Basic principles of split air-conditioner installation

A split air conditioner is a set consisting of outdoor and indoor units connected by copper lines that form a refrigeration circuit. Location of both units and routing of the pipework significantly affect both the performance and correct operation of the equipment and the aesthetic appearance of the place where it is installed. This article presents several important requirements related, among other things, to selecting the location of the outdoor and indoor units, preparing connections of installation components, joining pipework, making electrical connections and ensuring correct condensate drainage, which may prove helpful when carrying out air-conditioning installation work.

Selecting the cooling capacity of the unit

When preparing to choose and purchase an air conditioner, the first step is to determine the cooling capacity the unit should have. From this stage it already largely depends whether the selected air-conditioning system will be able to provide the thermal conditions desired by users in the room. For example, selecting a system with underestimated cooling capacity will result in ineffective cooling of the room – the unit may then be unable to reach the specified air temperature. Conversely, selecting a unit with excessive cooling capacity may lead to higher operating costs and certainly higher purchase cost. Applying a unit of appropriate capacity will depend, among other things, on room volume, air change rate and heat gains.

Selecting the outdoor unit location

Proper selection of the outdoor unit location should ensure open space around the building free of obstacles. If the unit is situated near walls or a roof overhang, the discharged heat must not be restricted, blocked or retained in any way. The risk of hot air discharged from the heat exchanger being recirculated back towards the fan should be minimised. Recommended clearance of the unit from walls and other obstacles should follow the manufacturer’s recommendations in the operating instructions and equipment specification. Typically, the distance of the outdoor unit from a wall or façade is at least several dozen centimetres, and from the front at least several tens of centimetres. When planning unit placement, appropriate access for possible repairs and inspections should be provided.

Recommended clearance of the unit from walls and other obstacles should follow the manufacturer’s recommendations in the operating instructions and equipment specification

PERMISSIBLE NOISE LEVEL Because of noise generated by compressor operation, it is not recommended to install the unit near windows, doors or too close to the property boundary. The Regulation of the Minister of the Environment of 14 June 2007 on permissible noise levels in the environment indicates that the permissible noise level in single-family residential areas is 50 dB(A) during the day and 40 dB(A) at night. For multi-family residential buildings it is 55 dB(A) during the day and 45 dB(A) at night. Mounting the outdoor unit directly to the wall may transfer vibration into the building structure and create stresses in the installation. Correct unit installation should include mounting on a support bracket, preceded by proper levelling of the bracket. To reduce vibration and additional noise, vibration-isolating pads must be used. The outdoor unit may also be placed on an appropriate foundation. In that case it is important to ensure optimal distance of the unit from the ground, which will reduce the risk of contact (e.g. with snow and dirt) and, when the unit operates in heating mode, ensure correct condensate drainage.

Selecting the indoor unit location

Installation of the indoor unit should respect clearances according to the equipment documentation – typically several dozen centimetres. For even distribution of the air stream, the indoor unit of the air conditioner should be placed as high as possible in the room (while maintaining adequate service access from the ceiling side). Furthermore, neither heat nor moisture sources should be located in the immediate vicinity of the indoor unit. Good practice is also to avoid strongly sunlit areas within the room. The indoor unit should be mounted with a slight slope towards the condensate outlet to ensure water drains from the drip tray. If gravity condensate drainage is not possible, space for a condensate pump should be provided. It is unacceptable to place any mechanical obstacles in front of the unit, as this may significantly affect heat removal from the room and reduce air-conditioner efficiency.

Distance between outdoor and indoor units

To ensure correct operation of the air-conditioning system, an appropriate distance between outdoor and indoor units should be maintained (the maximum pipework length not requiring additional refrigerant charge is usually up to several metres – depending on the type and cooling capacity of the unit). Increasing the distance between units will require adding refrigerant to the system. For this reason it is important to follow the manufacturer’s recommendations in the installation manual and equipment documentation. Excessively long pipework may reduce air-conditioner capacity.

