6
Manual RS8EN502 © Danfoss 02-2010
AK-CC 550
Hot gas application
Defrost
Depending on the application you may choose between the fol-
lowing defrost methods:
Natural:
Here the fans are kept operating during the defrost
Electric:
The heating element is activated
Hotgas:
Here the solenoid valves are controlled so that the
hotgas can flow through the evaporator
Defrost sequence
1) Pump down
2) Defrost
3) Waiting position after defrost
4) Draining (drain delay. Hotgas only)
5) Drip off
6) Delay of fan
Hot gas defrost (application 6 only)
This type of connection can be used on systems with hotgas
defrost, but only in small systems in, say, supermarkets – the
functional content has not been adapted to systems with large
charges
Relay 2 is used for suction valve
Relay 4’s change-over function can be used by the bypass valve
and/or the hotgas valve.
Must not be used together with PMLX and GPLX valves, unless a
time delay relay is installed, which ensures that the PMLX/GPLX
valve is closed completely before the hotgas is turned on.
Drip tray heating element
It is possible to control a heating element in the drip tray for
hot gas defrosting. When defrosting is commenced, the heating
element is activated. The heating element remains activated until
a set time after defrosting has ended by time or temperature.
Start of defrost
A defrost can be started in different ways
Interval: Defrost is started at fixed time intervals, say, every
eighth hour. An interval must ALWAYS be set to
a "higher" value than the period set between two
defrostings when a schedule or network signal is used.
Refrigeration time: Defrost is started at fixed refrigeration time
intervals, in other words, a low need for refrigeration will
”postpone” the defrost
Schedule: Here defrost can be started at fixed times of the
day and night. However, max. 6 times
Contact: Defrost is started with a contact signal on a digital input
Network: The signal for defrost is received from a system unit
via the data communication
Adaptive defrost: Here defrosting is started based on intelligent
registering of evaporator performance.
Manual: An extra defrost can be activated from the controller’s
lower-most button
All the mentioned methods can be used at random – if just of
them is activated a defrost will be started.
Stop of defrost
Defrosting can be stopped by either:
• Time
• Temperature (with time as safety).