22
RW SERIES REVERSIBLE CHILLER INSTALLATION MANUAL
Control Features cont.
Low Pressure (DI-3 and DI-6)
The low-pressure switches shall be a normally closed (NC) switch
that monitors the systems compressor suction line refrigerant
pressure. The input shall be checked 15 seconds before
compressor start up to insure the pressure switch is closed and
then ignored for the first 2 minutes after the compressor output
(DO-1 or DO-2) is enabled. If the switch is open continuously for
(30) seconds the compressor output for that circuit will be disabled.
The compressor will not restart until the short cycle time delay
has been satisfied. If a low-pressure fault occurs in one circuit the
other compressor will continue to operate based on the heating or
cooling demand.
Compressor 1 Alarm Output (DO-5)
The compressor 1 alarm output will be enabled when stage 1 is in
the lockout mode and will be disabled when the lockout is reset.
Compressor 2 Alarm Output (DO-6)
The compressor 2 alarm output will be enabled when stage 2 is in
the lockout mode and will be disabled when the lockout is reset.
Test Mode
The unit controls system can be put into test mode to eliminate
startup delays to aid in trouble shooting. To put the unit into test
mode hold the “ESC” and “Down Arrow” keys until LED 8 begins to
flash. The control will remain in test mode until power is cycled or
after 30 minutes.
Reversible Chiller Setpoint Control
This control software is by default set to operate in ‘Aquastat’
mode, which requires external setpoint logic to generate the Y1
or Y2 call. The mode may be changed to ‘Setpoint’ by use of the
‘Settings’ menu in the MUI in the ‘Mode’ item which is on the 5th
line from the top.
CAUTION! Setpoint mode is not recommended on
applications that have more than two water-to-water
heat pumps installed. Unique temperature setting
should be set for each unit on a common load.
To operate in setpoint mode, consider the following:
•
The selected mode must be changed from Aquastat
to Setpoint
•
The ‘Y1’ input must be activated. This may be done by
connecting ‘R’ to ‘Y1’ on the terminal board, or by commanding
Y1 to ‘ON’ in the Maint menu of the MUI, or by commanding
the ComprEnable network variable from the BAS.
•
The Heat/Cool mode is by default in the cooling mode, and
may be set to heating by connecting R to O/B on the terminal
board, or by commanding the ‘B’ item in the Maint menu of the
MUI, or by commanding the reversing valve variable from the
BAS network.
•
The setpoint mode temperature sensor can be selected to
either Load LW Temp (Leaving Water) or Load EW Temp
(Entering Water Temp). The default is set for Entering Water
Temp control.
•
The cooling setpoint and the heating setpoint are two separate
setpoints, and can be adjusted in the MUI Settings menu.
•
When the controlling temperature sensor is set to select the
Load EW Temp, the setpoint control will operate in a PID
(Proportional-Integrating-Derivative) mode. In this mode,
the temperature rate of change and direction of change will
be part of deciding whether or not to add or reduce capacity.
Additionally the amount of difference between setpoint
and temperature AND the length of time that the difference
existed are used to determine if adding or reducing capacity
is needed.
o
The tuning parameters for this mode should only be
adjusted if you know why you are choosing the value that
you plan to use. You should keep a permanent record of
the beginning values and record any changes that you
make. The parameters used in PID operation and their
(default values) are:
• D NegThrshld (-0.03)
• Int Rate (200)
• Stage Delay (30)
• Gain (2)
• D PosThrshld (0.04)
• PIDY1 Ref (7.2)
• PID Y1 Diff (7)
• PID Y2RefShift (5)
• PID Y2 Diff (6)
