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SECTION 2 - PRODUCT DESCRIPTION
MICROCOMPUTER CONTROL CENTER
The microcomputer control center, shown in Figure
5 on page 20, provides automatic control of chiller
operation including compressor start/stop and load/un-
load anti-recycle timers, condenser and chilled water
(CHW) pumps, unit alarm contacts and run signal con-
tacts. The microcomputer control center comes online
as soon as the main power switch is activated. Imme-
diately, the microcomputer control center will begin to
check all variables with a frequency ranging from 30
seconds to almost continuous monitoring.
The microprocessor controls the unit's capacity by
matching the actual leaving chilled water temperature
(or condenser water temperature in heat pump applica-
tions), to the user-defined setpoint. Factors that may
cause the system's actual leaving chilled water tem-
perature to fluctuate are:
• Changes in ambient temperature
• Loop flow rate
• Load
• Loop volume
The control system reacts to such changes by adjusting
the number of compressors that are on, and the loading
of each compressor to keep the leaving water tempera-
ture at the setpoint.
The control system logic monitors the rate at which the
leaving water temperature is approaching the setpoint
to ramp up or down compressor capacity as required.
The VSD allows the compressor capacity to match the
load.
Displayed data and programmable setpoints are de-
tailed in SECTION 6 - OPERATION in this manual.
20
FIGURE 5 - CONTROL CENTER USER INTERFACE
Extreme Conditions – During extreme or unusual
conditions, the chiller control system will avoid shut-
down by varying capacity. By monitoring motor cur-
rent and suction and discharge pressures, the chiller
can maintain maximum available cooling output with-
out shutting down.
Unit safeties are provided for the chiller to perform au-
to-reset shutdown for the specific conditions detailed
in SECTION 6 - OPERATION in this manual.
OPTIONS
The following options are factory-mounted unless oth-
erwise noted.
Evaporator Options
Factory Insulation – Factory-applied thermal insula-
tion of the 3/4 in. (19 mm) flexible, closed-cell plastic
type is attached with vapor-proof cement to the follow-
ing components:
• Evaporator shell and tube sheets
• Suction connection
• Auxiliary tubing
Insulation can also be provided on the condenser to
meet specific application needs.
FORM 201.30-ICOM1 (519)
ISSUE DATE: 05/22/2019
LD16388a
LD19539
JOHNSON CONTROLS
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