Operating manual Document nr. : 022091 Version : V2.3
MC 785-SC Client : General Page : 7 of 32
The SUCTION part (compressor-side):
Readout selection on the SUCTION display.
By pressing the left SELECT key next to the SUCTION display once or more, the following
values can be shown on the display:
SThe suction pressure in Bars, LED Bar next to the display lights up.
SThe calculated suction temperature (depends on coolant) in degrees Celsius, LED’s
Bar and OC light up.
SThe suction temperature, of temperature sensor-1, in degrees Celsius, LED OC lights
up.
SThe operation hours of one of the compressors, to select another compressor, press
the left UP or DOWN keys. To show which compressor has been selected for readout,
the corresponding LED in the compressor bar will light up and the LED Hrs. will light
up.
SCurrent control signal in percentage, LED % lights up.
Further, there are two more LEDs ( and ) in the SUCTION display panel, these LED’s
indicate if the control signal is increasing or decreasing the compressor power.
Showing status of the compressors.
In the COMPRESSOR panel the status of the compressors is shown in different ways which
can be selected by the left MODE/SELECT key. These readout modes are;
SNormally the LED’s Service and Fail will not be lit, then the LED bars indicate:
Upper LED bar shows which compressors are active.
Lower LED bar shows which compressors are running in time delay.
Or
SLEDs Service and Fail are lit, then the LED bars indicate:
Upper LED bar shows which compressor is in service.
(These compressor(s) will not be selected for controlling by the controller).
Lower LED bar shows which compressor is in failure.
Readout or changing the suction pressure (/temperature) setpoint.
By pressing the left SET key, the suction pressure setpoint is shown in the SUCTION display.
To indicate this the Bar lights up. By pressing the left SELECT key, the setpoint will be shown
in degrees Celsius (also adjustable), LEDs Bar and OC light up.
To change the setpoint value now press the left UP or DOWN keys. 10 seconds after the keys
have been released the new setpoint will be active and the controller will return to its normal
display function again. Notice that the controller calculates the temperature signals to pressure
signals and controls on the pressure signals.
Setting a compressor in or out of service.
To put a particular compressor out of function, it must be set in service.
To see which compressors are in service press the PRG key together with the left
MODE/SELECT key. The LED Service will light up and the LED bars show:
Upper LED bar shows which compressors are in service and
Lower LED bar shows the currently-selected compressor.
With the left UP and DOWN keys another compressor can be selected. The compressor to be
put in or out service can be put in or out of service by pressing the left MODE/SELECT key.
Resetting operation hours of a particular compressor.
Read out the operation hours on the SUCTION-display by pressing the left SELECT key once
or more, until the LED Hrs lights up. Then select the compressor which has to be set to zero
with the left UP and/or DOWN keys. Now press the RESET/ALARM key, hold it down and
press simultaneously on the left MODE/SELECT key to set the selected compressor operation
hours to zero.
