An air source heat pump “dual supply” system offers both summer cooling and winter heating. By combining air conditioning and underfloor heating, it provides seasonal comfort with one unit. The system automatically switches modes with the seasons, enhancing comfort while saving on energy costs. Compared to traditional refrigerant-based systems, the dual supply system avoids excessive dehumidification, providing a healthier indoor environment with balanced humidity.
System Advantages
- Enhanced Comfort: Traditional refrigerant-based systems often over-dehumidify, leading to overly dry air. The dual supply system, however, uses water-based heat transfer, avoiding indoor dryness and creating a more comfortable experience.
- Significant Energy Savings: Operating costs are a quarter of electric floor heating and half of gas boilers, making it more economical than regular air conditioning.
- Multi-Functional Integration: The system integrates air conditioning and heating capabilities, meeting climate control needs year-round with a single unit.
Choosing the System and Calculating Loads
When selecting an air source heat pump for dual supply, it is crucial to match it with the building’s load needs. This choice ensures the unit’s stable operation across various conditions.
Unit Type: Household air-source heat pump dual supply systems commonly use split units. The outdoor unit includes parts like the compressor and air-cooled heat exchanger. The indoor unit (hydronic module) has a water-cooled heat exchanger, water pump, and buffer tank.
Cooling Load (Q1) Calculation Method: In automatic systems, add each room’s hourly cooling load, taking the maximum value. If room usage is uncertain, use the cumulative maximum hourly load, multiplied by a usage factor between 0.5 and 0.7.
Heating Load (Q2) Calculation Method: For continuous floor heating, total heat load is added directly. For intermittent heating, multiply by an extra factor of 1.05 to 1.2. Then, refer to performance tables for unit specifications and capacity charts.
Load Calculation
The unit’s cooling (Qc) and heating capacities (Qh) must meet seasonal cooling (Q1) and heating (Q2) needs. Below are the standard steps for calculations:
- Summer Cooling Load (Qc) Calculation:
- Winter Heating Load (Qh) Calculation:
Confirming Cooling and Heating Capacity: Here, Qc and Qh represent the unit’s nominal cooling and heating capacities. Generally, set the dust and dirt factor (β1) at 1.1. Correction factors, K1 and K2, adjust for outdoor temperatures in winter and summer. The defrosting factor (K3) should also be included. Selected units must satisfy Qc ≥ Q1 and Qh ≥ Q2.
Terminal Unit Selection
Terminal unit design directly affects system performance and temperature distribution. Different terminal equipment and configurations are required for cooling and heating.
- Cooling Terminal: Horizontal Concealed fan coil units in bedrooms are commonly used for cooling. Cooling load and supply/return water temperatures determine the fan coil model and specifications, ensuring efficient cool air distribution.
- Heating Terminal with Underfloor Water Heating: The underfloor heating design must consider pipe layout, loop length, diameter, and spacing. This approach ensures even indoor temperature distribution. Key calculation steps include:
- Heat Emission per Square Meter: Calculate the needed heat emission per unit area for each room.
- Pipe Spacing and Layout: Select pipe spacing (150mm – 300mm) and diameter based on heat needs, ensuring even heating.
- Flow Rate and Pressure Control: Maintain water flow between 0.25 m/s and 0.6 m/s, with hydraulic loss in the least favorable loop under 30 kPa.
Conclusion
In summary, the air source heat pump dual supply system is ideal for modern climate control. It excels in efficiency, comfort, and energy savings. With suitable unit selection and optimized terminal design, it provides reliable year-round heating and cooling. The dual supply system minimizes issues seen in traditional air conditioning. Its cost-effectiveness and environmental benefits make it a popular choice. Selecting the right system gives users a healthier, eco-friendly living environment and improved quality of life.
