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d. Uponrequestto startthe compressor,thecon-

trol system shall start the chilled water pump,

condenser water pumps, and tower fans, if

appropriate, and verify that ﬂows have been

established. The controller shall then com-

pare the entering/leaving chilled water tem-

perature with the chilled water set point. If

the chilled water temperature is less than the

chilled water set point plus a speciﬁed dead-

band, the control system will shut down the

condenser water pump and tower fans and

wait for the cooling load to be established.

e. A user-conﬁgurable ramp loading rate, effec-

tive during the chilled water temperature pull-

down period, shall control the rate of slide

valve opening to prevent a rapid increase in

compressor power consumption. The con-

trols shall allow conﬁguration of the ramp

loadingrate ineither degrees/minuteof chilled

water temperature pulldown or percent mo-

tor amps/minute. During the ramp loading

period, a message shall be displayed inform-

ing the operator that the chiller is operating

in ramp loading mode.

f. The chiller controls shall be supplied as stan-

dard with a two chiller lead/lag and a third

chiller standby system. The control system

shall automatically start and stop a lag or sec-

ond chiller on a two chiller system. If one of

the two chillers on line goes into fault mode,

the third or standby chiller shall be controlled

as a lag chiller. The two chiller lead/lag sys-

tem shall allow manual rotation of the lead

chiller and a staggered restart of the chillers

after a power failure. Sequencing shall be

based on leaving or entering chiller water

temperature.

g. The control system shall include compressor

runtimetimers toprotect themotor fromrapid

cycling (a 15-minute minimum start-to-start

timer and a 1-minute minimum stop-to-start

timer). In addition, the compressor will be in-

hibited from restarting if more than 8 manual

starts within a 12-hour period have occurred.

h. The control system shall automatically shut

down the compressor to minimize energy us-

age whenever the leaving chilled water tem-

perature is5F(3C)below the desired chilled

water set point or the chilled water tempera-

ture is below its set point and the chilled wa-

tertemperaturedifference is less than a speci-

ﬁed value. The chilled water pump will re-

main on, and when the leaving chilled water

temperature rises above the set point by a

user-conﬁguredamount,thecompressor shall

automaticallyrestart. Duringthe shutdown pe-

riod, a message shall be displayed informing

the operator a recycle restart is pending.

i. The control center shall monitor line voltage,

and if loss of voltage, high or low line volt-

age, or single cycle dropout is sensed, the

chiller shall shut down. Upon restoration of

line voltage, if the auto-restart after power

failure algorithm is enabled, the chiller shall

automatically resume the mode of operation

prior to shutdown.

j. The control system shall allow conﬁguration

of reset of the chilled water temperature set

point based on any one of the following

criteria:

• Chilled water reset based on water tem-

perature rise across the evaporator.

• Chilled water reset based on an external

4-20 mA signal.

• Chilled water reset based on a remote tem-

perature sensor (such as outdoor air).

When reset is active, a message shall be dis-

played indicating the type of reset in effect.

k. The control center shall limit amp draw of

the compressor to the rated load amps (RLA)

or to a lower value (ranging from 40% to

100%) of compressor RLA. The control cen-

ter shall allow conﬁguration of demand limit

based on either a user input or an external

4-20 mA signal. When demand limit is ac-

tive, a message shall be displayed indicating

the source of the demand signal.

STATUS FUNCTION

Inaddition to thedefault screen, statusscreens

shall be accessible to view the status of every

point monitored by the control center

including:

• Evaporator pressure

• Condenser pressure

• Compressor discharge temperature

• Motor winding temperature

• Number of compressor starts

• Control point settings

• Discrete output status of various devices

• Compressor motor starter status

• Optional spare input channels (16

maximum)

SCHEDULE FUNCTION

The chiller controls shall be conﬁgurable for

manual or automatic start-up and shutdown.

In automatic operation mode, the controls

shall be capable of automatically starting and

stopping the chilleraccordingtoastoreduser

programmableoccupancy schedule. The con-

trols shall include built-in provisions for ac-

cepting a minimum of three, 365-day occu-

pancyschedules, (the local time schedule shall

be Schedule 01, the ice build time schedule

shall be Schedule 02, and the CCN default

schedule shall be 03). Each schedule shall al-

low a minimum of 8 separate occupied, un-

occupied periods. All of the 8 occupied pe-

riods can be scheduled by individual day for

anyday of theweek.A separate scheduleshall

be provided for holidays. Schedules shall al-

low speciﬁcations of Daylight Savings start/

end and up to 18 user-deﬁned holidays up to