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The topics are:-

  • Unit installation – fan-coils (PART 1)
  • Unit installation – condensers (PART 2)
  • Refrigerant piping
  • Drainage
  • Ductwork
  • General installation considerations

Piping Design (Wall Mounted Split Systems) :-

A suction accumulator will have been fitted in the outdoor unit, if and where required.  The way pipework is installed must be in such a way as to prevent drainage of liquid into the compressor and to ensure the adequate return of oil. Routing the piping as directly as possible between indoor and outdoor units is most effective to minimise the amount of refrigerant to be charged into the system.


To summarise, the following points should be kept in mind when installing the refrigerant piping:

  • Refrigerant lines should be as short and direct as possible,
  • 410a copper pipe is thicker in it's wall size than the R22.  If possible install the 410a copper pipping.
  • Tubing should be located to allow easy use of access panels and system components,
  • Locations where copper tubing will be exposed to the elements or possible damage, otherwise a protective covering (e.g. metal trunking or ducting) should be used.  Regular intervals should be used where tubing runs along walls and rafters, depending on size of tube, and whether hard drawn or annealed, (approximately 1 metre intervals for annealed or small diameter tube).  The location must be such as to prevent condensation on the tubing from dripping onto the electrical equipment,
  • Tubing should not be exposed to external sources of heat such as furnace rooms or direct sunlight,
  • Insulate tubing with expanded closed cell rubber pipe insulation or similar materials. Excessive suction vapour superheating reduces unit capacity dramatically, with losses of up to 50% in summer,
  • Horizontal suction lines should be straight and pitched at least 10 mm every 3 metres towards the compressor,
  • Liquid refrigerant should be tubed so that it will not drain to the compressor head (from the discharge line) or crankcase (from the suction line) by using some form of U bend just before the compressor. In long suction lines, liquid and oil will drain into the trap,
  • Where tubing runs through a floor or wall it should be protected by a sleeve. PVC pipe is adequate. The ends should be sealed with a sealing compound to avoid chafing and other problems,
  • Above all, the installation of tubing should be neat and tidy and not offensive to the eye. Vertical runs should be checked using a level; horizontal runs can merge as much as possible with existing panels, allowing for the slope in long runs of 10 mm per 3 metres. Bends should be made with either a bending spring or mechanical bender or if limited for space, manufactured or welded elbows,

Support for Refrigeration Piping:-

Where required, refrigerant piping must be supported properly when installed.  Good support throughout the system means not only fewer problems, but better functionality.  Good piping and tubing support offers numerous advantages:

  1. No sagging and eventual cracking,
  2. Good oil handling characteristics,
  3. No bad effects from vibration,
  4. Longer service life for the piping,
  5. Less chance of liquid hammer damage.


The support system must be able to absorb the stresses caused by vibration and expansion in order for the piping to withstand service conditions.  It must be able to carry the deadweight of the piping, which includes the pipe’s weight, insulation and the load it carries.  In addition, concealment of the external piping is necessary to prevent extra heat absorption and protect the piping’s insulation.

Where piping penetrates a roof or even a vertical wall, to ensure weatherproofing of the penetration a Dektite® should be used and if running across ceilings or vertical walls "clamps" should be used.



Plastic Trunking Enclosures






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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