You're right to look into that! The markings "SWD" and "HID" on overcurrent protective devices (OCPDs) used as switches are important for ensuring the correct application and safety of the equipment. Here's the breakdown: SWD - "Switching Duty" This marking indicates that the circuit breaker is designed and tested to be used as a switch for general purpose lighting circuits. SWD breakers are suitable for frequent on/off switching of lighting loads. Important: SWD-rated breakers are NOT specifically designed for high inrush HID lighting loads. They can be used on general purpose circuits that may contain some HID lighting, but not if the circuit is primarily HID. HID - "High Intensity Discharge" This marking signifies that the circuit breaker is specifically designed and tested to handle the high inrush current associated with H

igh I

ntensity D

ischarge lighting. HID lighting includes types such as: Metal Halide High-Pressure Sodium Mercury Vapor HID lighting has a characteristic high initial current draw when the lamps are started. A standard circuit breaker might trip nuisance trips when starting HID loads. HID-rated breakers have a specially designed time-delay tripping curve that allows them to withstand the inrush current while still providing overload and short-circuit protection.

In Summary

If you are using a circuit breaker as a switch for general-purpose lighting (incandescent, LED, fluorescent, and perhaps a small amount of HID) and where frequent switching is expected, look for the

SWD marking. If you are using a circuit breaker as a switch for dedicated circuits containing HID lighting, you MUST use a breaker marked HID.

Important Considerations



NEC Compliance

The NEC requires proper identification and application of OCPDs. Using the wrong type can lead to nuisance tripping, damage to the breaker or lighting system, and potentially unsafe conditions.

Manufacturer's Instructions

Always refer to the manufacturer's instructions for the specific circuit breaker you are using. The instructions will provide detailed information on the breaker's application, limitations, and installation requirements.*

Consult a Qualified Electrician: If you are unsure about the proper application of circuit breakers, especially in commercial or industrial settings with HID lighting, consult with a qualified electrician. They can assess the load requirements and ensure that the correct OCPDs are installed. Flag for review