Vacuum pumps are necessary to properly service an air conditioning system. A deep vacuum applied to a sealed system allows more complete removal of moisture and other contaminants. Commercially available pumps are quite capable of creating deep vacuum, but their cost may be prohibitive for occasional use by car enthusiasts or hobbyists. Cheaper styles of vacuum pumps require compressed air and may not reach the depth of vacuum sought for servicing a neglected air conditioning system. Refrigerator compressors are more than capable and can be had for little, or no cash outlay.
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Things you need
- Tube cutter
- Protective eyewear
- Manifold gauge set
Assure the absence of refrigerant in the system of the contributing appliance by recycling or venting, depending on the type of refrigerant and local laws and regulations. Remove the compressor from the refrigerator by cutting the inlet and outlet plumbing lines. Make the cuts at least 6 inches from the compressor body for ease of use as a vacuum pump. Remove any clamps or hold-downs that fasten the compressor power cord to the body of the appliance.
Remove the compressor support from the body attaching points and remove the support and compressor as an assembly. Modify the support frame to keep the top-heavy compressor upright, if necessary. Connect the compressor power cord to a proper electric outlet. Determine the suction side of the compressor by placing a piece of paper over the cut plumbing line. The discharge line will lightly blow the paper away while the suction side will hold the paper in place. Disconnect the power supply.
Attach a fitting to the suction line of the compressor that suits the manifold gauge set intended for use. You can find compression fittings that convert the suction line to a 3/8-inch tapered male nipple in hardware stores. This is the most common configuration for manifold gauge set service hoses. Soldering may be necessary should no suitable compression fittings be available.
Test your new vacuum pump by attaching the service hose of your manifold gauge set to the suction port created. Close the manifold hand valves and energise the pump. Monitor the compound gauge needle for movement into the vacuum range. A healthy compressor will show maximum achievable vacuum within a minute or two. Ideal results will register 29 inches of mercury (hg) or more. Incomplete or extremely slow action may indicate a weak compressor.
Tips and warnings
- Dorm size, or tabletop mini-fridges, are most desirable for their compact size. Most discarded refrigerators in these sizes are damaged in a way that caused the refrigerant to leak out, saving you the bother of proper disposal.
- Always wear protective eyewear when cutting metal or working around pressurised gases and liquids. Check local laws and regulations regarding venting or disposing of refrigerants.