Emerson Copeland Scroll ZH04K1P Manual page 32

Condition
Defective
system control
components
Power circuit
open
Burned motor
winding
The Scroll
compressor does
not run, no buzz
sound can be heard
High discharge
pressure /
suction
pressure
Compressor
The Scroll
operating
compressor trips on
outside the
motor protection
design limits
C6.2.26/1013-1116/E
Cause
Check if the pressure control or thermostat works
properly or if the controls are open.
Check the fuse for a tripped circuit breaker or for an
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 functioning protection
system can be the result. For sizing information
please consult with Contactor manufacturer data
sheet. If the application of the compressor is
changed the contactor sizing should be rechecked.
Check for unbalanced voltage.

For high discharge pressure:
- Check for 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 fan 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.
 For high suction pressure, check the "evaporator
superheat" first to diagnose the problem:
- 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.

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.
- Check the compressor suction and discharge
pressures while it is running. Make sure they
are within the operating envelope.
Corrective action
29