Hot water heat pumps
Innovation under pressure
As standard, immersion heaters are not used in any Kensa models, due to their costly implications on end users. Furthermore, Kensa has pioneered an approach to domestic hot water production in its ground source heat pump models removing the requirement for thermostats.
The maximum output water temperature of a heat pump depends upon many factors, including the hot water flow rate through the domestic hot water cylinder coil, the ground temperature and flow rate. So controlling the maximum temperature with a fixed temperature switch is nearly always going to result in a lower water temperature than would otherwise be possible.
The maximum temperature that the heat pump can achieve is directly related to the refrigerant circuit’s maximum pressure, as advised by the compressor manufacture. Kensa has innovated this approach by using a refrigerant pressure switch to terminate the domestic hot water cycle, thus always achieving the hottest water possible leaving the heat pump. Once the heat pump has terminated the domestic hot water cycle an internal timer prevents another cycle from beginning for two hours. This timer is adjustable during the commissioning process.
How it works
When there is a demand for hot water the heat pump switches from space heating mode to hot water mode and the heat pump outlet temperature is increased. The maximum temperature from a heat pump is generally around 50°C, although Kensa High Temperature and Hybrid models are able to deliver hot water to 60°C. The higher the hot water production, the lower the heat pump efficiency.
This hot water is generally piped through an indirect coil mounted in a separate hot water tank and hence the expected tank temperature will be around the 45-48°C range.
Mains pressure cylinder
Any Kensa ground source heat pump can be linked to a mains pressure cylinder to provide domestic hot water although the required output temperature – 45-50ºC – will certainly impact efficiency. One alternative is to provide a mains pressure cylinder complete with immersion heaters and, if possible, link to an Economy Seven, or preferably, an Economy Ten tariff so the water can be heated during low cost periods. If only Economy Seven is available, a larger cylinder might be required to reduce the occasions when higher priced electricity is required to produce hot water.
All cylinder manufacturers provide models which can receive an input from solar panels, if installed, to reduce dependence upon electricity.Read more
Blending the advantages of the standard Twin Compact and High Temperature model, the Hybrid Twin Compact provides efficient heating and higher water temperatures; ideal for scenarios where buildings are modern or well insulated, but the end user requires higher than average hot water temperatures, without the burden of any direct electric top-up for the hot water.Read more
After living with the system over this cold spell we have heat and hot water when we want, the hot water temperature and pressure is lovely, and we have never run out, even after a long hot bubble bath!
We would advise everyone to fit a Kensa heat pump.
Mr & Mrs Coombe, Somerset
Domestic Hot Water on Ground Source Heat Pumps Fact Sheet Version 3
Secondary Hot Water Returns (FS) Fact Sheet Version 5
Bivalent Space Heating with Underfloor and DHW Application Information Sheet Version 3
Space Heating with Underfloor and Domestic Hot Water Production via Solar and Ground Source Heat Pump (Twin Coil) Application Information Sheet Version 3
Space Heating and DHW (AIS) V1 Application Information Sheet Version 1
Space Heating and DHW with Buffer Vessel Application Information Sheet Version 4
Space Heating with DHW and Rads (AIS) V1 Application Information Sheets Version 1
Space Heating with Radiators and Underfloor and Domestic Hot Water Production Application Information Sheets Version 3
Single Coil Domestic Hot Water Cylinder Technical Information Sheet Version 8.2
Twin Coil Domestic Hot Water Cylinder (TIS) Technical Information Sheet Version 8.2
Hot Water Cylinder Selection Guide (TIS) V3 Technical Information Sheet Version 3
Advance Stainless Steel Unvented Hot Water Cylinders for Heat Pump Systems Installation and Commissioning Manual Version 6.4
How to get the best efficiencies Our Technical Director Guy Cashmore explains that whilst the design of the ground side of a ground source heat pump installation is key, for good efficient performance from any heat pump installation, the design of the hot side is equally important.