Water Pumps Control (Freeze Prevention) - Carrier AquaEdge 19XR Controls Operation And Troubleshooting

OVERRIDE CONDITION
High condenser pressure CONDENSER
override PRESSURE
(Unit Type Heat/Cool=1 in

Configuration Menu 
Fac-
tory Parameters. Before
configuring Unit Type = 1
the condenser shell side
must be verified to be 300
psig design or higher.)
High condenser pressure CONDENSER
override PRESSURE
(Unit Type Cool Only = 0 in

Configuration Menu 
Fac-
tory Parameters. This corre-
sponds to a condenser with
standard 185 psig design
pressure.)
Low evaporator tempera- CALC EVAP SAT TEMP
ture override or
EVAP REFRIG LIQUID
TEMP
High motor temperature COMP MOTOR WIND-
override ING TEMP
High current override PERCENT LINE
CURRENT
Low discharge superheat Discharge Superheat
override (DSH)
Low source temperature Leaving water tempera-
protection override ture (heating mode)

WATER PUMPS CONTROL (FREEZE PREVENTION)

NOTE: In order to energize the chilled and condenser pump to
prevent evaporator and condenser tube freeze-up, the hydraulic
system should be enabled first (this can be configured in the
Configuration Menu  FACTORY PARAMETERS screen).
Evaporator Freeze Prevention —When the evaporator satu-
rated refrigerant temperature or evaporator refrigerant tempera-
ture is less than the EVAP REFRIG TRIPPOINT + REFRIG
OVERRIDE DELTA T (configurable from 2° F to 5° F (1.1° C
to 2.8° C) in the Configuration Menu  PROTECTIVE LIM-
IT CONFIG screen), an OVERRIDE—LOW EVAP REFRIG
TEMP event will occur.
For any running status, if either of the conditions below is
true then unit will shut down under Alarm PROTECTIVE
LIMIT - EVAPORATOR FREEZE (State 261):
• Evaporator saturated refrigerant temperature or evapora-
tor refrigerant temperature is equal to or less than the
EVAP REFRIG TRIPPOINT (33 F [0.6 C] for water,
(configurable for brine in Configuration Menu  PRO-
TECTIVE LIMIT CONFIG screen) plus 1° F (0.56° C).
• Leaving chilled water temperature or entering chilled
water temperature is less than EVAP REFRIG TRIP-
POINT plus 1° F (0.56° C).
NOTE: If the chiller is in recycle mode, it will transition to
TRIPOUT, and the CHILLED WATER PUMP will remain on.
The alarm will be clearable when the evaporator saturated
refrigerant temperature, evaporator refrigerant temperature,
leaving chilled water temperature, and entering chilled water
temperature rise 5° F (2.8° C) above the EVAP REFRIG
TRIPPOINT.
Table 15 — Override Parameters
FIRST STAGE
OVERRIDE
CAPACITY
PARAMETER
INHIBIT
> COND PRESS
OVERRIDE HIGH
> COND PRESS
OVERRIDE LOW
< EVAP SAT
OVERRIDE TEMP
(EVAP SAT
OVERRIDE TEMP
= EVAP TRIP-
POINT + EVAP
OVERRIDE
DELTA T)
> COMP MOTOR
TEMP OVERRIDE
PERCENT LINE
CURRENT >
100%
< DSH
REQUIRED + 1
< LWT PROTEC-
TION SETPOINT
– 2° F (1.1° C)
DEFAULT VALUE/ SECOND STAGE
CONFIGURABLE
RANGE
250 psig/200-260 > COND PRESS
psig OVERRIDE HIGH +
2.4 psi
140 psig/90-170 psig > COND PRESS
OVERRIDE LOW +
2.4 psi
< EVAP SAT OVER-
RIDE TEMP - 1° F
(0.56° C)
200 F/150-200 F COMP MOTOR
(93.3 C/65.6-93.3 C) WINDING TEMP >
COMP MOTOR
TEMP OVERRIDE +
10 F (5.6 C)
PERCENT LINE
CURRENT > 105%;
102% WHEN 32VS
VFD INSTALLED
< DSH REQUIRED –
3
Condenser Pump Control — The chiller will monitor the con-
denser pressure and may turn on the condenser pump. If the
condenser pressure is greater than or equal to the COND
PRESS OVERRIDE, and the entering condenser water tem-
perature is less than 115 F (46.1 C), the condenser pump will
energize to try to decrease the pressure and Process Alert -
High Condenser Pressure Chiller Off (Alert 157) will be gener-
ated. The pump will turn off when the condenser pressure is 3.5
psi (24.1 kPa) less than the pressure override and the condenser
refrigerant temperature is less than or equal to the entering con-
denser water temperature plus 3° F (1.7° C).
NOTE: COND PRESS OVERRIDE is found in the Configu-
ration Menu  PROTECTIVE LIMIT CONFIG screen.
Condenser Freeze Prevention — This control helps prevent
condenser tube freezing by energizing the condenser pump re-
lay. The PIC 5 module controls the pump and, by starting it,
helps to prevent the water in the condenser from freezing.
When the chiller is off and condenser saturated refrigerant
temperature is less than or equal to the condenser freeze point,
the condenser water pump will be energized (Alarm State 262,
PROTECTIVE LIMIT - CONDENSER FREEZE). The fault
state will clear and the pump will turn off when the condenser
saturated refrigerant temperature is more than 5° F (2.7° C)
above the condenser freeze point and the entering condenser
water temperature is greater than the condenser freeze point. If
the chiller is in recycle shutdown mode when the condition oc-
curs, the controls will transition to a non-recycle shutdown.
NOTE: In order for the chilled water pump and the condenser
water pump to operate from IOB4 to prevent freeze-up, the
Dedicated Hydraulic IOB option must be enabled in Configu-
ration Menu  FACTORY PARAMETERS.
23
OVERRIDE
CAPACITY
TERMINATION
DECREASE
< COND PRESS
OVERRIDE HIGH
— 1 psi
< COND PRESS
OVERRIDE LOW
— 1 psi
> EVAP SAT
OVERRIDE TEMP
+ 2° F (1.1° C)
COMP MOTOR
WINDING TEMP <
COMP MOTOR
TEMP OVERRIDE
– 2° F (1.1° C)
PERCENT LINE
CURRENT <=
100%
> DSH REQUIRED
+ 2
>LWT PROTEC-
TION SETPOINT +
0.5° F (0.3° C)