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LESSON

2LECTURE

COMPRESSORS, CONDENSERS,FILTERS & DRYERS

SUB-OBJECTIVE

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() LO/ SIDE FILTER-DRIER

Some systems include a low-side filter-drier at the compressor end of thesuction line. These may be a part of the original system or may be placed inthe system, for a short time, to clean it up Fig. 4.2.1 is a typical suction linefilter-drier. The filter-drier used in the suction line should offer little resistanceto the flow of the vaporied refrigerant. This is because the pressuredifference between the pressure in the evaporator and the inlet to thecompressor should be small.

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2) COMPRESSOR LO/ SIDE OR SUCTION SERVICE VALVE

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!any systems have some means that allow the service technician to connectgauges to the system, chec/ pressures and add or ta/e out refrigerant or oil.

' typical compressor suction service valve is pictured in Fig. 4.2.2. This valveis connected to the compressor at the compressor inlet union.

The suction line from the evaporator is attached at the low-side inlet. Sealingcaps protect the charging and gauge opening port and the valve stem whenthe valve is not in use.

!ore recent domestic models do not have service valves. The servicetechnician must use a saddle valve.

2)( COMPRESSOR

The refrigeration compressor is a motor-driven device, which moves the heat-laden vapor refrigerant from the evaporator and compresses 0sueees it intoa small volume and to a high temperature.

The various types of pumping mechanisms 0compressors used are e3plainedlater in this chapter.

1) COMPRESSOR 5I65-SIDE SERVICE VALVE

The compressor high-side service valve provides a shutoff between thecompressor and the condenser. (t also provides an opening for a high-pressure gauge or a gauge manifold.

ith the valve closed 0all the way in, it is possible to disconnect thecompressor from the condenser without any lea/age of refrigerant from the

condenser.

hen the valve stem is all the way out, the opening for the gauge is closed.

Fig. 4.2.2 illustrates a cross-section of the service valve. (t is not used on allrefrigerating system.

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3) OIL SEPARATOR

)efrigeration compressors get their lubrication from a small amount of speciallubricating oil place inside the compressor cran/case or housing. This oil iscirculated to various compressor parts. (n a hermetic 0airtight system, this oil

also lubricates the motor bearings.

hen the compressor operates, small amounts of oil will be pumped out withthe hot compressed vapor. ' small amount of oil throughout the system doesno harm.

6owever, too much oil in such parts as the condenser, refrigerant flowcontrols, evaporator and filters interferes with their operation.

(t is possible to separate the oil from the hot compressed vapor. This involvesplacing an oil separator between the compressor e3haust and the condenser.

The location and operation of such a separator is shown in Fig. 4-2-7. Theseparator is enlarged in the illustration to help show details.

The oil separator is a tan/ or cylinder with a series of baffles or screens, whichcollect the oil. The oil separated from the hot, compressed vapors, drops tothe bottom of the separator.

' float arrangement controls a needle valve, which opens an oil return line tothe compressor cran/case. hen the oil level is high enough, the float risesand opens the needle valve.

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This oil returns uic/ly to the compressor cran/case, as the pressure in theseparator is considerably higher than the pressure in the compressor

cran/case.

"il separators are uite efficient. 8ery little oil passes on into the system.They are most commonly used in large commercial installations.

7) CONDENSER

The condenser in the refrigeration cycle removes the condensation heat fromthe refrigerant vapor. This heat is pic/ed up in the evaporator. #omesticrefrigerators commonly use the four following types of condensers 0see fig.4.2.4.

1. Finned-static 0natural convection

2. Finned-forced convection.

7. ire-static

4. late-static

(llustrated in view ', Fig. 4.2.4 is a common finned type static condenser.Static means that air circulation through the condenser tubing and fins is by

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natural convection9 that is, warm air tends to rise. 's the air in contact with thefins and tubes becomes heated, it rises and cooler air ta/es its place. Thetubes and fins are usually made of copper or steel.

8iew :, Fig. 4.2.4 is a forced convection fin type condenser.

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henever the compressor is operating, the motor driven fan forces air through thecondenser.

Shown in view * is a wire type condenser, which uses small metal wires,braed or spot-welded to the condenser tubing. (t is usually of the static type.

The plate type condenser is pictured in view #. (n this type, the condensertubes are soldered or braed to a flat metal surface.

This is a very common type of condenser construction. (t is used on manychest type freeers. The condenser tubes are attached to the inside0insulation side of the freeer;s outer shell.

This type of condenser is very easy to /eep clean. (t is only necessary to wipeoff the surface of the cabinet shell. To get proper removal of heat from therefrigerant vapor, always /eep the condenser clean.

*ommercial systems use three types of condenserscoolingtowers> are being used in connection with water cooled condensers.

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9) LI:UID RECEIVER

The liuid receiver is a storage tan/ for liuid refrigerant. hen arefrigerating mechanism has one, the refrigerant is usually pumped out of thevarious parts and stored in it during servicing. (ts use ma/es the uantity ofrefrigerant in a system less critical.

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"ccasionally one may find a liuid receiver built into the bottom of thecondenser. !ost receivers have service valves. See Fig. 4.2.?. ' fine coppermesh in the outlet prevents dirt from entering the refrigerant control valves.

%iuid receivers are used on most systems with the low-side float type, of thee3pansion valve, type refrigerant control.

*apillary tube systems do not use them because the entire liuid refrigerant isstored in the evaporator during the off part of the cycle. reater use of

hermetic systems and capillary tube refrigerant controls has removed theneed for liuid receivers in domestic systems and in many small commercialunits.

"n larger commercial systems the receiver provides enough reserve liuidrefrigerant to insure that the liuid line refrigerant is sub cooled and free offlash gas.

The receiver must provide enough room for refrigerant during automatic pumpdowns 0for defrost purposes and when some of the evaporators are not inuse.

;) LI:UID LINE FILTER-DRIER

(t is common practice to install a filter-drier in the liuid line. This tan/-li/eaccessory /eeps moisture, dirt, metal and chips from entering the refrigerantflow control. hat is more, the drying element in the filter removes moisture,which might otherwise freee in the refrigerant flow control.

!oisture is also harmful when mi3ture with oil in a system. (t forms, sludge@sand acids. (t is especially harmful to hermetic units. ' liuid line filter drier isshown in Fig. 4.2.?

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Some filter dryers are euipped with a sight glass, which will indicaterefrigerant level.

!any sight glasses also have a chemical, which will change color when thesystem has moisture in it.

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hile copper tubing is commonly used to carry the liuid refrigerant from thecondenser to the evaporator, domestic units often use steel. These lines aremounted in bac/ of the refrigerator cabinet or are hidden behind the brea/erstrip at the refrigerator doorCamb 0frame.

The lines are soldered or braed to fittings. (t is important to avoid pinching orbuc/ling these lines. They must also be supported to prevent wear orbrea/age from vibration.

)efrigerant lines in commercial units may be connected by soldering, braingor by flared fittings.

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