Installation and operation manual
34
EWWD440~850AAYNNO**
Packaged water-cooled water chillers
4PW25558-1B
Symptom 8: Despite chilled water temperature is high, unit does not
perform full load operation
Symptom 9: Unit water outlet temperature is unstable
Symptom 10: Frequent ON-OFF of compressor
If problems persist after checking above items, contact your dealer.
Safety devices
As the unit comes with safety devices, safe operation is guaranteed.
If the safety device is activated, the error pilot lamp lights up when the
unit stopped operation (hereafter described as "Abnormal stop"),
details of the safety device that was activated is displayed in the
graphic panel display.
The fact that unit falls into an abnormal stop condition is signalled to
the remote controller too.
Abnormal stops of the unit can be divided into 2 groups:
■
Unit error
Unit errors indicate a critical malfunction such as a discharge
high-pressure error or a chilled water overcool error that has
effect on the entire unit. Both compressors stop.
■
Individual compressor error
Individual compressor errors indicate the error of an individual
compressor such as a motor overload.
The entire alarm is indicated and the error-side compressor
stops. The compressor of the side where the error does not
occur continuous to operate.
Refer to
"I/O timing of various contacts" on page 29
timing to the remote controller in case of errors.
Safety devices for unit errors
P
OSSIBILE
CAUSES
C
ORRECTIVE
ACTION
Immediately after starting the unit
(Of the order of 10 minutes)
Unit operates reading the target
temperature differently for preventing
sudden drop of unit water
temperature, and for preventing
thermo stop due to sudden increase
of capacity control opening. (See
"Water temperature control
immediately after unit start" on
page 27
Current limiting function is activated
Adjust capacity control load forcedly
so that operating current reaches
predetermined amperage or less for
the protection of power circuit. (See
"Current limiting function" on
page 23
Demand function is activated
Adjust capacity control opening
forcedly so that demand function is
activated and operating current
reaches predetermined value or
less. (See
)
Operating condition falls outside of
recommended operation range
When operating condition falls
outside of recommended operation
range, in some cases capacity
control load may have been adjusted
for the protection of unit forcedly.
Discharge superheat level is low
Adjust capacity control load forcedly
when discharge superheat
temperature is 9°C or less for
preservation of the lubrication
system.
P
OSSIBILE
CAUSES
C
ORRECTIVE
ACTION
Unit water flow rate is unstable
Condenser water flow rate is
unstable
Make flow rate stable.
Mixing of air into water system
Perform air purge.
Sudden change of condenser water
inlet temperature occurs frequently
Adjust ON-OFF setting of cooling
tower and setting of water regulating
valve like 3-way valve etc.
P
OSSIBILE
CAUSES
C
ORRECTIVE
ACTION
Low cooling load of the system
Increase set point of thermo reset
differential for a try (See
Excessively low chilled water flow
rate
Increase flow rate.
Low equipment holding water
quantity
Increase minimum holding water
quantity.
WARNING
Contact your dealer in the event of abnormality (smell
of burn, etc).
Continuing operation with persisting abnormalities may
result in breakdown, electric shock or fire.
1. Discharge pressure high error
P
OSSIBILE
CAUSES
D
ETAILS
OF
ACTIVATION
• Extremely high condenser water
temperature
• Low condenser water quantity
• Bad contamination condition
inside condenser
• Some valve of the unit closed
• Excess charging of refrigerant
High pressure switch is activated
2. Suction low pressure error
P
OSSIBILE
CAUSES
D
ETAILS
OF
ACTIVATION
• Low unit water flow rate
• Too low condenser water
temperature
• Bad contamination condition
inside evaporator
• Some valve of the unit closed
• Refrigerant gas leakage
Suction pressure falls short of set
point continuously for a certain time
3. Antifreeze error
P
OSSIBILE
CAUSES
D
ETAILS
OF
ACTIVATION
• Low unit water flow rate
• Fluctuation of flow rate
• Low target temperature setting
• Extremely low equipment holding
water quantity
Freeze-up protection thermostat is
activated
4. Unit water failure
P
OSSIBILE
CAUSES
D
ETAILS
OF
ACTIVATION
• Low unit water flow rate
• Fluctuation of flow rate
• Mixing of air into system
Unit water interruption relay turns
ON for 5 seconds in a row (The first
15 seconds after starting are
ignored)
5. Cooling water interruption error
P
OSSIBILE
CAUSES
D
ETAILS
OF
ACTIVATION
• Low cooling water flow rate
• Fluctuation of flow rate
• Mixing of air into system
Cooling water interruption relay turns
ON for 5 seconds in a row (The first
15 seconds after starting are
ignored)
