5 models, 8 to 18kW
compact design

BoxAir Inverter

4 models, 3 to 22 kW
variable speed control


6 models, 10 to 31kW
split system

EasyMaster Indoor Split

6 models, 10 to 31kW
(Indoor) split system


8 models, 6 to 36kW
(Indoor) split system

Air Source Heat Pumps (Air-Water)

Air Source Heat Pumps (ASHP) explained

An Air Source Heat Pump (ASHP) consists of an evaporator and condensor (monobloc system) and typically is positioned outdoor. Here, it draws air through an evaporator where latent heat energy stored in the air is extracted. For split-systems, there will be an indoor unit housing the condensor, compressor and ancillary components with the fan and evaporator located outdooor.


  • Lower efficiency in winter periods


  • Lower capital cost
  • Simple installation
  • Eligible for RHI


What is the efficiency of air source heat pumps?

MasterTherm air source heat pumps boast market leading COP’s (coefficient of performance). A prime example is the BoxAir 45 7-22kW Inverter air source heat pump with a COP of 5.06. However, air source heat pumps are susceptible to weather change. As the extenral temperature drops, so does the COP and overall system efficiency.

What are the space requirements?

The outdoor unit must be placed in open space with good air flow. An important factor is to allow as much space as possible in front of the fan to prevent recirculation. The optimum position is on a southern wall, on a sunny elevation. Units can be wall or roof (flat) mounted if required. For split systems, the maximum distance between evaporator and condensor is 15m.

Will the heat pump heat the house in freezing weather?

MasterTherm heat pumps have the capacity to provide 100% of the heating and hot water demand of the building. All air source heat pumps have in-built immersions fitted as standard. Primarily used in the defrost cycle, in the event of a catastrophic failure, immersions will act as a backup device.

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.

Our best selling, most efficient heat pump

Czech manufactured air source heat pump with regulated output. Inverter technology further reduces energy costs by up to 20% compared to fixed output heat pumps. BoxAir Inverter 30I, COP of 4.6 at A7W35.

BoxAir Inverter