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Important Note: Never close the compressor suction
line to test its pumping efficiency. This will seriously dam-
age the compressor and void its warranty.
• The compressor may run backwards (noisy opera-
tion) for 1 or 2 seconds at shutdown. This does not
harm the compressor.
• These scroll compressors have copper plated steel
suction tubes. If removal and reconnection becomes
necessary, use silfos with minimum 5% silver or sil-
ver braze material with flux.
• Operating pressures and current draws may differ
from standard reciprocating compressors. See Sec-
tion XV for typical cooling performance data.
Reciprocating Compressor
The PGC48 includes a reciprocating compressor with a
crankcase heater. See the caution for the PGC48 be-
fore starting cooling operation.
CAUTION
To avoid severe personal injury or fire,
refrigerant must be removed from both
the low and the high pressure sides of
the system before heat is applied.
Operating Instructions (cooling)
CAUTION
On PGC48 Only: To avoid damage to the
compressor, engage the electrical dis-
connect switch to the compressor unit
four hours prior to operating air condi-
tioner after the electrical disconnect is off
for a prolonged period of time (during
vacation, etc.). This time lapse allows the
compressor crankcase to attain a proper
operating temperature.
(NOTE: Mechanical cooling cannot be reliably provided
at ambient temperatures below 50° F. If low ambient
cooling will be required a downflow economizer is avail-
able. See Section XIV.)
1. Turn on the electrical power supply to the unit.
2. Place the room thermostat selector switch in the
COOL position (or AUTO if available, and if auto-
matic changeover from cooling to heating is desired).
3. Set the room thermostat to the desired temperature.
Figure 20
High Pressure Protection Devices
Scroll Compressors
PGC 24, 30, 36, 42, 60, and PGB58 units include scroll
compressors. The installer and servicer should be aware
of the following differences between scroll compressors
and reciprocating compressors:
• These scroll compressors include a thermostat (ex-
ternal compressor protector) mounted to the top of
the compressor. THIS PROTECTIVE DEVICE
SHOULD NEVER BE BYPASSED FOR ANY PUR-
POSE.
• On a scroll compressor, due to its inherent ability to
handle liquid refrigerant, a crankcase heater is not
required.
CAUTION
To avoid severe personal injury or fire,
refrigerant must be removed from both
the low and the high pressure sides of
the system before heat is applied.
• The scroll compressors use white oil which is com-
patible with 3GS. If the addition of oil in the field is
required, 3GS may be used .