Knob and Tube problems

[linnenji]

I am remodeling a room into a home office and decided to take the opportunity with the walls ripped off to update the knob and tube fuse circuit that powered that room, the garage, and a bathroom. I have rewired all of these completely with new circuits into the circuit breaker box and have removed the fuse circuit from the fuse box. A problem has developed however in the fact that an exterior light that is being fed power from a different fuse had it's neutral return tied into the fuse circuit that has been disconnected.

Was this common/acceptable to 'cross' circuits like this? I don't have a lot of experience with knob and tube, but this just seemed to me like it was not an ideal wiring job to begin with. It is very possible that this exterior light was a retrofit at some point after the house had been built.

To fix the problem, do I just need to tie in the neutral from the light fixture in with the neutral from the circuit that it is being powered from?

Everything else on the fuse that is powering the exterior light works fine when the fuse is installed...however, the fuse has been removed until I can remedy this situation.

Any suggestions/comments would be appreciated. Thanks!

[HayZee518]

In the knob n tube era it was common to run a main distribution line [no 8 solid] along one side of a joist with its neutral mate [also no 8] on the other side on porcelain knobs. anytime they needed a hot, they'd tap off the main line and the same with a neutral. they may have fused the neutral as you have found out. essentially all neutrals go back to the neutral bus in the "new" panel, unfused. wires were run on one side of a stud, paired with a neutral with no support other than a cast iron box and a jute fiber called loom. in more than well to do houses this tap off was fused with just a porcelain fuseblock, exposed with no cover over it, but accessible in the attic. Ideally you should run a neutral with a hot to the circuit in question. I wouldn't trust old knob and tube because most of it was 14 gauge. I've seen circuits not function because of a cold solder joint.