COMPRESSOR CHECKS
WARNING
ELECTRIC SHOCK HAZARD
Turn off electric power before service or installation. Extreme care must be used, if it becomes necessary to work on equipment with power applied.
Failure to do so could result in serious injury or death.
Locked Rotor Voltage (L.R.V.) Test
Locked rotor voltage (L.R.V.) is the actual voltage available at the compressor under a stalled condition.
Single Phase Connections
Disconnect power from unit. Using a voltmeter, attach one lead of the meter to the run “R” terminal on the compressor and the other lead to the common “C” terminal of the com- pressor. Restore power to unit.
Determine L.R.V.
Start the compressor with the volt meter attached; then stop the unit. Attempt to restart the compressor within a couple of seconds and immediately read the voltage on the meter. The compressor under these conditions will not start and will usually kick out on overload within a few seconds since the pressures in the system will not have had time to equalize. Voltage should be at or above minimum voltage of 197 VAC, as specified on the rating plate. If less than minimum, check for cause of inadequate power supply; i.e., incorrect wire size, loose electrical connections, etc.
Amperage (L.R.A.) Test
The running amperage of the compressor is the most impor- tant of these readings. A running amperage higher than that indicated in the performance data indicates that a problem exists mechanically or electrically.
Single Phase Running and L.R.A. Test
NOTE: Consult the specification and performance section for running amperage. The L.R.A. can also be found on the rating plate.
Select the proper amperage scale and clamp the meter probe around the wire to the “C” terminal of the compres- sor. Turn on the unit and read the running amperage on the meter. If the compressor does not start, the reading will indicate the locked rotor amperage (L.R.A.).
External Overload
The compressor is equipped with an external overload which senses both motor amperage and winding tem- perature. High motor temperature or amperage heats the overload causing it to open, breaking the common circuit within the compressor.
Heat generated within the compressor shell, usually due to recycling of the motor, is slow to dissipate. It may take anywhere from a few minutes to several hours for the overload to reset.
Checking the External Overload
WARNING
ELECTRIC SHOCK HAZARD
Turn off electric power before service or installation. Extreme care must be used, if it becomes necessary to work on equipment with power applied.
Failure to do so could result in serious injury or death.
WARNING
BURN HAZARD
Certain unit components operate at temperatures hot enough to cause burns.
Proper safety procedures must be followed, and proper protective clothing must be worn.
Failure to follow this warning could result in moderate to serious injury.
With power off, remove the leads from compressor termi- nals. If the compressor is hot, allow the overload to cool before starting check. Using an ohmmeter, test continu- ity across the terminals of the external overload. If you do not have continuity; this indicates that the overload is open and must be replaced.
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