Contractors 
Contractors The Confusion Around Older Panels and Interlock Compatibility
For decades, American homes have relied on electrical panels from manufacturers that have changed hands, merged into larger corporations, or been completely rebranded. This often leads homeowners and electricians to assume that older panels are no longer supported—especially when trying to install a safe, code-compliant generator interlock kit. In reality, most of these panels remain fully compatible because the underlying mechanical design has barely changed over time. A major turning point in this continuity was ABB’s acquisition of GE Industrial Solutions in 2018, which brought GE’s entire electrical distribution division—including decades of legacy breaker architecture—under ABB. Through this acquisition, ABB also became the modern steward of several earlier panel lines that had already transitioned into GE ownership, including Thomas & Betts. By preserving the long-established GE breaker spacing and mechanical geometry, ABB ensured that even panels dating back to the 1960s remain fully compatible with modern interlock kits. This consolidated lineage demonstrates that while company names and ownership have changed, the mechanical foundations of these panels have remained stable.
Why the Interlock Principle Hasn’t Changed in 50 Years
The core safety principle behind every 2-way interlock kit remains unchanged: only one power source—generator or utility—can be active at any time. This is achieved through a mechanical sliding plate that blocks one breaker when the other is turned on. Whether a panel was manufactured in 1970 or 2024, the underlying physics and safety standards are the same. As the National Electrical Code evolved, manufacturers continued to follow standardized spacing, alignment, and handle-throw distances. Even as companies merged or were absorbed into larger corporations, the internal mechanical geometry of their panels remained consistent—allowing modern interlock kits to work across multiple generations of equipment.
Decades of Mergers That Shaped the Panel Industry
The electrical manufacturing industry has consolidated dramatically over the last fifty years. Dozens of once-independent panel manufacturers are now part of a few large corporations. Eaton is a prime example. After acquiring Westinghouse’s electrical division, integrating Bryant’s later product lines, and absorbing Challenger, Crouse-Hinds, and Cutler-Hammer, Eaton became the modern successor to multiple legacy manufacturers.
Historic Brands Like Gould, Sylvania, and Others Still Influence Today’s Panels
Gould evolved into ITE/Gould before eventually becoming part of Siemens. Siemens maintained the breaker architecture, making older Gould and ITE panels compatible with Siemens-style interlock kits. GTE Sylvania followed a similar path—its panels evolved into Challenger, and Challenger later became part of Eaton, extending compatibility across generations. General Switch Co., although defunct, manufactured durable mid-century panels with spacing that still aligns well with modern interlock requirements.
How Murray, Siemens, Leviton, and Other Brands Fit Into Today’s Compatibility
ITE, a major innovator in breaker design, was acquired by Siemens in the 1980s, and Siemens preserved ITE’s engineering, creating compatibility across ITE, Gould/ITE, Murray, and Siemens panels. Murray was later merged fully into Siemens, which is why Murray and Siemens breaker designs align perfectly today. Modern brands such as Leviton follow current NEC spacing standards, making their load centers easily compatible with engineered interlocks. Midwest, known for outdoor service equipment, became part of Eaton and shares common breaker spacing. Square D, now part of Schneider Electric, has maintained consistent QO and Homeline lines for decades, making them some of the most interlock-friendly products on the market.
The Legacy of Square D and Why Its Panels Remain Highly Compatible Today
Square D is one of the most iconic and enduring names in the electrical industry, with a history that stretches back more than a century. Founded in 1902 as the Detroit Fuse and Manufacturing Company, the brand eventually adopted the name “Square D” in reference to its distinctive trademark: a bold letter “D” inside a square. For decades, Square D became synonymous with premium, American-made electrical equipment used in homes, factories, and commercial buildings. In 1991, the company was acquired by Schneider Electric, a global leader in energy and automation solutions. Despite the acquisition, Schneider preserved the core engineering principles and product lines that made Square D so recognizable—most notably the QO and Homeline panel series. These breaker families have remained remarkably consistent in their spacing, handle geometry, and mechanical layout, which is why Square D panels from the 1960s, 1980s, and today all share strong compatibility with modern interlock kits.
Why Interlock Kits Still Work Despite Industry-Wide Change
Even with decades of mergers, acquisitions, and corporate transitions, the most crucial engineering details of electrical panels—breaker spacing, handle throw distance, and mechanical geometry—have remained consistent across generations. Company names may have changed, but the mechanical standards behind these panels have not. This continuity is exactly why modern interlock kits work reliably on older, discontinued, or rebranded panels. Homeowners with legacy electrical systems can safely integrate generator backup power without replacing their entire panel, because interlock kits are engineered around design principles that have remained structurally stable throughout the electrical industry’s long history of evolution.
