Carrier AquaEdge 19DV series, Управление, эксплуатация и устранение неисправностей

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DEMAND LIMIT
The PIC6 controls provide a feature for limiting AVERAGE
LOAD CURRENT or MOTOR KILOWATTS by limiting ca-
pacity via guide vane control/VFD control. The limit may be
applied in two ways. The first is called ACTIVE DEMAND
LIMIT, which is equal to a BASE DEMAND LIMIT value (set
in the SETPOINT screen, default value 100%). ACTIVE DE-
MAND LIMIT may also be forced to be different from BASE
DEMAND LIMIT by manually overriding (forcing) the value
via a CCN network device. If the DEMAND LIMIT SOURCE
exceeds the ACTIVE DEMAND LIMIT by 5% or less, capaci-
ty will be inhibited. If the DEMAND LIMIT SOURCE ex-
ceeds the ACTIVE DEMAND LIMIT by more than 5%, ca-
pacity will be decreased.
Alternatively, the limit may be applied by AUTO DEMAND
LIMIT INPUT, an optional 4 to 20 mA input. This demand
limit control option (4 to 20 mA DEMAND LIMIT TYPE) is
externally controlled by a 4 to 20 mA signal. The option is set
up on the Configuration Menu

GENERAL CONFIGURA-
TION screen. When enabled, 4 mA will set ACTIVE DE-
MAND LIMIT to 100% of the DEMAND LIMIT SOURCE
(regardless of the value of BASE DEMAND LIMIT), and 20
mA will set ACTIVE DEMAND LIMIT to the value config-
ured for DEMAND LIMIT AT 20 mA in the Configuration
Menu

SERVICE PARAMETERS screen.
OVERRIDE CONTROL
Capacity overrides can prevent some safety shutdowns caused
by exceeding the motor amperage limit, evaporator refrigerant
low temperature safety limit, motor high temperature safety
limit, and condenser high pressure limit. In these cases there
are two stages of capacity control:
1. When the value of interest crosses the first stage set point
into the override region, the capacity is prevented from
increasing further, and the status line on the PIC6 control-
ler indicates the reason for the override. Normal capacity
control operation is restored when the value crosses back
over the first stage set point, leaving the override region.
2. When the value of interest is in the override region and
further crosses the second stage set point, the capacity is
decreased until the value meets the override termination
condition. The PIC6 controls resume normal capacity con-
trol operation after the override termination condition has
been satisfied. (In the case of high discharge superheat,
there is an intermediate stage.)
Table 14 summarizes these override parameters.
Other types of override events do not override control guide
vane or VFD operation, but are reported:
• High compressor discharge temperature override — If the
COMP DISCHARGE TEMP is greater than the COMP
DISCHARGE ALERT threshold, then high discharge tem-
perature override will be displayed in the main screen until
the COMP DISCHARGE TEMP is less than the COMP
DISCHARGE ALERT threshold – 2°F (1.1°C).
• High compressor bearing temperature override — If one of
the compressor bearing temperatures is greater than the
compressor bearing temperature Alert ( Configuration
Menu

Protective Limit Config ) threshold, then High
Bearing Temp Override shall be active until all of the com-
pressor bearing temperatures are less than Comp Bearing
Temp Alert minus 2°F (1.1°C).
• Low Discharge Superheat Temperature Override — This
override is ignored during the first 5 minutes after chiller
start-up.
Table 14 — Override Parameters
OVERRIDE CONDITION OVERRIDE PARAMETER
FIRST STAGE
CAPACITY INHIBIT
DEFAULT VALUE/
CONFIGURABLE
RANGE
SECOND STAGE
CAPACITY DECREASE
OVERRIDE
TERMINATION
High condenser pressure over-
ride (Unit Type Heat/Cool=1 in
Configuration Menu

Factory .
Before configuring Unit Type = 1
verify that unit is able to withstand
pressure - note all North America
units are of 72 PSI design.)
CONDENSER
PRESSURE > COND PRESS
OVERRIDE HIGH 55 psig/20 to 56 psig > COND PRESS OVER-
RIDE HIGH + 2.4 psi < COND PRESS
OVERRIDE HIGH —
1 psi
High compressor discharge
temperature COMP DISCHARGE TEMP >COMP DIS-
CHARGE ALERT 200°F/125 to 200°F
(93.3°C/51.7 to 93.3°C) COMP DISCHARGE
TEMP
<COMP DISCHARGE
ALERT-2°F (1.1°C)
High compressor bearing
temperature COMP BEARING TEMP >COMP BEARING
TEMP ALERT DV 104°F/90 to 120°F
(40°C/32.2 to 48.9°C) COMP BEARING
TEMP
<COMP BEARING
TEMP ALERT DV-2°F
(1.1°C)
Low evaporator temperature
override CALC EVAP SAT TEMP
or
EVAP REFRIG LIQUID
TEMP < EVAP SAT OVER-
RIDE TEMP (EVAP
SAT OVERRIDE
TEMP = EVAP TRIP-
POINT + EVAP
OVERRIDE DELTA T) < EVAP SAT OVERRIDE
TEMP - 1°F (0.56°C) > EVAP SAT OVER-
RIDE TEMP + 2°F
(1.1°C)
High motor temperature override COMP MOTOR WINDING
TEMP > COMP MOTOR
TEMP OVERRIDE 200°F/150 to 200°F
(93.3°C/65.6 to 93.3°C) COMP MOTOR WIND-
ING TEMP > COMP
MOTOR TEMP OVER-
RIDE + 10°F (5.6°C) COMP MOTOR WIND-
ING TEMP < COMP
MOTOR TEMP OVER-
RIDE – 2°F (1.1°C)
Rectifier Overload (32VS VFD
only) RECTIFIER OVERLOAD >100 % >102 % <98 %
High current override PERCENT LINE
CURRENT PERCENT LINE
CURRENT > 100
%
PERCENT LINE CUR-
RENT > 105
% ; 102 %
WHEN 32VS VFD
INSTALLED
PERCENT LINE CUR-
RENT <= 100
%
Low discharge superheat override Discharge Superheat (DSH) < DSH RE 1 < DSH REQUIRED –3 > DSH RE 2
Low source temperature protec-
tion override Leaving water temperature
(heating mode) < LWT PROTEC-
TION SETPOINT –
2°F (1.1°C) >LWT PROTECTION
SE 0.5°F
(0.3°C)