Carrier 16JB Bedienungsanleitung PDF herunterladen (Seite 26)

Guide speciﬁcations (cont)

d. Network Window Function:

Each Chiller LID (Local Interface Device)

shall be capable of viewing multiple point

values and statuses from other connected on

a common network, including controller

maintenance data. The operator shall be

able to alter the remote controller’s set

points or time schedule and to force point

values or statuses that are operator forcible.

The LID shall also have access to the alarm

history ﬁle of all like controllers connected

on the network.

e. Capacity control shall be by means of elec-

tronically modulating the steam control valve

actuator to maintain the temperature of the

leaving chilled water. Load modulation shall

be from 100% to 10% of machine full load

under normal ARI conditions. The steam

control valve shall be precisely positioned by

a PID (Proportional Integral Derivative) con-

trol algorithm to ensure precise control

(± .5 F [±.3 C]) of desired chilled water tem-

perature without hunting or overshooting

the set point.

f. The microprocessor control system shall in-

clude a programmed sequence to ensure

machine readiness prior to machine

start-up. The microprocessor shall automati-

cally activate and interlock the chilled water

pump, cooling water pump, cooling tower

fans upon chiller activation.

g. Upon request to start the chiller, the control

system shall start the chilled water pump and

verify chilled water ﬂow. The controller shall

then compare the entering or leaving chilled

water temperature with the chilled water set

point. If the chilled water temperature is less

than the chilled water set point, the control

system shall enter the recycle mode until a

cooling load has been established. Once a

cooling load has been established the control

system shall start the cooling water pump

and verify ﬂow, before starting tower fan(s),

solution pump(s) and refrigerant pump.

Once the refrigerant pump is started the

control system shall then initiate a pro-

grammed warm-up cycle. The controller

shall then compare the strong solution tem-

perature leaving the generator and the leav-

ing chilled water temperature. If the high-

stage solution temperature is equal to or

greater than 158 F (70 C), and the leaving

chilled water is decreasing in tempera-

ture the control system shall enter ramp

loading mode. A message shall be displayed:

‘‘Running Temp Control, Temperature

Ramp Loading.’’

h. The control system shall automatically sense

impending abnormalities in the absorption

operating cycle and take one or all of the fol-

lowing actions to either self-correct and/or

limit the machine from approaching cycle

crystallization line:

• inhibit steam control valve position

until concentration drops below preset

threshold*

• drive steam valve to closed position

until concentration drops below preset

threshold*

• initiate non-recycle shutdown of the chiller

if safety shutdown threshold exceeded†

*Message will be displayed: ‘‘run capacity

limited, high concentration.’’

†Message will be displayed: shutdown in

progress, dilution cycle.’’

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

tive during the chilled water temperature

pulldown period, shall control the rate of

steam control valve opening to limit start-up

steam demand. The controls shall allow con-

ﬁguration of the ramp loading rate in

degrees per minute of chilled water

temperature pulldown. During the ramp

loading period, a message shall be displayed

informing the operator that the chiller is op-

erating in ramp loading mode.

j. The control system shall automatically cycle

the machine to minimize energy usage

whenever the leaving chilled water tempera-

ture is 3 F (1.7 C) below the desired chilled

water set point. The chilled water pump

shall remain on, and when the leaving

chilled water temperature rises above the set

point by a user-conﬁgured amount, the

chiller shall automatically restart. During the

shutdown period, a message shall be

displayed informing the operator a recycle

restart is pending.

k. The control center shall allow reset of the

chilled water temperature set point based on

any one of the following criteria:

• Chilled water reset based on an external

4 to 20 mA signal.

• Chilled water reset based on a remote

temperature (such as outdoor air).

• Chilled water reset based on water

temperature rise across the evaporator.

When reset is active, a message shall be

displayed indicating the type of reset in

effect.

l. The control center shall limit the opening of

the steam control valve to 50% (user-

conﬁgurable) open at start-up until the

warm-up period has been completed and

ramp loading is enabled.

m. When the stop button is pressed, or remote

contacts open the control center shall imme-

diately drive the steam control valve to the

closed position and initiate the normal shut-

down sequence including dilution cycle. The

display shall indicate ‘‘shutdown in progress,

dilution cycle.’’

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