Specifications

E. CHILLER CONTROL
The unit shall have distributed microprocessor-based control architecture consisting of a 15-inch VGA
touch-screen operator interface, a controller for each compressor and a unit controller.
The touch-screen shall display the unit operating parameters, accept setpoint changes (password
protected) and be capable of resetting faults and alarms. The following trended parameters shall be
displayed:
• Entering and leaving chilled water temps
• Entering and leaving condenser water temps
• Evaporator saturated refrigerant pressure
• Condenser saturated refrigerant pressure
• Percent of 100% speed (per compressor)
• % rated load amps for entire unit
In addition to the trended items above, other real-time operating parameters are also shown on the
touch-screen. These items can be displayed in two ways: by chiller graphic showing each component
or from a color-coded, bar chart format. At a minimum, the following critical areas must be monitored:
Complete fault history shall be displayed using an easy to decipher, color coded set of messages that
are date and time stamped. The last 25 faults shall be downloadable from the USB port drive.
Automatic corrective action to reduce unnecessary cycling shall be accomplished through pre-emptive
control of low evaporator or high discharge pressure conditions to keep the unit operating through
abnormal transient conditions.
System specific, chiller plant architecture software shall be employed to display the chiller, piping,
pumps and cooling tower. Chiller plant optimization software for up to 3 chillers shall also be
available to provide automatic control of: evaporator and condenser pumps (primary and standby), up
to 4 stages of cooling tower fans and a cooling tower modulating bypass valve or cooling tower
variable frequency drives.
The unit controller shall support operation on a BACnet®, Modbus® or
LONWORKS® network via a
factory-installed communication module.
Factory mounted DDC controller(s) shall support operation on a BACnet®, Modbus® or
LONWORKS®
network via one of the data link / physical layers listed below as specified by the successful Building
Automation System (BAS) supplier.
• BACnet MS/TP master (Clause 9)
• BACnet IP, (Annex J)
• BACnet ISO 8802-3, (Ethernet)
• L
onTalk® FTT-10A. The unit controller shall be LONMARK ® certified.
Catalog WMC-4 53