If you have ever opened your electrical panel and noticed that there is no single main breaker at the top that shuts off all the power, you likely have what is known as a split-bus panel. These panels were common in homes built from the 1950s through the early 1980s, and there are still thousands of them installed in homes across the Aiken, SC area and the broader CSRA region.
Split-bus panels were legal and considered acceptable when they were installed. But the National Electrical Code changed in 1981, and these panels no longer meet modern safety standards. Understanding what a split-bus panel is, why it is considered obsolete, and what your options are will help you make an informed decision about your home's electrical system.
How a Split-Bus Panel Works
A standard modern electrical panel has a single main breaker at the top. When you flip that breaker to the off position, all power to every circuit in the panel is disconnected. This provides a simple, immediate way to shut off all electricity to your home in an emergency.
A split-bus panel works differently. Instead of one main breaker, the panel is divided into two sections. The upper section contains up to six double-pole breakers that are fed directly from the utility power. These breakers control the highest-draw circuits in the home, such as the electric range, water heater, dryer, and air conditioning system. One of those upper breakers feeds the lower section of the panel, which contains all the branch circuit breakers for lights, outlets, and smaller loads.
The key distinction is that there is no single disconnect. To shut off all power to the home, you have to flip up to six breakers in the upper section individually. This is where the design gets its name: the bus bar is split into two sections with separate feeds.
The Six-Throw Rule
The design of split-bus panels was based on what electricians call the "six-throw rule" or "six-handle rule." Under older versions of the National Electrical Code, it was acceptable to have a service disconnect that required up to six hand movements to shut off all power. The idea was that in an emergency, a homeowner or firefighter could turn off all electricity within six motions of the hand.
This rule was eliminated from the NEC in 1981. The code was revised to require a single service disconnect, meaning one main breaker that shuts off all power with a single motion. The reasoning was straightforward: in an actual emergency, such as a fire, electrical shock, or flooding, requiring someone to identify and flip six separate breakers is too slow, too confusing, and too error-prone. A single main breaker is faster, simpler, and safer.
Since 1981, any new electrical installation in the United States has been required to have a single main disconnect. Split-bus panels are grandfathered in where they already exist, meaning you are not required by law to replace one simply because it is old. However, the fact that they no longer meet code has practical implications for insurance, home sales, and safety.
Why Insurance Companies Flag Split-Bus Panels
Insurance companies have become increasingly particular about what electrical equipment they are willing to insure. Split-bus panels appear on many insurers' lists of outdated or concerning electrical equipment, alongside Federal Pacific and Zinsco panels.
The insurance concerns with split-bus panels are not primarily about the panel itself being defective in the way that FPE or Zinsco panels are. Rather, the concerns are about age and capacity. A split-bus panel is at minimum 45 years old. Any electrical equipment that old has experienced decades of thermal cycling, corrosion, and wear. The connections inside the panel may be loose, the bus bars may show signs of overheating, and the breakers themselves may be reaching the end of their reliable service life.
Additionally, split-bus panels are typically rated for 100 or 150 amps, which was adequate for the electrical demands of a 1970s home but is often insufficient for modern usage. Running a panel near its capacity for extended periods accelerates wear on every component in the system.
Some insurance companies will insure a home with a split-bus panel but at higher premiums. Others may require an inspection or a letter from a licensed electrician confirming the panel's condition. And some will decline coverage altogether until the panel is replaced. If you receive a notice from your insurer about your electrical panel, it is worth taking seriously.
Safety Concerns Beyond the Code
Even if a split-bus panel was in perfect condition when it was installed, there are legitimate safety concerns that come with age and changing electrical demands.
No single emergency disconnect. The most obvious safety issue is the lack of a single main breaker. If there is an electrical emergency in your home, such as sparking, the smell of burning insulation, or a flooded basement, you need to be able to shut off all power quickly. With a split-bus panel, you have to know which breakers in the upper section need to be turned off, and you have to find and flip each one individually. In a dark, smoky, or flooded situation, this is a significant disadvantage compared to a single main breaker.
Age-related deterioration. Every split-bus panel still in service is at least four decades old. Over that time, the internal connections are subject to thermal expansion and contraction with every heating and cooling cycle. Bus bar connections loosen. Breaker contacts wear. Wire insulation becomes brittle. These are normal aging processes that affect all electrical equipment, and they increase the risk of overheating, arcing, and failure.
Capacity limitations. Most split-bus panels were installed with 100-amp or 150-amp service, which was appropriate for the era. Modern homes with central air conditioning, electric water heaters, multiple large appliances, home office equipment, and potentially electric vehicle chargers typically need 200-amp service. Running a panel at or near its maximum rated capacity puts additional stress on every component and increases the risk of overheating.
Obsolete breakers. Finding replacement breakers for some split-bus panel models can be difficult or impossible. When a breaker in the panel fails and needs replacement, the correct part may no longer be manufactured. Using incorrect or aftermarket breakers that do not properly fit the panel creates additional safety hazards.
The Upgrade Process
Replacing a split-bus panel with a modern panel is a standard job for a licensed electrician. The process typically involves the following steps:
Assessment and planning. The electrician evaluates your current electrical system, determines your actual capacity needs, and designs the new panel layout. This includes identifying all existing circuits, checking wire sizes, and determining whether any circuits need to be reconfigured to meet current code.
Permitting. A panel replacement requires an electrical permit from the local jurisdiction. In Aiken County, this involves submitting the scope of work and paying the permit fee. The permit ensures the work will be inspected for code compliance.
Utility coordination. The utility company, typically Dominion Energy in the Aiken area, must be contacted to schedule the temporary disconnection of power at the meter. This is necessary because the service entrance conductors carry live utility power that cannot be de-energized by the homeowner or electrician.
Panel installation. On installation day, the utility disconnects power at the meter. The electrician removes the old split-bus panel and installs a new 200-amp main breaker panel. All existing circuits are reconnected to new, properly rated breakers. The grounding system is verified and updated as needed. The installation typically takes six to eight hours for a straightforward replacement.
Inspection and restoration. After the installation is complete, a county electrical inspector examines the work to verify code compliance. Once the inspection passes, the utility reconnects power at the meter. The entire process, from permit to final inspection, typically takes one to two weeks, though the actual hands-on work is completed in a single day.
What You Gain from the Upgrade
Replacing a split-bus panel is not just about meeting code. The upgrade provides tangible benefits that affect your daily life, your safety, and your finances.
You get a single main breaker that shuts off all power with one motion. You get a panel rated for 200 amps, which can handle modern electrical demands with room to spare. You get new circuit breakers with current safety features, including the ability to add AFCI and GFCI protection as required by modern code. You get properly labeled circuits that make it easy to identify what each breaker controls. And you get a panel that will not raise concerns with your insurance company or during a home inspection.
For many homeowners, the peace of mind alone is worth the investment. Knowing that your electrical panel is modern, code-compliant, and capable of handling your home's electrical demands is a simple but significant improvement in your home's safety.
Next Steps
Unity Power & Light has extensive experience upgrading split-bus panels for homeowners throughout the Aiken, SC area. If you have a split-bus panel and want to understand your options, we provide thorough assessments that explain exactly what your home needs and what the upgrade will involve.
We handle every aspect of the replacement, including permitting, utility coordination, installation, and inspection. Our flat-rate quotes mean no surprises, and every job is completed to current NEC standards.