19
Chiller Shutdown Sequence —
Chiller shutdown
begins if any of the following occurs:
• Local OFF button is pressed
• A recycle condition is present (see the previous section)
• The time schedule has gone into unoccupied mode when
in either Network or Local Schedule control mode
• The chiller protective limit has been reached and chiller
is in alarm
• The start/stop status (CHIL_S_S) is overridden to stop
from the network when in Network mode
If the chiller is normally shut down from running, a soft-
stop shutdown will be performed. The soft-stop feature closes
the guide vanes of the compressor automatically if a non-alarm
stop signal occurs before the compressor motor is deenergized.
Any time the compressor is directed to STOP (except in the
cases of a fault shutdown), the guide vanes are directed to close
and VFD will be commanded to minimum speed for a variable
speed compressor. The compressor shuts off when any of the
following is true:
• PERCENT LOAD CURRENT (%) drops below the
SOFT STOP AMPS THRESHOLD
• ACTUAL GUIDE VANE POSITION drops below 4%
• Four minutes have elapsed since the stop was initialized
When any of these conditions is true, the shutdown se-
quence stops the compressor by deactivating the compressor
start relay. The guide vanes are then commanded to the fully
closed position. The oil pump relay will be turned off after
120 seconds post-lube.
Finally, the chilled water/brine pump and condenser water
pump are shut down.
Oil Lubrication Control —
As part of the pre-start
checks executed by the controls, the oil sump temperature is
compared to the evaporator saturated refrigerant temperature.
If the oil temperature is less than 140 F (60 C) and less than
evaporator saturated refrigerant temperature plus 50° F
(27.8° C), the start-up will be delayed until either of these con-
ditions is no longer true. Once this temperature is confirmed,
the start-up continues.
The oil heater relay is energized whenever the chiller com-
pressor is off and the oil sump temperature is less than 140 F
(60 C) or the oil sump temperature is less than the evaporator
saturated refrigerant temperature plus 53° F (29.4° C). The oil
heater is turned off when either of the following conditions is
true:
• Oil sump temperature is more than 152 F (66.7 C)
• Oil sump temperature is more than 144 F (62.2 C) and
more than the evaporator saturated refrigerant tempera-
ture plus 55° F (30.6° C).
The oil heater is always off when the compressor is running.
Default setting for 19XR6/7 chiller energizes the oil
pump for 30 seconds after each 30 minutes of the oil heat
relay being energized in order to stir the oil for more evenly
distributed heating.
The oil stir configuration can be adjusted in Service Pa-
rameters as follows: Oil Stir Cycle (19XR6/7):
0
no Oil Stir.
1
Oil Stir for 30 seconds per 30 minutes
2
Oil Stir for 1 minute per 4 hours
3
Oil Stir for first 50 hours of chiller in not running
status (as Option 1) followed by no Oil Stir (as Option 0).
Control Points
SET POINT — The set point can be configured at the Setpoint
menu (“USER” access level).
The set point is determined by the heat/cool mode, EWT
(entering water temperature) option, and ice build option. See
Table 13 — Set Point Determination
NOTES:
1. The ice build option is disabled when heat/cool mode is set to
Heating.
2. When the ice build option is enabled and ice build is active, the
control point is the Ice Build Set Point and the controlled water
temperature is the leaving chilled water temperature.
CONTROL POINT TEMPERATURE — Capacity control
is based on achieving and maintaining a control point tempera-
ture, which is the sum of a valid set point (from the SETPOINT
screen) and a temperature reset value. In Cooling mode, the
control point temperature is equal to the set point plus tempera-
ture reset. In Heating mode, the control point temperature is
equal to the set point minus temperature reset.
The control point can be viewed directly on the main screen
or the General Parameters menu.
TEMPERATURE RESET — Three types of chilled water or
brine reset are available and can be viewed or modified on the
Reset Configuration screen.
The default screen indicates when the chilled water reset is
active. The control point Reset on the General Parameters
screen indicates the amount of reset.
To activate a reset type, access the Reset Configuration
(RESETCFG) screen and input all configuration information
for that reset type.
Reset Type 1: 4 to 20 mA Temperature Reset — Reset Type
1 is an automatic reset utilizing a 4 to 20 mA analog input sig-
nal provided from any external sensor, controller, or other de-
vice which is appropriately configured. For this type, Degrees
Reset At 20 mA is configured in the RESETCFG table.
Reset Type 2: Remote Temperature Reset — Reset Type 2 is
an automatic water temperature reset based on a remote tem-
perature sensor input signal. This function can be accessed by
setting the following configurations:
1. Configure the remote temperature at which no reset oc-
curs (Remote temp
NO RESET).
2. Configure the remote temperature at which full reset oc-
curs (Remote temp
FULL RESET).
3. Enter the amount of reset (Deg Reset Water DT Full).
Reset Type 3: Controlled Water Temp Delta Reset — Re-
set Type 3 is an automatic controlled water temperature reset
based on heat exchanger temperature difference. This function
can be accessed by setting the following configurations:
1. Configure the controlled water temperature delta T at
which no reset occurs (Controlled Water DELTA T
NO RESET).
2. Configure the controlled water temperature delta T at
which full reset occurs (Controlled Water DELTA T
FULL RESET).
3. Enter the amount of reset (Deg Reset Water DT Full).
CAPACITY CONTROL — Capacity
control
provides
chilled or condenser water temperature control by modulating
the position of the inlet guide vane 1, and VFD speed for vari-
able speed compressors.
EWT
CONTROL
OPTION
HEAT/COOL MODE
COOLING
HEATING
Disabled
Cooling LCW Set Point
Heating LCDW Set Point
Enabled
Cooling ECW Set Point
Heating ECDW Set Point