Plan your cold room refrigeration system
Designing a cold room starts with the application: required temperature, room size, product load, door openings, installation location, refrigerant choice, and local regulations. A reliable cold room refrigeration system normally combines a condensing unit, evaporator, expansion valve, solenoid valve, controller, filter drier, refrigerant piping, sensors, and electrical protection.
Use the checklist below to plan a walk-in cooler or freezer before selecting products
Key decisions before building a cold room
| Decision | What to check | Why it matters |
|---|---|---|
| Application | Cooler, freezer, food retail, restaurant, hotel, dairy, meat processing, bakery, laboratory, or pharmaceutical storage | The application affects temperature range, product load, pull-down requirements, humidity, controls, and alarm needs. |
| Target temperature | Chilled storage, frozen storage, or dual-temperature operation | Cooler and freezer rooms need different evaporator, compressor, defrost, and control strategies. |
| Room size and product load | Room volume, product temperature, loading frequency, and door openings | High traffic or warm product loading increases the required cooling capacity. |
| System type | Self-contained, remote condensing unit, or centralized system | The system type affects installation complexity, heat rejection, service access, noise, and refrigerant strategy. |
| Condensing unit location | Rooftop, ground level, outdoor wall, indoor technical room, or machine room | Location affects ambient temperature, pipe routing, ventilation, service access, and noise. |
| Refrigerant path | A1 retrofit, A2L, CO₂, A3 where applicable, or other approved low-GWP options | Refrigerant choice affects safety requirements, component compatibility, charge limits, system pressure, and regulation. |
| Expansion technology | TXV or electronic expansion valve | The choice affects control precision, system cost, commissioning, monitoring, and suitability for advanced systems. |
| Controls and monitoring | Temperature control, defrost, alarms, fans, lighting, pressure inputs, and remote monitoring | Controls help maintain stable temperature, support defrost, protect the system, and alert operators. |
| Safety and compliance | Local regulations, A1, A2L, A3 or CO₂ requirements, electrical protection, ventilation, leak detection, and service access | Safety requirements vary by refrigerant, charge, room size, installation location, and local codes. |
Full bill of materials for a walk-in cooler or freezer
A complete walk-in cooler or freezer requires more than the refrigeration unit. Use this bill of materials as a planning checklist.
| Category | Standard walk-in cooler / freezer | Additional checks for A2L refrigerants | Additional checks for CO₂ systems |
|---|---|---|---|
| Structural enclosure | Insulated wall panels, ceiling panels, floor panels, structural supports, panel joints | Check room volume in relation to refrigerant charge and ventilation needs | Check system layout and equipment access for CO₂-rated components |
| Door and sealing | Insulated door, door frame, hinges, handle, door closer, emergency release, threshold, gaskets | Check sealing and ventilation strategy if leak detection or mitigation is required | Check safe access and service layout around CO₂ equipment |
| Refrigeration unit | Condensing unit or compressor/condenser assembly, evaporator or unit cooler | Use A2L-approved equipment approved for the selected refrigerant | Use CO₂-rated refrigeration architecture and pressure-rated components |
| Refrigerant flow control | Thermostatic expansion valve, electronic expansion valve, solenoid valve, check valve, shut-off valves | Check valve and coil compatibility with the A2L- approved equipment approved for the selected refrigerant | Use CO₂-approved valves and components rated for CO₂ pressures |
| System protection | Filter drier, sight glass, pressure switches, pressure sensors, service valves | Check safety shut-off logic, leak detection, and alarm integration where required | Check high-pressure safety devices, pressure sensors, and CO₂-specific protection |
| Controls | Cold room controller, temperature sensors, defrost control, fan control, alarms, monitoring | Check whether leak detection, ventilation, or safety reset must be integrated into controls | Check controllers and sensors suitable for CO₂ system pressure and control logic |
| Electrical | Control panel, wiring, power supply, protective devices, lighting, switches | Check ignition-source control and suitability of electrical components near possible leak points | Check electrical and control requirements for high-pressure CO₂ system components |
| Refrigerant piping | Liquid line, suction line, discharge line, insulation, pipe supports, penetration sealing | Check pipe routing, refrigerant charge, and compatibility with safety requirements | Use CO₂-rated piping, fittings, and installation practices |
| Commissioning | Leak test, evacuation, refrigerant charge, superheat, subcooling, defrost, alarms, controller settings | Verify charge limits, detection logic, ventilation response, and service labeling | Verify pressure settings, safety devices, controls, and CO₂ operating conditions |
How to size a condensing unit for a cold room
Select the condensing unit based on the real cooling load, not only the room volume. The required capacity depends on the target temperature, ambient temperature, insulation, product load, door openings, operating hours, evaporator design, refrigerant, required pull-down time and other heat loads such as lights, fan, machinery, personal, defrost loads etc.
