In recent years, CO₂ transcritical booster (TCB) systems have emerged as the most common global CO₂ refrigeration architecture. Leveraging R-744 for both medium- (MT) and low-temperature (LT) refrigeration loads, this system design is one of the few all-natural refrigeration architectures available today. Since all CO₂ TCB systems are based on the same core design principles, technicians should familiarize themselves with fundamental start-up procedures.

Before powering up a CO₂ TCB system, technicians should verify that basic system design and safety measures are followed.

• Switch off facility circuit breakers and power switches. Do not risk powering up the system until all basic system pre-start checks have been performed.
• Verify that piping is rated for high pressures. Use proper stainless steel and/or copper piping per high-pressure piping chart (per local building codes). Ensure the correct piping of liquid and suction lines throughout the system. Extra care should be taken when brazing liquid lines and suction lines that are the same diameter.
• Pressure test, evacuate and charge with vapor. Test to ensure that piping, welds and joints are sealed correctly by pressurizing the system with a dry nitrogen charge (per manufacturer recommendations). Once the system piping has been tested, evacuate the system (aka “pull a vacuum”) and begin charging with R-744 vapor.
• Charge compressors with oil if compressor racks are not pre-charged with oil. Compressors should be charged with oil between the second and third vacuum cycles.
• Connect and verify supervisory control system wiring, including proper connections of all input/outputs (I/Os). Check, test and proof sensors, transducers, valves and variable-frequency drive (VFD) signals.
• Confirm pressure safeties to ensure that all mechanical pressure-relief and/or check valves are installed in individual sections of the system and set for system start-up (in accordance with local building codes).

Once all pre-start procedures are completed, technicians can power up the system before charging with liquid R-744.

• Set valves, controls, compressors and gas cooler fan to “start” and verify that all essential system components are set at the start position.
• Charge with liquid CO₂ after the system reaches adequate pressure (minimum of 100 psig).
• Verify system stabilization by running the system until evaporators reach their proper setpoints, and then check for key indicators of system stabilization.

Copeland’s new E3 supervisory control for CO₂ applications is designed to help technicians and end users simplify the commissioning and management of CO₂ TCB systems.

• System visibility via a touch-screen display or remote, web-enabled access.
• Smart Alarms elevate preemptive alarms so technicians can address issues that require immediate attention.
• System-wide management and automation via the seamless integration of all system compressors, control valves and components.
• Customization support for multiple interface views and functionalities for different end user roles and job functions.

From compressors and valves to VFDs, case controls and leak detection, their CO₂ product portfolio simplifies CO₂ system management and allows technicians to achieve insights into key aspects of refrigeration system performance.