Start Of Defrost; Stop Of Defrost; Defrost Sequence - Danfoss AK-CC55 User Manual

User Guide | Controller for appliance control, AK-CC55
Defrost
Depending on the application, you may choose between the
following defrost methods:
Natural: Here the fans are kept operating during the defrost
Electric: The heating element is activated
Hot gas: Here the solenoid valves are controlled so that the hot
gas can flow through the evaporator. Simple hot gas can
also be used, in which the compressor units will operate
during defrosting (simple hot gas can also be used in the
compact version).
The compact version has defrosting with brine.
Hot gas defrost (only for application 5 in the Single Coil version)
This type of connection can be used on systems with hot gas
defrost, but only in small systems, e.g. supermarkets – the
functional content has not been adapted to industrial systems
with large charges.
Relay 2 is used for the suction valve
Relay 3 is used for the bypass valve
Relay 4 is used for the hot gas valve
If the valves PMLX and GPLX are used, the delay time "d23" will
have to be properly set.
It is not possible to start a manual hot gas defrost via the display or
the app.

Start of defrost

A defrost can be started in different ways:
Interval:
Defrost is started at fixed time intervals like e.g. 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.
Week 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.
Max. thermostat runtime:
When the aggregate time has passed a preset value, a defrost will
be initiated.
Manual:
An extra defrost can be activated from the defrost button (though,
not with application 6) or via a parameter setting.
All the mentioned methods can be used randomly – if just one of
them is activated a defrost will be started.
© Danfoss | DCS (vt) | 2019.09

Stop of defrost

Defrosting can be stopped by either:
• Time
• Temperature (with time as safety).
Compressor
If the defrosting method is set to "Gas, " the compressor will be
"On" during the defrost cycle. (Only for application situations that
include a compressor output).
Fans
The fans can be stopped or operated during defrosting. They
can also run and then be stopped at a set temperature. The
temperature signal is obtained from the defrost stop sensor.

Defrost sequence

1) Pump down
2) Defrost
3) Waiting position after defrost
4) Draining (drain delay. Hot gas only)
5) Drip off
6) Delay of fan
Hot gas application
Real-time clock
The controller has a built-in real-time clock which can be used to
start defrosts. This clock has a power reserve of four days.
If the controller is equipped with data communication, the clock
will automatically be updated from the system unit.
Bypass valve
Suction valve
Hot gas valve
BC308437742037en-000101 | 41