For high ambient conditions, use the selected condensing unit’s performance data at the expected outdoor temperature. A condensing unit selected only at standard conditions may be undersized if it operates in a hot outdoor location, rooftop installation, poorly ventilated area, or machine room with high surrounding temperature.
| Sizing step | What to do |
|---|---|
| 1. Define the application | Identify whether the room is a cooler, freezer, dual-temperature facility, restaurant walk-in, grocery store, processing room, or storage room. |
| 2. Set the target temperature | Define room temperature, evaporating temperature, and whether the room must pull down warm product quickly. |
| 3. Estimate the heat load | Include product load, transmission load, door openings, people, lights, fans, defrost, equipment heat and any other heat load affecting the refrigerated space. |
| 4. Check ambient conditions | Correct the selection for expected condensing temperature and outdoor or machine-room ambient conditions. |
| 5. Choose refrigerant and system type | Select the refrigerant path before final component sizing. |
| 6. Verify component compatibility | Check the condensing unit, evaporator, expansion valve, solenoid valve, controller, filter drier, and piping together. |
| 7. Validate in selection tools | Use validated selection data and software before finalising the system. |
Danfoss Coolselector®2 can support selection of condensing units, compressors, valves, and other system components, and the commercial applications module can help calculate cold room loads for a specific refrigerant.
TXV or EEV: which expansion valve should you choose?
Both thermostatic expansion valves and electronic expansion valves regulate refrigerant flow into the evaporator. The right choice depends on application complexity, refrigerant, control strategy, budget, service expectations, and required monitoring.
| Decision factor | TXV | EEV |
|---|---|---|
| Best fit | Standard walk-in coolers and freezers with stable operating conditions | Systems needing higher control precision, monitoring, adaptive control, or advanced refrigerant strategies |
| Complexity | Lower | Higher |
| Commissioning | Mechanical setup and superheat adjustment | Requires compatible controller, sensors, and parameter setup |
| Budget | Usually lower initial cost | Usually higher initial cost but more control capability |
| Monitoring | Limited without extra sensors and controls | Better fit where system data, alarms, and control integration are required |
| Refrigerant transition | Must be checked for refrigerant compatibility, capacity, and bulb charge | Must be checked for refrigerant parameters, controller compatibility, and operating range |
| Service needs | Familiar technology for many installers | Requires technician familiarity with electronic control and diagnostics |
What does a solenoid valve do in a cold room?
A solenoid valve controls refrigerant flow in the refrigeration circuit. In cold room systems, it is commonly used for shut-off and control functions in liquid, suction, or hot gas lines.
If the solenoid valve is incorrectly selected or sized, the system may experience unstable refrigerant flow, pressure drop, poor evaporator feed, pump-down problems, or unreliable control. Always check refrigerant type, pipe location, capacity, pressure drop, valve size, coil type, and operating conditions before final selection.
Danfoss EVR and related solenoid valves are positioned for controlling refrigeration circuits across liquid, suction, and hot gas lines.
Optyma™ condensing units for easier cold room installation
Optyma™ condensing units are designed for small and medium cold room applications where installers need a compact, reliable, and practical refrigeration solution. As packaged condensing units, they help simplify system planning by combining key refrigeration functions in one outdoor unit and supporting efficient operation across different cold room applications.
For installers, Optyma™ supports a more straightforward installation process by reducing the number of separate system elements that need to be selected and integrated on site. The range is designed for easy installation, practical service access, and compatibility with current and future refrigerant strategies, including lower-GWP and A2L-ready options.
When used together with Danfoss cold room controllers, expansion valves, solenoid valves, and filter driers, Optyma™ condensing units support a complete cold room solution that is easier to select, install, commission, and maintain.
