The Century Pool Pump Motor 1.5HP 1 Phase 60Hz 230/115V P56J with the model number B129 is a replacement motor designed for various in-ground pool pumps. Here's a breakdown of its key features:  

Key Features:

• Horsepower: 1.5 HP (Horsepower), providing sufficient power for many residential pool filtration systems.  
• Phase: Single Phase, which is the standard electrical service for most homes.  
• Frequency: 60 Hz (Hertz), the standard electrical frequency in North America.  
• Voltage: Dual Voltage, capable of operating at either 230 volts or 115 volts. This offers flexibility during installation, but it must be wired for the correct voltage.  
• Frame Size: P56J, which is a specific motor frame size indicating the mounting dimensions and shaft specifications. This ensures it will fit pumps designed for this frame type. It is also referred to as a 56J frame.  
• Speed: Typically operates at a single speed, around 3450 RPM (revolutions per minute), which is standard for pool pump motors.  
• Enclosure: Usually an Open Drip Proof (ODP) enclosure, which means it's designed to prevent falling moisture and solid objects from entering the motor. It is intended for use in a covered or protected environment.
• Shaft: Often features a threaded shaft for easy connection to the pump impeller.  
• Thermal Protection: Typically includes thermal overload protection to prevent the motor from overheating and being damaged.
• Brand: Century (also associated with A.O. Smith), a well-known and reputable manufacturer of pool pump motors.
• Compatibility: Designed as a direct replacement for many popular in-ground pool pump brands and models that utilize a motor with these specifications, including some Hayward and other brands using a 56J frame motor.  

In summary, the Century B129 motor is a reliable 1.5 HP single-speed replacement motor for in-ground pool pumps requiring a P56J (or 56J) frame, capable of running on either 115V or 230V power. It's a common choice for maintaining efficient water circulation and filtration in residential swimming pools.  

When replacing a pool pump motor, always ensure the new motor matches the specifications of the old one for proper compatibility and performance. Consulting your pump's manual or a pool professional is recommended.