Surge Protection —
The PIC II monitors surge, which
is a fluctuation in compressor motor amperage. Each time
the fluctuation exceeds an operator-specified limit (SURGE
DELTA % AMPS), the PIC II counts the surge. If more than
5 surges occur within an operator-specified time (SURGE
TIME PERIOD), the PIC II initiates a surge protection shut-
down of the chiller.
The surge limit can be adjusted from the OPTIONS screen.
Scroll down to the SURGE DELTA % AMPS parameter, and
use the INCREASE or DECREASE softkey to adjust the
percent of surge. The default setting is 10% amps.
The surge time period can also be adjusted from the
OPTIONS screen. Scroll to the SURGE TIME PERIOD
parameter, and use the INCREASE or DECREASE soft-
key to adjust the amount of time. The default setting is
8 minutes.
Access the display screen (COMPRESS) to monitor the
surge count (SURGE PROTECTION COUNTS).
Lead/Lag Control —
The lead/lag control system
automatically starts and stops a lag or second chiller in a
2-chiller water system. A third chiller can be added to the
lead/lag system as a standby chiller to start up in case
the lead or lag chiller in the system has shut down during
an alarm condition and additional cooling is required.
Refer to Fig. 15 and 16 for menu, table, and screen selection
information.
NOTE: The lead/lag function can be configured on the LEAD-
LAG screen, which is accessed from the SERVICE menu
and
EQUIPMENT
SERVICE
table.
See
Table
2,
Example 19. Lead/lag status during chiller operation can be
viewed on the LL_MAINT display screen, which is ac-
cessed from the SERVICE menu and CONTROL ALGO-
RITHM STATUS table. See Table 2, Example 11.
Lead/Lag System Requirements:
• all chillers in the system must have software capable of
performing the lead/lag function
• water pumps MUST be energized from the PIC II controls
• water flows should be constant
• the CCN time schedules for all chillers must be identical
Operation Features:
• 2 chiller lead/lag
• addition of a third chiller for backup
• manual rotation of lead chiller
• load balancing if configured
• staggered restart of the chillers after a power failure
• chillers may be piped in parallel or in series chilled water
flow
COMMON POINT SENSOR INSTALLATION — Lead/
lag operation does not require a common chilled water point
sensor. Common point sensors (Spare Temp #1 and #2) can
be added to the CCM module, if desired. Spare Temp #1 and
#2 are wired to plug J4 terminals 25-26 and 27-28 (J4 lower,
respectively).
NOTE: If the common point sensor option is chosen on a
chilled water system, each chiller should have its own com-
mon point sensor installed. Each chiller uses its own com-
mon point sensor for control when that chiller is designated
as the lead chiller. The PIC II cannot read the value of com-
mon point sensors installed on the other chillers in the chilled
water system.
If leaving chilled water control (ECW CONTROL OP-
TION is set to 0 [DSABLE] TEMP_CTL screen) and a com-
mon point sensor is desired (COMMON SENSOR OPTION
in LEADLAG screen selected as 1) then the sensor is wired
in Spare Temp #1 position on the CCM.
If the entering chilled water control option (ECW CON-
TROL OPTION) is enabled (configured in TEMP_CTL screen)
and a common point sensor is desired (COMMON SENSOR
OPTION in LEADLAG screen selected as 1) then the sensor
is wired in Spare Temp #2 position on the CCM.
When installing chillers in series, a common point sensor
should be used. If a common point sensor is not used, the
leaving chilled water sensor of the upstream chiller must be
moved into the leaving chilled water pipe of the downstream
chiller.
If return chilled water control is required on chillers piped
in series, the common point return chilled water sensor should
be installed. If this sensor is not installed, the return chilled
water sensor of the downstream chiller must be relocated to
the return chilled water pipe of the upstream chiller.
To properly control the common supply point temperature
sensor when chillers are piped in parallel, the water flow through
the shutdown chillers must be isolated so no water bypass
around the operating chiller occurs. The common point sen-
sor option must not be used if water bypass around the
operating chiller is occurring.
CHILLER COMMUNICATION WIRING — Refer to the
chiller’s Installation Instructions, Carrier Comfort Network
Interface section for information on chiller communication
wiring.
LEAD/LAG OPERATION — The PIC II not only has the
ability to operate 2 chillers in lead/lag, but it can also start
a designated standby chiller when either the lead or lag chiller
is faulted and capacity requirements are not met. The lead/
lag option only operates when the chillers are in CCN mode.
If any other chiller configured for lead/lag is set to the
LOCAL or OFF modes, it will be unavailable for lead/lag
operation.
Lead/Lag Chiller Configuration and Operation
• A chiller is designated the lead chiller when its LEAD/
LAG CONFIGURATION value on the LEADLAG screen
is set to ‘‘1.’’
• A chiller is designated the lag chiller when its LEAD/LAG
CONFIGURATION value is set to ‘‘2.’’
• A chiller is designated as a standby chiller when its LEAD/
LAG CONFIGURATION value is set to ‘‘3.’’
• A value of ‘‘0’’ disables the lead/lag designation of a chiller.
To configure the LAG ADDRESS value on the LEAD-
LAG screen, always enter the address of the other chiller on
the system. For example, if you are configuring chiller A,
enter the address for chiller B as the lag address. If you are
configuring chiller B, enter the address for chiller A as the
lag address. This makes it easier to rotate the lead and lag
chillers.
If the address assignments in the LAG ADDRESS and
STANDBY ADDRESS parameters conflict, the lead/lag func-
tion is disabled and an alert (!) message displays. For
example, if the LAG ADDRESS matches the lead chiller’s
address, the lead/lag will be disabled and an alert (!)
message displayed. The lead/lag maintenance screen
(LL_MAINT) displays the message ‘INVALID CONFIG’ in
the LEAD/LAG CONFIGURATION and CURRENT MODE
fields.
The lead chiller responds to normal start/stop controls such
as the occupancy schedule, a forced start or stop, and remote
start contact inputs. After completing start-up and ramp load-
ing, the PIC II evaluates the need for additional capacity. If
additional capacity is needed, the PIC II initiates the start-up
of the chiller configured at the LAG ADDRESS. If the lag
chiller is faulted (in alarm) or is in the OFF or LOCAL modes,
the chiller at the STANDBY ADDRESS (if configured) is
requested to start. After the second chiller is started and is
39
Summary of Contents for HERMETIC CENTRIFUGAL LIQUID CHILLERS 19XR
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