Mydax, Inc.
1M150W
Water Cooled Chiller
Designed for Lockheed Martin
5
System Electrical Diagram
Refer to drawing #D2923, the system electrical diagram. The central component of the electrical system is the M1001
controller. It is microprocessor-based and communicates with and/or controls various other circuit boards and
components. Most controller circuitry is laid out on circuit boards mounted in the main control cabinet. The controller is
powered as long as the system circuit breaker is set, receiving 24 VAC power from a bulkhead-mounted transformer.
The controller "reads" the RTD's in the system via board M1002, the Input Circuit Board, mounted on the frame. RTD's
are included for the recirculating temperatures, as well as for the refrigerant circuit. Also routed through the M1002
board are the 100 Ohm and 120 Ohm precision RTD calibration resistor circuits. The refrigerant valve drive signals and
the phase monitor circuit are routed through the M1004 power board.
The system interlock loop is controlled by the M1002 board. In this application the interlock loop consists of the
refrigerant over pressure switch, the TANK EMPTY level sensor, one power relay coil and a relay pole (RL1,B). The
RESET switch serves to feed power to the relay, which energizes the contactor. When energized, the contactor feeds
power back to the relay so the RESET switch may open up without cutting off power to the relay. If the refrigerant
switch or the level sensor trips, power to the loop is interrupted. The microprocessor senses this via the contactor
connection at pin 23 of the M1002 board. Provided the system has power, if the loop trips out, the controller drives the
PUSH RESET error message. Other diagnostic messages are also sent if the level sensors are tripped. The loop must be
reset when the fault condition, if present, is resolved.
The M1002 board also routes signals for the FILL TANK level sensor. If this sensor trips, the controller displays the
FILL TANK error message. A compressor crankcase heater is provided and is powered as long as the system circuit
breaker is set and AC line voltage is present.
The M1003 board reads the DI resistivity probes; the DI solenoid valve is driven from a digital output from the M1004
board.
A special feature exists on the M1010 board which engages a relay at a user-defined flow rate. The output of the relay is
wired to a BNC connector located on the rear panel of the unit, labeled "Flow OK". Further description of this is
provided in the
Installation
chapter.
