My Grandson, Dustin, who is an electrician, recently purchased an older home in the Topeka, Kan., area and texted me about a wiring issue he noticed when accessing some electrical boxes. He noted that the connections in the boxes did not contain wire nuts, but were instead soldered and then taped. He was wondering if this was a common method of wiring in older homes. I told him that this was a popular method of splicing conductors before wire nuts were invented. I’ve known about soldering and taping connections since I had seen this outdated method in older homes in the Phoenix area when I was an electrician in the 1970s and ‘80s.

First, some history

I had to do some research to determine when wire nuts were invented, since I have been making connections with them since the early 1960s. The first screw-on wire connector (what is commonly called a wire nut) was introduced in about 1914 by electrician William Marr.

The accepted practice for making electrical connections in an electrical system used to be a process called “solder and tape.” Typically, a mechanic (an electrician) would first run the wires required, then another electrician would polish the exposed conductors and twist them together to make a secure mechanical connection. Next, the ends of the wires would be firmly joined by dipping the wire connection in a pot of molten solder, and after they cooled, the wires would then be wrapped with a rubber insulating tape. 

Innovation drives progress

Over time, this process proved to be time-consuming and dangerous, as Marr discovered firsthand when he inadvertently spilled a scorching solder pot while working in a customer’s home. Convinced that there had to be a safer and more efficient way of joining two electrical conductors, Marr worked in his basement shop until he invented the first pressure-type wire connector (a set-screw version that was the forerunner to the modern-day wire connector or wire nut). 

Marr’s twist-on wire connectors were introduced in the United States in about 1933. These early wire nuts were cone-shaped, had a metal crimp sleeve with a screw connection to the conductors, and a cap made of ceramic or porcelain that provided the insulated cover over the connection.

What to do with old methods

The soldering method of electrical connections with electrical tape may still be found in older homes and has some drawbacks. Temperature fluctuations, material quality and load capacity can certainly affect existing terminations. 

Over the many years of electrical installations at a variety of locations, I have seen many of these older soldered terminations become brittle with heat associated with various electrical loads on the conductors and insulation deterioration. This degradation could potentially lead to equipment failure, causing overcurrent protective devices to trip and result in arcing and fires.

I have also noticed that, where these older systems are encountered and there isn’t any evidence of deterioration, the best short-term method of dealing with them is to not disturb the connection. However, this may not be possible if new luminaires, receptacles and other electrical equipment must be installed on the circuit. When disrupting the connection, decide how much of the circuit needs replacing. This will depend on the wiring method involved in the original installation. 

Other old wiring practices

Knob-and-tube wiring was typically used in the United States from 1880 until the 1940s when nonmetallic-­sheathed cable (commonly called Romex) became the popular wiring method. For knob-and tube wiring, replacement of the branch circuit with NM cable with an enclosed equipment grounding conductor back to the panelboard should be done. There are still existing older homes with internal wiring of the knob-and-tube method in many older neighborhoods. (See “Classic Knob-and-Tube Wiring Is Still in Use,” ELECTRICAL CONTRACTOR, July 2021.)

Where ungrounded NM cable is the wiring method in an older home, the recommendation would be to replace the entire branch circuit back to the circuit’s origin. 

Where these older wiring methods are used, the best way to deal with them is complete replacement of the internal wiring method in the home. Remember, electrical wiring systems reach their end-of-life after about 50 years. This might be an opportunity to drum up business with customers who have older wiring. 

Evgeny Korshenkov / stock.adobe.com