Timed Keep Warm Function
Instantaneous HIU’s generally include a stand-by mode ‘keep warm’ function, which keeps the primary pipework to the HIU and the domestic hot water plate warm, to ensure a quick hot water response.
The amount of energy used to maintain this function is often underestimated and in many cases not even considered. It’s Important that the Keep Warm function is thermally controlled so that it uses a minimal amount of heat network energy.
ModuSat XR HIUs are electronically controlled, which means the ‘keep warm’ function can be programmed by the resident and switched off during periods of no demand. Also, the electronic control ensures that the minimum amount of primary flow is used to accurately match the hot water plate set point.
Keep Warm & the BESA HIU Test Standard
One of the tests under the BESA HIU standard is to Measure the return temperature with Keep Warm facility switched on. This data is used along with space heating and DHW return temperatures to calculate the overall Volume Weighted Average Return Temperature (VWART).
Real life VWART and network efficiency can be greatly improved by reducing the Keep Warm temperature settings and enabling residents to set their own schedules for the timing of the keep warm function to reflect more realistic periods of occupation.
A key feature of the Evinox ModuSat® XR’s Smart Connected Control is its ability to provide remotely adjustable Keep Warm set points and scheduling, meaning that real life average annual return temperatures can be further reduced, with a suitable balance struck between the speed of DHW delivery for the home owner and the overall network efficiency requirements of the operator.