Why choose Optyma™ for cold rooms?
| Installer need | How Optyma™ helps |
|---|---|
| Faster installation | Packaged condensing unit design helps reduce installation complexity compared with building up the refrigeration system from individual components. |
| Easier commissioning | Optyma™ solutions can be combined with Danfoss controllers that support simple setup, start-up guidance, and practical commissioning. |
| Reliable cold room operation | Optyma™ condensing units are designed for commercial refrigeration applications where stable cooling performance and serviceability are important. |
| Refrigerant flexibility | Optyma™ supports refrigerant transition strategies, including lower-GWP and A2L-ready options depending on the selected model. |
| Practical service access | The packaged design helps installers and service technicians work with a defined unit architecture instead of a fully custom-built outdoor system. |
| Complete system compatibility | Optyma™ works as part of a wider Danfoss cold room system with controllers, valves, expansion devices, filter driers, and other refrigeration components. |
Can one system serve both a chilled room and a freezer room?
A chilled room and a freezer room can sometimes be served by one broader refrigeration architecture, but the decision depends on temperature levels, load profile, system size, energy strategy, redundancy needs, and service requirements.
| Design option | Best fit | Main considerations |
|---|---|---|
| Separate systems | Smaller sites, restaurants, hotels, or applications where simple service and redundancy are important | Higher number of units, but simpler separation between cooler and freezer operation |
| Shared system with multiple evaporators | Sites with related temperature zones and suitable controls | Requires careful capacity control, defrost strategy, pressure control, and valve selection |
| Centralized system | Larger stores, supermarkets, or facilities with several cold rooms | Better fit where multiple rooms, monitoring, and system-level control are needed |
| CO₂ system architecture | Larger or sustainability-driven applications | Requires CO₂-specific design, high-pressure components, and trained service support |
A2L cold room design: additional components and safety checks
A2L refrigerants are mildly flammable lower-GWP refrigerants. They can support the transition away from higher-GWP refrigerants, but they should be used as part of an A2L-ready system design.
| A2L design area | What to check |
|---|---|
| Refrigerant charge | Check charge limits based on refrigerant, room size, application, equipment listing, and local regulations. |
| Leak detection | Confirm whether refrigerant leak detection is required and how alarms or safety actions should be triggered. |
| Ventilation | Check whether mechanical ventilation, emergency ventilation, or natural circulation is required. |
| Components | Confirm compatibility of compressor, condensing unit, evaporator, valves, fans, controllers, sensors, and electrical components. |
| Electrical safety | Check ignition-source control and whether components near possible leak points are suitable for the application. |
| Safety controls | Check whether compressor shutdown, valve isolation, fan activation, manual reset, or alarm handling is required. |
| Local regulations | Confirm applicable standards and local Authority Having Jurisdiction requirements before installation. |
A2L walk-in cooler installations may require leak detection, safety shut-off valves, ventilation or fan evacuation, manual reset, A2L-compatible electrical components, refrigerant labeling, and compatible controls and sensors depending on refrigerant charge, system design, room volume, equipment listing, and local code requirements.
CO₂ cold room design: components and commissioning checks
CO₂, also known as R744, is a very low-GWP refrigerant option, but it operates at higher pressures than many legacy refrigeration systems. CO₂ systems therefore require components, valves, sensors, piping, and controls designed for CO₂ operation.
| CO₂ design area | What to check |
|---|---|
| Pressure rating | Confirm that valves, sensors, piping, safety devices, and controls are rated for the relevant CO₂ pressure levels. |
| System architecture | Define whether the project uses a transcritical, cascade, secondary, pump-circulated, or other CO₂ architecture. |
| Expansion and bypass control | Use CO₂-compatible valves and controls for pressure and refrigerant flow management. |
| Commissioning | Check pressure settings, safety devices, controller logic, valve operation, and system stability. |
| Service readiness | Ensure technicians have the tools, training, and procedures needed for CO₂ systems. |
Danfoss CCMT is an electrically operated valve designed specifically for CO₂ refrigeration systems and can function as an expansion valve or gas bypass valve in CO₂ applications where precise pressure and flow control are required.
