Compressor description by Ralkin

Bitzer Octagon Transcritical CO₂ Compressor: Model 4PTC-7.F3K

The BITZER Octagon series for transcritical CO₂ applications is a specialized compressor range developed based on the well-proven OCTAGON semi-hermetic reciprocating compressor technology. Designed specifically for the high pressures and demanding conditions of transcritical CO₂ systems, this series offers a wide application range suitable for various system configurations, allowing for both sub- and transcritical operation. The compressors are an established, reliable alternative to conventional systems, featuring high energy efficiency and robust construction.

Model Identification

• 4: Index for the number of cylinders (4 cylinders).
• P: Identification letter for bore x stroke.
• T: Identification letter for transcritical CO₂ application.
• C: Identification letter for the OCTAGON series.
• 7: Code for motor size.
• F3: Motor code (specific electrical configuration).
• K: Identification letter for the oil charge type.

Technical Features

• High Pressure Strength: Housing is designed for high pressure strength with no bottom plate. Maximum permissible pressure levels are up to 160 bar on the high-pressure side and 100 bar on the low-pressure side.
• Wear-Resistant Drive Gear: Features further developed multilayer bearings for enhanced durability.
• High Energy Efficiency: Achieved through a suction gas-cooled motor (very suitable for speed regulation), very efficient working valves, special drive gear geometry, and cylinder heads with separate, thermally isolated high and low-pressure chambers.
• Low Vibration Design: The 4-cylinder design is quiet and low-vibration, particularly well-suited for operation with a frequency inverter to increase and control capacity.
• Wide Application Range: Suitable for both sub-critical and transcritical CO₂ systems.

Specifications & Data

• Base Model Configuration: 4PTC-7K
• Motor Version: 1 (Corresponding to model code '7' in the data table)
• Displacement (at 1450 min⁻¹): 4.3 m³/h
• Number of Cylinders: 4
• Oil Charge: Data not explicitly listed for this specific size in the summary column, but typically standard for this range (see Oil Charge section).
• Weight: 102 kg
• Pipe Connections:
  • Discharge Line (DL): 18 mm
  • Suction Line (SL): 22 mm
• Motor Connection: Star (Y) connection for standard frequencies (380..420V Y/3-50Hz and 440..480V Y/3-60Hz). Note: Specific connection for motor code F3 should be verified with BITZER, as it differs from the standard codes listed.
• Electrical Data (for base motor version 1):
  • Max. Operating Current: 15.3 A
  • Max. Power Consumption: 8.2 kW
  • Starting Current (Locked Rotor): 82.4 A
• Oil Charge Options:
  • Type K (BSE85K): Standard oil charge for standard applications.
  • Type Z (BSG68K): For applications with suction pressure >40 bar and/or high pressure >120 bar (e.g., heat pumps).
• Crankcase Heater:
  • Specification: 230V, 0..140 W self-regulating PTC heater (for 4PTC series, likely 0..120W based on the 4PTC-6K entry range, or 0..140W if grouped with larger sizes; the text specifies 0..120W for 4MTC-7K..4KTC-10K, and 0..140W for 4JTC-10K..4CTC-30K. As 4PTC is smaller than 4MTC, it likely uses the 0..120W heater).
  • Requirement: Generally required due to the high solubility of CO₂ in the oil.