knob and tube wiring
- Thread starter domnic
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mopowr steve
Senior Member
- Location
- NW Ohio
- Occupation
- Electrical contractor
Depends, do you have a 1920's code book?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Do you mean fused at the correct size? If evidence of over fusing you'll need to install Type S fuses.
There may be local codes, Washington has restrictions on insulation.
I would find it remarkable if a 1920 house with K&T has not had the wiring changed...
There may be local codes, Washington has restrictions on insulation.
I would find it remarkable if a 1920 house with K&T has not had the wiring changed...
- Occupation
- Licensed Electrician
The short answer is, yes. The more correct answer is dependent on the details of the installation.
peter d
Senior Member
- Location
- New England
Legal? It probably is. Adequate? Not a chance in hades.
MNSparky
Senior Member
- Location
- Minneapolis, MN
- Occupation
- Electrical Contractor - 2023 NEC
I agree with 480sparky. I've worked on a lot of K&T and I get asked the OPs question frequently by realtors, home inspectors, home owners, etc. The way I explain it is the K&T system was probably code compliant when it was installed. The problem (meaning it being unsafe) isn't with the K&T itself or the original installation, its with what has been done to it over the years. Being buried in insulation, improper connections (flying splices and taps, concealed splices and taps), and overloading circuits.
So, I usually answer the question with a "it's probably not code compliant" after explaining the above to them. Then the next question is always "how much to rewire the house?"... That usually starts another long discussion...
IF you have vintage untouched K&T (you see only taped soldered joints, stuff like loom, cloth/rubber conductors and no nm extensions, no open wirenut splices etc.) , I would say that it is legal b/c it met the code at the time of installation-really no different code wise than other old wiring methods- there is nothing in the NEC that says older wiring that met code when installed must be removed when encountered.
Even if covered by insulation, not necessarily illegal- K&T rule about that came about in the 1987 NEC, so if insulated before that (if you could verify it somehow) its technically legal, if done since that time- code violation.
Bear in mind that even today K&T can be installed when allowed by special permission/extended per the code: See 394.10 in the 2014.
Dr Duke
Member
- Location
- North Dakota USA
Not that I would, cause I like to sleep at night, but I wonder where you could even buy knob and tube to install or extend under these special provisions? Wonder who manufactures it?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
You would probably have to get it salvaged from demos and rewires.
ptonsparky
Tom
- Occupation
- EC - retired
The shop I started with had boxes of knobs and tubes. Brand new. They are still in business and may still have them.
- Location
- Massachusetts
Properly installed it is one of the safest wiring methods out there. The fact the conductors are not near each other to short out and it's run on ceramic knobs and tubes keeps it from touching combustable materials.
The problems arise when DIYs splice other methods into it.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It is also a large potential [sic] problem for people or equipment that is electrosensitive.
And properly wired, at the time, K & T may have what are now prohibited shared neutrals.
- Location
- Massachusetts
Put me down as a non-believer in 'electrosensitivity'.
I will agree K&T wiring practices can result in higher gauss readings.
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