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Condition
The scroll
compressor does
not run, no buzz
sound can be heard
The scroll
compressor trips on
motor protection
AGL_HP_ST_ZHK1P_EN_Rev00
Cause
Corrective action
Compressor
Check if there is continuity on the compressor external
motor
protector. If the compressor is warm, it may require
protector open
considerable time to cool down.
Def ective
Check if the pressure control or thermostat works
system control
properly or if the controls are open.
components
Power circuit
Check the f use for a tripped circuit breaker or for an
open
open disconnected switch.
If motor burned due to undersized contactors, you will
observe that the contacts welded together. Complete
motor burnout on all three phases despite the presence
of a f unctioning protection system can be the result. For
Burned motor
sizing inf ormation please consult with Contactor
winding
manuf acturer data sheet. If the application of the
compressor is changed the contactor sizing should be
rechecked.
Check f or unbalanced voltage.
▪
For high discharge pressure:
-
-
-
High discharge
pressure /
suction
▪
pressure
For high suction pressure, check the "evaporator
superheat" first to diagnose the problem:
-
▪
Low superheat at the evaporator outlet is
characterized by oversized selection of the
expansion valve or incorrect bulb sensor mounting.
The valve may freeze up in the open position due to
accumulation of debris in the system. For a system
with very short refrigeration lines an accumulator is
recommended.
Compressor
Check the compressor suction and discharge pressures
operating
while it is running. Make sure they are within the
outside the
operating envelope.
design limits
If all operating conditions are normal, the voltage
supply at the compressor terminals is balanced and
Def ective
within limits, the compressor crankcase temperature is
motor
within normal limits, and the amperage drawn is within
protector
the specified range, the motor protector may be
def ective.
Check f or system leaks.
Check the system design. Make sure the
discharge line is correctly sized: undersized
discharge line can increase discharge
pressure. This is also true for an undersized
condenser. Correct the component selection as
needed.
Check the f an motor, make sure it is running
properly in the right direction. Check the
condenser: if dirt has been accumulated it will
clog the airflow; clean as necessary. High
discharge pressure is also caused by an
overcharged system and high ambient
temperature surrounding the condenser.
High superheat at the evaporator outlet: this is
likely in case of excessive pressure-drop in the
liquid line or too much vertical lift on the pipe
work.
33
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