3.1.5 Defrost function
During operation the air heat exchanger is cooled by the energy exchange, at the same time the humidity cau-
ses it to become covered in frost at low outdoor temperatures. iTec has an automatic function to defrost the air
heat exchanger using the energy from whatever heat source is currently active.
Defrosting is initiated by low temperature in the refrigerant circuit after the air heat exchanger and, among
other things, is dependent on outdoor temperature, humidity and operating time. The length of defrosting var-
ies depending on the extent of freezing of the air heat exchanger. Defrost continues until the air heat exchang-
er is free of ice and the temperature starts to rise in the refrigerant circuit. After completed defrosting the heat
pump returns to the operating mode before defrosting.
3.1.6 Cooling function
The heat pump produces cooling through a similar process as the defrosting function.
Cooling function is started by the heat pump control unit and is primarily temperature controlled. The house's
heating system is cooled by transferring heat to the refrigerant circuit, which is then given off in the air heat
exchanger.
If the hot water heater is installed, the control unit will alternate between cooling and hot water production
with prioritisation for the hot water requirement.
3.1.7 Electronic expansion valve
When the refrigerant passes the expansion valve the pressure and temperature of the refrigerant are reduced.
In this way the energy in the outdoor air is available to the refrigerant circuit. By automatically regulating the
opening degree of the expansion valve we optimise the flow in the refrigerant circuit in different operating
conditions. Control of the electronic expansion valve is based on the measurements of temperatures and pres-
sures in the refrigerant circuit and outside air.
3.1.8
Auxiliary heat
The auxiliary heater is included in iTec Total. An auxiliary heater consists of an immersion heater, which is loca-
ted on the supply pipe before the reversing valve.
If the auxiliary heater is installed it engages AUTO mode automatically when the heat demand is greater than
the heat pump’s capacity.
Immersion heaters in iTec Total series intended for 400V supply have three heating elements (IMM.HEAT 1, 2
and 3) and can be controlled in five power stages.
Products for 230V have two heating elements (IMM. HEAT 1 and 2) and are controlled in three power stages.
The two stages 4 and 5 cannot be engaged when the compressor is in operation as opposed to stages +4 and
+5 where it is possible.
User Guide
iTec
Thermia Värmepumpar VUJSI102
11
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