Sheet Steel fabricated low voltage Bus Tie Duct system in air-insulated, non segregated construction. Our Bus Ducts are designed to meet the required voltage, ampere and fault level ratings. . NABCO warehouses are packed with the electrical control and safety products your customers need to recover from an outage sooner, perform routine maintenance or extend the life of their aging electrical infrastructure. EVERY EMERGENCY IS BUSINESS AS USUAL FOR NABCO. Your NABCO team is ready to. . Circuit breakers are mechanical switching devices capable of breaking currents under specified abnormal circuit conditions.