Johnson Controls YEWS Series, Installation, Operation And Maintanance Instructions

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compressor overload protection module.
Compressor overload protection is achieved as following:
Motor protector sense the current of each phase of motor
current and the temperature of motor, and send
corresponding signals to the I/O Board.Then compare the
values with MLA setpoints and active to protect the motor
once the the values is higher than MLA setpoints.It
protects the compressor motors from damage due to:
Current overload, current imbalance (the error of the
current of each phase), miswire, motor over temperature,
uncalibrated, supply power phase loss.
The control panel include: Microcomputer keyboard, HMI
and microprocessor board.
2.8 Control panel
The HMI consists of a liquid crystal display, with light
emitting diode backlighting for outdoor viewing of
operating parameters and program points. It can display 8
rows and 120 characters in 2 languages (English or
Chinese). The keyboard has 20 keys, which is divided into
two kinds: Funtion keys and Programme keys.
The standard control function of microprocessor board
includes: chiller alarm contactor controlling, chilled water
pump controlling, chiller auto resetting when it is repower
on after a period of power off, optimizing the system
automaticly according to the running conditions
Unit operating firmware is stored in non-volatile memory
(Flash Memory) to protect chiller from failture for power
off. All field programmed setpoints are retained in the
EPROM register. A lithium battery backed real time clock
(RTC) supply the clock for the system control, and the
battery has 3 years memory.
2.9 Motor protection
The microprocessor provides the overcurrent protection to
ensure that the motor is free from the damages due to
excessive voltage and other overcurrent problems.
After the Star/Delta starter started for more than 10
seconds, the microprocessor will shut down and lock the
chiller for fault if the current exceeds the current
setpoints. It is required to reset the system switch
manually to eliminate the fault before restart the system.
And prior to start the chiller which stopped due to
overcurrent, chec-king should be done on the motor,
wiring and refrigerant system.
When it is found that the current is lower than 10% of
MLA (Max Loading Amps), the low current protection
will be initiated and the unit should be stopped. In that
case, prior to restart the system, unit resetting should be
done manually.
Motor protector
Motor protector is used to protect motor from overheat,
There are three PTC (Positive Temperature Coefficient)
thermistor installed in each phase of motor winding. The
resistance of thermistor will keep in 1K when the
temperature is lower than 125
℃
, however, the resistance
of thermistor will increase as its temperature rise. When
the resistance value of sensor reach upto 13K, the motor
protector will be active and cut off the power supply of
motor. The chiller is not allowed to restart until the motor
is cooled down and the resistance value of sensor drop
down to 3.25K.
2.10 Keyboard control
Display
The parameters of each refrigerant circuit can be
displayed in 2 languages (English or Chinese),
All the displayed parameters are listed as follows:
Entering/Leaving chilled water temperature
Entering/Leaving cooling water temperature(Entering/le-
aving hot water temperature are diaplayed in heatpump
mode).
Time and date, start and stop time at ordinary days,
arrangement on holidays and status of manual setting.
YEWS-E Water Cooling Screw Chiller/Heat Pump