Service manual

18
COPELAND SCROLL COMPRESSOR
Scroll Gas Flow
Compression in the scroll is
created by the interaction of
an orbiting spiral and a
stationary spiral. Gas enters
an outer opening as one of the
spirals orbits.
The open passage is sealed off
as gas is drawn into the spiral.
By the time the gas arrives at
the center port, discharge
pressure has been reached.
Actually, during operation, all
six gas passages are in various
stages of compression at all
times, resulting in nearly con-
tinuous suction and discharge.
As the spiral continues to orbit,
the gas is compressed into an
increasingly smaller pocket.
1
23
54
A90198
Fig. 11 – Scroll Compressor Refrigerant Flow
The compressors used in these products are specifically designed to
operate with designated refrigerant and cannot be interchanged.
The compressor is an electrical (as well as mechanical) device.
Exercise extreme caution when working near compressors. Power
should be shut off, if possible, for most troubleshooting techniques.
Refrigerants present additional safety hazards.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant.
CAUTION
!
The scroll compressor pumps refrigerant through the system by the
interaction of a stationary and an orbiting scroll. (See Fig. 11.) The
scroll compressor has no dynamic suction or discharge valves, and
it is more tolerant of stresses caused by debris, liquid slugging, and
flooded starts. The compressor is equipped with an internal
pressure relief port. The pressure relief port is a safety device,
designed to protect against extreme high pressure. The relief port
has an operating range between 550 to 625 psi differential pressure
for Puronr and 350 to 450 psi differential pressure for R--22.
Scrolls have a variety of shut down solutions, depending on model,
to prevent backward rotation and eliminate the need for cycle
protection.
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.
Internal 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 (55--550 psid (35.1--38.7 kg/cm2). 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 is 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.
Test sensor wires for continuity, open above 239--257F_F
(115--125_C) and resets at 151--187_F (66--86_C).