Pump Down Procedure
Many times a full recovery of the system refrigerant charge is NOT necessary:
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Making a repair on a part of the system, other than the condenser.
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Removing the condenser to replace
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Isolating a part of the system for testing
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Performance evaluation of the compressor (testing the valves)
To remove refrigerant from a part an air conditioning system, a technician has to perform a recovery and pump down procedure.
PLEASE NOTE, although pump down is permissible and can lower the repair cost to the client, most refrigerants are "blends" the only way to ensure (AND GUARANTEE) a proper charge is to remove all refrigerant and recharge by weight with new virgin refrigerant
DO NOT attempt a pump down on a system that has "Micro-channel" coils. For more information on Micro-channel coils you should read the following article Micro-Channel Coils
Some air conditioning systems have built in receiver (storage) for convenient pumping down, however a similar process still must be followed.
You will need specialized refrigeration tools for completing the pump down correctly, including a recovery machine, manifold gauges, and a torque wrench set.
These Basic steps will provide an overview:
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- Turn the system to cooling mode
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- Open the disconnect box (be sure you can turn it off quickly)
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- Remove the caps on top of the suction line and liquid line service valves
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- Attach a set of gauges to the gauge ports
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- With the unit running, close (turn clockwise) the liquid line service valve using a refrigeration wrench
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- Monitor the pressures; ready your refrigeration wrench in the suction line service valve
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(The next steps should be done almost simultaneously to avoid damage to the compressor)
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- When the pressures on both sides approach zero, close the suction line service valve
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- Turn off the condenser (Pull the disconnect to stop compressor operation)
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. Leave the system "open" to avoid build up of any residual refrigeratn in the system
Refrigerant within the low-pressure side of the air conditioning system should be very minimal at this point. So, you can do necessary repair work, or parts replacement work on the unit. Important: You can not perform repairs on the condenser or compressor as they will still contain refrigerant. If you use a separate refrigerant cylinder, then you can pump down the entire system into your cylinder and then perform maintenance on all air conditioning parts. But this is the quicker method. If your air conditioning unit has a built in receiver, maintenance on your AC/R system can be carried out anywhere except for the receiver.