To replace an evaporator, pump down the system and disconnect the liquid and suction lines. Then remove the expansion valve and the evaporator. Make the necessary repairs or install a new evaporator as required. Replace the expansion valve and connect the liquid and suction lines. Remove moisture and air by evacuating the system. When the evaporator is back in place, pump a deep vacuum as in starting a new installation for the first time. Check for leaks and correct them if they occur. If leaks do occur, be certain to repair them; then pump the system into a deep vacuum. Repeat the process until no more leaks are found.
Using the gauge manifold and a vacuum pump, pump down the system. Most of the refrigerant will be trapped in the condenser and the receiver. To remove the compressor from service, proceed as follows:
1. Once the pump down is complete, the suction valve should already be closed and the suction gauge should read a vacuum. Mid-seat the discharge service valve. Open both manifold valves to allow high-pressure vapor to build up the compressor crankcase pressure to 0 psi.
2. Front-seat (close) the discharge service valve. Then crack the suction service valve until the compound gauge reads 0 to 1 psi to equalize the pressures and then front-seat the valve.
3. Joints should be cleaned with a grease solvent and dried before opening. Unbolt the suction service and discharge service valves from the compressor. DO NOT remove the suction or discharge lines from the compressor service valves.
4. Immediately plug all openings through which refrigerant flows using dry rubber, "cork" stoppers, or tape.
5. Disconnect the bolts that hold the compressor to the base and remove the drive belt or disconnect the drive coupling. You can now remove the compressor.
Systems using hermetic compressors are not easily repaired, as most of the maintenance performed on them consists of removal and replacement.
1. Disconnect the electrical circuit including the overload switch.
2. Install a gauge manifold. Use a piercing valve (Schraider) if needed.
3. Remove the refrigerant using an EPA approved recovery/recycling unit.
4. Disconnect the suction and discharge lines. Using a pinching tool, pinch the tubing on both the suction and discharge lines, and cut both lines between the compressor and the pinched area.
5. Disconnect the bolts holding the compressor to the base and remove the compressor.
Do not forget to pump down the system and equalize the suction and head pressure to the atmosphere, if applicable. Wear goggles to prevent refrigerant from getting in your eyes. After replacement, the procedures given for removing air and moisture and recharging the system can be followed; however, the procedures may have to be modified because of the lack of some valves and connections. Follow the specific procedures contained in the manufacturer's manual.
Q34. What are the two major pieces of maintenance equipment used for refrigeration work?
Q35. Before attempting transfer of refrigerantfrom a container to a cylinder, you should precool the receiving cylinder for what reason?
Q36. What is the purpose of evacuating a refrigeration system?
Q37. You should continue to operate the vacuum pump during evacuation of a system until what condition is obtained?
Q38. What method of charging a system is generally recommended?
Q39. What are the three methods used to detect refrigerant leaks?
Q40. When you pump down a system, where is the refrigerant stored?Continue Reading