knob and tube - 2 circuits?

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Old 08-15-15, 06:01 AM
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knob and tube - 2 circuits?

Hi all, thanks in advance for your help.

I have a 3-plex with some limited knob and tube (mostly lights). Recently I found that I have one circuit feeding two suites, which need to be separated as each suite has a panel.

When diagnosing the problem, I ran into a junction box where the hot is split (one going to each suite) but only one neutral. Any idea how to split this up? How is the neutral going through both circuits, while the hot leads are split? here is a picture with one of the hots disconnected.

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Old 08-15-15, 06:18 AM
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Which hot did you disconnect? The hot from the panel or the hot going to one of the suites?

I say you cannot split this into two completely separate circuits.

Knob and tube wiring may have two circuits with a shared neutral (same panel). in this case the two hots must be connected to opposite legs of a 120/240 volt circuit or connected to the same 15 amp single breaker.

For example the neutral may run in the wall between the two suites while one hot runs along the far wall of one suite and the other hot runs along the far wall of the other suite.

It is permissible to decommission an upstream portion of K&T wiring and run new wiring to re-energized the undisturbed downstream portion of K&T except that new wiring from two different circuits or panels may not re-energize subsections of a downstream portion that share a neutral.

You should string new wiring for both sides, decommissioning all of this K&T wiring.

Some insurance companies will not cover you if any portion of K&T remains energized.
 

Last edited by AllanJ; 08-15-15 at 07:01 AM.
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Old 08-15-15, 07:19 AM
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The junction was just a place where the circuit went in two directions. You only had a single circuit. Bring two xx-2 cables to the junction box. Splice one cable to each of the old cables.
 
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Old 08-15-15, 08:07 AM
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But there is only one neutral. If I bring 2 cables, what do I do with the extra neutral?
 
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Old 08-15-15, 08:10 AM
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One goes to the left cable, one to the right cable. The original feed is abandoned.
 
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Old 08-15-15, 09:10 AM
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there are three cables. Two hots (one to each suite) and one neutral (feeding BOTH suites). Are you suggesting that I pigtail the neutrals and feed one hot with one circuit and the other with the second circuit?
 
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Old 08-15-15, 09:14 AM
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Which hot did you disconnect? The hot from the panel or the hot going to one of the suites?

I say you cannot split this into two completely separate circuits.

Knob and tube wiring may have two circuits with a shared neutral (same panel). in this case the two hots must be connected to opposite legs of a 120/240 volt circuit or connected to the same 15 amp single breaker.

For example the neutral may run in the wall between the two suites while one hot runs along the far wall of one suite and the other hot runs along the far wall of the other suite.

It is permissible to decommission an upstream portion of K&T wiring and run new wiring to re-energized the undisturbed downstream portion of K&T except that new wiring from two different circuits or panels may not re-energize subsections of a downstream portion that share a neutral.

You should string new wiring for both sides, decommissioning all of this K&T wiring.

Some insurance companies will not cover you if any portion of K&T remains energized.
In the picture, the disconnected wire is feeding one of the suites. I was troubleshooting at this point.

The hots as you accurately state is connected to the same 15 amp breaker.

The suites are up and down, so rewiring the upper suite would be relatively easy (through the attic). The second suite, which is sandwiched between the third floor suite and the main floor suite, is a bit more problematic.

I was hoping for an easier solution as I am likely a couple years away from being able to address all the K and T in the building
 
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Old 08-15-15, 09:47 AM
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The two cables will allow you to split the feeds off to the correct unit. You are splitting at the junction box.
 
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Old 08-15-15, 09:53 AM
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The two cables will allow you to split the feeds off to the correct unit. You are splitting at the junction box.
But I am not splitting the neutral. How would i go about splitting the neutral?
 
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Old 08-15-15, 10:13 AM
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From the junction box going downstream (load side), 3 knob and tube individual conductors (hot, hot, neutral) disappear into the woodwork separately.

You can't run two separate feed cables to the original junction box as an upgrade of the "first half" (upstream part) of the overall K&T conglomeration. But you can run one new feed cable to the original junction box, withdrawing the old K&T feed wires.

At the junction box, unhook the downstream hot K&T wire that serves the fixtures of the suite that is eaier to rewire. Withdraw it from the box. Use colored tape to identify all of the fixtures that went dead.

Now you can rewire all of the affected fixtures to all new attic cabling while leaving the original junction box (with or without a new feed cable) to serve the other (middle) suite.

Each fixture that went dead and got rewired to all new cabling would have its old hot K&T wire withdrawn (or snipped off completely) and its old K&T neutral snipped off to about two inches of the back of the box, kept inside, and covered with tape or wire nut. Since each fixture so treated is now disconnected from the old K&T neutral, the brand new cable with neutral (and bypassing the old junction box) can serve it correctly. The old neutral ends have to remain in the fixture boxes until those wire segments are known to have been severed from the old K&T neutral network.
 

Last edited by AllanJ; 08-15-15 at 11:06 AM.
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