Specific application recommendations
The use of a suction line accumulator is strongly
recommended in reversible-cycle applications.
This because of the possibility of a substantial
quantity of liquid refrigerant remaining in the
evaporator, which acts as a condenser during the
heating cycle.
This liquid refrigerant can then return to the
compressor, either flooding the sump with
refrigerant or as a dynamic liquid slug when the
cycle
switches back to a defrost cycle or to normal
cooling operations.
Sustained and repeated liquid slugging and
flood back can seriously impair the oil’s ability
to lubricate the compressor bearings. This
situation can be observed in wet climates where
it is necessary to frequently defrost the outdoor
coil in an air source heat pump. In such cases a
suction accumulator becomes mandatory.
Suction line accumulator
Defrost and reverse cycle
The Danfoss WSH scroll compressor has the
ability to withstand a certain amount of liquid
refrigerant dynamic slug. However we advise that
the system is unloaded to the minimum capacity
step for defrost or when the cycle is reversed.
Apart from residual moisture in the system
after commissioning, water could also enter the
refrigeration circuit during operation. Water in
the system shall always be avoided. Not only
because it can quickly lead to electrical failure,
sludge in sump and corrosion but in particular
because it can cause serious safety risks.
Common causes for water leaks are corrosion and
freezing.
Corrosion: Materials in the system shall be
compliant with water and protected against
corrosion.
Freezing: When water freezes into ice its volume
expands which can damage heat exchanger
walls and cause leaks. During off periods water
inside heat exchangers could start freezing when
ambient temperature is lower than 0°C. During
on periods ice banking could occur when the
circuit is running continuously at too low load.
Both situations should be avoided by connecting
a pressure and thermostat switch in the safety
line.
Water utilizing systems
29
FRCC.PC.028.A5.02
Application Guidelines
