▪
The defrosting sequence starts when the temperature of the brine reaches its set parameter for defrost-
ing.
▪
The compressor is stopped so that the defrosting sequence does not load the compressor unnecessari-
ly. But the compressor is not stopped when it produces hot water because the water heater is cooled
during the defrosting sequence. The fan on the outdoor unit is stopped to reduce the duration of the
defrosting sequence.
▪
The shunt valve in the heat pump opens so that warm brine from the defrosting tank is mixed with the
cold brine circulating to the outdoor unit. The mixture has an approximate temperature of 15°C.
▪
The brine, heated to 15°C, melts the ice layer on the coil. At the same time, the brine liquid cools due to
heat exchange.
▪
When the brine is no longer cooled to temperatures below 11°C the coil is assumed to be sufficiently
defrosted.
▪
The shunt valve closes the flow of warm brine from the defrosting tank.
▪
Operation returns to normal.
3.3
Speed (rpm) controlled circulation pumps
Applies to certain heat pump models only.
A heat pump requires optimum conditions in both the heating system and brine circuit in order to run as effi-
ciently as possible. The temperature difference between the heating system’s supply line and return line must
be between 7 and 10°C. For the brine circuit a temperature difference of 3°C between the input and output line
applies. If the differences are larger or smaller than the quoted values, the heat pump will not work at 100%
efficiency and savings may be reduced.
A heat pump with speed-controlled circulation pumps ensures that the required temperature differences are
maintained. The control equipment detects if the balance is wrong and increases or decreases the speed of the
circulation pumps as necessary.
3.4
HGW technology
Applies to certain heat pump models only.
HGW technology is a new and unique method of water heating.
During heating of the heating system water, a small proportion is diverted through an additional heat ex-
changer and is used to heat the domestic water in the water tank. A shunt valve controls the flow between the
hot water and the heating system.
User Guide
Domestic heat pumps
VUGFE102
Danfoss Heating Solutions
8
