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70
System Start-Up
Systems operating with superheat in excess of 16 degrees:
A. Could cause excessive compressor cycling on internal winding thermostat
which leads to compressor motor failure.
B. Lowers the efficiency of the evaporator by reducing the heat transfer ca-
pability.
Measuring Superheat
A. Measure the suction pressure at the suction line gauge access port locat-
ed near the compressor.
B. Using a Refrigerant / Temperature chart, convert the pressure reading to
a corresponding saturated vapor temperature.
C. Measured the suction line temperature as close to the expansion valve
bulb, as possible.
D. Subtract the saturated vapor temperature obtained in Step B from the ac-
tual suction line temperature obtained in step c. The difference between the
two temperatures is known as "superheat".
Note: When adjusting superheat, recheck the system subcooling before
shutting the system "Off".
7. Once the checks and adjustments for the operating circuit has been com-
pleted, check and record the:
ambient temperature;
compressor oil level (each circuit);
compressor suction and discharge pressures (each circuit);
superheat and subcooling (each circuit);
Record this data on an "Operator's Maintenance Log" shown in Table 12.
8. Press the STOP key at the Human Interface Module in the unit control
panel to stop the system operation.
9. Repeat Steps 1 through 8 for the number 2 refrigeration circuit.
10.After shutting the system off, check the compressor's oil's appearance.
Discoloration of the oil indicates that an abnormal condition has occurred.
If the oil is dark and smells burnt, it has overheated because of: compres-
sor is operating at extremely high condensing temperatures; high super-
heat; a compressor mechanical failure; or, occurrence of a motor
burnout.
If the oil is black and contains metal flakes, a mechanical failure has
occurred. This symptom is often accompanied by a high compressor
amperage draw.
If a motor burnout is suspected, use an acid test kit to check the condition
of the oil. Test results will indicate an acid level exceeding 0.05 mg
KOH/g if a burnout occurred.
CSRA-SVX02A-EN
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