Jetson
www.JetsonHVAC.com
65
Smart Controls
Every model is furnished with a
microprocessor controller that cycles the
compressors to maintain the leaving water
temperature over a wide range of operating
conditions. A convenient alphanumeric LCD
display that is updated once per second. Inputs
are made using large function keys with menu
driven prompts. Schedules are available with a
seven-day built-in time clock. Terminals are
provided for remote stop-start and for remote
reset of the leaving water temperature setpoint.
The controller features 12 analog and 4 digital
inputs as well as 4 analog outputs. Nonvolatile
memory is used for all control functions.
Additional optional features include diagnostic
sensors for pressure and temperature on each
refrigerant circuit, current sensors for each
compressor, and a RS-485 port allowing
communication with other manufacturer’s
control systems.
Figure 21 -Keypad Controller Display
Building Communications
When the FWCD Series chiller is used in
conjunction with a building management
system (BMS), the chiller can be monitored
and given input from a remote location. The
chiller can be set up to fit into the overall
building control strategy by using remote
run/stop input, remote demand limit reset
and/or remote chilled water reset functions.
As standard, the unit controller Ethernet port is
always ready to talk BACnet® IP and
Modbus™ TCP/IP (Modbus RTU uses the
RS485 network port). BACnet® MS/TP,
Johnson N2 and LonTalk® are optional
protocols that can be factory-installed. The unit
controller can facilitate hundreds of control
points, including the following popular BMS
communications:
• Remote Off/Auto signal (input from BMS)
• Demand Limit Reset signal (input from
BMS)
• Chilled Water Temperature Reset signal
(input from BMS)
• Customer Alarm relay (view only)
• Chiller Run Indication (view only)
• Entering Chilled Water Temperature (view
only)
• Leaving Chilled Water Temperature (view
only)
• Chilled Water Flow Switch input (view
only)
• Condenser Pump relay (view only)
• Chilled Water Pump relay (view only)
System Protection
A complete safety lockout system with alarms
protects the FWCD Series chiller operation to
potentially avoid compressor and evaporator
failures. The unit controller directly senses
pressures, temperatures, amperage, motor
faults, etc. All control variables that govern the
operation of the chiller are evaluated every
second for exact control and protection. The
following is an abbreviated list of safeties that
are incorporated into the standard chiller
algorithm control.
• No Flow Protection – To protect the
chiller from no water flow to the
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General