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