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PKG-SVX027D-EN
Diagnostics
Troubleshooting
System Checks
WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury.
When it is necessary to work with live electrical
components, have a qualified licensed electrician or
other individual who has been properly trained in
handling live electrical components perform these
tasks.
Before proceeding with technical trouble charts or controls
checkout, complete the following system analysis:
1. Measure actual supply voltage at the compressor and
an motor terminals with the unit running. Voltage must
be within the range listed on the motor nameplate.
Phase imbalance must be less than 2.0%.
2. Check all wiring and connections to be sure that they
are intact, secure and properly routed. The as wired
system diagrams are provided in the unit control panel.
3. Check that all fuses are installed and properly sized.
4. Inspect air filters and coils to be sure that airflow to the
unit is not restricted.
5. Check the zone thermostat settings.
6. Ensure that the fan is rotating in the proper direction. If
phasing is wrong at the main power terminal block, the
fan and compressors will not run correctly.
7. Inspect ductwork and duct connections for tightness.
Operating Procedures
Install pressure gauges on the discharge and suction line
access valves. When the unit has stabilized (after
operating approximately 15 minutes at full load), record
suction and discharge pressures. System malfunctions
such as low airflow, line restrictions, incorrect refrigerant
charge, malfunctioning of expansion valves, damaged
compressors, etc. will result in pressure variations which
are outside the normal range.
Note: If phasing at the main incoming power terminal is
incorrect, switch two of the three incoming power
leads. If a compressor has been replaced and the
phase is changed at the compressor, it will run
backwards and discharge pressure will be very low.
To resolve incorrect compressor wire phasing,
change phasing at the compressor.
It is important that pressures be measured under stable
and constant conditions in order for the readings to be
useful.
Voltage Imbalance
Voltage imbalance on three-phase systems can cause
motor overheating and premature failure. Maximum
allowable imbalance is 2.0%, and the readings used to
determine it must be measured at the compressor
terminals.
Voltage imbalance is defined as 100 times the sum of the
division of the three voltages from the average voltage. If,
for example, the three measured voltages are 221, 230,
227, the average is:
221 + 230 + 227
3
= 226 volts
Therefore, the percentage of voltage imbalance is:
100*(226-221)/226 = 2.2%
In this example, 2.2% imbalance of more than 2.0% exists,
be sure to check the voltage at the unit disconnect and
terminal block switch. If an imbalance at the unit disconnect
switch does not exceed 2.0%, the imbalance is caused by
faulty wiring within the unit. Be sure to conduct a thorough
inspection of the unit electrical wiring connections to locate
the fault, and make any repairs necessary.
Table 21. Potential unit issues and solutions
Problem Possible Cause Remedy
Drain pan is overflowing Plugged drain line Unit not level Clean drain line Level unit
Standing water in drain pan Unit not level Plugged drain line Level Unit Clean drain line
Wet interior insulation Coil face velocity too high Improper trap design
Drain pan leaks/overflowing Condensation on
surfaces
Reduce fan speed Design trap per unit installation
instructions Repair Leaks Insulate surfaces
Excess dirt in unit Missing filters Filter bypass Replace filters Reduce filter bypass
Microbial growth (mold) Standing water in drain pan See "Standing water in drain pan" above
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