Friedrich 9 - Manual (Page 36)

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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.
ComPRESSoR CHECkS
ELECTRIC SHOCK HAZARD
WARNING
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.
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 overload
External overload VPak 9, 12, 18 k Btus
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.
Internal overload VPak 24 k Btus
The overload is embedded in the motor windings to
sense the winding temperature and/or current draw. The
overload is connected in series with the common motor
terminal.
1. With no power to unit, remove the leads from the com-
pressor terminals. Allow motor to cool.
2. Using an ohmmeter, test continuity between terminals
C-S and C-R. If no continuity, the compressor overload is
open and the compressor must be replaced.
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 compressor.
Turn on the unit and read the running amperage on the me-
ter. If the compressor does not start, the reading will indicate
the locked rotor amperage (L.R.A.).
overloads
The compressor is equipped with an external or internal
overload which senses both motor amperage and wind-
ing temperature. High motor temperature or amperage
heats the overload causing it to open, breaking the com-
mon circuit within the compressor.
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.
WARNING
BURN HAZARD
ELECTRIC SHOCK HAZARD
WARNING
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.
Internal Overload