Servicing of refrigerators

5-Servicing of refrigerators5-1Troubleshooting procedure(general) -obtain description of problem by user -identify, confirm and determine possible cause consult service manual Trouble shooting chart knowledge, right instrument and tool experience and judgment needed -identify specific remedy 5-2 Trouble shooting chart - unit will no run -Refrigerator section too warm -Refrigerator section too cold -Freezer section and Refrigerator section too warm -Freezer section too cold -Unit runs all the time -Stuck motor compressor -Frost or ice on finned evaporator -Unit runs all the time temperature normal -Freezer runs all the time temperature too cold -Freezer runs all the time temperature too warm -Rapid ice build up on the evaporator -Doors on freezer compartment freezes shut -Freezer works and then warms up -Gradual reduction in freezing capacity5-3 Hermetic unit servicing guide To service successively, know how should perform when in good condition 5-3-1 External servicing 5-3-1-1cabinet -shelving -door -seal 5-3-1-2Electrical -connection ,open ckt, short ckt Ground fault -main supply -Functional check/ thermostat, motor, starting device. 5-3-2 Internal servicing - lack of refrigerant Evaporator partially frosted -sweating or frosted suction line Liquid refrigerant in suction line, caused by Brocken thermostat or too much refrigerant - internal electric, motor and connections are rare (3 Out of 1000)only by air & water in compressor - Liquid refrigerant in compressor, removes the oil as it evaporate to the condenser and valve may broken as the compressor tries to pump.-Restriction on High side/capillary tube, filter, dryer continuous running, no refrigeration, condenser cooler than normal.

5-3-3 Most frequent service operations - locating & repair refrigerant Leakage - Purging and Charging - cleaning or replacing capillary tube - Replacing or installing filter Dryer - Replacing compressor - Replacing evaporator and condenser Must attach gauges and servicing devices

5-3-4 Radio and TV Interference slight snap or click in radio or TV as the refrigerator start or stop. can be Reduced by grounding the motor frame Excessive interference of continuous nature indicate -loose connection or fault on mechanism of motor Worn brush Badly pitted commutator or loose connection - static charge build up on belt driven compressor ground the motor and compressor5-3-5 Motor compressor burnouts mechanisms - moisture, dirt and air in the system -Too much current/ inaccurate safety device -Stiff compressor -Low voltage -lack of refrigerant -poor cooling of motor -high head pressure/ high temperature -Oil break down takes place forms carbon and sludge if discharge line Temp. reaches 177C condenser should be large enough/air flow efficiently. Purge the system, clean the condenser with brush & gas pressure/ Air, CO, NO Indications strong pungent odor of the refrigerant when a piercing valve is just opened just a little.5-3-6 Starting a stuck compressor when the unit has not been Run for log time or a small piece of dirt in compressor, does not start when connected. Methods Using extra capacitor in main winding. turn on for 1 to 2 seconds/ 3 to 4 attempts this will reverse the rotation. Use an extra voltage for a second/ connect 120V motor with 240V supply. An extra torque method/ connect 240V, 100F start capacitor across terminals of the run capacitor for no more than one second.5-3-7 Short cycling Unit starts and stops too frequentlyCauses thermostat not mounted securely loose connection in the starting relay

Avoid taping the relayIf the relay will not function correctly without being taped, it should be replaced.5-3-8 Watt reading to determine motor troubleTo observe the condition of the motor, using wattage consumption (watts drawn). combined reading/ 1 to 1 seconds running winding reading5-3-9 Dismantling systems (to replace parts/ motor compressor, condenser, capillary tube, evaporator, accumulator, filter-dryer) - disconnect electrical circuit -clean the entire mechanism -install service valve and gauge manifold -remove the refrigerant/ according to E.P.A regulation. -cut the tubing and remove the part to be replaced. - Measure the amount of oil when old system removed.Removing the refrigerant using service valve or service valve attachment plug purged using recovery/recycling unit.Using piercing valve or valve adaptor. well ventilated area and goggles

Removing the motor compressor procedure -disconnect electric circuit -install gauge manifold -discharge the refrigerant -disconnect the lines use pinching tool use tubing cutter -clean fittings at the compressor, put brazing flux on connection, heat the joint, pull the tubing out of the fittings. Plug openings immediately. -Remove the motor compressor -If oil cooler line, pinch it and break. Removed compressor tubing should be sealed.Assembling the hermetic system -clean and test the rest system -Add filter drier -clean capillary tube, evaporator, suction line, oil cooler tubing, hot gas deforest lines by forcing refrigerant through it. Filter dryer, capillary tube may be removed for circulation -Install filter dryer, suction line, discharge line and oil cooler lines. Braze the joints. -perform thorough leak test. Usually pressurized to 1 140kpa with nitrogen, bubble solution applied to joints it is possible to immerse parts in water tank. 5-4 Condenser trouble -Leak -Lint and dirt on external part Install piercing valve Purge the refrigerant repair the leak test evacuate Charge and check outIf not repair, Replace5-5 Repairing Evaporators Stainless steel Aluminum couple/ aluminum and copper5-5-1 Stainless steel/Brazed or weld(TIG) -Locate the leak - Discharge -clean -Purge nitrogen when brazing -polish the weld -Test the leak

