Service Manual

18
LG SCROLL COMPRESSOR
The compressors used in these products are specifically
designed to operate with designated refrigerants and cannot
be interchanged.
LG produced scroll compressors are designed to operate
and function as the typical orbiting scroll on a fixed scroll
design. Refrigerant flow and compression is basically the
same.
Characteristics of the LG Scroll Compressor:
Internal Motor Overload Protection (OLP): This is an
inherent protection system sensing both motor winding
temperature and motor current. This is designed to open the
common wire on single phase units and stop the motor
operation if motor high temperature or over current
conditions exist. Trip of the OLP opens the common line.
Vacuum protection device: If the suction side of the
compressor is blocked or limited, an extremely low vacuum
situation is formed by the optimum efficiency of the scrolls.
The high vacuum pressure causes the arc at the internal
power terminal and cause tripping of the internal overload or
breaker or damage to the compressor. This compressor is
equipped with internal protection that opens if this high
vacuum condition exists and bypasses high pressure gas to
the low pressure and the internal overload may trip. In the
case of refrigerant pump down, the unit can operate with
pump down but this protection may not allow the refrigerant
to be pumped down completely.
Inte rnal Pressure Relief (IPR): The internal pressure relief
is located between the high and low pressure of the
compressor and is designed to open when the difference of
the suction and discharge pressure is 500- 550 psid. When
the IPR valve opens, the high temperature gas bypasses
into the motor area and will trip the motor OLP.
Quiet Shut Down Device: The LG scroll has a shut down
device to efficiently minimize the shut down sound. The
reversing sound is minimized by a check valve located in
the discharge port of the scroll sets. This slows the
equalization of the high side to low side upon shut down to
prevent the scrolls from operating backwards.
Discharge Temperature Protection: The compressor
discharge temperature may be monitored by a temperature
sensor mounted on the top cap of the compressor. Wire
diagrams may refer to this as a discharge temperature
switch (DTS). This is to protect against excessively high
scroll temperatures due to loss of charge or operating
outside the compressor envelope. This temperature sensor
opens to stop the compressor if temperatures exceed
239- 257_F (115- 125_C) and resets at 151- 187_F
(66- 86_C). The DTS will break the Y signal in the 24 volt
circuit if it trips open.
NOTE: The LG generation 2 compressor models will not
have this temperature switch.
Test sensor wires for continuity, open above 239- 257_F
(115- 125_C) and resets at 151- 187_F(66-86_C).
If replacement is deemed necessary, perform the following
to replace sensor:
1. Locate top cap and discharge temperature sensor
A12342
2. Carefully remove sensor cover
A12343
3. Expose the sensor holder