Carrier 19EF Series, Руководство по запуску и эксплуатации

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Lead/Lag Control —
Lead/lag is a control system pro-
cess that automatically starts and stops a lag or second chiller
in a 2-chiller water system. Refer to Fig. 13 and 14 for menu,
table, and screen selection information. On machines that
have PSIO software with Lead/Lag capability, it is possible
to utilize the PIC controls to perform the lead/lag function
on 2 machines. A third machine 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 condi-
tion and additional cooling is required.
NOTE: Lead/lag configuration is viewed and edited under
Lead/Lag in the Equipment Configuration table (located in
the Service menu). Lead/lag status during machine opera-
tion is viewed in the MAINT04 table in the Control Algo-
rithm Status table. See Table 2.
Lead/Lag System Requirements:
• all machines must have PSIO software capable of per-
forming the lead/lag function
• water pumps MUST be energized from the PIC controls
• water flows should be constant
• CCN Time Schedules for all machines 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 can be added to the 8-input
option module, if desired. Refer to the certified drawings for
termination of sensor leads.
NOTE: If the common point sensor option is chosen on a
chilled water system, both machines should have their own
8-input option module and common point sensor installed.
Each machine will use its own common point sensor for con-
trol, when that machine is designated as the lead chiller. The
PIC cannot read the value of common point sensors installed
on other machines in the chilled water system.
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 machine.
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 that no water by-
pass around the operating chiller occurs. The common point
sensor option must not be used if water bypass around the
operating chiller is occurring.
MACHINE COMMUNICATION WIRING — Refer to the
machine’s Installation Instructions, Carrier Comfort Net-
work Interface section on page 40 for information on ma-
chine communication wiring.
LEAD/LAG OPERATION — The PIC control provides the
ability to operate 2 chillers in the LEAD/LAG mode. It also
provides the additional ability to start a designated standby
chiller when either the lead or lag chiller is faulted and
capacity requirements are not met. The lead/lag option op-
erates in CCN mode only. If any other chiller configured for
lead/lag is set to the LOCAL or OFF modes, it will be un-
available for lead/lag operation.
NOTE: Lead/lag configuration is viewed and edited in Lead/
Lag, under the Equipment Configuration table of the Service
menu. Lead/lag status during machine operation is viewed
in the MAINT04 table in the Control Algorithm Status
table.
Lead/Lag Chiller Configuration and Operation — The con-
figured lead chiller is identified when the LEAD/LAG
SELECT value for that chiller is configured to the value of
‘‘1.’’ The configured lag chiller is identified when the LEAD/
LAG SELECT for that chiller is configured to the value of
‘‘2.’’ The standby chiller is configured to a value of ‘‘3.’’ A
value of ‘‘0’’ disables the lead/lag in that chiller.
To configure the LAG ADDRESS value on the LEAD/
LAG Configuration table, always use the address of the other
chiller on the system for this value. Using this address will
make it easier to rotate the lead and lag machines.
If the address assignments placed into the LAG
ADDRESS and STANDBY ADDRESS values conflict, the
lead/lag will be disabled and an alert (!) message will
occur. For example, if the LAG ADDRESS matches the lead
machine’s address, the lead/lag will be disabled and
an alert (!) message will occur. The lead/lag maintenance
screen (MAINT04) will display the message ‘INVALID
CONFIG’ in the LEAD/LAG CONFIGURATION and
CURRENT MODE fields.
The lead chiller responds to normal start/stop controls such
as occupancy schedule, forced start/stop, and remote start
contact inputs. After completing start up and ramp loading,
the PIC evaluates the need for additional capacity. If addi-
tional capacity is needed, the PIC 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, then
the chiller at the STANDBY ADDRESS (if configured) is
requested to start. After the second chiller is started and is
running, the lead chiller shall monitor conditions and evalu-
ate whether the capacity has reduced enough for the lead
chiller to sustain the system alone. If the capacity is reduced
enough for the lead chiller to sustain the CONTROL POINT
temperatures alone, then the operating lag chiller is stopped.
If the lead chiller is stopped in CCN mode for any reason
other than an alarm (*) condition, then the lag and standby
chillers are stopped. If the configured lead chiller stops for
and alarm condition, then the configured lag chiller takes the
lead chiller’s place as the lead chiller and the standby chiller
serves as the lag chiller.
If the configured lead chiller does not complete the start-up
before the PRESTART FAULT TIMER (user configured value)
elapses, then the lag chiller shall be started and the lead chiller
will shut down. The lead chiller then monitors the start re-
quest from the acting lead chiller to start. The PRESTART
FAULT TIMER is initiated at the time of a start request. The
PRESTART FAULT TIMER’s function is to provide a tim-
eout in the event that there is a prestart alert condition pre-
venting the machine from starting in a timely manner. The
timer is configured under Lead/Lag, found in the Equipment
Configuration table of the Service menu.
If the lag chiller does not achieve start-up before the
PRESTART FAULT TIMER elapses, then the lag chiller shall
be stopped and the standby chiller will be requested to start,
if configured and ready.
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