The North American commercial refrigeration market is entering a new stage in its transition toward natural refrigerants.
For several years, transcritical CO₂ refrigeration growth has been driven mainly by centralized rack systems used in supermarkets. That pattern is now beginning to change as compact CO₂ condensing units become more widely available for smaller and more application-specific installations.
According to a July 2026 industry report, North America had approximately 5,120 supermarkets using transcritical CO₂ refrigeration systems in 2025, representing an increase of roughly 75% compared with 2023. Manufacturers are now introducing compact CO₂ condensing units or pursuing the certifications required to bring more products into the regional market.
This development may expand the use of R744 beyond large supermarkets into:
- convenience stores;
- small-format grocery stores;
- restaurants and food service;
- cold rooms and walk-in freezers;
- food-processing facilities;
- distribution centers;
- independent refrigeration loads;
- extensions and retrofit projects.
Industry participants see packaged CO₂ condensing units as a practical way to introduce natural refrigerants into smaller projects that do not require a complete centralized rack. ([Natural Refrigerants][1])
For refrigeration equipment manufacturers, however, adopting CO₂ is not simply a matter of replacing one refrigerant with another.
R744 has distinctive pressure, temperature and safety characteristics. Reliable operation therefore depends on accurate sensing throughout the refrigeration circuit and the surrounding environment.
Why CO₂ Condensing Units Are Attracting More Attention
A condensing unit combines major refrigeration components—including the compressor, heat-rejection equipment and controls—into a packaged system that can serve an independent load.
This architecture can be attractive for projects such as:
- small store expansions;
- refrigerated display areas;
- remote cold rooms;
- walk-in coolers and freezers;
- additional capacity for an existing facility;
- application-specific refrigeration zones.
Compared with installing a complete centralized rack, a packaged condensing unit can provide a more focused path for integrating CO₂ refrigeration into a new build, remodel or capacity expansion.
The recent North American market discussion also indicates growing interest in CO₂ condensing units for smaller cold-storage and food-processing applications, particularly where remote installation and precise room control are required. ([Natural Refrigerants][1])
R744 Creates New Requirements for Sensor Performance
CO₂, designated as R744, is a natural refrigerant with a global warming potential of 1. It is non-flammable and is increasingly used in commercial and industrial refrigeration. ([danfoss.com][2])
However, CO₂ refrigeration systems operate at substantially higher pressures than many legacy HFC systems. Components developed for transcritical R744 applications may be rated for working pressures around 140 bar or above, depending on the position and system design. ([danfoss.com][3])
This creates several sensing challenges:
- Pressure must be measured accurately across a wide range.
- Temperature data is required for control, protection and efficiency optimization.
- CO₂ leakage must be detected because high concentrations can create an asphyxiation risk.
- Sensors must withstand vibration, pressure cycles and changing temperatures.
- The sensing system must support fast control and fault diagnosis.
CO₂ refrigeration therefore requires a coordinated sensing architecture rather than a single monitoring component.
1. High-Pressure Monitoring in CO₂ Refrigeration Systems
Pressure measurement is one of the most important sensing functions in an R744 condensing unit.
Typical pressure-monitoring positions may include:
- compressor suction;
- compressor discharge;
- gas cooler outlet;
- liquid receiver or flash tank;
- evaporator inlet and outlet;
- high-pressure regulating valve;
- gas bypass line;
- oil-management circuit.
The controller uses these pressure signals to regulate compressors, valves, fans and protection functions.
Why Pressure Accuracy Matters
Incorrect or unstable pressure data can affect:
- superheat control;
- gas-cooler pressure optimization;
- compressor protection;
- capacity regulation;
- valve positioning;
- refrigerant charge diagnosis;
- system efficiency.
In transcritical operation, high-side pressure control is closely connected with ambient temperature and gas-cooler performance. A reliable pressure signal enables the controller to adjust the operating point while avoiding unsafe pressure conditions.
Recommended Winsen Pressure Sensors
WPCH04 Ceramic Pressure Transmitter
Тхе WPCH04 General Type Ceramic Pressure Transmitter offers pressure ranges from 0–0.2 MPa up to 0–40 MPa, a response time of no more than 1 ms and multiple output options, including 4–20 mA, 0–5 V and 0.5–4.5 V. Winsen identifies air conditioners and gas or liquid pressure control among its application areas. ([winsen-sensor.com][4])
Its potential value for refrigeration OEMs includes:
- wide selectable pressure ranges;
- fast response for closed-loop control;
- compact transmitter structure;
- temperature-compensated signal output;
- customizable connectors and outputs.
WPCK07 Diffused Silicon Pressure Transmitter
For applications requiring broader pressure-range selection or more industrial output options, the WPCK07 Diffused Silicon Pressure Transmitter supports ranges up to 100 MPa and provides several output formats, including 4–20 mA, voltage and I²C. It is designed for applications including HVAC and industrial process control. ([winsen-sensor.com][5])
Potential installation points include:
- compressor discharge pressure;
- high-pressure line monitoring;
- receiver pressure;
- process and safety monitoring;
- remote refrigeration control systems.
