Vogt Tube-Ice HFO10, Service Manual

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9-5
Compressor Motor Protection — Field Diagnosis
The protective devices SE-E1 or SE-E2 monitor motor and discharge gas temperatures, rotating direction, and
check for phase loss.
•
Temperature monitoring . Locks out immediately if pre-set temperatures for the motor, discharge gas,
or the oil are exceeded. Acceptable temperature range is -22° to 140°F (-30 to 60°C).
•
Compressor Rotation . Checks the rotation direction during the first 5 seconds of compressor operation.
If the compressor starts with the wrong rotation direction, the module locks out immediately.
•
Phase Loss . Checks for phase loss in the first 5 seconds of compressor operation and opens relay contact
immediately if phase loss occurs. The contact closes after 6 minutes. If three-phase losses occur within
18 minutes, or 10 within 24 hours, the module locks out.
•
Reset. To reset after a lock out, power must be removed from the module for 5 seconds.
Compressor Motor Burnout
Compressor motor burnout can have several causes, including:
•
Low Line Voltage . A compressor motor is designed to operate within the range of ±10% of its nameplate
voltage. Low voltage requires the motor windings to carry more current at the same compressor load.
When this current becomes too high or is applied for an extended period, the motor windings overheat,
resulting in a failure.
•
Loss of Refrigerant . The semi-hermetic compressor motor is maintained at proper operating
temperature by passing cool suction gas over the motor windings. A loss of refrigerant can cause the
winding to overheat, resulting in a failure or burnout.
•
High Head Pressure . The system is designed to operate at 130 psig (9 bar). Excessive head pressure
increases the refrigeration load on the compressor. This increase can cause the windings to overheat,
resulting in a failure or burnout.
•
Moisture . Moisture in contact with refrigerant oil and the presence of heat will form hydrochloric or
hydrofluoric acid. The acid will destroy the insulation on the motor windings, causing a short circuit,
which can increase motor temperatures in excess of 3,000°F (1,649°C). This extreme temperature will
also create a sludge or black residue in the system.
•
Mechanical Failure . Mechanical failure has been determined to be a major cause of motor burnout.
Bearing wear or wipe-out may allow the rotor to drag, overheating the windings and causing a burnout.
Whenever a compressor fails because of a motor burnout, it is important to thoroughly clean the system before
replacing the damaged compressor, or a new compressor may also become damaged.