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The topics are:-

  • Reasons for de-commissioning a system
  • Conditions that affect de-commissioning a system
  • Carrying out the de-commissioning a system



Reasons for de-commissioning a system :-

Why is it sometimes necessary to de-commission a split air conditioning system?

  • Replacement or upgrade of a system,
  • Relocation of the system or the outdoor unit,
  • Temporary disconnection of outdoor unit for alterations to the surrounding area.

There may be other reasons that a system is de-commission however whatever they maybe, the conditions and procedures are the same.

Conditions that affect de-commissioning a system :-

Generally, a system being de-commissioned requires either:

  1. The system pumped down so that the refrigerant charge is stored within the outdoor unit, or
  2. The refrigerant charge is reclaimed if the system is in-operative

It should be noted that the current version of HB40 Part 2 Systems other than self contained low charge systems states that ‘all refrigerant must be reclaimed from all parts of the system at the time of decommissioning, unless the system is being decommissioned for service or immediate re-commissioning’. In essence, a system that is to be de-commissioned for an extended period of time requires the refrigerant charge be reclaimed and the system charged with a dry nitrogen holding charge.


Carrying out the de-commissioning a system :-

The procedures in de-commissioning a split air conditioning system are relatively simple. If the system is operative, then provided the system has service valves, it is generally a simple case of pumping the system down. Essentially, to pump a system down, the following steps should be taken:

  • Service gauges be fitted – specifically the compound gauge to the suction service valve.
  • It should be remembered that to pump a system down, it must be operating in a cooling mode. In a summer period, this is relatively simple. However, to do this in a winter period may be difficult. To overcome this, some systems (wall mounted systems) have a "pump down‟ button on the PC board in the outdoor unit. This forces the system to operate in a cooling mode regardless of what the controller is telling the system to do. Where systems don‟t have this function, the room temperature sensor may need to be heated to simulate a cooling requirement.
  • Once the system is running in a cooling mode, the liquid line service should be closed. The suction pressure should be monitored and once the pressure reaches slightly lower than atmospheric pressure (say -5kPa) then the system should be shut down. If the pressure rises rapidly, this is an indication that there may be still residual refrigerant in the compressor crankcase.

Restart the system and again pump the suction pressure down to -7 kPa and shut the system down. If the pressure remains at that point or rises very slowly, close the liquid line service valve and tag off or unplug the electricity supply.

  • If the refrigerant charge is to be reclaimed, this should be done according to the procedures outlined in the Learner Resource Manual UEENEEJ072A – Fundamental concepts and refrigerant handling for split air conditioning systems.
  • The system is now ready for disconnection.

Once the fan-coil unit has been disconnected, if it is to be re-used, then the piping connections should be quickly sealed to prevent the infiltration of moisture. Additionally, the outdoor unit suction and liquid service valve flares should be capped.

Finally, the system should be tagged or labelled indicating its status; so that in future it is known what condition the unit is in and what will be required to re-install the system.




This page was last modified on 6th June 2010 and maybe out of date with regards to its information at the time of reading this article. The information above is only intended for use a guide and should not be 100% relied upon as a substitute for official manufacturer technical advice. Quality Electrics disclaims responsibility for any damage, claim, or liability any person may incur, whether caused by negligence or otherwise, as a result of anything contained in our articles.


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