Compressor description by Ralkin

The BITZER 2FHC-3K is part of the legacy Octagon CO2 compressor series, engineered specifically for the demanding requirements of subcritical R744 (Carbon Dioxide) applications. Designed with reinforced components to handle high operating pressures, this model serves as a critical component in the low-temperature stage of commercial and industrial cascade refrigeration systems, rejecting heat into secondary circuits rather than ambient air.

Model Identification Breakdown

• 2: Number of cylinders.
• F: Identification letter for bore x stroke (displacement indicator).
• HC: Series identifier, denoting the OCTAGON series housing optimized for subcritical CO2 pressures.
• 3: Motor size code / Nominal horsepower rating.
• K: Oil charge identifier, indicating the use of standard CO2 ester oil.

Technical Features

• Cylinder Configuration: A robust 2-cylinder design providing balanced mechanical operation suitable for medium-capacity cascade applications.
• High-Pressure Reinforcement: Unlike standard HFC compressors, this unit is built to withstand the elevated standstill pressures inherent to CO2 systems, typically rated for up to 40 bar suction and 53 bar discharge pressures.
• Oil Return System: Engineered with specific clearance and geometry considerations to manage the high solubility of CO2 in oil, ensuring reliable oil return to the crankcase.
• Cascade Compatibility: Universally deployed in the low-temperature stage of cascade systems, working in tandem with higher-stage compressors (ammonia, R134a, etc.).

Specifications & Data

• Refrigerant: R744 (Carbon Dioxide).
• Application Type: Subcritical CO2 (Low-stage in cascade systems).
• Lubrication: Requires BITZER-approved Polyolester (POE) oil designed for CO2, specifically types BSE85K or BSE60K.
• Crankcase Heater: A self-regulating PTC crankcase heater is mandatory to prevent CO2 from condensing into the oil during off-cycles, which would otherwise lead to critical lubrication failure upon startup.
• Safety Precaution: Due to high operating pressures, proper pressure relief systems and ventilation protocols are required during maintenance of cylinder heads or valve plates.