18
2.4 Heat exchanger
– MHX 85,
continued
Control system
The MHX 85 heat exchanger is controlled
via a controller that controls the speed of
the fans.
The key features of the controller are:
Onboard temperature sensor (NTC
type)
Microproccesor based control in ac-
cordance with preselected strategy
Minor and major alarm output
Polarity protection
Input voltage -40 V DC to -60 V DC
Power consumption max. 120 W
Part
Function
RS 232
To be used for factory testing or to get further information from
the controller
Alarm LED
Gives signal about alarms:
Flashing = minor alarm (high temperature)
Constant = major alarm (fan or sensor failure)
Both alarms can be monitored (potential free contact) on the
power/alarm plug.
Sub-D 9 pin, male Power and alarm plug
Pin designation:
1
N/C
2
+ 48 V DC
3
+ 48 V DC
4
Minor alarm +
5
Major alarm +
6
0 V DC
7
0 V DC
8
Minor alarm ÷
9
Major alarm ÷
Control strategy
This shows the control strategy for the controller:
See the table on the next page for an explanation of the values.
Continued overleaf
