How much circuit breaker is in the elevator distribution box

Elevator distribution boxes typically use circuit breakers rated according to the elevator motor load, often ranging from 30 A to 400 A, with selective coordination required between upstream and downstream devices.

Typical Ratings and Types

Elevator distribution boxes house circuit breakers that protect the elevator motor, control circuits, and associated equipment. Common ampere ratings for elevator control switches and breakers include 30 A, 60 A, 100 A, 200 A, and 400 A, depending on the motor size and system voltage (208 V, 240 V, 480 V, or 600 V) as specified by manufacturers like Siemens. Breakers are usually thermal/magnetic (inverse-time) types to provide both overload and short-circuit protection.

Coordination and Safety

According to the National Electrical Code (NEC 620. 62), overcurrent devices in elevator disconnecting means must selectively coordinate with upstream feeders to ensure that only the affected circuit trips during a fault, preventing unnecessary shutdowns of other elevators or systems. This often requires two or more tiers of overcurrent protection, with branch breakers in the distribution box coordinated with upstream feeder breakers.

Selection Considerations

Motor Load: Breaker size should match the full-load current of the elevator motor, typically using the 80% rule for continuous loads. Type of Breaker: Solid-state soft starters may have built-in overload protection, so the distribution box breaker primarily provides short-circuit protection. Fuse Coordination: Some elevator systems use Class J fuses in the control switch, which must coordinate with upstream breakers for selective protection.

Future Expansion: Distribution boxes should leave space for additional breakers or upgrades, ensuring flexibility and safety.

Practical Example

For a 40 HP elevator motor, the feeder breaker might be rated around 1900 A for magnetic trip settings, while the branch breaker in the distribution box is sized to protect the motor and control circuits, typically documented by the manufacturer to ensure selective coordination. The exact rating depends on the motor voltage, type of starter, and system configuration. In summary, the circuit breaker in an elevator distribution box is selected based on motor load, system voltage, and NEC coordination requirements, with typical ratings ranging from 30 A to 400 A, using thermal/magnetic breakers or coordinated fuses to ensure safe and reliable operation.