Siemens HHJXD63B300 Molded Case Circuit Breaker

The rated current is 300A. Use that rating when coordinating the breaker with the circuit load and conductor ampacity.

The breaker is rated 600VAC. Check the circuit voltage against this rating, and evaluate interrupting capacity separately at the operating voltage.

Its interrupting rating is 100kAIC at 480V. For a 480V installation, the available fault current at the installation point must not exceed that rating.

The thermal-magnetic trip provides long-time and instantaneous protection. The thermal element responds to sustained overloads, while the magnetic element responds rapidly to high fault current.

The thermal trip is fixed, while the magnetic trip is adjustable. The adjustment lets you tune the instantaneous response for circuit coordination without changing the thermal overload setting.

The conductor range is 3/0 AWG-500 MCM. Select conductors within that terminal range, then check their ampacity against the circuit requirements.

Both the mounting and terminal connections are bolt-on. Plan for bolted fastening when installing the breaker and making its electrical connections.

The operating temperature rating is 40 °C. Include the installation's thermal environment in your selection so the breaker is used within its temperature rating.

The Siemens HHJXD63B300 has three poles, providing a protected current path for each of three phase conductors. Use the pole count when selecting protection for the circuit's phase conductors.