How to recharge home air conditioning

Written by chris moore
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You should recharge a home air conditioning unit only if you have extensive knowledge of the unit. You need to know the exact type of refrigerant used in your air conditioning system along with its specifications on the design operating pressure; the unit's subcooling and superheat should be about -12.2 degrees Celsius. Given all of this required knowledge and the environmental laws governing the use of refrigerant, letting a professional handle this job is often best. To do it yourself, you can either recharge the unit from the high side or the low side.

Skill level:

Things you need

  • Screwdriver
  • Refrigerant canister or cylinder
  • Pressure gauge recharge kit

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  1. 1

    Turn off the air conditioner compressor while leaving it plugged in. You will likely need to remove one side panel from the air conditioning unit by removing its mounting screws to access the compressor. If it is a window-based unit, remove it from the window first.

  2. 2

    Attach the centre manifold hose on the pressure gauge set to the canister or cylinder of refrigerant. Purge the line of air by throttling the regulator on the canister and either the plain or compound gauge--whichever gauge you will be using.

  3. 3

    Connect the plain pressure gauge hose on the gauge set to the air conditioner's liquid line service valve if you are recharging the unit from the high side. If you are recharging from the low side, connect the compound gauge hose to the suction service valve. Whichever hose you use, compound or plain, the other hose won't be used.

  4. 4

    Open the regulator for the gauge you connected to the air conditioner; open it only slightly. Throttle the refrigerant can's regulator and observe the gauge that you are using. Close the can's regulator once the gauge reaches the unit's design operating pressure.

  5. 5

    Turn on the air conditioner and check the subcooling if you charged it through the high side; check the superheat if you charged it from the low side. Shut off the unit and repeat the previous step if the subcooling or superheat is inadequate.

  6. 6

    Disconnect the gauge kit from the air conditioner (shut the compressor off again be fore you do this) and reinstall the air conditioning unit as needed.

Tips and warnings

  • If the air conditioning unit uses a capillary tube expansion device, which does not contain a valve or any moving parts, it is best to charge the unit at the high side.
  • Always wear protective gloves and clothing when handling refrigerant.

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