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The head pressure reference output will be on whenever the
condenser pump is operating; it may also be manually operated
in
CONTROLS TEST.
When the head pressure differential is less
than the value entered for
DELTA P AT 0%,
the output will
be
maintained at 4 mA. The output is 2 mA when the chiller is not
running.
Lead/Lag Control —
The lead/lag control system auto-
matically 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. 20 and 21 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 3, Example 22.
Lead/lag status during chiller operation can be viewed on the
LL_MAINT display screen, which is accessed from the SER-
VICE menu and CONTROL ALGORITHM STATUS table.
See Table 3, Example 12.
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 USAGE AND INSTALLA-
TION — Refer to 19XR,XRV Lead Lag Schematics, Appen-
dix B. Lead/lag operation does not require a common point
chilled water sensor. Common point sensors (Spare Temp#1
and #2) may be added as described below, if desired.
If using leaving chilled water control (
ECW CONTROL
OPTION
is set to 0 [DSABLE] on the TEMP_CTL screen) and
a common point sensor is desired
(COMMON SENSOR OP-
TION
in LEADLAG screen selected as 1) then the sensor is
wired into the Spare Temp #1 position on the CCM (terminals
J4-25 and J4-26).
If the entering chilled water control option is enabled (
ECW
CONTROL OPTION
is selected to 1 [configured in the
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 (terminals J4-27 and J4-28).
NOTE: If the common point sensor option is chosen on a
chilled water system, each chiller should have its own common
point sensor installed. Each chiller uses its own common point
sensor for control when that chiller is designated as the lead
chiller. The PIC II cannot read the value of common point sen-
sors installed on the other chillers in the chilled water system.
When installing chillers in series, either a common point
sensor should be used (preferred), or the
LEAVING CHILLED
WATER
sensor of the upstream chiller must be moved into the
leaving chilled water pipe of the downstream chiller. In this ap-
plication the
COMMON SENSOR OPTION
should only be en-
abled for the upstream chiller if that chiller is configured as the
Lead.
If
ENTERING CHILLED WATER
control is required on
chillers piped in series, either a common point sensor should be
used (preferred), or the
ENTERING CHILLED WATER
sensor
of the downstream chiller must be relocated to the
ENTERING
CHILLED WATER
pipe of the upstream chiller. In this applica-
tion the
COMMON SENSOR OPTION
should only be enabled
for the downstream chiller if that chiller is configured as the
Lead. Note that
ENTERING CHILLED WATER
control is not
recommended for chillers installed in series due to potential
control stability problems.
To properly control the
LEAVING CHILLED WATER TEM-
PERATURE
when chillers are piped in parallel, the water flow
through the shutdown chiller(s) should be isolated so that no
water bypass around the operating chiller occurs. However, if
water bypass around the operating chiller is unavoidable, a
common point sensor in the mixed
LEAVING CHILLED WA-
TER
piping should be provided and enabled for the Lead
chiller.
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 op-
tion only operates when the chillers are in CCN mode. If any
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
LEADLAG: CONFIGURATION
value on the LEAD-
LAG screen is set to “1.”
• A chiller is designated the lag chiller when its
LEADLAG: CONFIGURATION
value is set to “2.”
• A chiller is designated as a standby chiller when its
LEADLAG: CONFIGURATION
value is set to “3.”
• A value of “0” disables the lead/lag designation of a
chiller.This setting should also be used when “normal”
operation without regard to lead/lag rules is desired (in
LOCAL or CCN mode).
When configuring the LAG ADDRESS value on the
LEADLAG screen of chiller “A” enter the address of the
chiller on the system which will serve as lag when/if chiller
“A” is configured as lead. For example, if the user is configur-
ing 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. Note that only the lag and standby chiller addresses
specified in the configured lead chiller's table are relevant at a
given time.
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 L
EADLAG: CONFIGU-
RATION
and
CURRENT MODE
fields. See Table below.
LEAD/LAG
CONFIGURATION
INVALID
CONDITIONS
1 (LEAD)
Local Addres (Lead) = Lag Address
Standby Chiller Option = Enable AND Local
Address (Lead) = Standby Address
Standby Chiller Option = Enable AND Local
Address (Lag) = Standby Address
2 (LAG)
Local Addres (Lead) = Lag Address
Standby Chiller Option = Enable AND Local
Address (Lag) = Standby Address
Summary of Contents for AquaEdge 19XR series
Page 69: ...69 Fig 33 19XR Leak Test Procedures a19 1625 ...
Page 154: ...154 Fig 64 Benshaw Inc Wye Delta Unit Mounted Starter Wiring Schematic Low Voltage a19 1873 ...
Page 161: ...161 Fig 69 Typical Low Voltage Variable Frequency Drive VFD Wiring Schematic 575 v ...
Page 162: ...162 Fig 69 Typical Low Voltage Variable Frequency Drive VFD Wiring Schematic 575 v cont ...
Page 186: ...186 APPENDIX B LEAD LAG WIRING 19XR Lead Lag Schematic Series Cooler Flow a19 1655 ...
Page 187: ...187 APPENDIX B LEAD LAG WIRING cont 19XR Lead Lag Schematic Parallel Cooler Flow a19 1717 ...