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The topics are:-

  • Pre-commission checks
  • Refrigerant gauges
  • Evacuation
  • Refrigerant charging
  • Operational conditions
  • Completion and "Hand Over‟

Pre-commission checks :-

Like any refrigeration or air conditioning system, split air conditioning systems require careful checking prior to starting or commissioning the system into operation.

The following items should be considered and checked prior to commissioning:-

  • Both indoor and outdoor units are secure.
  • Electrical wiring has been installed as per AS/NZ3000 requirements. If you are not a qualified electrician do not attempt to wire up this system.
  • All the piping has been installed in a professional manner – no kinking of piping; piping is secure; pipe insulation covers all of the necessary piping.
  • Condensate drain lines are connected correctly and drain water properly externally.
  • Ducting plenums are fitted and sealed so that no leakage of air occurs. (This is, in "Ducted" systems only)
  • Dry nitrogen pressure is present (at pressure testing level) in system. This shows that piping and system is "tight‟ and won‟t leak refrigerant after commissioning.

Refrigerant gauges:-

Commissioning a split air conditioning system requires the system to be fitted with service gauges. The type used depends on the system's refrigerant. Those systems that operate on R22 are able to be commissioned using "standard‟ gauges that use and connect to ¼” flare fittings, whilst systems that use R410a require dedicated gauges for this refrigerant (these connect to ½” UNF flare fittings).


It should be remembered that when connecting to smaller split systems, the schrader access port will read suction pressure when the system is operating in a cooling mode. Connecting the compound gauge to this access point and operating the system on heating will almost certainly damage the gauge beyond repair.

It is important to check the unit before connecting gauges and determining where in the system the access point is fitted and what pressure will be present during either cooling or heating operation.

Finally, to ensure the minimum loss of refrigerant (when handling refrigerant), ball valves or similar should be used.


Most, if not all split air conditioning systems today are pre-charged.

Low / High pressure gauges


Suction liquid / Gas valves

(this joint is faulty ! )

That is, a specific amount of refrigerant has been factory charged into the outdoor unit ready to be released into the system. Before this can be released into the system, it is mandatory that system be evacuated using a refrigeration vacuum pump. A refrigeration vacuum pump is a specialised tool that is capable of pulling vacuums on a system to the required levels stated in the Refrigerant Handling Code of Practice 2007 HB40 2007 Part 2.


Vac pumps are available in two styles:

  • Single stage vacuum pump,
  • Two stage vacuum pump,

Two stage vacuum pumps are more efficient at pulling deeper vacuums.

Vacuum measurement:-

A deep vacuum cannot be measured accurately by simply reading the compound gauge on a gauge manifold set as they really can only measure a partial vacuum. To measure a deep vacuum a vacustat must be used. Vacustats (arrow point to it) are available in a variety of styles however the most popular style are the electronic type that enable vacuum measurement in a number of units.

Important Note when vacuuming a "split air system":-

When vaccuming with a Vacustat pressure gauge, it must always read 400 (microns) which equals to 30 psi on the gauges for most machines however, it is a must for Daiken machines. The 400 microns is the pressure on the copper tubing.  This reading  can be taken by two method.

  • The standard Vacuum pump method, or
  • By rigging up the nitrogen bottles and testing that way. When using Nitro for testing purposes the brazed joints should stand a pressure of about 500 psi in the gauges. This will certainly show you if you have any leaks in the joints...

In basic "hands on the tools" terms:-

If you haven't got an electronic Valcust temperature gauge all you have to do is watch the blue/red // low/high pressure gauges. When you begin vacuuming watch the spindle on the gauges reverse to a minus situation.  When it reverts back to a "ZERO" position just leave the vacuum pump running for about 10-15 minutes, that should do it.


Keep a close eye on the gauges because when you finish vacuuming and shut off the valves if you spindle starts to rise back up well then you know you have a leak. On the air conditioner unit itself the smaller valve is called the "liquid valve". When ever opening up the valves you must always open up the liquid value first.

When you are finished vacuuming, before you disconnect the pump you must shut off all the valves so that the oil does not get sucked back up into the system.  Only after disconnecting the yellow gauge pipe from the vaccum do you turn off the 240v supply.






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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