Danfoss AK-CH 650 User Manual

AK-CH 650 Capacity controller RS8ER302 © Danfoss 2016-02 89
Defrost
The controller can perform a central defrost of the entire cold
brine circuit.
When a defrost is commenced, the compressors stop (selectable),
and the pumps continue to circulate the cold brine.
Defrost can be stopped by time, or when the cold brine has
reached a set temperature.
After defrost has been stopped, it is possible to specify a drip
delay time before the compressors restart.
There is the option for the defrost function to use an output for
activation of external automatic controls.
Defrost start
Defrost can be started in several ways.
- Manual defrost
After activation, the setting automatically returns to OFF once
defrost has been completed.
- External contact signal
Defrost start is performed with a signal on a DI input.
The signal must be a pulse signal of at least 3 seconds' duration.
Defrost starts when the signal changes from OFF to ON.
- Internal schedule
Defrost is started via a weekly program set in the controller.
The times are related to the controller's clock function. Up to 8
defrosts per day can be set.
- Network signal
Defrost can be started via a signal from the network (system
manager).
Defrost stop
The following types of defrost stop can be selected:
Stop by temperature with time as security
Here the temperature of the cold brine is measured. Once the
temperature is equal to the set stop temperature, defrost is
stopped.
Stopping defrost by S4 or S3 temperature may be selected.
If the defrost time exceeds the set max. defrost time, defrost is
stopped. This happens even if the temperature for defrost stop
has not been reached. At the same time as defrost is stopped, the
alarm message "Defrost time has been exceeded" is output. The
alarm is automatically acknowledged after 5 min.
Stop by time
Here a permanent defrost time is set. Once this time has elapsed,
defrost is stopped.
Manual stop
A defrost in progress can be stopped manually by activating
the "Stop defrost" function.
Start after defrost
It is possible to input a drip delay after defrost, so that any water
droplets can drip o the evaporators before refrigeration is
restarted. This ensures that the evaporator is as free as possible of
water on refrigeration restart.
Defrost output
It is possible to dene a defrost output to control external auto-
matic controls during defrost. The output will be activated during
defrost itself, but deactivated during any drip delay that might be
input.
Compressors
It is possible to dene whether normal compressor capacity con-
trol is to be active during defrost or not.
Pumps
Pump control will always be active during defrost.
Status
It is possible to read o the following status values for defrost:
- Defrost status (ON/OFF)
- Current temp. at defrosting sensor
- Duration of defrost in progress or last completed defrost
- Average duration of the last 10 defrosts.

Danfoss AK-CH 650 Specifications

General

Brand	Danfoss
Model	AK-CH 650
Category	Controller
Language	English