Pipe sizing and refrigerant line routing
Pipe sizing affects refrigerant velocity, pressure drop, oil return, system efficiency, and compressor reliability. Refrigerant pipes should be sized for the refrigerant, capacity, line length, elevation change, and operating temperature.
| Line type | What to check |
|---|---|
| Liquid line | Pressure drop, refrigerant velocity, insulation needs, and compatibility with selected refrigerant |
| Suction line | Oil return, pressure drop, insulation, velocity, and evaporator operating conditions |
| Discharge line | Discharge temperature, pressure rating, vibration, heat exposure, and routing |
| Building penetrations | Fire stopping, sealing, insulation continuity, condensation control, and service access |
| Long pipe runs | Pressure drop, oil return, refrigerant charge, and manufacturer guidance |
| A2L systems | Charge, leak risk, routing through occupied areas, leak detection, ventilation, and local regulations |
| CO₂ systems | Pressure rating, safety devices, compatible fittings, CO₂ service requirements, routing through occupied areas, and leak detection |
Split vs. packaged cold room systems
Small and medium-sized rooms can be built with different refrigeration system layouts. The right choice depends on available space, installation complexity, service access, refrigerant strategy, and how much flexibility the site requires.
| System type | How it works | Best fit | Danfoss fit |
|---|---|---|---|
| Split / remote condensing unit system | The evaporator is installed inside the cold room, while the condensing unit is installed outside, on a rooftop, or near the building. | Small and medium cold rooms where heat rejection should be kept outside the refrigerated space and installers need flexibility in system design. | Optyma™ condensing units, Optyma™ Control, expansion valves, solenoid valves, filter driers, and cold room components support this type of installation. |
| Packaged / monoblock-style system | Refrigeration components are supplied in a more compact, integrated unit to simplify installation. | Smaller cold rooms where installation speed, compact design, and reduced on-site complexity are priorities. | Danfoss supports compact cold room concepts with packaged condensing unit options and compatible controls and refrigeration components. |
| Centralized system | Multiple cold rooms or refrigerated areas are connected to one central refrigeration system. | Larger stores or facilities with several rooms, multiple temperature zones, or broader monitoring needs. | Danfoss controllers, system managers, valves, sensors, and refrigeration components support more advanced cold room system architectures. |
Electrical requirements for cold room refrigeration systems
Electrical requirements depend on system size, compressor type, fan motors, defrost method, controller, sensors, lighting, alarms, refrigerant type, and local electrical codes. Always confirm requirements with qualified electrical and refrigeration professionals.
| Electrical area | What to check |
|---|---|
| Power supply | Voltage, phase, frequency, load, and local electrical requirements |
| Protection | Circuit protection, overload protection, disconnects, and safe service access |
| Controls | Controller power, control wiring, sensors, alarms, fans, defrost, and safety interlocks |
| Defrost | Electric defrost load, drain heater, timing, protection, and controller setup |
| Monitoring | Alarm outputs, remote monitoring, communication wiring, and integration with BMS or supervisory systems |
| A2L systems | Electrical component suitability, ignition-source control, leak detection, ventilation, and safety reset logic |
| CO₂ systems | Pressure sensors, safety controls, valve control, leak detection and high-pressure system protection |
Refrigerant selection framework for new cold room builds
| Refrigerant path | Best fit | Key design considerations |
|---|---|---|
| Lower-GWP A1 refrigerants | Existing systems, retrofit paths, and projects needing non-flammable refrigerant continuity | Check compressor approval, expansion valve setup, oil compatibility, component sizing, and regulations. |
| A2L refrigerants | New lower-GWP systems where A2L-ready equipment and safety requirements can be met | Check charge limits, leak detection, ventilation, electrical safety, component compatibility, and local regulations. |
| CO₂ / R744 | Projects prioritizing very low GWP and a non-flammable refrigerant pathway | Requires CO₂-specific architecture, pressure-rated components, CO₂ controls, leak detection and trained service capability. |
| R290 / propane | Selected compact or self-contained applications where charge limits and safety requirements can be met | Requires strict safety compliance because propane is highly flammable. |
| Legacy HFC systems | Existing installed base or short-term continuity where allowed | Check phase-down rules, service availability, retrofit options, and long-term refrigerant strategy. |
Danfoss product quick-reference by system need
| System need | Danfoss product area |
|---|---|
| Condensing unit for small and medium cold rooms | Optyma™ condensing units |
| Room temperature, defrost, alarms, fans, and protection | Optyma™ Control and broader ADAP-KOOL controller ranges |
| Refrigerant injection and superheat control | Thermostatic expansion valves and electronic expansion valves |
| Refrigerant circuit shut-off and control | EVR and related solenoid valves |
| Moisture, acid, and particle protection | DML / DCL filter driers |
| Pressure and temperature monitoring | Sensors and pressure controls |
| A2L refrigerant leak detection | A2L refrigerant detection sensors |
| CO₂ pressure and flow control | CO₂-compatible valves and controls, including CCMT for selected CO₂ applications |
| System selection and sizing | Coolselector®2 and Danfoss selection tools |
FAQ
Cold room system design and component selection
Best condensing unit for a commercial walk-in freezer?