Making a wall opening and routing trunking

Drilling a wall opening for routing cables and pipes between outdoor and indoor units should be done with a slight slope towards the outdoor side. To protect the lines and maintain aesthetics, good practice is to use a plastic duct in the building partition and a rose cover. The whole assembly should be properly sealed, protecting free spaces against water accumulation. From an aesthetic point of view, in rooms it is most advantageous to run the installation in trunking under plaster. Where this is not possible, maintaining appropriate appearance of the installation and protecting it is achieved by placing all lines in installation trunking.

Preparing copper lines

One of the errors at the material preparation stage is using uninsulated copper pipes (another common problem is choosing lines of doubtful quality, e.g. too thin wall thickness and unknown composition). Using pre-insulated pipes compliant with PN-EN 12735-1, in addition to reducing energy losses, protects against moisture condensing on the outer wall of the pipes. When routing the lines, care should be taken that the insulation is not broken or damaged.

Capping pipes

Caps on pipework, usually made of plastic and fitted over the pipe end (Fig. 4), should be removed only immediately before connection work begins. Otherwise moisture and dust may deposit on the internal surface of the copper line. Failure to cap a copper pipe after cutting may allow contaminants into its interior (swarf, dust, cement mortar, plaster fragments from the wall, or moisture). Therefore, during processing and installation of the element it should also be properly protected for that time.

Processing copper pipes – cutting and deburring

Special pipe cutters are used for cutting copper pipes; they ensure square edges during cutting. This method reduces the risk of chips and distortion at pipe ends. It should be remembered, however, that during cutting part of the pipe is rolled inward and a so-called burr is formed; burr size depends on the condition of the cutting tool, material type and cutting speed. The burr must be removed e.g. with a deburrer or scraper. This is very important because burr fragments circulating in the system could damage it. During deburring (preparing the pipe surface after cutting by removing sharp edges and residual burrs), the pipe should be tilted vertically downward and the process carried out from the lower side so that swarf falls onto the ground and does not travel through the interior of the copper line. Errors during copper pipe cutting also include pressing the cutter too hard, resulting in pipe deformation.

Bending pipes

An unacceptable error made by installers is bending pipes without appropriate equipment in the form of a dedicated pipe bender. Significant reduction of cross-section at a kink, which may result from incorrect bending, disrupts refrigerant flow and is a potential cause of, for example, excessive pressure drop in the suction line of the system.

Making flare (screwed) connections

Indoor and outdoor units are connected by pipework using flare (screwed) connections. Making such a connection requires forming appropriate flares on the pipework, which is one of the more important steps in air-conditioner installation. Remember to place the nut before flaring and to remove all residues after cutting the pipe. A correctly made flare and its proper tightening directly affect the tightness of the entire installation. Therefore, if any irregularities are found in the flare, and also when the connection has to be dismantled and remade, the expanded part should be cut off and the flare made again. Pipework prepared and fitted with nuts (Fig. 8) is connected to the indoor and outdoor units of the air conditioner by first tightening by hand and then using a torque wrench. Failure to use a torque wrench or overtightening the connection may strip the thread (if this happens on system pipework, the nut will need replacing and the flare remade, and possibly lines will need brazing). A very serious error creating a risk of losing the equipment warranty is stripping the thread of the factory-fitted valve on the air-conditioning unit.

Condensate drainage

Correct installation should allow condensate to be drained by gravity or by means of a suitably selected condensate pump. In the first case, remember to maintain an appropriate pipe slope so that water drains spontaneously from the indoor unit. Discharging condensate directly onto the ground may dampen building walls and foundations or be a nuisance for people when condensate is discharged onto a pavement or walkway. The most common solution is discharging condensate to a sewage drain. Using an external tank to collect condensate may also be troublesome because of the need for regular emptying. After making the condensate drain, its free flow should be checked. A technological solution for condensate drainage that is gaining popularity is a condensate disperser. Instead of being discharged as a liquid stream, water is discharged in atomised form. This allows it to be used e.g. for condenser cooling.

