McQuay WDC

Product Manual PM WSC/WDC 21
• Condenser water temperature control. Capable of four stages of tower fan control plus an optional analog
control of either a three-way tower bypass valve or variable speed tower fan motor. Stages are controlled
from condenser water temperature. The three way valve can be controlled to a different water temperature
or track the current tower stage. This allows optimum system performance based upon specific job
requirements.
• Lead-lag and load balance. The standard MicroTech is capable of compressor lead-lag decisions and
balancing compressor loads between two McQuay compressors, whether on separate chillers or mounted
on a WDC Dual Compressor unit. This feature assures optimum efficiency under any load condition.
• Auto-logging. This feature takes a snapshot of the operating conditions at the peak conditions each week
and retains this data in memory.
Nonvolatile Memory
Since MicroTech’s memory is nonvolatile, battery backup to protect the programs and settings in case of power
loss is unnecessary.
Versatile Communications Capabilities Give You Even More Control
For complete flexibility there are four ways to interface with the MicroTech controller:
1. Direct entry and readout locally at the panel on the unit
2. (1) plus digital and analog input/output signals for certain functions such as:
• Enable run input
• Alarm signal output
• 4-20ma or 0-5 VDC input for reset and load limiting
• Pump and tower fan control.
• Analog output for variable speed fan or tower bypass
3. Remote monitoring by PC-hard wired or via modem-local control still in effect
4. Interfaced with Building Management System, open protocol, with full read and write capability
PC Communications
Not only can you operate MicroTech from the keypad/display or via interconnection to the BMS, but an
optional software package lets you control it from any IBM MS/DOS compatible personal computer.
Communicating with the MicroTech is accomplished using a single twisted pair RS-232 or RS-422/485
communications protocol. Operators can monitor chiller information remotely on a personal computer. By
adding an optional modem interface, all chiller operations can be controlled from a remote location through
standard telephone lines. The modem communication can be added to the unit control at any time.
MicroTech can also handle multiple unit installations with the optional Chiller System Control (CSC) panel. This
feature allows communications with the individual unit controllers to permit sophisticated sequencing control
strategies. In addition, the System Controller can control and access all information available at the unit
controllers. The end result is optimum operating efficiency.