What are Split Bus Panels?

A split bus panel is an electrical panel with two separate bus bars. Bus bars are metal bars that hold the circuit breakers and carry electrical current. Most modern electrical panels have a single bus bar that runs the length of the electrical panel.

A split bus panel will have a large breaker somewhere on the top bus bar that feeds power to the lower bus bar. In addition, the top bus bar is responsible for larger appliances. The lower bus bar, typically holds breakers for general lighting and outlets in the home.

The “Six Throw” Rule

The National Electrical Code states you must be able to shut off the electrical power with a maximum number of six throws or breakers. If a split bus panel requires more than 6 throws to turn off all of the electrical power in the home, the panel would be out of code.

In a split bus panel, there is not a single main shut-off. Instead, there are typically up to 5 or 6 large (220) breakers at the top supplying dedicated circuits to the home’s larger appliances, then one breaker usually labeled as “Main” or “main lighting”… that supplies electrical current for the rest of the home.

In the split bus panel shown directly above, the panel appears to conform to the 6 throw rule, so it’s considered acceptable, just an older style of panel.

In the panel shown at the top though,….the panel doesn’t conform to the 6 throw rule. It would take 10 moves to turn off all power. An electrician would likely recommend correcting this for improved safety, and these type of panel upgrades are typically expensive.

History And Issues of Split Bus Panels

Split Bus panels were allowed from 1965 to 1981. After 1981, they were discontinued due to arising problems. As technology improved, homes required more electricity and split bus panels needed more room. Electricians or handyman often overloaded these panels by adding single-pole breakers to the top bus bar which caused overheating, arcing, and damage. Between these issues, and some split bus panels not conforming to the “6 Throw Rule” mentioned above, most split bus panels have been replaced over the years.

Honest Home Inspections, LLC evaluates electrical panels during our home inspections. If you’re in Northwest Louisiana and you would like your home inspected, please give me a call at 318-510-8313.