Proper Fuse for Knob and Tube


Old 03-22-07, 12:06 AM
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Proper Fuse for Knob and Tube

I have Knob and Tube wirng. All looks to be in real good shape. No funky additions or branches.

I keep reading that I MUST use 15amp fuses regardless of the wire size.

I have 12ga wire so what is the correct amp fuse I should be using.

Thank you
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Old 03-22-07, 07:49 AM
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If you can confirm that the ENTIRE CIRCUIT is wired with 12 gauge COPPER wire, then you can use 20A fuses. Best to use type S (tamperproof), which require an adapter (readily available at home centers) that screws into the existing edison-base (light bulb type) fuse socket, if that is what you have.

Where did you read that you have to use 15A fuses regardless of wire size?
Old 03-22-07, 09:58 AM
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I have never heard of or seen knob and tube done with #12, only #14. Are you certain that it's all #12? If so, you may use a 20A fuse; if you have #14 anywhere on the circuit, you have to use a 15A fuse.
Old 03-22-07, 10:57 PM
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Its ALL 12ga. looked in every outlet and switch. It was not any spliced stuff going into the boxes. I can see the old K & T sheathing/insulation so I know it came from above. I even had a couple walls removed for other purposes and saw the K & T coming down in a couple of the rooms. ( Hey, you never seen K & T in 12ga, well in my other posts, others have never seen 48" on center joists either. I guess this house is weird)

Anyways, what I was saying is I even took my calipers and measured the thickness of each bare wire and they were all 12ga. Now this does not mean that at the fuse box there is something different, but as I said before, no tampering has been done to my knowledge. I have been in the attic where all the wiring comes down to the house.

Before this post I was just bouncing around the net and in many places they said 15ga. I most of the places they did not specify, maybe assuming all K & T was 14ga. But in 3 places they said 15amp regardless of wire size. Hence my post.

Thanks for the responses.

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