Carrier 19XL Ice Build Control

4. Lead chiller temperature pulldown rate of the CHILLED

WATERtemperature is less than 0.5° F (0.27° C) per

minute.

5. The lag chiller status indicates it is in CCN mode and is

not faulted. If the current lag chiller is in an alarm con-

dition,then the standby chiller becomes the active lag chiller,

if it is conﬁgured and available.

6. The conﬁgured LAG START TIMER entry has elapsed.

The LAG START TIMER shall be started when the lead

chillerramp loading is completed. The LAG STARTTIMER

entry is accessed by selecting Lead/Lag from the Equip-

ment Conﬁguration table of the Service menu.

When all of the above requirements have been met, the

lagchiller is forced to a START mode. The PIC control then

monitorsthe lag chiller for a successful start. If the lag chiller

fails to start, the standby chiller, if conﬁgured, is started.

LagChiller Shutdown Requirements —The following con-

ditionsmust be met in order for the lag chiller to be stopped.

1. Leadchiller COMPRESSOR MOTOR LOAD value is less

than the lead chiller percent capacity plus 15%.

NOTE: Lead chiller percent capacity = 100 – LAG PER-

CENT CAPACITY

The LAG PERCENT CAPACITYvalue is conﬁgured on

the Lead/Lag Conﬁguration screen.

2. The lead chiller chilled water temperature is less than

the CONTROL POINT plus

⁄

of the WATER/BRINE

DEADBAND.

3. The conﬁgured LAG STOP TIMER entry has elapsed.

The LAG STOP TIMER is started when the CHILLED

WATER TEMPERATURE is less than the CHILLED

WATER CONTROL POINT plus

⁄

of the WATER/

BRINEDEADBAND and the lead chiller COMPRESSOR

MOTOR LOAD is less than the lead chiller percent

capacity plus 15%. The timer is ignored if the chilled

watertemperature reaches 3° F (1.67° C) below the CON-

TROL POINT and the lead chiller COMPRESSOR

MOTORLOAD value is less than the lead chiller percent

capacity plus 15%.

FAULTEDCHILLER OPERATION — If the lead chiller

shuts down on an alarm (*) condition, it stops communica-

tionto the lag and standby chillers. After 30 seconds, the lag

chillerwill now become the acting lead chiller and will start

and stop the standby chiller, if necessary.

Ifthe lag chiller faults when the lead chiller is also faulted,

the standby chiller reverts to a stand-alone CCN mode of

operation.

If the lead chiller is in an alarm (*) condition (as shown

on the LID panel), the RESET softkey is pressed to clear

the alarm, and the chiller is placed in the CCN mode, the

lead chiller will now communicate and monitor the RUN

STATUSof the lag and standby chillers. If both the lag and

standbychillers are running, the lead chiller will not attempt

to start and will not assume the role of lead chiller until

eitherthe lag or standby chiller shuts down. If only one chiller

is running, the lead chiller will wait for a start request from

theoperating chiller. When the conﬁgured lead chiller starts,

it assumes its role as lead chiller.

LOAD BALANCING — When the LOAD BALANCE

OPTION is enabled, the lead chiller will set the ACTIVE

DEMANDLIMIT in the lag chiller to the lead chiller’s COM-

PRESSOR MOTOR LOAD value. This value has limits of

40% to 100%. When setting the lag chiller ACTIVE

DEMAND LIMIT, the CONTROL POINT will be modi-

ﬁed to a value of 3° F (1.67° C) less than the lead chiller’s

CONTROLPOINT value.If the LOAD BALANCE OPTION

is disabled, the ACTIVE DEMAND LIMIT and the CON-

TROL POINT are forced to the same value as the lead

chiller.

AUTO. RESTARTAFTER POWER FAILURE — When

an auto. restart condition occurs, each chiller may have a

delay added to the start-up sequence, depending on its lead/

lagconﬁguration. 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

waterﬂow veriﬁcation. The PIC controls ensure that the guide

vanesare closed. After the guide vane position is conﬁrmed,

the delay for lag and standby chiller occurs prior to ener-

gizing 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 motors from being energized simul-

taneously.This will help reduce the inrush demands on the

building power system.

Ice Build Control

IMPORTANT:TheIce Build control option is only avail-

able on chillers with PSIO Software Version09 and

higher.

Ice build control automatically sets the chilled WATER/

BRINE CONTROL POINT of the chiller to a temperature

where an ice building operation for thermal storage can be

accomplished.

The PIC can be conﬁgured for ice build operation. Con-

ﬁguration of ice build control is accomplished through

entries in the Conﬁg table, Ice Build Setpoint table, and the

IceBuild Time Schedule table. Figures 16 and 17 show how

to access each entry.

The Ice Build Time Schedule deﬁnes the period during

which ice build is active if the ice build option is

ENABLED. If the Ice Build Time Schedule overlaps other

schedules deﬁning time, then the Ice Build Time Schedule

shall take priority.During the ice build period, the WATER/

BRINECONTROL POINT is set to the ICE BUILD SET POINT

for temperature control. The ICE BUILD RECYCLE

OPTION and ICE BUILD TERMINATION entries from a

screen in the Conﬁg (conﬁguration) table provide options

forchiller recycle and termination of ice build cycle, respec-

tively.Termination of ice build can result from the ENTER-

INGCHILLED WATER/BRINEtemperature being less than

theICE BUILD SET POINT, opening of the REMOTE CON-

TACTinputs from an ice level indicator, or reaching the end

of the Ice Build Time Schedule.

ICE BUILD INITIATION— The Ice Build Time Schedule

provides the means for activating ice build. The ice build

time table is named OCCPC02S.

Ifthe Ice Build Time Schedule is OCCUPIED and the ICE

BUILD OPTION is ENABLED, then ice build is active and

the following events automatically take place (unless over-

ridden by a higher authority CCN device):

1. Force CHILLER START/STOP to START.

2. ForceWATER/BRINECONTROL POINT to the ICE BUILD

SET POINT.

3. Removeany force (Auto) on the ACTIVE DEMAND LIMIT.

NOTE:Items 1-3 (shown above) shall not occur if the chiller

is conﬁgured and operating as a lag or standby chiller for

lead/lagand is actively controlled by a lead chiller. The lead

chiller communicates the ICE BUILD SET POINT, desired

CHILLERSTART/STOP state, and ACTIVE DEMAND LIMIT

to the lag or standby chiller as required for ice build, if con-

ﬁgured to do so.