Knob & Tube

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MJGero

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Not to bring up a long debated topic, but we are having an office debate. 394.12 (5) states that K & T shall not be used in hollow spaces that are insulated.
The debate is not that K & T is permitted, and that insulating over is a good thing, but it is that the code specifically does not state that you cannot insulate over it. The code does not state where insulation is permitted, rather that K & T wiring is not permitted to be installed in an insulated space.
Does anyone agree with this "legal" interpertation of the code?
 
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lakee911

Senior Member
Location
Columbus, OH
It says that it shall not be used there.

Are you saying that you are not using it there because its pre-existing and that this code doesn't dictate where insulation can and can not go?

If you concealed a junctionbox in the wall, we all think that is a code violation and is the same concept.
 
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MJGero

Member
the question is that the NEC does not state that insulation cannot be put over K & T. it states that K & T cannot be in an insulated space. it is "inferred" that insulation cannot go over K & T.

the code states juction boxes shall be accessable.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
MJGero said:
the question is that the NEC does not state that insulation cannot be put over K & T. it states that K & T cannot be in an insulated space. it is "inferred" that insulation cannot go over K & T.

the code states juction boxes shall be accessable.
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Technically, if K & T is present in an area that is about to be insulated, it needs to be upgraded to a means that is suitable for use in the area in question.

In reality though, I have never seen that done. The people putting the insulation in don't know about the requirement and if they did they probably wouldn't care anyway. In fact, they probably don't even know what kind of wiring they are insulating over and don't even know the difference between K & T and NMS.

K & T was allowed to have splices without boxes many years ago and I still see it once in a while in old houses.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
MJGero said:
the question is that the NEC does not state that insulation cannot be put over K & T. it states that K & T cannot be in an insulated space. it is "inferred" that insulation cannot go over K & T.
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No inference needed. 394.10 addresses the installation. 394.12 addresses the use. 394.12 states that it is prohibited to use it in insulated spaces. There is no exception to whether or not it was installed prior to the insulation or not, the prohibition of it's use still stands.
 
480sparky

480sparky

Senior Member
Location
Iowegia
MJGero said:
the question is that the NEC does not state that insulation cannot be put over K & T. it states that K & T cannot be in an insulated space. it is "inferred" that insulation cannot go over K & T.

the code states juction boxes shall be accessable.
Click to expand...

No where in the NEC does it state I cannot direct-bury a 1900-box to splice UF in my yard, either.
 
bluesmoke...oops

bluesmoke...oops

Senior Member
Location
Tri-Cities, Washington
MJGero said:
the question is that the NEC does not state that insulation cannot be put over K & T. it states that K & T cannot be in an insulated space. it is "inferred" that insulation cannot go over K & T.
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It is not inferred. 394.12(5) flat out says that you can't put it in a hollow spaces where the insulating material envelops the conductors. How much clearer are you looking for?
 
acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
MJGero said:
Not to bring up a long debated topic, but we are having an office debate. 394.12 (5) states that K & T shall not be used in hollow spaces that are insulated.
The debate is not that K & T is permitted, and that insulating over is a good thing, but it is that the code specifically does not state that you cannot insulate over it. The code does not state where insulation is permitted, rather that K & T wiring is not permitted to be installed in an insulated space.
Does anyone agree with this "legal" interpertation of the code?
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Split hairs all you want, in the end K&T and insulation are not allowed in the same space. I say if you install insulation you must remove the K&T.
 
480sparky

480sparky

Senior Member
Location
Iowegia
acrwc10 said:
Split hairs all you want, in the end K&T and insulation are not allowed in the same space. I say if you install insulation you must remove the K&T.
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If you want to split hairs: Technically, you don't need to remove the K&T.... you just can't use it. :D
 
acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
I should add, when K&T was installed in a house originally,if the house was insulated, do you think they installed the insulation before the K&T??????????? why would it make a difference if it is insulated 4 days 40 years or later?
Most K&T is out lived its useful service life already, why would you argue to leave it and worse make its environment more severe?
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
acrwc10 said:
I should add, when K&T was installed in a house originally,if the house was insulated, do you think they installed the insulation before the K&T??????????? why would it make a difference if it is insulated 4 days 40 years or later?
Most K&T is out lived its useful service life already, why would you argue to leave it and worse make its environment more severe?
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I don't think that in wall insulation was even available when K & T was being installed. I may be wrong, but I have never seen a house with insulation installed in the 20's and 30's. The closest thing to it was a type of fiber that was put on the outside, nothing in the walls.

why would it make a difference if it is insulated 4 days 40 years or later?
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It doesn't. Either way it's not allowed.
 
acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
K8MHZ said:
I don't think that in wall insulation was even available when K & T was being installed. I may be wrong, but I have never seen a house with insulation installed in the 20's and 30's. The closest thing to it was a type of fiber that was put on the outside, nothing in the walls.



It doesn't. Either way it's not allowed.
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Exactly, if the old houses were never insulated, how could the code be addressing anything other then "old K&T" and "new insulation" :D
 
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