Domestic Hot Water Heat Pump Service Manual
5
The electric heater is activated in case of:
Failure of the heat pump operation, this requires an override command from the end user to be confirmed
Too high or too low air temperature
The quantity of hot water produced is not enough.
Note:
The amount of water heated by the electric heater is at a reduced volume; see the performance data for
these values.
Heating circuit
As depicted in the figure below, the heat pump cycle can be divided in four main processes: compression (1-2),
condensation 2-3), expansion (3-4) and evaporation (4-1) described below.
At the suction of the compressor (1) the superheated gas refrigerant enters the compressor at a low pressure.
In the compressor, the gas is compressed to a higher pressure and temperature level (2).
The gas is first de-superheated and condensed in the condenser, exchanging heat with the water stored in the
tank.
The refrigerant exits the condenser in a subcooled, liquid form (3)
Through the thermostatic expansion valve the pressure of the refrigerant is lowered to allow its evaporation at a
lower temperature (4)
The refrigerant is evaporated in the fin-coil heat exchanger that uses forced air as a heat source (1)
The process goes on until the power supply to the compressor is stopped.
Note:
the extensive use of the
electric heater leads to a higher electricity consumption and it may lead to high
electricity bills. The operation with the heat pump normally consumes more than 3 times less electricity than the
operation with electric heater. The energy released to the condenser (2-3) is, in fact, the sum between the free energy
extracted from the air in the evaporator (1-4) and the energy supplied to the compressor (2-1). On average, the energy
absorbed by the evaporator is more than double of the energy used to run the compressor.
Safety instructions
– Heating circuit
Only skilled and trained technicians shall carry out repair and service of the heat pump circuit.
Before opening the heating circuit, discharge the refrigerant to a level that allows safe working conditions.
The refrigerant can be toxic if inhaled or if in high concentrations.
Special attention should be given if the work is carried out with an open flame.
