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Hello,

While conducting minor renovations to a vacant group home, knob and tube wiring was discovered in the ceiling. It is definitely a possibility that other circuits in the group home would also be knob and tube type.

As per CEC, would it be required to remove only the discovered part of the knob and tube and replace with standard wiring method or would the code mandate replacement of all of the knob and tube type wiring.

On a safety perspective, all of the knob and tube wiring (discovered and undiscovered) should be replaced. I suppose the AHJ would also have a similar requirement. But is there an acceptable and safe scenario, where only the discovered part of knob and tube wiring and circuit is replaced and the remaining part of knob and tube wiring is inspected for insulation deterioration and left in place to be replaced during a major renovation project. Is wiring permit usually approved on partial replacement of knob and tube wiring? Also is there a possibility of safety hazard when the two different type of wiring are present at the same time i.e. knob and tube and standard conduit?

Thank you.
 

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PPE Saves Fingers
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Off the top of my head, the CEC doesn't say much about knob and tube wiring, it's more of an insurance issue, as in most companies will only give you temporary insurance and a limited amount of time to remove and replace with a more modern method.

The issue with Knob and Tube is mainly that the insulation has deteriorated over the years since install, and oft time it means the home is old enough that at least one of the tenants/owners has done some interesting DIY to the electrical (and probably every other system)
 

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If you look at bulletins for ESA, it discusses knob and tube wiring. If its inspected, they will accept it providing its up to standards. HOWEVER, with that being said, as was mentioned, its the insurance companies that dictate whether they will insure someone with knob and tube wiring. Yes ,problem with knob and tube? 1 - The age, so the insulation might be questionable. ( 2 ) all terminations were not made within boxes. They could tap off at any spot and head into the sunset.These joints should have been soldered and taped.....but not always the case. I have seen a nice tape jpb, and wires wrapped around another underneath....and . ( 3 ) no ground in the system. So before doing a pile of work, I would have them check with insurance and see if they will even cover them once work is done. We did a rush job, insurance was to be cancelled at the end of the week,,,,homeowner did not want to tear apart walls....so had to isolate knob and tube on 2nd floor.....and install one run of emt to 2nd level,with 3 circuits, and tap off to each room. ( It was a really old house, so was the best option at that point. )
 

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Estwing magic
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I just finished a renovation rough-in where knob and tube was existing. There were some stray ends coming from other areas of the home that weren't being renovated. I waited for inspection and asked the inspector what to do. He said to put the hots into an accessible box and cap them off. I ran some into switch boxes and the rest into JB's accessible from the attic. The stray neutrals I just capped off and left them where they were.

Like others have said, insurance companies might get pi$$y but I have a green sticker from the inspector and, with this job, that's all that counts.
 

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unless there is a specific recall on a product the CEC does not mandate upgrades. It requires the K&T to be safe for the purpose it was installed and maintained to provide that reliable service. See 2-300. So if you find K&T in good repair it is still legal code wise. If however you found that sections had shed their insulation or sections were damaged then that must be repaired or removed. The other very common offence related to K&T is the replacement of 2 wire receptacles with 3 wire receptacles without GFCI protection.
Insurance companies do not like risk so many will not insure a house with K&T to reduce their risk. K&T required specific skills and knowledge that has not been passed on to my generation never mind the younger ones.
The biggest cause of the increased risk is related to alterations and expansions from the K&T without the requisite skills by homeowners and even electricians.
 

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Electrical Contractor
Trying to retire or at least slow down a bit, but life not cooperating
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You can only feed K&T, you can't take power from it ( no ground ).
A GFCI breaker or GFCI receptacle allows the use of grounded receptacles.
As long as the porcelains and insulation is soft and supple, K&T should last another 100 years:whistling2:

http://www.iafss.org/publications/fss/9/3/view
 
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