5-5-2 Aluminum/Aluminum solder, braze, weld, Epoxy - Locate -Remove refrigerant -Clean/repair right after cleaning Sand File clean with epoxy cleaner -Mix the epoxy with catalyst -Apply/ make sure there is no positive pressure -Allow for hardening -Sand the patch -Test leaks/ if still leak, remove and install new patch5-5-3 Aluminum and copper coupling Avoid brazing aluminum/ over heat easily (annealing) Aluminum solder(92-100%Zinc) melting temperature(370-430C) Aluminum solder / TIG5-6 Hermetic service valves and adapters - with service valve(most hermetic do not have) -Fitting to which valves may be attached (valve removed after servicing) -Neither service valve nor fitting -Process tube Service valve To check internal pressure To discharge/Charge/ Add refrigerant To add oil To evacuate the system To make easy to replace dryer, motor, compressor evaporator and refrigerant control.5-7 Process tube and adapter Adapted in two ways install piercing valve on process tube cut the end of process tube Process tube left at the factory is used by technician to mount process tube adapter on it as a means of attaching manifold line. Adapter sizes; 3/16, , 5/16, and 3/8 inch

To attach process tube clean/ use sand paper cut off the tip of process tube using cutting pliers or cutter. Wear goggles when charging and discharging Discharge a system in well ventilated area If process tube is short, braze an extension maintain internal pressure to blow out metal chips while cutting. attach the adapter with process tube.5-8 Locating refrigerant leakageSince leaks are usually tiny, detecting device are required.Leak detection methods bubble solution Fluorescent dyes Refrigerant dyes Halide torch detection Electronic detector Pressure testing5-8-1 Bubble solution water-soap/ common patented solution/ long lasting bubble film5-8-2 Electronic Leak detection most sensitive principle difference in heat conductivity of gases dielectric differences of gasses operation Turn on and adjust in normal operation pass the probe over the suspected surface the detector will give sound or light or both because the new gas changes the resistance in the circuit.5-8-3 Pressure Testing Connecting gauge manifold without allowing air, moisture, dirt depends on the system - both suction and discharge service valve -suction service valve adapter on compressor -process tube only -process tube too short/ not reachable

Procedure apply pressure to the system/NO, CO or same refrigerant At the start 5 to 30 psi is necessary(positive pressure) look at the name plate for test pressure, if not given never go over 170 psi. if any leak detected by pressure reduction ?/pressure drop after an hours. if no detected, test again at or above normal condensing pressure for the refrigerant used.If leak found, recheck after repaired.To repair leakage The repair depend on the material(scrape surface) -steel/ gray-white, hard-magnet -copper/reddish, non magnetic -Aluminum/white, soft, non magnetic SteelCopperBrazedAluminumepoxyTIGResistance welding5-9 Refilling refrigerant using vacuum pump Purging Removing unwanted air, vapour, dirt or moisture Neutral gas or recommended refrigerant allowed to flow to force unwanted air and vapours. Evacuating The system must contain only refrigerant by connecting the system to a vacuum pump and allowing to run for some time while a deep vacuum is drawn on the system. Evacuating procedure -connect the gauge manifold -close valve A and open valve B -switch on vacuum pump -when sufficient negative pressure created, switch off pump and open valve A -Slightly open the refrigerant cylinder valve and charge the system until it makes frost in the evaporator. -Then check the pressure to be stable at list for 24hrs. -Pinch off the process valve and braze it.5-10 Refilling refrigerant in the absence of vacuum pump -Connect the gauge manifold -Fully close the pump hose(above) valve one hose to cylinder and one hose to the suction line. -connect a nipple to sucking inlet by brazing -purge the system/ connect a short piece of capillary tube to the dryer of the refrigeration system. For flushing, the motor has to run for short time as the same time the cylinder valve should be opened. -close the cylinder valve and let the motor produce vacuum.-Control the status of the vacuum at the manifold gauge-Close and seal the attached capillary tube-Open the cylinder gas for short time, since the motor is running, the gas distributed within the system and the pressure will decrease. If the pressure decreased, add more refrigerant.-If there is too much refrigerant in the system(1-2bar), purge some refrigerant by opening the capillary tube attached to the filter dryer.-If there is too much gas, icing will start at outlet of the compressor.-Check the newly maintained pressure If it reads the desired value of 1 to 2 bars5-11 Servicing capillary tubes Cleaning -Disconnect at both ends(if possible) -Attach to tube cleaner (up to 20,000psi) -Build up pressure to force the wax and dirt out -Flush the tube with refrigerant - Install new filter dryer and reconnect the capillary tube. -If needed new tubes must have same inside diameter and same length with the one removed -If there is indication the wax is the cause, the oil should be removed and replaced with wax free oil5-12 Testing rebuilt system -After the system has been assembled, tested, evacuated and charged with oil and refrigerant it should be run with a thermometer control for at least for 24hrs to determine the behaviour -A recording thermometer should be used -If possible the cabinet should be placed in warm room(38C)