McQuay MDB075B, Manual

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Operation
Electrical Connection
Wiring regulations about wire diameter differs from country to country. Please refer to your LOCAL
ELECTRICAL CODES for field wiring rules. Be sure that installation comply with such rules and regulations.
General Precaution
Ensure that the rated voltage of the unit correspond to the name plate before carrying out proper wiring
according to the wiring diagram.
Provide a power outlet to be used exclusively for each unit. A power supply disconnect and a circuit breaker
for over-current protection should be provided in the exclusive line.
The unit must be GROUNDED to prevent possible hazard due to insulation failures
Every wiring must be firmly connected.
Every wiring should not touch the refrigerant piping, compressor and any moving parts of fan motor.
Operational Check
After all wiring is completed and the system is charged with refrigerant, make sure the unit is operating
properly. Check that :-
Condenser fans are running with warm air blowing off the condensing unit.
Evaporator blowers are running and discharging cool air from ducts.
Suction line and liquid line pressures are in the region of 75 psig and 275 psig respectively.
Sequential Controller
It is allowed to configure the controller to suit individual’s need with details below :
Model Selection
1. Number of Compressor
The control can be configured into 6 main types base on number of compressors
by changing “
R42 ” values :
Number of Compressor R42 value
a. Cooling / heater* 2 Compressor 20k
b. Cooling / heater* 3 Compressor 47k
c. Cooling / heater* 4 Compressor Open
d. Heat pump 2 compressors 1k
e. Heat pump 3 compressors 3.3k
f. Heat pump 4 compressors 9.1k
Note : * Cooling or heater model depending on SW1 and SW2 setting. Factory setting for number of
compressor is based on air conditioner models.
2. Number of Heater
Number of Heater SW1(dip1) SW2(dip2)
a. No heater (0 heater) off off
b. 1 heater on off
c. 2 heaters on / off on
Note : Factory preset : SW1 = off; SW2 = off ~ no heater