McQuay ACZ 045A, Installation, Operation And Maintenance Manual

Page: 47 / 104

IOMM ACZ/AGZ-1 47
Unit Set Points and Calibration
The control software is installed and tested by the factory before shipping. No periodic calibration of
the controller is necessary. All control and safety set points must be checked by the installing
contractor and adjusted as necessary before starting the unit.
The “setpoint” control knob adjusts the leaving water setpoint. The “Control Band” knob adjusts the
controller temperature control band. To set, divide the chilled water temperature range by the number
of unloading steps and add 0.5°F.
Optional Sensors
Optional sensor kits, available from the factory, can be installed in the field. The optional sensor kits
have the same characteristics as the leaving water sensor.
Field Wiring
Interconnecting wiring for the control panel may consist of the following:
•
115Vac power wiring
•
Analog input signals
•
Digital input signals
•
Digital output signals
•
Communications to a personal computer
Power Wiring
The installing contractor provides the unit voltage power source, disconnect, fuses and necessary
wiring for these circuits. All wiring must conform to the National Electrical Code and applicable local
building codes. If the evaporator heater power source (120Vac) is supplied from a separate external
supply, remove wires 540 and 545 as indicated on the unit wiring diagram.
Power Supplies
There are several internal power supplies used by the controller and related circuitry. The regulated
5Vdc power is supplied by RSP1 and provides power to pressure transducers. Do not use this power
supply to operate external devices. A 24Vac power supply is available for the alarm bell option. Wire
according to the unit wiring diagram.
Analog input signals
All sensors and transducers required for normal chiller operation are installed and wired at the factory.
All optional analog input signal wiring is provided by the installing contractor must be twisted,
shielded pair (Belden #8760 or equal). The optional demand limit and remote reset signals are 0 to
10Vdc signals. The controlling range of the remote reset signal is from 2Vdc to 10Vdc.
Digital input signals
Remote contacts for all digital inputs into the Global UNT controller must be dry contacts suitable for
the 24Vac control signals from the control panel. Do not connect 120Vac power to the digital inputs or
24Vac from an external power source.
Remote Stop/Start
If remote stop/start control is selected, remove the jumper between terminals #140 and #141 on TB-7
and install the input between these terminals. When the remote stop/start switch is open, the
controller will be in the unoccupied mode.