User manual
Document no. : 031221
Version : V3.3
MC 785-ECU
Client: Heinen & Hopman
Page: 4 of 12
WARNING:
First switch-off the MC 785-ECU controller, in case there’s work to be done on or around the fans.
2
Functional specifications
The MC 785-ECU can control a 0/10 Vdc PI output on temperature or air pressure base.
In the MANUAL mode the output can be set manually in a fixed position. In the AUTOMATIC mode it
can be adjusted on base of temperature or pressure.
Adjustments to the settings of the range and the P(I) are made by means of the internal parameters.
3
Operation
During normal operation the left-hand display shows the measured temperature and the right-hand
display the measured air pressure. The output display shows the output level of the analogue output.
Switching the thermostat on and off.
By pressing the
ON/OFF
key the thermostat is turned on or off. If the thermostat is in the
OFF
position, the control function is off and OFF is shown in the display.
Relay 2 is active when the controller is on and out when the controller is off.
Changing the set point.
Press the
SET
key. The set set point will blink in the display. By pressing the
UP
or
DOWN
keys
the set point can be changed. After pressing the
SET
key again the new set point will be
accepted.
Choice of temperature/pressure control
By pressing the
T
or
P
key, a choice can be made between temperature or pressure control. If
the LED above the
T
key is lit, the control is on the base of temperature. The set point display
shows the temperature set point again and the
C LED next to the set point display is illumi-
nated. If the LED above the
P
key is lit, the control is done on the base of air pressure. The set
point display shows the pressure set point again and the Pa LED next to the set point display
will be illuminated.
Choice of manual and automatic mode.
The MC 785-ECU normally operates in Automatic-mode. If the controller is in the manual mode
and the digital input contact-2 (AUTO-Override) is closed, than the controller switches to
automatic and stays in that mode until it’s switches manual to the manual mode. It doesn’t
matter in what position the digital input contact-2 is. If the controller is in the automatic mode,
the LED ‘Automatic’ next to the OUTPUT display will light on to indicate the AUTO mode and
the controller is automatically controlled by pressure or temperature. The choice and adjust-
ment of temperature/pressure-settings is described as above.
If the LED ‘Manual’ is on than the output level of the analogue output can be adjusted manually.
On the set point display the required level can be set by pressing the
SET
key and then
pressing the
UP
and
DOWN
keys to set the required value.
In the manual position (if P41=1) the rotation direction of the fan can be changed by pushing the
UP
+
DOWN
keys together for more than 2 seconds. In the reverse position relay 3 is on
instead of relay 2. The reverse position is shown by a negative value on the output display.
The external fan switch (dig.in-1) can be used to reverse the fan rotation (as P41=2) or to stop
the fan (as P41=3), this disables the manual
UP
+
DOWN
key-function.
By pressing the
AUTO/MAN
key a choice can be made between automatic and manual mode.
