Final answer:
The correct sizing for disconnection means and branch circuit conductors for an electric furnace is 125 percent of the total nameplate load, according to the National Electrical Code (NEC) for safety and capacity reasons.
Step-by-step explanation:
The disconnection means and branch circuit conductors for an electric furnace should be sized not less than 125 percent of the total nameplate load shown on the furnace. This requirement is based on the National Electrical Code (NEC) which generally specifies that conductors for fixed loads, such as a furnace, must be capable of carrying 125% of the continuous load. This provides a safety buffer to accommodate potential inrush currents and ensure the integrity of the electrical system under load conditions.
Safety regulations limit continuous use to 80% of the breaker current capacity to prevent overloads and potential hazards. For instance, if the nameplate on the electric furnace indicates a 10 kW load, the circuit conductor should be capable of handling 12.5 kW (125% of 10 kW) to be compliant with NEC standards and provide adequate safety.