Select a low-temp unit with adequate BTU/hr for freezer load, e.g., Danfoss Optyma™ Plus for -10°F.
How do I size a refrigeration system for a walk-in cooler, and does the refrigerant choice change what equipment I need?
Calculate heat load from product, infiltration, and ambient, then match BTU/hr to compressor capacity.
What do I need to build a walk-in cooler from scratch with A2L refrigerant — and are there extra safety components required by the AIM Act?
- According to ASHRAE Standard 15-2022 and the U.S. EPA AIM Act, building a walk-in cooler with A2L refrigerant requires:
- Core components: Insulated panels, door, condensing unit, evaporator, piping, expansion valve, controller, lighting.
- Safety components:
- Leak detection sensors that trigger alarms and shut down compressors when refrigerant concentration exceeds 25% of the Lower Flammability Limit (LFL).
- Mechanical ventilation ≥ 1 air change/hour.
- Refrigerant charge limits ≤ 0.150 kg/m³ of room volume for certain A2Ls in occupied spaces.
- Emergency shut-off controls accessible to operators.
- AIM Act compliance: Proper refrigerant labeling, leak repair within 30 days, and safe disposal procedures per 40 CFR Part 82 — Protection of Stratospheric Ozone.
What expansion valve do I need for a walk-in freezer, and should I go with a thermostatic or electronic valve?
Use a thermostatic expansion valve sized for low-temp load and refrigerant type, e.g., Danfoss TE5 or TU series. Do not use nominal capacity of TXV when matching evaporator capacity.
What controller should I use for a commercial walk-in cooler?
Use an electronic controller with temperature, defrost, and alarm functions, e.g., Danfoss ERC series.
What are the commissioning steps after installing a new walk-in cooler — what do I need to check before handing it over?
Verify components match capacity wise for proper balance. Verify pressure tests, vacuum, refrigerant charge, controller settings, and temperature stability. Ensure proper voltage with compressors running and verify discharge temperature is within manufacturers specifications.
What components do I need for a small dairy plant that needs both a chilled room and a freezer — can I run them off the same system?
For a small dairy plant:
- Core components: Insulated panels, hygienic flooring, condensing unit(s), evaporators, humidity control, wash-down lighting.
- Dual-zone operation:
- Feasible using a multiplex refrigeration rack with separate evaporators and controls for each zone.
- Independent temperature regulation (e.g., chilled room at 39°F, freezer at -0.4°F).
- Requires load calculation and defrost management per ASHRAE Standard 90.1 for energy efficiency.
How do I get the refrigerant charge right for a walk-in cooler, and what happens if I put in too much or too little with A2L?
Use manufacturer’s guidelines based on pipe length, evaporator, and condenser volume. Verify with subcooling comparing to manufacturers specifications.
What pipe sizing guidelines apply to a walk-in cooler refrigeration system?
Follow refrigerant-specific velocity and pressure drop limits per ASHRAE standards.
How do I select an electronic expansion valve vs a thermostatic valve for a walk-in cooler?
Choose EEV for precise control and variable load; TEV for simpler, fixed-load systems.
Where's the best place to put a condensing unit for a walk-in cooler — rooftop, ground level, or inside? What are the trade-offs?
- Rooftop: Saves floor space; requires weather protection; harder service access.
- Ground level: Easy maintenance; shorter pipe runs; may require security fencing.
- Indoor machine room: Stable conditions; weather protection; requires ventilation per ASHRAE Standard 15-2022; higher installation cost.
What do I need to know about running refrigerant lines through a building to a walk-in cooler — how long can they be, and what are the rules?
Use shortest route possible, support lines, and insulate suction lines.