YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls

FORM 201.28-NM1.1
ISSUE DATE: 8/29/2012
rator heater is turned OFF. Both evaporator heater outputs
will always be turned ON and OFF together. An
under voltage condition will keep the heater OFF until
full voltage is restored to the system.The heater will
protect the evaporator from freeze-up down to -29°C(-
20°F ).
Compressor Heater Control
Each compressor has its own heater. The purpose of
the heater is to assure refrigerant does not condense
in the compressor. There is no oil sump, but refrigerant
could possibly condense in the rotors or the motor
housing.The heater will be OFF whenever the respective
compressor is running. As soon as the compressor
shuts OFF, the heater will turn ON as long as all motor
temperature sensors in the compressor read less than
70°C (158°F). The heater will turn OFF, if any internal
compressor motor temperature sensor reads more than
71.1°C (160°F).
Alarms
Each system has its own alarm. The Alarm output is ON
(dry contact closed) when no fault condition is present
and OFF (dry contact open) to indicate an alarm
situation. The Alarm will be activated (contacts open),
if any of the following are true.
• A System is faulted or inhibited from starting for
more than 5 seconds.
• The Unit is faulted or inhibited from starting for
more than 5 seconds.
• A System is locked out.
• The Unit is locked out.
• Power is removed from the chiller.
Chiller Run Contact
The Chiller Run dry contact is closed whenever any system
is running. It is open when all systems are shut OFF.
Flow Switch Control
A chilled liquid flow switch of suitable type MUST be
connected between Terminals 2 and 13 of 1TB to provide
protection against loss of liquid flow, which will
cause evaporator freeze-up if the chiller is permitted
to run.
Remote Run / Stop
A Remote Run/Stop input is available for each system.
BASIC OPERATING SEQUENCE
Start Sequence and Loading
SECTION 7 - OPERATION
To initiate the start sequence of the chiller, the following
conditions must be satisfied before the precharge
of the DC Bus will take place:
• UNIT SWITCH must be ON.
• At least one System Switch is ON
• Run permissive inputs (Remote Cycling Contacts)
must be closed.
• No unit faults exist.
• No unit start inhibits exist.
• At least one system not faulted or inhibited.
• The Daily Schedule is calling for the chiller to
run.
• The Flow Switch is closed.
• Leaving Chilled Liquid Setpoint is above the
Setpoint plus CR (Setpoint High Limit).
Once the precharge takes place, if the anti-recycle timer
is timed out the chiller control system on the Chiller
Control Board will select the number of compressors
to start and begin operation of the compressors. The
compressor(s) speed will be ramped to the minimum
start frequency and increase speed as needed in an effort
to regulate the leaving chilled liquid temperature
to meet the desired Setpoint.Unit Warnings
UNIT WARNING
Unit Warning Operation
Unit warnings are caused when a condition is present
requiring operator intervention to restart the unit.
All setpoints, program values, and options should be
checked before operating the unit. Warnings are not
logged to the history buffer. If a unit warning is in
effect, the message will be displayed to the operator
when the STATUS key is pressed.
Low Battery Warning
The LOW BATTERY WARNING can only occur at
unit power-up. On micropanel power-up, the RTC battery
is checked to see if it is still operational. If it is,
normal unit operation is allowed. If the battery voltage
is determined to be low, the following warning message
is displayed indefinitely.
UNIT WARNING: !! LOW BATTERY !!
CHECK SETPOINTS/PROGRAM/OPTIONS/TIME
JOHNSON CONTROLS 87
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