12 models, 7 to 65 kW
compact design

AquaMaster Inverter

5 models, 3 to 48 kW
variable speed control

AquaMaster Inverter Combi

3 models, 3 to 22Kw
integral DHW tank

Water Source Heat Pumps (WSHP)

Water Source Heat Pumps (WSHP) Explained

A Water Source Heat Pump (WSHP) harnesses latent heat in water. The heat pump will extract water be it from a river, pond, or more commonly a waterwell. The water is filtered and then taken back to a heat exchanger at the heat pump where the latent heat is extracted. The water is then returned and the process starts again depositing the water back to the river, pond or second waterwell. When using a waterwell, there must be a minimum distance of 10m between the wells, preferably ‚downstream‘.


  • a small number of suitable locations
  • may require chemical treatment


  • High efficiency
  • Short payback time
  • Lower cost


What is the efficiency of Water Source Heat Pumps (WSHP)

It is the most effective type of heat pump. Groundwater is a constant average temperature of approx. 10 ° C that does not change with temperature changes on the surface. It is therefore the ‚hottest‘ source supply. COPs for water-water units can be in excess of 5. Savings are typically better with a water-water unit at around 80%.

Requirements for collector/source: waterwell

Water is extracted through a waterwell drilled to depths of between 40-70m. Temperatures of open loop waterwell systems are in the region of 10*c.

It is necessary to ensure that there is a sufficient source of natural water. For an average house, we would require approximately 0.5 liters / sec.

We would always recommend conducting hydrogeological assessments by way of pumping tests. The well will be pumped for a minimum of 14 days to ascertain the ‚recharge rate‘ of said well. If, after 14 days, the well is not exhausted of water or affecting neighbouring wells, then installation can commence. The Environment Agency/Natural Resources Wales (NRW) may need to issue permits dependant on the amount of water required. Please discuss with your installer.

Requirements for collector/source river, pond etc.

This is a similar solution to above, with the disadvantage of a lower source temperature of approximately 5*c.

There are two types of extraction here, both closed and open loop. Closed loop uses a brine/antifreeze solution pumped through PE pipe placed on the bed of a river/lake/pond.

There is also the possibility of using an open loop system whereby water is extracted at one point, taken to the heat pump and discharged at another point (located downstream). When extracting from a stream, we would recommend installing a ‚sump‘ with natural filtration methods. Please discuss with your installer.

Sizing ground-water heat pumps

The AquaMaster range can be used in either a monovalent system, or bivalent. They have the capacity to provide 100% of the heating and hot water requirement when sized correctly. It is critical that the ground collector be sized according to house demand and not the capacity of the heat pump.

How to maximise your savings

1st The heat pump

The heat pump must be sized to meet 100% of the demand of a building. Oversizing and undersizing may result in excessive running costs. MasterTherm Online Control combined with the latest technology and a robust design allows us to offer 7-year warranty on all parts of the heat pump. MasterTherm heat pumps must only be installed by certified personnel. For units under 45kW, please ensure that your installer is a member of the microgeneration certification scheme (MCS).

2nd Efficiency or heating factor (COP)

The higher the input temperature of the heat pump and the lower the output temperature, the higher the efficiency. A desuperheater can, when fitted, produce higher and more efficient domestic hot water. Hot water runs when the compressor is running as a "byproduct" to heat domestic hot water.

3rd System solutions

MasterTherm heat pumps are designed and equipped with control and pumps to circulate heat to the desired distribution system. There is no requirement to incude additional pumps. Everything required is included in the appliance. Simple and reliable installation.

High Efficiency Heat Pumps, AQ45I, COP 6,3 at W10W35

Inverter technology with the latest BLDC compressors and electronic injection pushes the performance, and increases the overall efficiency. Expect all the usual MasterTherm refinements including 7 year warranty and internet control.

AquaMaster Inverter