Carrier AquaEdge 19XRV series Start-Up, Operation And Maintenance Instructions Manual Download Page 47

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4. Lag chiller temperature pulldown rate (

TEMP PULL-

DOWN DEG/MIN

) of the chilled water temperature

is less than 0.7 K per minute.

5. The standby chiller is not running as a lag chiller.
6. The configured

LAG START TIMER

configured in the

lag (acting lead) chiller has elapsed. The

LAG START

TIMER

is started when the lag (acting lead) chiller’s

ramp loading is completed.

5.27.7 - Load balancing

When the

LOAD BALANCE OPTION

(see LEADLAG

screen) is enabled, the lead chiller sets the

ACTIVE DE-

MAND LIMIT

in the lag chiller to the lead chiller’s com-

pressor motor load value

MOTOR PERCENT KILOWATTS

AVERAGE LINE CURRENT

on the MAINSTAT

screen). This value has limits of 40% to 100%. In addition,
the

CONTROL POINT

for the lag chiller must be modified

to a value of 1.67 K less than the lead chiller’s

CONTROL

POINT

value. If the

LOAD BALANCE OPTION

is dis-

abled, the

ACTIVE DEMAND LIMIT

and the

CONTROL

POINT

are both forced to the same value as the lead chiller.

5.27.8 - Auto. Restart after power failure

When an auto. restart condition occurs, each chiller may
have a delay added to the start-up sequence, depending on
its lead/lag configuration. The lead chiller does not have a
delay. The lag chiller has a 45-second delay. The standby
chiller has a 90-second delay. The delay time is added after
the chiller water flow is verified. The PIC III ensures the
guide vanes are closed. After the guide vane position is
confirmed, the delay for lag and standby chillers occurs
prior to energizing the oil pump. The normal start-up
sequence then continues. The auto. restart delay sequence
occurs whether the chiller is in CCN or LOCAL mode and
is intended to stagger the compressor motor starts.
Preventing the motors from starting simultaneously helps
reduce the inrush demands on the building power system.

5.28 - Ice build control

The selectable ice build mode permits use of the chiller to
refreeze or control the temperature of an ice reservoir which
may, for example, be used for thermal storage. This mode
differs from water or brine chilling in that termination
(indication that the need for cooling has been satisfied) is
based on input(s) other than the temperature which is
being controlled during operation.

NOTE: For ice build control to operate properly, the PIC
III must be in CCN mode.

The PIC III can be configured for ice build operation.
•

From the SERVICE menu, access the EQUIPMENT
SERVICE table. From there, select the OPTIONS
screen to enable or disable the

ICE BUILD OPTION

See Table 3, Example 17.

•

The

ICE BUILD SETPOINT

can be configured from

the SETPOINT display, which is accessed from the
PIC III main menu. See Table 3, Example 9.

•

The ice build schedule can be viewed or modified from
the SCHEDULE table. From this table, select the ice
build schedule (OCCPC0S) screen. See Fig. 8 and the
section on Time Schedule Operation, page 19, for more
information on modifying chiller schedules.

The ice build time schedule defines the period(s) during
which ice build is active if the ice build option is enabled.
If the ice build time schedule overlaps other schedules, the
ice build time schedule takes priority. During the ice build
period, the

CONTROL POINT

is set to the

ICE BUILD

SETPOINT

for temperature control. The

ICE BUILD

RECYCLE

and

ICE BUILD TERMINATION

parameters,

accessed from the OPTIONS screen, allow the chiller
operator to recycle or terminate the ice build cycle. The ice
build cycle can be configured to terminate when:
•

the

ENTERING CHILLED WATER

temperature is

less than the

ICE BUILD SETPOINT

. In this case,

the operator sets the

ICE BUILD TERMINATION

parameter to 0 (the default setting) on the OPTIONS
screen.

•

the ICE BUILD CONTACTS input from an ice level
indicator are opened. In this case, the operator sets
the

ICE BUILD TERMINATION

parameter to 1 on

the OPTIONS screen.

•

the chilled water temperature is less than the

ICE

BUILD SETPOINT

and the ICE BUILD CONTACTS

input from an ice level indicator are open. In this case,
the operator sets the

ICE BUILD TERMINATION

parameter to on the OPTIONS screen.

•

the end of the ice build time schedule (OCCPC0S)
has been reached.

5.28.1 - Ice build initiation

The ice build time schedule (OCCPC0S) is the means for
activating the ice build option. Ice Build is enabled if:
•

a day of the week and a time period on the ice build
time schedule are enabled. The SCHEDULE screen
shows an X in the day field and ON/OFF times are
designated for the day(s),

•

and the

ICE BUILD OPTION

is enabled.

The following events take place (unless overridden by a
higher authority CCN device).
•

CHILLER START/STOP

is forced to START.

•

The

CONTROL POINT

is forced to the

ICE BUILD

SETPOINT

•

Any force (Auto) is removed from the

ACTIVE

DEMAND LIMIT

note:

A parameter’s value can be forced, that is, the value

can be manually changed at the ICVC by an operator,
changed from another CCN device, or changed by other
algorithms in the PIC III control system.

note:

The Ice Build steps do not occur if the chiller is

configured and operating as a lag or standby chiller for
lead/lag operation and is actively being controlled by a lead
chiller. The lead chiller communicates the

ICE BUILD

SET POINT

, the desired

CHILLER START/STOP

state,

and the

ACTIVE DEMAND LIMIT

to the lag or standby

chiller as required for ice build, if configured to do so.

5.28.2 - Start-up/recycle operation

If the chiller is not running when ice build activates, the
PIC III checks the following conditions, based on the

ICE