Diagnostics; Troubleshooting; System Checks; Operating Procedures - Trane SCWM Series Installation, Operation And Maintenance Manual

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
Table 27. Potential unit issues and solutions
Problem
Drain pan is overflowing
Standing water in drain pan
Wet interior
Excess dirt in unit
Microbial growth (mold)
PKG-SVX027A-EN
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
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
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.
Possible Cause
Plugged drain line Unit not level
Unit not level Plugged drain line
Coil face velocity too high Improper trap design
Drain pan leaks/overflowing Condensation on
surfaces
Missing filters Filter bypass
Standing water in drain pan
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.
= 226 volts
3
Clean drain line Level unit
Level Unit Clean drain line
Reduce fan speed Design trap per unit
installation instructions Repair Leaks Insulate
Replace filters Reduce filter bypass
See "Standing water in drain pan" above
Remedy
surfaces
71