Engineering note: Final pressure-sensor selection must be based on the actual maximum working pressure, proof pressure, burst pressure, refrigerant and lubricant compatibility, process connection, sealing structure and required certification. Product suitability for direct R744 contact should be confirmed during project evaluation.
2. Temperature Sensing for Control and Efficiency
Pressure data alone cannot fully describe the condition of a refrigeration system.
Temperature sensors are required to monitor thermal conditions throughout the cycle and support calculations such as:
- superheat;
- subcooling;
- compressor discharge temperature;
- gas-cooler outlet temperature;
- evaporator performance;
- cabinet or cold-room temperature.
Typical temperature-sensing points include:
- suction line;
- discharge line;
- gas cooler;
- receiver;
- evaporator inlet;
- evaporator outlet;
- refrigerated cabinet;
- cold-room air return.
Recommended Winsen Temperature Sensors
Pt100-CSMD Thin-Film Platinum Resistance Sensor
Тхе Pt100-CSMD is a compact thin-film platinum resistance temperature sensor with a measurement range of −50°C to 400°C.
It offers:
- high measurement stability;
- compact SMD packaging;
- fast response;
- good vibration and shock resistance;
- suitability for liquid, gas, steam and solid-surface temperature measurement. ([winsen-sensor.com][6])
Pt1000-CSMD Thin-Film Platinum Resistance Sensor
Тхе Pt1000-CSMD provides the same −50°C to 400°C measurement range in a compact 3.2 × 1.6 × 0.5 mm package. Its higher nominal resistance can be valuable in circuits where reducing lead-wire influence and simplifying signal acquisition are important. ([winsen-sensor.com][7])
These sensing elements can support customized probe assemblies for:
- pipe-surface temperature monitoring;
- compressor discharge monitoring;
- gas-cooler temperature control;
- cabinet and cold-room temperature sensing;
- electronic control boards.
The final probe enclosure, cable, thermal interface and sealing design should be developed according to the refrigeration equipment structure.
3. CO₂ Leak Detection for Personnel and Equipment Safety
Although R744 is non-flammable, a significant leak can displace oxygen in enclosed or poorly ventilated spaces.
CO₂ is also colorless and odorless, which means leakage may not be noticed without a dedicated detector. Industry safety guidance highlights high pressure and high-concentration exposure as important hazards that must be considered when designing and servicing R744 systems. ([Copeland][8])
CO₂ leak sensors may be installed in:
- equipment rooms;
- refrigerated storage rooms;
- compressor compartments;
- convenience stores;
- machine enclosures;
- indoor condensing-unit installations;
- service and maintenance areas.
Because CO₂ is heavier than air under typical indoor conditions, detector placement should be determined through a site-specific risk assessment and applicable codes rather than relying on a single universal mounting position.
Recommended Winsen CO₂ Leak Sensor
MH-410D NDIR Industrial CO₂ Sensor
Тхе MH-410D NDIR Industrial CO₂ Sensor is a compact infrared sensor designed for industrial CO₂ concentration measurement.
Available measurement ranges include:
- 0–2,000 ppm;
- 0–6,000 ppm;
- 0–1% vol;
- 0–3% vol;
- 0–5% vol;
- higher ranges available according to project configuration.
It provides UART and analog-voltage outputs, temperature compensation, stable linear output and a typical T90 response time below 30 seconds. ([winsen-sensor.com][9])
NDIR technology is particularly suitable for CO₂ monitoring because it:
- directly detects the infrared absorption characteristics of CO₂;
- does not rely on oxygen;
- offers good target-gas selectivity;
- has no consumable electrochemical reaction;
- supports long-term continuous monitoring.
The MH-410D can be integrated into:
- fixed CO₂ leak alarms;
- commercial refrigeration control panels;
- machine-room monitoring equipment;
- ventilation-control systems;
- portable inspection instruments.
Alarm thresholds, measurement range and calibration strategy must be selected according to local safety regulations, room volume, ventilation design and equipment risk assessment.
4. From Individual Sensors to Intelligent Refrigeration Control
A modern CO₂ condensing unit requires multiple sensor signals to operate safely and efficiently.
A typical sensing and control chain may work as follows:
- Pressure sensors measure high-side and low-side operating conditions.
- Temperature sensors monitor pipe, compressor and refrigerated-space temperatures.
- The controller calculates superheat, thermal load and operating efficiency.
- Valves, compressors and fans are adjusted dynamically.
- A CO₂ sensor monitors the surrounding environment for leakage.
- If abnormal conditions occur, the system can activate alarms, ventilation, shutdown or pressure-protection functions.