Pressure tightness test and vacuum in the system

After making flare connections in the circuit, a very serious error is releasing refrigerant into the system without performing a tightness test with compressed nitrogen; in case of a leak this would result in refrigerant release to the atmosphere. Performing a pressure test guarantees effective checking of the tightness of the entire system. The test should be carried out in accordance with the guidelines in PN-EN 378-2, which describes pressure test range requirements. Then a vacuum is created in the system using a vacuum pump to remove moisture and non-condensable gases present in the circuit.

Making electrical connections

When making electrical connections of the air-conditioning system, cables should be properly tightened to the terminals between indoor and outdoor units using screws (in a manner corresponding to the markings at the terminals on both units) or according to the fixing method provided by the manufacturer. The electrical cable used should be continuous, without unnecessary joints and branches, and should have ferrules applied. After routing and carefully laying the cables in the installation and securing them, the connection points must be protected by fitting covers.

Description of the tightness test procedure: 1. Check that the ambient temperature during the tightness test complies with the requirements of PN-EN 378-2; 2. Increase pressure to PS at a rate of approximately 1 bar/2 min; 3. After reaching PS, close the valve on the regulator; 4. Maintain PS for min. 40 min, monitoring pressure in the system (make a note); 5. Observe the pressure gauge reading from a safe place (make a note); 6. Reduce pressure to zero; 7. Record the tightness test result (positive/negative).

APPROPRIATE personnel competence confirmed by a certificate Air-conditioning installation is an activity in which risks to life, health or the natural environment may occur. These risks are mainly related to the physical and chemical properties of refrigerants and to the pressures and temperatures present in equipment and installations. Therefore the issue of an appropriate competence and qualification level gains additional importance. For installations covered by the so-called F-gas Act, personnel involved in installation, maintenance and repair of air conditioners should hold appropriate authorisations confirmed by a certificate. When commissioning an installation company or a self-employed person, one must be aware that they must hold an F-gas certificate for undertakings – enabling activity for third parties. This does not, however, remove the need for each installer performing activities involving refrigerant during installation to hold an F-gas certificate for personnel (natural persons). Additional confirmation of qualifications of personnel installing refrigeration equipment may be a competence certificate according to PN-EN 13133 – “Refrigerating systems and heat pumps – Competence of personnel.” It should be remembered, however, that systems are increasingly charged with refrigerants of reduced GWP, which may be mildly flammable (e.g. R32). Prospects for development of refrigeration equipment leading to widespread use of ecological refrigerants that are also flammable draw attention to personnel competence regarding flammable refrigerants as specified in ISO 22712 and the need for training against its requirements. Because air-conditioner installation involves electrical connections, a SEP group 1 qualification certificate is required, authorising installation of equipment and systems with rated voltage up to 1 kV. It is also worth checking whether warranty retention for the purchased unit requires installation by an installer authorised by the given manufacturer.

Summary

Ensuring appropriate and efficient operation of an air-conditioning system depends on a number of factors, from selection of the unit and the place where it will be installed, through planning the installation route, implementation by a competent installer of the pipework installation process with all connections and system components, to issues related to performing the tightness test, evacuating the system and first start-up. Periodic servicing and maintenance of the system should also not be forgotten, as this affects not only comfort of using air conditioning but also the health and safety of users.

References

Regulation of the Minister of the Environment of 14 June 2007 on permissible noise levels in the environment. Journal of Laws 2007 No. 120 item 826. Construction, operation and use of split air conditioners. Training materials of the Central Refrigeration Centre “COCH” in Kraków. Accredited refrigeration competences (PN-EN 13313). COCH website, [accessed: 04.07.2023]. Source: /kompetencjechlodniczewedlugnormy-pn-en-22712/ Authors: MSc Eng. Łukasz JURASZ - Central Refrigeration Centre “COCH” in Kraków Eng. Miłosz GRATKOWSKI - Central Refrigeration Centre “COCH” in Kraków Article available in the journal Chłodnictwo&Klimatyzacja No. 5/2023 www.chlodnictwoiklimatyzacja.pl