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SERVICING
Locked Rotor Test
If fuse, circuit breaker, ground fault protective device, etc.
has tripped, this is a strong indication that an electrical
problem exists and must be found and corrected. The
circuit protective device rating must be checked and its
maximum rating should coincide with that marked on the
equipment nameplate.
Before checking for locked rotor, the compressor terminals
should be checked for open windings (see Resistance Test)
and the run capacitor and start capacitor (if used) should
be checked thoroughly (see Checking Capacitor).
With power ON:
Line voltage now present.
1. Check the serial data plate for the compressor locked
rotor amps (LRA) rating.
2. Using an ampmeter, measure the amperage reading
for the run and common wires to the compressor.
Since the compressor motor overload will likely
trip soon after drawing locked rotor amps, this
measurement should be taken as soon as the
compressor starts.
3. If the amperage reading roughly equals the
compressor LRA rating and all other checks have
been completed, locked rotor amps has been verified.
Testing crankcase heater (Optional Item)
The crankcase heater must be energized a minimum of
four (4) hours before the condensing unit is operated.
Crankcase heaters are used to prevent migration or
accumulation of refrigerant in the compressor crankcase
during the off cycles and prevents liquid slugging or oil
pumping on start up.
A crankcase heater will not prevent compressor damage
due to a floodback or over charge condition.
Disconnect ALL power before servicing.
1. Disconnect the heater lead in wires.
2. Using an ohmmeter, check heater continuity - should
test continuous. If not, replace.
WARNING
WARNING
Refrigeration Repair Practice
Always remove the refrigerant charge in a proper manner
before applying heat to the system.
When repairing the refrigeration system:
Disconnect ALL power before servicing.
1. Never open a system that is under vacuum. Air and
moisture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of
the tubing with sand cloth or paper. Brazing materials
do not flow well on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and
pipe chips.
5. When brazing, sweep the tubing with dry nitrogen to
prevent the formation of oxides on the inside surfaces.
6. Complete any repair by replacing the liquid line drier
in the system, evacuate and charge.
Brazing Materials
Copper to Copper Joints - Sil-Fos used without flux
(alloy of 15% silver, 80% copper, and 5% phosphorous).
Recommended heat 1400°F.
Copper to Steel Joints - Silver Solder used without
a flux (alloy of 30% silver, 38% copper, 32% zinc).
Recommended heat - 1200°F.
Aluminum to Aluminum & Copper to Aluminum Joints
– ZA-1 Brazing Rods use Flux System Cesium-Based
Polymer System (alloy of 78% Zinc and 22% Aluminum).
Melting point 826°F Flow point 905°F.
Standing Pressure Test (Recommended Before
System Evacuation)
To avoid the risk of fire or explosion, never use oxygen,
high pressure air or flammable gases for leak testing of a
refrigeration system.
To avoid possible explosion, the line from the nitrogen
cylinder must include a pressure regulator and a pressure
relief valve. The pressure relief valve must be set to open at
no more than 450 PSIG.
DANGER
WARNING
WARNING
WARNING
23
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