Cold Room Compressor Sizing: How Many HP Do You Need?
Room volume alone cannot determine the compressor size a cold room needs. The starting point is a cooling load calculation, followed by an assessment of the compressor and other system components that can meet that load at the design conditions. The catalogue HP rating is not enough on its own.
How many HP does a 20 cubic metre cold room need?
There is no single HP rating that suits every 20 m³ cold room. Two rooms of the same size may have different target temperatures, insulation, door opening patterns, product intake quantities and incoming product temperatures. These differences change the required cooling capacity.
For example, storing products that are already chilled creates a different load from cooling incoming warm products within a specified time. Storing frozen products and freezing products also need separate assessments.
What information is needed for compressor selection?
Prepare the following information for the load calculation and equipment assessment:
- Room and insulation: Internal dimensions, panel material and thickness, and floor and ceiling insulation.
- Target temperature and product: Room operating temperature, product type, daily intake, incoming temperature and required cooling or freezing time.
- Usage: Door dimensions and opening frequency, people working inside, and additional heat loads such as lighting, fans and defrost.
- Installation environment: Ambient temperature, condenser location and ventilation conditions.
- System and electricity: Refrigerant, model details of any existing equipment, and supply voltage, phase and frequency.
Danfoss’s cold room design and component selection guide likewise includes product, insulation, door use and additional heat sources in the load calculation, alongside checks for ambient conditions and component compatibility when selecting equipment.
What is the difference between HP and cooling capacity?
HP is a unit of power. A compressor’s catalogue HP class does not directly express its cooling capacity. Cooling capacity is given in W or kW at specified operating conditions. Two models in the same HP class should not be assumed to provide the same cooling capacity.
The evaporating temperature in a capacity table is not the room air temperature; it is the temperature at which the refrigerant evaporates in the evaporator. Condensing temperature is also different from ambient temperature. The room thermostat setting therefore cannot simply be used as the evaporating temperature when reading the table.
An example from the Zingfa QR3-74 capacity table
The Zingfa QR3-74, listed in our catalogue as 3 HP, has the following cooling capacities in its manufacturer’s datasheet:
| Evaporating temperature | Cooling capacity |
|---|---|
| -5 °C | 7,891 W |
| -10 °C | 6,189 W |
| -15 °C | 4,692 W |
These figures apply to R404A, 50 Hz, 45 °C condensing temperature, 35 °C return gas temperature and 8.3 K subcooling. The source is the datasheet’s “Refrigerating capacity (watts)” table.
The example shows how one model’s capacity changes with evaporating temperature. It is not a model recommendation for a particular room size; different operating conditions require the corresponding capacity data.
Manufacturer capacity tables for the Zingfa models
The figures below are taken from each model’s linked datasheet, from the 45 °C condensing column of the “Refrigerating capacity (watts)” table. All models R404A, 50 Hz. See the relevant datasheet for other evaporating and condensing temperatures.
QR series. Test condition: 35 °C return gas, 8.3 K subcooling.
| Model | Power | Phase | -5 °C evaporating | -10 °C evaporating | Datasheet |
|---|---|---|---|---|---|
| Zingfa QR-44 | 2 HP | Single phase 220 V | 4,836 W | 3,690 W | |
| Zingfa QR3-44 | 2 HP | Three phase 380 V | 4,836 W | 3,690 W | |
| Zingfa QR-58 | 2.5 HP | Single phase 220 V | 6,291 W | 4,876 W | |
| Zingfa QR3-58 | 2.5 HP | Three phase 380 V | 6,291 W | 4,876 W | |
| Zingfa QR3-74 | 3 HP | Three phase 380 V | 7,891 W | 6,189 W | |
| Zingfa QR3-90 | 4 HP | Three phase 380 V | 8,763 W | 6,521 W | |
| Zingfa QR3-112 | 5 HP | Three phase 380 V | 11,155 W | 8,496 W | |
| Zingfa QR3-124 | 6 HP | Three phase 380 V | 13,155 W | 10,150 W | |
| Zingfa QR3-134 | 7 HP | Three phase 380 V | 14,123 W | 10,950 W |
QL series. Test condition: 32 °C return gas, 0 K subcooling.
| Model | Power | Phase | -25 °C evaporating | -30 °C evaporating | Datasheet |
|---|---|---|---|---|---|
| Zingfa QL-52 | 2.5 HP | Single phase 220 V | 2,627 W | 1,890 W | |
| Zingfa QL3-52 | 2.5 HP | Three phase 380 V | 2,627 W | 1,890 W | |
| Zingfa QL-62 | 3 HP | Single phase 220 V | 3,085 W | 2,164 W | |
| Zingfa QL3-74 | 3 HP | Three phase 380 V | 3,653 W | 2,562 W | |
| Zingfa QL3-112 | 5 HP | Three phase 380 V | 5,360 W | 3,811 W | |
| Zingfa QL3-134 | 7 HP | Three phase 380 V | 6,788 W | 4,956 W |
How should a model that meets the load be assessed?
Meeting the calculated load is one part of selection. The model must remain within the manufacturer’s permitted operating limits and be assessed together with the evaporator, condenser, expansion device and other components. Chilled storage and freezing applications require consideration of product load, cooling time and defrost arrangements as well as target temperature.
Using a fixed temperature difference or safety percentage for every room and choosing the first model that meets the resulting figure is therefore insufficient. Final selection should be verified by the refrigeration professional designing the system, using the calculation and manufacturer data.
Single phase or three phase?
The electrical supply must match the voltage, phase and frequency on the model’s label. According to the manufacturer’s datasheets, the QR-44 and QR3-44, QR-58 and QR3-58, and QL-52 and QL3-52 pairs have identical cooling-capacity tables. In our catalogue, Zingfa models of 4 HP and above are listed in three phase only.
Browse our Zingfa compressor catalogue for models and the technical documents linked from their product pages. For product information, pricing and current availability, contact TURA Soğutma.