This multi-parameter approach improves both control quality and diagnostic capability.
| Monitoring Parameter | Main System Value |
|---|---|
| High-side pressure | Gas-cooler and regulating-valve control |
| Suction pressure | Compressor load and evaporator monitoring |
| Discharge temperature | Compressor protection |
| Suction temperature | Superheat calculation |
| Refrigerated-space temperature | Product and food preservation |
| Ambient CO₂ concentration | Leak warning and ventilation linkage |
Sensor Selection Priorities for R744 Equipment Manufacturers
When selecting sensors for a CO₂ condensing unit, equipment manufacturers should evaluate more than nominal accuracy.
Pressure Range and Overload Capability
The sensor range should cover both normal operating conditions and expected abnormal pressures without sacrificing useful resolution.
Media Compatibility
Pressure-contact materials, seals and process connections must be compatible with CO₂, refrigeration oil and the expected temperature range.
Температурна компензација
Pressure and gas measurements should remain stable across the complete operating-temperature range of the condensing unit.
Време одзива
Fast sensor response helps the controller manage compressors and high-pressure valves during rapidly changing loads.
Vibration Resistance
Compressors, fans and transportation can expose sensors to sustained vibration and mechanical shock.
Output and Communication
Common options include:
- 0.5–4.5 V;
- 0–5 V;
- 4–20 mA;
- I²C;
- UART;
- RS485.
The output should match the control architecture and cable distance.
Functional Safety and Diagnostics
For safety-related monitoring, designers should consider:
- open- and short-circuit diagnosis;
- sensor fault identification;
- redundant measurement;
- alarm latching;
- independent shutdown logic.
Recommended Winsen Sensor Combination
For an R744 commercial condensing-unit project, the following products can form the starting point for technical evaluation:
| Monitoring Need | Recommended Winsen Product | Key Value |
|---|---|---|
| CO₂ refrigerant leak detection | MH-410D NDIR CO₂ Sensor | Optional high-concentration ranges, UART and analog output |
| Refrigeration pressure monitoring | WPCH04 Pressure Transmitter | Up to 40 MPa, fast response, compact integration |
| High-pressure industrial monitoring | WPCK07 Pressure Transmitter | Wide range up to 100 MPa and multiple outputs |
| Pipe and surface temperature | Pt100-CSMD | High stability and −50°C to 400°C range |
| Compact electronic temperature sensing | Pt1000-CSMD | Compact SMD package and reliable long-term measurement |
These products should be matched to the final system requirements through technical evaluation, validation testing and application-specific customization.
Opportunities for Sensor Manufacturers and Refrigeration OEMs
The expansion of CO₂ condensing units creates more than a new refrigeration-equipment category.
It also increases demand for:
- high-range pressure sensing;
- accurate temperature measurement;
- compact CO₂ leak detection;
- integrated control electronics;
- remote fault monitoring;
- predictive maintenance;
- customized OEM sensor assemblies.
As CO₂ systems move into smaller stores and packaged equipment, sensor size, cost, integration efficiency and production consistency become increasingly important.
This provides an opportunity to bring industrial-grade sensing capability into more compact and standardized refrigeration products.
Постављана питања
What is a CO₂ condensing unit?
A CO₂ condensing unit is a packaged refrigeration system using R744 as the refrigerant. It generally includes a compressor, gas cooler or heat exchanger, control components and related safety devices for serving an independent refrigeration load.
Why are CO₂ condensing units becoming more popular?
They provide a practical way to use a natural refrigerant in convenience stores, cold rooms, small-format retail, food-service and retrofit projects without installing a complete centralized rack.
Why do R744 systems require high-pressure sensors?
CO₂ refrigeration operates at considerably higher pressures than many traditional HFC systems, particularly on the transcritical high side. Pressure sensing is therefore essential for control and protection.
Can a conventional indoor-air-quality CO₂ sensor detect an R744 leak?
Only when its range, response time and environmental design match the leak-monitoring requirement. Refrigeration applications may require percentage-level measurement rather than a standard 2,000 ppm indoor-air-quality range.
Which Winsen sensor is recommended for CO₂ leakage?
The MH-410D offers configurable measurement ranges up to 5% vol and higher project options, making it a suitable candidate for fixed CO₂ leak-detection equipment.
Can Winsen pressure sensors be installed directly in an R744 circuit?
The required pressure rating may be available, but direct compatibility must be confirmed based on CO₂ and oil compatibility, sealing, pressure connection, temperature, vibration and certification requirements.
Conclusion: Reliable CO₂ Refrigeration Starts with Accurate Sensing
The North American CO₂ refrigeration market is evolving from primarily centralized supermarket racks toward a wider range of packaged and distributed systems.
CO₂ condensing units can make R744 technology more accessible for convenience stores, cold rooms, food processing, retail expansions and independent refrigeration loads. But their successful adoption depends on reliable pressure control, accurate temperature measurement and effective CO₂ leak monitoring.
Winsen provides pressure, temperature and NDIR CO₂ sensing technologies that can support the development of compact, intelligent and reliable R744 refrigeration equipment.
For sensor selection, customized pressure ranges, probe design, communication output or sample evaluation, please contact our engineering and sales team.
