Heat pumps and Zoning/TRVs

[DamonHD]

https://www.beama.org.uk/resourceLibrary/university-of-salford---beama-trv-energy-house-report.html

 

Unlike gas central heating systems, TRVs are often omitted from ASHP installations based on concerns that they may reduce system efficiency and increase energy use. However, open-circuit design relies upon accurate sizing calculations and use of an appropriate weather compensation curve, neither of which can be guaranteed. Furthermore, open-circuit design limits occupant control and can lead to overheating in rooms with uncontrolled heat gains. Tests were therefore conducted to measure how trimming room temperatures using TRVs influences internal conditions, ASHP efficiency, and space heating energy consumption.

[JohnMo]

14 minutes ago, DamonHD said:

https://www.beama.org.uk/resourceLibrary/university-of-salford---beama-trv-energy-house-report.html

 

Unlike gas central heating systems, TRVs are often omitted from ASHP installations based on concerns that they may reduce system efficiency and increase energy use. However, open-circuit design relies upon accurate sizing calculations and use of an appropriate weather compensation curve, neither of which can be guaranteed. Furthermore, open-circuit design limits occupant control and can lead to overheating in rooms with uncontrolled heat gains. Tests were therefore conducted to measure how trimming room temperatures using TRVs influences internal conditions, ASHP efficiency, and space heating energy consumption.

Only thing you have to watch is actual engagement water capacity with a heat pump or boiler. To prevent short cycling you need to maintain 20L of system capacity per min output kW - any radiator or UFH circuit operated by a TRV or thermostat is basically excluded from the capacity calculation. Plus you need to ensure minimum flow rate is maintained in all operating modes. If you are not careful this can drive a buffer or volumiser. A buffer will add costs for vessel and additional pump, it can lead to flow temperature distortion and reduced CoP. A volumiser adds cost during install.

[JohnMo]

Observations the untrimmed room temperature is higher than that used for trimmed, TRV and smart trv, so no surprise you use less energy by lowering the room. Your CoP will remain similar as you have the same flow temperature. 

 

Achieving a reduced house temp via running a second set point would have resulted in an increased CoP and further reduced energy consumption - due to lower flow temperature. So why not add use native controller for the heat pump to manage setbacks, if you need them. Or just get house to sit at a stable lower temperature and take a win for simplicity, less cost upfront.