History of Wire Connectors | Terminals

Electrical splice connections have evolved over the past 130 years as engineers and manufacturers continue to innovate to ensure safe, secure, and reliable wire and cable connections.

In the early days of wiring, single-sheathed copper wire was laid inside the walls or ceilings of houses and buildings and supported by porcelain knob insulators or flexible fabric jackets. Wires would be connected by twisting and/or soldering two different wires together. These connections are held together by rubber insulation tape or sometimes left bare inside the junction box. Knob and tube wiring had many advantages and disadvantages and was used until the 1930’s and can still be seen in some older buildings today.

Just before World War II, the cable and wire industry took a giant leap forward with the advent of rubber fabric-coated wire sheathing, metal conduit and new wire connectors. Rubberized fabrics allowed fire and zero wires to run together, but still without a ground wire. Metal conduit allows a group of wires to be run through a metal tube, which can also double as a grounding method. The conduit could be run through wood and metal framing and bare areas without exposing people to live wires.

Around 1933, electrical contractor William Marr introduced the latest connection method in the United States, the twisted wire connector. This connection method, also known as the wire-nut connector, did not become the standard until recently, when the company introduced more reliable connection methods, such as lever or push-in connectors.

Today, flexible metal conduit is still used, although PVC conduit may be more suitable for harsh environment applications. In addition, wires are now often coated with a non-metallic sheath made primarily of plastic. The connectors used with these wires have also changed considerably. While you may still see screw connections or twisted-wire connectors in junction boxes, lever or push-in connectors have become the norm.

Old connections vs. new connectors
However, these older methods of splicing wire connections have not completely disappeared, as they still offer advantages. For example, soldering provides a low-process solution for connecting wires. It is also a process that has been automated.

Although soldering has been around for centuries, it still has drawbacks. The workplace environment, temperature fluctuations, material quality and the inherent variability of user skills can negatively impact the consistency of the process. Some solders cannot be used at high temperatures and the strength of the joint usually remains low, even if the joint is additionally held together by an adhesive. Hand soldering is a time-consuming and inexact science, and the use of molten metal and lead-based solders is dangerous. Many countries have mandated a switch to lead-free or composite solder made from lead and tin, which makes some connections weaker.

To reduce installation time and make connections easier to fit into smaller spaces, twisted wire connectors were created. If you open a junction box in many homes, you will see a plethora of colorful connectors with multiple wires powering many different electrical applications. When Marr developed the twisted wire connection, he was looking for a faster, safer way to make electrical connections. As an electrical contractor, he was injured by melting solder and was looking for a low-risk wiring method. Eventually, he developed a connection in which the wires were screwed together. This would eventually lead to connectors that you could screw together with your fingers. The wires were initially encapsulated in ceramic and later in plastic.

Twisted wire connectors save installation time, require less operating space, and reduce costs. However, advantages came with it. Most twisted-wire connections depend heavily on the skill of the installer and, as a result, reliability is consistently inconsistent. They can also fail when exposed to vibration, pressure, temperature fluctuations or corrosion. The color coding of caps, the number required, and the wire gauge that should be used with each cap can be confusing and potentially dangerous as well. As with all older connections, you must fit the correct wire with the proper size cap to form the correct connection.

Later, terminal blocks were developed to provide installers with modular insulation blocks to hold multiple wires together. Terminal blocks secure wires within a single terminal, often arranged in groups, and connect to a ground or to switches and receptacles. Terminal blocks are becoming more common in residential wiring but have been the norm in industry for a long time. Today, this technology has been extended to lever-actuated connectors, which are completely tool-free for installation and automatically ensure a solid electrical connection.

XALXMAW DF’s range provides the company with connectors rated over the entire temperature range, which is critical when working in extremely cold or hot temperatures. Planning says it was only a product discovery issue that triggered the change. “We can still use twisted wire caps, but XALXAMW Lever wire nut connectors are faster and easier.”

What the future looks like
The connectors of the future will only be smaller, faster, stronger, more durable, and rugged enough to withstand harsh environments. Old methods of splicing may never completely disappear, but connector manufacturers will continue to evolve and introduce exciting new products.