DIVEX MHE-02, Installation, Operating And Maintenance Manual

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KI-OM-523 R2 Chapter 1
1.3.6 CONTROL SYSTEM
The 24 VDC control circuit is used to control the contactors, relays, timer and the safety
circuits in the system. The contactors, controlled by switches mounted in the control panel
door, switch the high voltage to the heaters and the pump.
The temperature of the output fluid is regulated by dumping excess capacity thereby
increasing the flow rate of fluid through the heater tank and lowering the output temperature
of the fluid outlet. The amount of fluid dumped is controlled by an electronic controller that
operates the actuator on the control valve. The amount to which the valve is opened is
determined by the controller based on feedback received from the PT100 temperature probe
mounted into the outlet manifold.
Several safety interlocks are incorporated into the control system which provide protection
against low fluid level in the heater tank, over-temperature and motor overload trip. The
control circuit also includes indication via illuminated rotary switches and the controller
display for operator feedback.
Fig 1.2 below shows the control panel layout and part
identification.
Fig 1.2 Control Panel Layout