Knob & Tube question

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goldstar

goldstar

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Location
New Jersey
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Electrical Contractor
In a case where K & T is present and cannot be removed or cannot be removed without causing major damage to the interior of a residence, is it acceptable to convert those circuits to GFI protected circuits ? I'm having a senior moment but somewhere in my memory bank I remember hearing this while taking a CEU course but I can't find anything in NEC Article 394. Is it possible that it might have been in the NJ Rehab Code ? If anyone knows the answer would you please cite a reference ?

Thanks,

Phil
 
Phil, any 2 wire circuit for receptacles are allowed to have GFCI installed and then use grounded recep.. downstream of the gfci. You cannot, however add to a circuit that does not have a ground. Look at 405.3(D) and then take a gander at 250.130(C)
 
Good answer Dennis.
I think this became code in 99.
3 prong outlets we're allowed to have gfci protection instead of the equipment grounding conductor.
But if you changed a light you would have to pull an equipment grounding conductor to it.
Now thier both the same.
Phil I think your right it does not specifically adress K&t. But the above mentioned method is accepted here.
 
Dennis and Buck, thanks for your replies. What I'm looking to do is isolate (2) K & T circuits that were never removed in an older home. The new homeowners are concerned about the K & T and want it removed but I can only do it to a certain point (without causing major damage) and will then have to terminate them in a plastic JB. The service is a fairly new 200 amp SQ D QO. I thought the right thing to do is convert these two circuits to ground fault and change the two-prong receptacles wherever I could.

Thanks for the code references but I couldn't find a 405.3 section

Regards,

Phil
 
Thier is no way to know if the gfci will trip on that old of a circuit.

If they have insulated around the K&T it's not allowed. As you know if you read 394.
 
Buck Parrish said:
Their is no way to know if the gfci will trip on that old of a circuit.
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As a rule, one can only know that a GFCI operated the last time it was tested, one can never know, definitively, that it will ever operate within design parameters ever again. But, otherwise, one can bring a "known ground" conductor to any point along the old circuit and test the GFCI.
Buck Parrish said:
If they have insulated around the K&T it's not allowed. As you know if you read 394.
Click to expand...
I'm guessing that any insulation there is older than the 1987 change in 394 that first prohibited contact with thermal insulation. The requirement is not retroactive, it just applies to insulation that has been applied after 1987.
 
al hildenbrand said:
As a rule, one can only know that a GFCI operated the last time it was tested, one can never know, definitively, that it will ever operate within design parameters ever againhe knew what I meant.. But, otherwise, one can bring a "known ground" conductor to any point along the old circuit and test the GFCI.I'm guessing that any insulation there is older than the 1987 change in 394 that first prohibited contact with thermal insulation. The requirement is not retroactive, it just applies to insulation that has been applied after 1987.
Click to expand...




As I read it. It sounds like any insulation makes it non compliant.I
 
Buck Parrish said:
As I read it. It sounds like any insulation makes it non compliant.I
Click to expand...
The Code is a new construction standard.

K&T can't be placed (present tense) in contact with insulation.

Up here in Minnesota there's legally installed K&T that was legally insulated for around half a century, up until the summer of 1987 when the '87 NEC was adopted. The NEC was silent on the matter of insulation until the 1987 change in Article 394 (then it was a paragraph and was 324-4). Those installations are not touched by 1987 change.

Now, there are some insulation programs happening presently, that remove old vermiculite and rock wool first, and then replace it with modern material. I can see that re-insulating, with any insulation, as you say, K&T is prohibited by the 2008 NEC 394.12(5). That's new construction.
 
Yes, being your from Minesota, I will concure ;) I know it gets cold up thier.

A lot of the houses I see here in the South have never had any insulation at all. That's what I was thinking...
Some I have been in where the k&T has not been disturbed. It still looks like a good system to me.
As long as they are not useing space heaters , wall ac's , insulation and such.
 
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