Dometic Basic Chiller Control Instructions De Montage page 4

EN
• Low current alarm to indicate if the system (pumps and compressor) is not actually
running when enabled
• Return or supply water control
7.2 Control functions
NOTE The product is factory-programmed with the options enabled for that
system. These options can only be enabled by a factory representative.
The built-in control application supports the following functions:
• Selection and sequencing of:
• up to six chillers
• one chilled water pump (CWP) and one or more sea water pumps (SWP)
• up to six electric heaters
• Sequencing of devices for run-time equalization
• Alarms and interlocks
• Load shedding
• Troubleshooting help
Sequencing for chillers, pumps, and heaters is the order in which they start up and
turn off. Sequencing is based on run-time, which is the amount of hours a specific
compressor, pump, or heater runs.
Users can select Normal, Econo, or Boost mode operation in a single-stage
configuration.
7.3 Inputs and outputs
The device is used to check analog inputs, digital inputs, and relay outputs to decide the
status of the system.
NOTE If a temperature sensor is defective or not connected, the device
generates an alarm for that sensor.
NOTE Faults must be verified and cleared via the PLC before re-enabling the
system or stage.
7.3.1 Analog inputs
Input
High limit temperature setpoint
4
Description
The high limit temperature sensor is continu-
ously checked whether in Cooling, Reverse
Cycle, or Electric Heat mode.
This sensor is used to detect a high temper-
ature condition in the supply water from
the chiller. If the chilled water temperature
is sensed to be greater or equal to 125°F
(51.67°C), all enabled compressor relays will
be de-energized, turning off the compressor(s)
if operating in reverse cycle mode. If elec-
tric heat is being used, all enabled heater re-
lays will be de-energized, turning off the heat-
ing element(s). As the temperature falls, the
compressor or electric heat relay will re-en-
ergize when the temperature reaches 110°F
(43.33°C).
A high temperature fault will be recorded and
displayed if the system exceeds the alarm set
point. In a high temperature situation, PLC will
not allow the compressor or electric heat re-
lay to be energized. The fault MUST be manu-
ally acknowledged on the active alarm screen
and cleared prior to re-enabling the system or
stage.
Input
Freeze temperature setpoint
Condenser freeze protection (optional)
Suction pressure
Discharge pressure
7.3.2 Digital inputs
Input
Safety
Flow switch (FS) - chilled water
Refrigerant hi - high side pressure limit
Description
The low limit temperature sensor is continu-
ously monitored whether in Cooling, Reverse
Cycle, or Electric Heat mode.
This sensor is used to detect a freeze condition
in the supply water of the chiller. If the chilled
water temperature is sensed to be equal to
or less than 38°F (3.33°C), then the compres-
sor relay will be de-energized, shutting off
the compressor. As the temperature rises, the
compressor relay will re-energize when the
temperature reaches 42°F (5.56°C).
A low temperature fault will be recorded and
displayed if the system falls below the alarm
set point. In a low temperature situation, PLC
will not allow the compressor or electric heat
relay to be energized. The fault MUST be man-
ually acknowledged on the active alarm screen
and cleared prior to re-enabling the system or
stage.
The system is equipped with a temperature
sensor mounted to the condenser coil. This
sensor is there to sense the coil temperature.
In heat mode if the coil temperature drops be-
low 40°F (4.44°C), the PLC controls will au-
tomatically lower the speed of the compres-
sor to half the speed that it was currently run-
ning. The display will indicate "Freeze Defrost"
while performing this operation.
The suction pressure is continuously moni-
tored by the PLC. If the suction pressure is be-
low the alarm set point for longer than the
programmed time delay, a fault will occur.
This low suction fault will be recorded and dis-
played on the alarm screen.
The discharge pressure is continuously moni-
tored by the PLC. If the discharge pressure is
above the alarm set point for longer than the
programmed time, a fault will occur. This high
pressure fault will be recorded and displayed
on the alarm screen.
Description
All discrete inputs will be checked before the
system will be enabled.
With the system in either heating or cooling
mode the flow switch MUST be closed prior
to system starting or a stage being enabled.
In operation if flow is lost for more than 10 con-
secutive seconds, the compressor or heat re-
lay will be disabled. A flow switch fault will be
recorded and displayed.
A CW Flow fault will be recorded and system
will be in lockout and a manual restart will be
required. The PLC will not allow the compres-
sor or electric heat relay to be energized for
the stage that has lost flow or the whole sys-
tem if a common flow switch is being used.
The PLC will immediately acknowledge an
open circuit if the HI pressure switch is tripped
and de-energize the compressor. It will record
and display high pressure fault on the alarm
screen. If the PLC detects a high pressure fault
during operation, a HP fault will be displayed
and recorded. The PLC will not allow the com-
pressor relay to be re-energized, until switch is
in the closed position.