house found K&T in it. Her insurance per year was more then half the cost of having an electrician come in and replace.
 
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