Overview
The Siemens D240 circuit breaker is a dual-pole, 40-ampere protection device engineered for residential and commercial electrical panel applications. Rated at 120/240 volts with an interrupt rating of 10 kA AIR, this Type QD breaker delivers reliable overload and short-circuit protection. Its HACR certification makes it ideal for heating, air conditioning, and refrigeration equipment circuits where heavy continuous loads demand dependable thermal-magnetic trip performance.
Key Features
- 40-amp capacity rated for 120/240 VAC operation
- 2-pole common-trip design ensures synchronized protection across both conductors
- Type QD 3/4-inch plug-in format for standard panel mounting
- Square D QO-compatible design allows installation in QO-series load centers without rewiring
- HACR and SWD (Switch, Disconnect) rated for diverse applications
- UL-listed and tested to UL 489 standards; CSA licensed
- Thermal-magnetic trip mechanism detects overcurrent and immediately disconnects power
Technical Specifications
The breaker measures 3 x 3 x 1 inches (length x width x height) and weighs 5.6 ounces. It occupies a 3/4-inch frame space on the bus bar, allowing compact integration into moderately populated panels. Operating temperature range is suitable for standard indoor electrical environments, typically -40°C to +65°C ambient. The 10 kA interrupt rating (AIR) provides adequate short-circuit capacity for most residential and light commercial loads.
Typical Applications
- Central air conditioning and heat pump circuits requiring HACR-rated protection
- Heavy-duty appliance circuits (electric ranges, dryers, water heaters) at 240V
- EV charging station circuits delivering 40-amp continuous load
- Commercial panel expansion where QO compatibility is required
- Replacement protection in existing Square D QO electrical systems
Compatibility & Replacements
The D240 is UL-classified as a direct plug-in replacement for Square D Type QO circuit breakers in QO load centers. No rewiring or panel modifications are required—simply snap the breaker onto the QO bussing. This interchangeability makes it an economical choice for retrofit installations and new construction alike. Siemens also offers GFCI and arc-fault variants (such as the QF240A) for applications requiring ground-fault or arc-detection protection. For different amperage requirements, Siemens manufactures similar 2-pole models at 20, 30, and 50-amp ratings in the same form factor.
