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Condenser Pump Control —
tor the CONDENSER PRESSURE and may turn on this pump
if the pressure becomes too high whenever the compressor
is shut down. CONDENSER PRESSURE OVERRIDE is used
to determine this pressure point. This value is found on
the Equipment Service1 LID table and has a default value
(Table 4). If the CONDENSER PRESSURE is greater than
or equal to the CONDENSER PRESSURE OVERRIDE, and
the ENTERING CONDENSER WATER TEMP (Tempera-
ture) is less than 115 F (46 C), then the condenser pump will
energize to try to decrease the pressure. The pump will turn
off when the condenser pressure is less than the pressure over-
ride less 5 psi (34 kPa), or the CONDENSER REFRIG (Re-
frigerant) TEMP is within 3° F (2° C) of the ENTERING
CONDENSER WATER temperature.
Condenser Freeze Prevention —
gorithm helps prevent condenser tube freeze-up by energiz-
ing the condenser pump relay. If the pump is controlled by
the PIC, starting the pump will help prevent the water in the
condenser from freezing. Condenser freeze prevention can
occur whenever the machine is not running except when it
is either actively in pumpdown or in Pumpdown Lockout
with the freeze prevention disabled (refer to Table 7).
When the CONDENSER REFRIG TEMP is less than or
equal to the CONDENSER FREEZE POINT, or the ENTER-
ING CONDENSER WATER temperature is less than or equal
to the CONDENSER FREEZE POINT, then the CON-
DENSER WATER PUMP shall be energized until the CON-
DENSER REFRIG TEMP is greater than the CONDENSER
FREEZE POINT plus 5° F (2.7° C). An alarm will be gen-
erated if the machine is in PUMPDOWN mode and the pump
is energized. An alert will be generated if the machine is not
in PUMPDOWN mode and the pump is energized. If in re-
cycle shutdown, the mode shall transition to a non-recycle
shutdown.
Tower-Fan Relay —
This control can be used to assist
the condenser water temperature control system (field sup-
plied). Low condenser water temperature can cause the chiller
to shut down on low refrigerant temperature. The tower fan
relay, located in the starter, is controlled by the PIC to en-
ergize and deenergize as the pressure differential between
cooler and condenser vessels changes in order to prevent low
condenser water temperature and to maximize machine ef-
ficiency. The tower-fan relay can only accomplish this if the
relay has been added to the cooling tower temperature con-
troller. The TOWER FAN RELAY is turned on whenever the
CONDENSER WATER PUMP is running, flow is verified,
and the difference between cooler and condenser pressure is
more than 30 psid (207 kPad) or entering condenser water
temperature is greater than 85 F (29 C). The TOWER FAN
RELAY is deenergized when the condenser pump is off, flow
is lost, the evaporator refrigerant temperature is less than the
override temperature, or the differential pressure is less than
28 psid (193 kPad) and entering condensing water is less
than 80 F (27 C).
IMPORTANT: A field-supplied water temperature con-
trol system for condenser water should be installed.
The system should maintain the leaving condenser wa-
ter temperature at a temperature that is 20° F (11° C)
above the leaving chilled water temperature.
The tower-fan relay control is not a substitute for a con-
denser water temperature control. When used with a Wa-
ter Temperature Control system, the tower fan relay control
can be used to help prevent low condenser water
temperatures and associated problems.
The machine will moni-
This control al-
39
Auto. Restart After Power Failure —
may be enabled or disabled, and may be viewed/modified in
the Config table of Equipment Configuration. If enabled, the
chiller will start up automatically after a single cycle drop-
out, low, high, or loss of voltage has occurred, and the power
is within ±10% of normal. The 15-min start-to-start timer
and the stop-to-start timer are ignored during this type of
start-up.
When power is restored after the power failure, and if the
compressor had been running, the oil pump will be ener-
gized for one minute prior to the evaporator pump energiz-
ing. Auto restart will then continue like a normal start-up.
→
Water/Brine Reset —
brine reset are available and can be viewed or modified on
the Equipment Configuration table Config selection.
The LID default screen status message indicates when the
chilled water reset is active. The CONTROL POINT tem-
perature on the Status01 table indicates the machine's cur-
rent reset temperature.
To activate a reset type, input all configuration informa-
tion for that reset type in the Config table. Then input the
reset type number in the SELECT/ENABLE RESET TYPE
input line.
1. Reset Type 1 (Requires optional 8-input module) — Au-
tomatic chilled water temperature reset based on a 4 to
20 mA input signal. This type permits up to ±30° F
(±17° C) of automatic reset to the chilled water or brine
temperature set point, based on the input from a 4 to
20 mA signal. This signal is hardwired into the number
one 8-input module.
If the 4 to 20 mA signal is externally powered from the
8-input module, the signal is wired to terminals J1-5(+)
and J1-6(–). If the signal is to be internally powered by
the 8-input module (for example, when using variable re-
sistance), the signal is wired to J1-7(+) and J1-6(–). The
PIC must now be configured on the Service2 table to en-
sure that the appropriate power source is identified.
2. Reset Type 2 (Requires optional 8-input module) — Au-
tomatic chilled water temperature reset based on a
remote temperature sensor input. This type permits
±30° F (±16° C) of automatic reset to the set point based
on a temperature sensor wired to the number one 8-input
module (see wiring diagrams or certified drawings).
The temperature sensor must be wired to terminal J1-19
and J1-20.
To configure Reset Type 2, enter the temperature of the
remote sensor at the point where no temperature reset will
occur. Next, enter the temperature at which the full amount
of reset will occur. Then, enter the maximum amount of
reset required to operate the machine. Reset Type 2 can
now be activated.
3. Reset Type 3 — Automatic chilled water temperature re-
set based on cooler temperature difference. This type of
reset will add ±30° F (±16° C) based on the temperature
difference between entering and leaving chilled water tem-
perature. This is the only type of reset available without
the need of the number one 8-input module. No wiring is
required for this type as it already uses the cooler water
sensors.
To configure Reset Type 3, enter the chilled water tem-
perature difference (the difference between entering and
leaving chilled water) at which no temperature reset oc-
curs. This chilled water temperature difference is usually
the full design load temperature difference. The differ-
ence in chilled water temperature at which the full amount
of reset will occur is now entered on the next input line.
Next, the amount of reset is entered. Reset Type 3 can
now be activated.
This option
Three types of chilled water or
1197
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Troubleshooting
