Combining Knob and Tube circuits


Old 06-30-15, 09:18 PM
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Combining Knob and Tube circuits

Luckily I've been able to eliminate most of the knob and tube in my home. What's left are several lighting fixtures and two outlets.

The remaining runs are all powered by three 20a breakers in the main panel. One of the breakers powers about 90% of the lighting, another powers two fixtures and an outlet, the last powers a single fixture and an outlet.

I can safely remove the last fixture/outlet run & breaker since they are not used. So that leaves the 'main' run and a second with two fixtures and an outlet I plan to remove.

Would it be safe to combine the two runs with a pigtail under one breaker (inside a box)? I plan to swap out the current 20a breaker with an AFCI breaker.

Lastly, is 20a overkill, or is there something with K&T that requires 20a?

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Old 06-30-15, 09:23 PM
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Would it be safe to combine the two runs with a pigtail under one breaker
Safe..... yes.

That means that your single breaker is the max that both circuits combined have available. A temporary hook up like that should not present any problem.

is 20a overkill, or is there something with K&T that requires 20a
The actual wire size is what determines breaker size. If the circuit is not heavily used then by all means switch to a 15A breaker. The 15A breaker will better protect the wiring and splices.
Old 07-01-15, 12:08 PM
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I was under the impression that all (most?) K&T wiring was 14ga wire, therefore should be protected as 15A circuits.

It could be that since there are often lots of splices throughout the house, it's sometimes hard to tell if 12ga wire was used for the whole circuit or not.

As Pete mentioned, 15A is probably the better answer since it doesn't sound like you have any high-draw fixtures remaining on this circuit.

On a side note, I'd seriously consider replacing the last of the K&T. It will likely be a load off (no pun intended) so you can officially say there is zero K&T in your house. This would help substantially when/if you sell and likely also with your insurance company. Just thought I would throw that in.
Old 07-01-15, 12:13 PM
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Would also suggest an AFCI breaker even if not required. It is intended to trip if there is any arcing do to insulation beginning to fail. Arcing could lead to a fire.

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