Melt Function; Control Of Two Compressors; Cyclic Control; Rail Heat - Danfoss AK-CC55 User Manual

User Guide | Controller for appliance control, AK-CC55

Melt function

This function will prevent the air flow in the evaporator from being
reduced by frost created by uninterrupted operation for a long
time.
The function is activated if the thermostat temperature has
remained in the range between -5°C and +10°C for a longer
period than the set melting interval. The refrigeration will then be
stopped during the set melting period. The frost will be melted
so that the air flow and hence the evaporator's capacity will be
greatly improved.

Control of two compressors

The two compressors must be of the same size.
They can run cyclically or sequentially.
When the controller demands refrigeration, it will first cut in the
compressor with the shortest operating time. After the time delay,
the second compressor will be cut in.

Cyclic control

When the temperature has dropped to "the middle of the dif-
ferential", the compressor with the longest operation time will be
cut out.
The running compressor will continue until the temperature has
reached the cut-out value. Then it will cut out. When the tempera-
ture again reaches the middle of the differential, a compressor will
again be started.
If one compressor cannot maintain the temperature within the
differential, the second compressor will also be started.
If one of the compressors has run on its own for two hours, the
compressors will be changed over so that operational time is bal-
anced.
The two compressors must be of a type that can start up against a
high pressure.
The compressor's settings for "Min. On time" and "Min. Off time"
will always have top priority during normal regulation. But if one
of the override functions is activated, the "Min. On time" will be
disregarded.

Rail heat

It is possible to pulse-control the power to the rail heat in order to
save energy. Pulse control can either be controlled according to
day/night load or dew point.
Relay or analogue output
A relay output can be used when long cycle times are permitted.
If fast pulsing is required, the AO1/PWM output can be used. The
output must be connected to an external power solid state relay.
The cycle time must be configured for the relay output in o43 or
Rail heat
for analogue output in P82.
Pulse control according to day and night
Various ON periods can be set for day and night operation.
A cycle time is set as well as the percentage part of the period in
which the rail heat is ON.
Pulse control according to dew point
In order to use this function, a system manager of the type AK-SM
is required which can measure dew point and distribute to the
appliance controllers. For this the rail heat's ON period is controlled
according to the distributed dew point.
Two dew point values are set in the appliance control:
Dew point
• One where the effect must be max. i.e.100%. (o87)
© Danfoss | DCS (vt) | 2019.09 BC308437742037en-000101 | 43