Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual page 66

A label that lists the configuration values of the controls is
located on the inside of the unit's control panel. These values
are based upon the original selection of the chiller. Jobsite con-
ditions may require a slight modification to these parameters.
If, after configuring a value for these points, surge preven-
tion is operating too soon or too late for conditions, these
parameters should be changed by the operator.
An example of such a configuration is shown below.
Refrigerant: HCFC-134a
Estimated Minimum Load Conditions:
44 F (6.7 C) LCW
45.5 F (7.5 C) ECW
43 F (6.1 C) Suction Temperature
70 F (21.1 C) Condensing Temperature
Estimated Maximum Load Conditions:
44 F (6.7 C) LCW
54 F (12.2 C) ECW
42 F (5.6 C) Suction Temperature
98 F (36.7 C) Condensing Temperature
Calculate Maximum Load — To calculate the maximum load
points, use the design load condition data. If the chiller full load
cooler temperature difference is more than 15 F (8.3 C),
estimate the refrigerant suction and condensing temperatures at
this difference. Use the proper saturated pressure and tempera-
ture for the particular refrigerant used.
Suction Temperature:
42 F (5.6 C) = 37 psig (255 kPa) saturated
refrigerant pressure (HFC-134a)
Condensing Temperature:
98 F (36.7 C) = 120 psig (1827 kPa) saturated
refrigerant pressure (HFC-134a)
Maximum Load ΔT2:
54 – 44 = 10º F (12.2 – 6.7 = 5.5º C)
Maximum Load ΔP2:
120 – 37 = 83 psid (827 – 255 = 572 kPad)
To avoid unnecessary surge prevention, add about 10 psid
(70 kPad) to ΔP2 from these conditions:
ΔT2 = 10º F (5.5º C)
ΔP2 = 93 psid (642 kPad)
Calculate Minimum Load — To calculate the minimum load
conditions, estimate the temperature difference the cooler will
have at 10% load, then estimate what the suction and condens-
ing temperatures will be at this point. Use the proper saturated
pressure and temperature for the particular refrigerant used.
Suction Temperature:
43 F (6.1 C) = 38 psig (262 kPa) saturated
refrigerant pressure (HFC-134a)
Condensing Temperature:
70 F (21.1 C) = 71 psig (490 kPa) saturated
refrigerant pressure (HFC-134a)
Minimum Load ΔT1 (at 20% Load): 2 F (1.1 C)
Minimum Load ΔP1:
71 – 38 = 33 psid (490 – 262 = 228 kPad)
Again, to avoid unnecessary surge prevention, add 20 psid
(140 kPad) at ΔP1 from these conditions:
ΔT1 = 2 F (1.1 C)
ΔP1 = 53 psid (368 kPad)
If surge prevention occurs too soon or too late:
SURGE PREVENTION
LOAD
OCCURS TOO SOON
Increase P1 by
At low loads
2 psid (14 kPad)
(<50%)
Increase P2 by
At high loads
2 psid (14 kPad)
(>50%)
SURGE PREVENTION
OCCURS TOO LATE
Decrease P1 by
2 psid (14 kPad)
Decrease P2 by
2 psid (14 kPad)
66
If variable evaporator flow is employed, changes to ΔT1 are
required proportional to the reduction in flow rate.
The differential pressure (ΔP) and temperature (ΔT) can be
monitored during chiller operation by viewing ACTIVE
DELTA P and ACTIVE DELTA T (HEAT_EX screen).
Comparing SURGE/HGBP DELTA T to ACTIVE DELTA T
will determine when the SURGE PREVENTION function will
occur. The smaller the difference between the SURGE/HGBP
DELTA T and the ACTIVE DELTA T values, the closer to surge
prevention.
Further adjustments can be made if response to surge preven-
tion or protection is not functioning as desired. VFD GAIN and
VFD INCREASE STEP can be adjusted to allow for more
aggressive changes in speed when surge prevention or protec-
tion is active.
CONFIGURE DIFFUSER
SARY — If the compressor is equipped with a variable
diffuser, (size 4 or 5 compressor) access the SETUP2 screen.
Scroll to DIFFUSER CONTROL and press the
softkey. Compare the diffuser and guide vane values (GUIDE
VANE 25% LOAD PT, GUIDE VANE 50% LOAD PT, GUIDE
VANE 75% LOAD PT, DIFFUSER 25% LOAD POINT,
DIFFUSER 50% LOAD POINT, DIFFUSER 75% LOAD
POINT) to the values located on the label inside the control
panel above the ICVC. See Fig. 10.
Compressors with variable diffuser control have actuators
tested and stamped with the milliamp (mA) value that results in
100% actuator rotation. This value is configured on the
SETUP2 screen. It is labeled DIFFUSER FULL SPAN mA.
MODIFY EQUIPMENT CONFIGURATION IF NECES-
SARY — The EQUIPMENT SERVICE table has screens to
select, view, or modify parameters. Carrier's certified drawings
have the configuration values required for the jobsite. Modify
these values only if requested.
EQUIPMENT SERVICE Screen Modifications — Change
the values on these screens according to specific job data. See
the certified drawings for the correct values. Modifications can
include:
• Chilled water reset (CHW SETPT RESET VALUE)
• Entering chilled water control (ECW CONTROL
OPTION)
• 4 to 20 mA demand limit (DEMAND LIMIT AT 20 mA)
• AUTO RESTART OPTION (Enable/Disable)
• REMOTE CONTACT OPTION (Enable/Disable)
Owner-Modified CCN Tables — The following EQUIP-
MENT CONFIGURATION screens are described for reference
only.
OCCDEFCS — The OCCDEFCS screen contains the Local
and CCN time schedules, which can be modified here or on the
SCHEDULE screen as described previously.
HOLIDAYS — From the HOLIDAYS screen, the days of the
year that holidays are in effect can be configured. See the
holiday paragraphs in the Controls section for more details.
BRODEF — The BRODEF screen defines the start and end of
daylight savings time. By default this feature is enabled. Enter
the dates for the start and end of daylight savings if required
for your location. Note that for Day of Week, 1 represents
Monday. Start Week and Stop Week refer to the instance of the
selected Day of Week during the selected month and year. To
disable the feature, change "Start Advance" and "Stop Back"
times to 0 (minutes). In the BRODEF table the user may also
identify a chiller as the time broadcaster for a CCN network.
There should be only one device on a CCN network which is
designated as the Time Broadcaster.
ALARM ROUTING — This is in the table SERVICE–>
EQUIPMENT CONFIGURATION–>NET_OPT under the
heading Alarm Configuration. Alarm Routing consists of an
8-bit binary number. Only bits 1, 2, and 4 (counting from the
CONTROL IF NECES-
ENABLE