40
Table 5 — Capacity Overrides Table Capacity Overrides
Remote Start/Stop Controls —
A remote device,
such as a timeclock that uses a set of contacts, may be used to
start and stop the chiller. However, the device should not be
programmed to start and stop the chiller in excess of 2 or
3 times every 12 hours. If more than 8 starts in 12 hours (the
STARTS IN 12 HOURS parameter on the MAINSTAT screen)
occur, an excessive starts alarm displays, preventing the chiller
from starting. The operator must press the
softkey on
the CVC to override the starts counter and start the chiller. If
the chiller records 12 starts (excluding recycle starts) in a slid-
ing 12-hour period, it can be restarted only by pressing the
softkey followed by the
or
softkey.
This ensures that, if the automatic system is malfunctioning,
the chiller will not repeatedly cycle on and off. If the automatic
restart after a power failure option (AUTO RESTART OPTION
on the OPTIONS screen) is not activated when a power failure
occurs, and if the remote contact is closed, the chiller will indi-
cate an alarm because of the loss of voltage.
The contacts for remote start are wired into the starter at ter-
minal strip J2, terminals 5 and 6 on the ISM. See the certified
drawings for further details on contact ratings. The contacts
must have 24 vac rating.
Spare Safety Inputs —
Normally closed (NC) discrete
inputs for additional field-supplied safeties may be wired to the
spare protective limits input channel in place of the factory-
installed jumper. (Wire multiple inputs in series.) The opening
of any contact will result in a safety shutdown and a display on
the CVC. Refer to the certified drawings for safety contact
ratings.
Analog temperature sensors may also be added to the mod-
ule (SPARE TEMP #1 and #2). The analog temperature sen-
sors may be configured to cause an alert or alarm on the CCN
network. The alert will not shut the chiller down. Configuring
for alarm state will cause the chiller to shut down.
Spare Safety Alarm Contacts —
One set of alarm
contacts is provided in the starter. The contact ratings are pro-
vided in the certified drawings. The contacts are located on
terminal strip JP, terminals 15 and 16.
Refrigerant Leak Detector —
An input is available
on the CCM module [terminal J15-5 (–) and J5-6 (+)] for a
refrigerant leak detector. Enabling REFRIGERANT LEAK
OPTION (OPTIONS screen) will allow the PIC II controls to
go into an alarm state at a user configured level (REFRIGER-
ANT LEAK ALARM mA). The input is configured for 4 to
20 mA by setting the DIP switch 1 on SW2 at the ON position,
or configured for 0 to 5 vdc by setting switch 1 at the OFF posi-
tion. The output of the refrigerant leak detector is displayed as
REFRIGERANT LEAK SENSOR on the MAINSTAT screen.
For a 0 to 5 vdc input, 0 vdc input represents 4 mA displayed
and 5 vdc input represents 20 mA displayed.
Condenser Pump Control —
The chiller will moni-
tor the condenser pressure (CONDENSER PRESSURE) and
may turn on the condenser pump if the condenser pressure be-
comes too high while the compressor is shut down. The con-
denser pressure override (COND PRESS OVERRIDE) parame-
ter is used to determine this pressure point. COND PRESS
OVERRIDE is found in the SETUP1 display screen, which is
accessed from the EQUIPMENT SERVICE table. The default
value is 230 psig (862 kPa).
If the CONDENSER PRESSURE is greater than or equal to
the COND PRESS OVERRIDE, and the entering condenser
water temperature (ENTERING CONDENSER WATER) is less
than 115 F (46 C), the condenser pump will energize to try to
decrease the pressure. The pump will turn off when the con-
denser pressure is 3.5 psi (24.1 kPa) less than the pressure over-
ride or when the condenser refrigerant temperature (CON-
DENSER REFRIG TEMP) is within 3º F (1.7º C) of the enter-
ing condenser water temperature (ENTERING CONDENSER
WATER).
Condenser Freeze Prevention —
This control algo-
rithm helps prevent condenser tube freeze-up by energizing the
condenser pump relay. The PIC II controls the pump and, by
starting it, helps to prevent the water in the condenser from
freezing. The PIC II can perform this function whenever the
chiller is not running except when it is either actively in pump-
down or in pumpdown/lockout with the freeze prevention
disabled.
When the CONDENSER REFRIG TEMP is less than or
equal to the CONDENSER FREEZE POINT, the CONDENS-
ER WATER PUMP is energized until the CONDENSER
REFRIG TEMP is greater than the CONDENSER FREEZE
POINT plus 5º F (2.7º C) and the ENTERING CONDENSER
WATER TEMPERATURE is greater than or equal to the
CONDENSER FREEZE POINT. An alarm is generated if the
chiller is in PUMPDOWN mode and the pump is energized.
An alert is generated if the chiller is not in PUMPDOWN
mode and the pump is energized. If the chiller is in RECYCLE
SHUTDOWN mode, the mode will transition to a non-recycle
shutdown.
Tower Fan Relay Low and High —
Low condenser
water temperature can cause the chiller to shut down when re-
frigerant temperature is low. The tower fan relays, located in
the starter, are controlled by the PIC II to energize and deener-
gize as the pressure differential between cooler and condenser
OVERRIDE
CAPACITY CONTROL
FIRST STAGE SET POINT
SECOND STAGE
SET POINT
OVERRIDE
TERMINATION
View/Modify
on CVC Screen
Default
Value
Configurable
Range
Value
Value
HIGH CONDENSER
PRESSURE
SETUP1
230 psig
(1586 kPa)
150 to 260 psig
(1032 to
1793 kPa)
>Override
Set Point
+10° F (6° C)
<Override
Set Point
REFRIGERANT
OVERRIDE DELTA
TEMPERATURE
(Low refrigerant temperature)
SETUP1
3° F (1.6° C)
2° to 5° F
(1° to 3° C)
≤
Trippoint
+ Override
∆
T - 1° F (0.56° C)
>Trippoint
+ Override
∆
T+2° F (1.2° C)
MANUAL SLIDE VALVE
LOAD/UNLOAD
COMPRESS
Automatic
–10 to +10 sec
None
Release of
Manual Control
MOTOR LOAD-
ACTIVE DEMAND LIMIT
MAINSTAT
100%
40 to 100%
≥
5% of
Set Point
2% Lower
Than Set Point
DISCHARGE SUPERHEAT
FRAME 1 AND 2 R-22 ONLY
OVERRIDE
Calculated Minimum
Superheat For
Conditions
–20 to 999
2° F (1.1° C)
Below Calculated
Superheat
1° F (0.56° C)
Above Calculated
Minimum Superheat
RESET
RESET
LOCAL
CCN