How the hydronic system impacts Heat Pump performance
Residential heat pumps are designed to perform their best at full capacity. In practice the heat-load (or cooling-load) of the connected house or small building changes constantly. Depending the outdoor temperature, user needs, zone temperature control and other variables, the hydronic system often operates in partial load conditions. This means the flow in the system decreases. Consequently, the differential pressure increases exponentially.
The flow- and pressure fluctuations influence the heat pump's performance. The use of a variable speed pump in the hydronic circuit sufficiently covers the pressure fluctuations. But if the heat pump is equipped with a fixed speed pump, technical issues with, for example, the compressor will be faced. At the same time, the heat pump will lose some of its efficiency resulting in a lower Seasonal Coefficient Of Performance (SCOP).
HPBV High Pressure Bypass Valve
Danfoss HPBV is a self-acting High Pressure Bypass Valve for residential heat pumps with a fixed speed pump. It offers a simple and cost-effective solution to ensure sufficient flow through the heat pump. By using an HPBV the heat pump controller gets the time to react quickly to changing conditions. Besides that, the water temperature sensor will be able to correctly measure the actual flow temperature. By ensuring the minimal flow, the number of alarms and/or compressor stops are significantly reduced.
The HPBV bypass valve is mounted in the between the supply and return connection of the hydronic loop. It automatically opens at increasing differential pressure.
Some of the technical specifications are:
- PN 16
- DN sizes: DN 25, 32, 40
- Delta P setting for DN 25, 32: 0.5 - 2.5 Bar (50 – 250 kPa)
- Delta P setting for DN 40: 1.0 - 3.0 Bar (100 – 300 kPa)
Features and benefits
By using HPBV bypass valves, heat pump systems benefit from:
Improved system reliability
Reduced downtime frequency
Improved end-user satisfaction
The heat pumps specifically benefit from:
Faster restarts of compressor after stop periods
Decrease in internal component damages
Decreased difference between listed and actual SCOP performance