Pump down procedure

If you have ever had somebody work on an air-conditioning system, you might have heard them say that they are going to do a pump down procedure. In this article I am going to go over what this means and the steps required to do one.

A pump down procedure allows a technician to access, or open up, the refrigerant circuit on the indoor section of a system without having to recover the refrigerant. In simpler terms, this means we can remove the indoor coil without having to take all the refrigerant out of the system. This also means we don’t have to put a full charge of refrigerant in the system when we are done, which saves you money.

When an evaporator coil needs to be pulled out of the air handler to be cleaned or replaced we have to cut the refrigerant lines. So, we need to take the refrigerant out of the system first. Just about every system still in service today has 2 valves on the outdoor unit that we can use for the “Pump-Down.”

If you have read the article on how air-conditioning and refrigeration systems work, then you understand that a compressor running in the cooling mode will be pushing liquid refrigerant into the indoor coil and pulling a gas back to the outdoor unit. For a pump down, we close the liquid valve and allow the compressor to pull all the gas out of the indoor coil and when it is done, we close the suction (gas) side valve.

Now, don’t go thinking you should do this your self, there are many things that need to be considered and the first one is that you need an EPA certification to even connect to the system.

But what are the things that you should know if a technician is proposing to do a pump down and when is it not a good idea? First, most refrigerants today are a blend of several gases. When the system is not running AND if there is a leak on the suction side (gas side), the leak could be allowing only one of the several gases to escape. This results in a mixture of gas that is not at the proper ratios and the system may not perform as well. Second, if the compressor is weak it may not be able to pull all the gas back and the pump down will not work. Finally, if there is a filter/drier in the refrigerant circuit located in the outdoor unit, and it needs to be replaced, a recovery will need to be performed.


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