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Design & installation Guide For McQuay MDS Multi System
Testing
CHAPTER
5
5.1 Hardware Diagram and Configuration
5.1.1 MDS Series Indoor Units
The indoor unit consists of a three-speed fan and an electronic expansion valve (electric heater and
swing function optional). The four temperature sensors respectively serve to measure the temperature
of the indoor, inlet coil, midlet coil and outlet coil. The MDS-A system can connect with a remove control
or remote receiver and, as a slave unit, communicates with outdoor units via RS485 interface. The DIP
switches on the controller determine the electric heater, power, unit model and address number.
MRS485 terminal resistor J2-1: ON/OFF indicate whether resistance is present or not.
Power supply
Temperature measurement
Communication port 1
Communication port 2
Memory 3
3-speed fan
Electronic expansion valve
indicator
Electric heater
Swing
SW1:DIP switch
for function setting
SW2: DIP switch for
indoor unit address setting
SW3: DIP switch
for model setting
Model 1 SW1.1 SW1.2 SW1.3 SW1.4 SW1.5 SW1.6
OFF: No
Electric heater 1 Electric heater 2 Pump Reserve Reserve Reserve
ON: Yes
Model 1 setting (SW1.1 SW1.6)