When you buy a house, odds are your cable will not be up to the newest codes (they change every three years). But that is no problem as long as there are no safety issues. And that is the key. When you buy a house you need to know what type of wiring is in the house and what condition it is in as to be safe. To determine this you need to know the problems we have with each type of cable and determine if you can live with it.

Note: The term "electrician" was not  used everywhere in the early days of wiring--catalogs often referred to them as "the electric light man."

Note: Though early knob and tube treated both AC wires as hot wires (black) and fused them both, DC, oddly enough, sometimes had a neutral. The three terminals for a old 1918 DC bell ringer were listed as ground, neutral, and live (Cushing 1918).

Service entrance

The beginning of the 1900s ushered in the electric era. Most  very early services started out as amperages between 30-60 amps--110 volts.  City folks got their power from new-born AC utilities while country folk got theirs from a generator. Some old houses still have the holes in the exterior walls with porcelain  tubes (with wires) still intact--though cut dead. This eventually evolved into 60-100 amp 110/220 volts and then up to 125/250.

            Once through the exterior wall, the knob and tube wire would terminate (hopefully) in a few screw-in fuses mounted against a wall at a height above head level  (because of the bare wires and terminals).  There were no inspections back in those days so it would not be too unlikely that an installer could hard wire directly from generator to load with no fuses. More affluent installations would use a fuse box or panelboard--some  made their own fuse boxes out of wood. Crouse-Hinds had a considerable number of panelboards in the 1916 Western Electric catalog. Thus panelboards had existed for many years previous. But one would have to be able to afford it and one would have to have the access to get one. In a large city access was not too difficult, but in the rural areas, you were on your own.

            As the simple wiring of knob and tube faded, fabric covered service cable came into use. Cable wiring was faster and safer and allowed for higher currents and allowed 3-conductor 220 volts to enter the house as opposed to the old 2-conductor110 volts. The fabric however, couldn't last forever and the UV in the outside light broke it down. If this is what you have at your house, you will be able to see the stranded neutral under the fabric where it is mounted against the outside siding. There is current flowing in this wire. It would be prudent to replace this cable ASAP.

The first wiring

To light the houses built before electricity you will sometimes see a hook overhead in the entrance way and immediately above the stairs in the hallways. The hooks held oil lanterns. High overhead they could illuminate a considerable area. The light was adaquate but dangerous--fire was always one drop away.

     Electricity was considerable safer and the entrance area and stairs were among the first to receive the light from electricity. Early organized wiring began in the city with wires run in ridgid conduit (steel pipe) from place to place. This was a bit too expensive for country folk,  and they opted for knob and tube type wiring. This became popular right after the turn of the century and it came in with a rush. The 1897 Sears catalog listed nothing for AC house wiring--just a few DC appliances. And then bingo--the1902 Sears catalog came onto the market with snap switches, fuses, rubber covered wire, and electric lights. Knob and tube material was there to wire your entire house for AC. What a difference just a few years make!

            Knob and tube had two conductors both of which had the same color insulation because early knob and tube treated both wires as hot wires. Each conductor  was mounted via porcelain knobs and cleats slightly off the framing members or with tubes through the wall or joist. Either way  the conductors were a few inches apart--like two clothes lines. The wires had to be protected--thus they were  inside a wall, ceiling, basement, attic--or just high overhead. They were also run inside wood molding (2 and 3 wire)--where the molding was grooved out for the wire. Wood molding was sometimes banned for obvious reasons and metal molding was used instead.  Knob and tube needed open air to dissipate heat and was not suppose to be surrounded by insulation. 

            There were times when knob and tube had to go from the attic to the basement and the owner did not want to rip the walls open. For these times, the wires were covered by a kick box (we call this a plenum, nowadays) or simply run through wrought pipe. The wires were kept apart in the kick box but were run next to each other through the pipe. Once in the basement or attic, the wires reverted back to the standard knob and tube installation. It's interesting to note that when running knob and tube the old instructions state that  you are not suppose to use a knob at a right angle turn. Instead you back two corner knobs off several inches from the corner,  and make a gradual turn with the wire. What's most interesting is that I have never seen it installed this way--the knobs were always used at right-angle turns.

            The conductor had a  rubber compound coating over its interior copper wire with a cotton saturated braid over that--newer "code wire" used a double braid. Each conductor had to be run --extremely time consuming. A slow burning weather-proof wire was also available. The insulation had two braids with a saturated fireproof composition over a highly polished weather proof third braid.  It was not to be used for outside work.

             It's interesting to note that early on, many electrical knob and tube loads were hard wired--no receptacles were used (they weren't invented yet) and light fixtures were sometimes hardwired to the knob and tube system with the light itself being attached to the framing if it was heavy. But most houses couldn't afford the fancy lights or even  switches and just hung cords from the wiring that contained a single bulb. The light's wire was spliced onto the main runs in the attic and sealed with  rubber tape and then friction tape. A braided cotton loom was used as conduit when the light fixture wires went through the overhead ceiling as well as through the joists.  Text and photos by Rex Cauldwell.