Knob and Tube wiring

Disclaimer: I'm not an electrician.

I'm not upset about the presence of knob and tube (KB) wiring in the house. Its an old building and KB wiring was what they used back in the day. Your experiences with KB will probably vary. The KB in my house is in very good condition, in fact the insulation is a pain to get off when you're stripping the ends. However, KB was installed in an era when there were fewer appliances drawing less current. Which has made me consider that using 'green' or 'energy star' appliances may be good for more than just the environment, they may be good for your house if you're living in an older building with KB wiring. Another concern is that most of the light fixtures and electrical outlets (basement, first floor, and second floor) are on one circuit (one breaker) and most of that is original KB wiring. So there's the potential for tripping the breaker fairly easily.

Many sites will tell you that you must replace it all and all of it right now, no delay, do it now. Now, go...what are you waiting for? Well that's all well and good, but I think we have to be realistic. In the last post I wrote about how Sara and I were going to work on the bathroom. Well when we took a look at the ceiling we discovered quite a bit of KB wiring. We had been told, during the inspection while buying the house, that there was 'a little' KB wiring left. We've found more than a little. It runs through the walls and ceiling of the entire first floor. Gutting it and replacing it in the next week just isn't going to happen. There has to be a compromise.

Heck, there's a lot 'new' wiring in the house that I don't like any more than the 'old' wiring. Too many tie-in's, too few junction boxes, too much electrical tape and too few wire nuts. The wires (akin to the plumbing) make the Gordian knot look like a simple overhand knot. So what to do?

KB wiring isn't always colored coded. When you take a look at a modern piece of household wiring (aka romex) there are three wires, one is just plain copper (ground), another is black ('hot') and the last is white ('neutral'). Its a nice convention. My KB wiring however is just a gummy black color. I needed to replace a run of KB wiring with some modern wiring and put in some junction boxes. Since I wasn't in a position to replace everything right back to the breaker box I needed to know the polarity of the KB wiring. So I killed the power to the entire house, went back and took off a small section of insulation from each wire of the KB wire run. Then I turned the power back on. So yes, I had live wires. I'm not particularly afraid of electricity. You have to be smart about it, but its not going to arc across the air and melt your eyes. I used a voltmeter with insulated alligator clips and measured the voltage drop from each wire to a ground (my shower pipe). The wire with the 120V drop is the 'hot' and the other (which may have a small voltage or none at all) is the neutral. Now I know how to splice in.

There's a lot of warning about splicing into KB on the web. I suspect some of it is because KB has some special requirements that your typical romex doesn't have. It was laid in a way to radiate away excess heat. That's why you'll see them laid about a foot or so apart and why they're not running through insulation (in many states its not legal to lay insulation over KB wiring). The connections between KB wiring weren't done in junction boxes, the wires were spliced together, twisted and soldered and so they can be damaged by yanking or pulling on the wire. I suppose the idea is that messing around with existing KB wiring might increase the liklihood of its failure. Its up to you.

After spending a day replacing some of it though I have vowed to largely rewire this house in the next year, the supplies are not very expensive and its mostly a matter of cursing, grunting and staring thoughtfully (and annoyed) as you try to figure out what the hell you're looking at. But since we're planning on gutting the inside we'll have greater access to the wiring and can replace it quickly and efficiently.

NOTE: While you're rewiring or adding onto a circuit in your home it'll all make sense to you,...now. But what about in five years, will you remember all the reasons you did what you did? Will you remember where that wire went? I doubt it. So for the wires I've been laying I've been using a sharpie to give some hints on the wire and I've been writing on the junction boxes indicated the date of installation and the breaker number that shuts down that box/outlet/fixture/wire. For example I recently added a GFI to my bathroom (in parallel to the other GFI...which was the only outlet in my bathroom) and here's what you'll see if you look at my wiring:

I like a good puzzle, but once its solved I prefer to move on. Within a year, a ten year old will be able to explain the wiring of this house to you and do it justice.