When choosing an air source heat pump water heater, there are two common operating modes: direct heating and circulating heating. Although circulating heating is more common, direct heating heat pumps are gaining attention. They are particularly effective in environments that require high-temperature hot water. Today, we will explore the working principles, pros and cons, and ideal use cases for both types of heat pumps. This will help consumers make informed decisions based on their needs.
Circulating air source heat pumps use a circulating water pump. The pump circulates water in the tank to gradually increase the water temperature. Initially, cold water exchanges heat with the refrigerant. The refrigerant releases heat, raising the water temperature. Once the water reaches a certain level, the system adjusts the cycle times to maintain a stable temperature.
Circulating heat pumps are often used in high-demand environments. These include large commercial projects and public facilities. They provide stable, high-temperature hot water for continuous use. However, as the water temperature increases, the heat exchange efficiency decreases. When the water temperature exceeds 45°C, the compressor’s pressure and temperature rise. This can reduce system efficiency.
Direct heating heat pumps have a simpler design. They do not require a circulating water pump. The refrigerant directly exchanges heat with the water. Direct heating heat pumps work more efficiently at lower water temperatures. The refrigerant can quickly release heat, achieving better heat exchange.
When the water temperature stays below 45°C, both direct heating and circulating heat pumps perform similarly in energy efficiency. However, direct heating heat pumps offer more stable operation. The compressor runs at lower pressures and temperatures, which extends its lifespan and improves efficiency.
Energy Efficiency
Direct heating heat pumps are more efficient with low-temperature water. The refrigerant can quickly exchange heat with water. Circulating heat pumps lose efficiency as the water temperature increases.
System Stability
Direct heating heat pumps have more direct heat exchange. This avoids overloading the compressor due to high temperatures, improving system stability.
Compressor Protection
Circulating heat pumps run at higher temperatures for long periods. This can cause the compressor to overheat, reducing its lifespan. In contrast, direct heating heat pumps maintain more stable conditions, protecting the compressor and extending its life.
Defrost Efficiency
Direct heating heat pumps work more efficiently in cold temperatures. Their refrigerant operates at lower temperatures, which increases evaporation efficiency. This prevents frost buildup and keeps the system running smoothly.
Choosing the right type of air source heat pump depends on the environment. Direct heating and circulating heat pumps each have their ideal use cases.
Direct Heating Heat Pumps: Best for both warm and cold climates. Without a circulating pump, they can quickly respond and provide stable high-temperature water. In warmer climates, they efficiently meet daily hot water needs. In colder climates, they efficiently use low-temperature refrigerants for stable heating. This makes them ideal for air source heat pumps in cold climates.
Circulating Heat Pumps: Ideal for commercial and large residential environments. These heat pumps provide stable hot water for long periods. Their efficiency decreases as water temperature rises, but they can still supply constant hot water. In environments like hotels or schools, circulating heat pumps are the best choice for commercial hot water supply solutions.
