Installing a Light Fixture with Knob and Tube Wiring |

Now this is probably not the sexiest post I’ve ever done, but after struggling to find any tutorials online that accurately depicted my experience, I thought I’d share my story with knob and tube wiring.

*Please Note* This post is just to share my experience with knob and tube electrical. I am not professionally trained, and strongly suggest each person do their own independent research before tackling any electrical home improvement projects.

Now, my house was built in 1920 and has been in my family for three generations. It has never had any significant electrical updates, and we have always hired an electrician whenever we wanted to install a new light fixture. When I decided to tackle this home improvement project without the help of a professional, I expected to struggle with a learning curve. After doing lots of research, I felt that I had a pretty solid sense of what I could expect.

Tools needed:

Voltage Detector; Voltage Tester, Wire Stripper/Cutter, Electrical TapeSafety Glasses; Philip’s Head  & Flathead Screwdrivers

The first step was to cut the power to the entire house. With modern electrical, you’d flip the breaker switch, but with knob and tube, I learned that you have to go beyond the fuse box and completely cut off power to the house. This might not be the same in all homes, but it was definitely the case with mine.

Installing a Light Fixture with Knob and Tube Wiring |

Next I removed the original light fixture, making sure to protect those eyes with safety glasses! Even though the power was cut, I always like to use a voltage detector just to make sure that nothing is hot. If there is power running through the socket, the detector will either display a red light or emit a chirping sound when touched to the wires.Installing a Light Fixture with Knob and Tube Wiring |

With modern electrical, you would generally have a ground, a neutral, and a hot wire. While I knew that a ground wire wouldn’t be present, all the literature I came across assured me that there would be one hot wire (black) and one neutral wire (white). Unfortunately, when I looked under the hood, something entirely different was revealed.

Installing a Light Fixture with Knob and Tube Wiring |

Two identical, thickly insulated wires with no flexibility. They seemed to be fossilized in place.  You can also vaguely make out how they run directly above where the mounting screws would be screwed into place (more on that later). Unfortunately, because these wires weren’t color coded, I needed a Voltage tester to identify the hot from the neutral.

To use the voltage tester, I first flipped the power back on. Then carefully touched the pins to the wires.

You’ll want to touch the base of the pin (where metal meets plastic) and, if they display 120 volts, you’ve properly identified the hot from the neutral (the hot will be the wire touching the black pin). If you receive a lower reading, you should switch the pins until 120 volts is displayed.

When I got to this step, I ran into yet another problem (naturally). Both of the wires gave a 120 volt output, meaning both wires were hot. The heck?! After doing further research I found that this situation occasionally occurs in older houses, and in this case, it doesn’t actually matter which you wires you decide to connect neutral and hot wires on the fixture. Sounds scary, but it’s true. The good news is that by introducing a ground wire to my electrical, I made my home a little safer than it was before. A small improvement, but I’ll take it!

Before proceeding, I turned the power off for a second time. Again making sure to use my voltage detector to be sure that the wires weren’t still hot. You really want to think of your power like a hose. Just because the water has been turned off, doesn’t mean there isn’t still water in the hose. By using a voltage detector, you can be certain you won’t get zapped by any lingering electricity.

Next I installed the mounting bracket to the ceiling. Remember earlier when I pointed out those the wires in the junction box that ran directly above where I would screw in my new mounting bracket? Because the wires were immobile, and the insulation on them was about 0.5″ in diameter, I had to downsize to a slightly shorter mounting screw so that the wire wouldn’t be pierced. Thankfully, most homes will have flexible wires, so this shouldn’t be an issue for most folks.

When mounting the bracket a.k.a. the “strap,” you want to make sure that the green screw is facing down towards you. You’ll ground the light fixture to this screw next.

Installing a Light Fixture with Knob and Tube Wiring |

Before moving forward, I grabbed a pair of combo wire strippers/cutters. Typically you’d trim the wires coming out of the junction box and then strip about 0.5″-1″ of the insulation off. Since the wires coming from my junction box were solid, and not made up of the typical thin copper strands, this wasn’t a necessary step for me. However I did need to strip down about 1″ of the insulation off from all three wires coming from the light fixture I was installing. If you’re working with standard modern wiring, you want to be sure to twist the copper strands on all wires clockwise.

Installing a Light Fixture with Knob and Tube Wiring |

At this point I needed to grab a buddy to hold the light fixture while I connected the wires. Rich was my buddy and only available photographer so unfortunately we didn’t have an extra pair of hands to take the rest of the installation photos. Thankfully, the rest is a pretty straightforward explanation.

Before connecting the hot and neutral wires, you want to ground the light fixture first. On newer homes you’ll have three wires that you’ll connect to the three wires on the light fixture: ground to ground, neutral to neutral, and hot to hot. The order you connect will be ground, neutral, then hot.

Since I didn’t have a ground wire coming from the junction box, I secured the ground (green) wire to the mounting bracket on its own. Taking the ground wire from the light fixture, I wrapped the twisted copper strands around the green screw in a clockwise motion. Then tightened the screw with a screwdriver.

Next, I took the neutral wire from the light fixture and twisted it together with the neutral wire coming from the junction box. This might sound obvious but you want to make sure you’re only twisting the exposed copper portions and not the plastic insulation. Since my house wires were immobile, I wrapped the neutral wire coming from the light fixture around the house wires in a clockwise motion. I finished this step off with securing these together with a wire nut and electrical tape, then repeated the same steps with the hot wires.

Then I carefully pushed the wires up into the junction box and secured the fixture to the mounting bracket using a screwdriver.

As a finishing touch, I replaced the Edison bulbs that came with the fixture with chrome capped bulbs before turning the power back on. They give off more light than Edison’s while maintaining the same industrial look I love.

Here’s what the finished product looks like!

Installing a Light Fixture with Knob and Tube Wiring |

Installing a Light Fixture with Knob and Tube Wiring |

Light Fixture is available through in-store only purchase at Lamps Plus. Bulbs used were purchased here.

  • So good to know! We want to put in a light fixture in one of the hallways so this will definitely help! Thanks

  • One of my fears too! Changing a lightbulb is no problem, but installing the whole thing? Awesome!

    • Thanks Brooke! I had my reservations, but it was a really empowering project to tackle :)

  • Oh gosh! You are so brave and adventures. I love the end result though. Thanks for sharing!