Compressor description by Ralkin

The 2MHC-05K is a hermetic compressor from the legacy BITZER Octagon CO2 series, engineered specifically for subcritical R744 (Carbon Dioxide) applications. It features a reinforced housing capable of withstanding the high pressures inherent to CO2 systems, making it ideal for use as the low-stage compressor in industrial cascade refrigeration setups.

Model Identification

• 2: Indicates the compressor has 2 cylinders.
• M: Identification letter for bore and stroke (displacement indicator).
• HC: Series identifier denoting the OCTAGON series housing, optimized for subcritical CO2 pressures.
• 05: Motor size code / Nominal horsepower.
• K: Oil charge identifier, indicating the standard CO2 ester oil charge.

Technical Features

• Subcritical CO2 Design: Built exclusively for R744 applications, capable of handling high working pressures (typically up to 40 bar suction / 53 bar discharge) and elevated standstill pressures.
• Lubrication System: Designed for use with BITZER-approved Polyolester (POE) oils specifically formulated for CO2, such as BSE85K or BSE60K, to accommodate the high solubility of the refrigerant in oil.
• Mandatory Crankcase Heating: Due to the extreme solubility of CO2 in oil, this model requires a self-regulating PTC crankcase heater to prevent oil dilution and foaming during standstill periods.
• Reinforced Housing: Constructed with thicker castings and reinforced cylinder heads compared to standard HFC compressors to ensure safety under high-pressure CO2 conditions.

Specifications & Data

• Model Series: BITZER Octagon CO2 (Legacy 2MHC..4NHC Group)
• Refrigerant: R744 (Carbon Dioxide)
• Application: Low-temperature stage of cascade systems (rejecting to NH3, R134a, or secondary fluids)
• Max Suction Pressure: 40 bar
• Max Discharge Pressure: 53 bar
• Lubricant Type: Polyolester (POE) - e.g., BSE85K, BSE60K