Responsible Refrigeration
By Barney Richardson
BARNEY RICHARDSON
Barney Richardson is the director of South African Refrigeration and Air Conditioning Contractors Association ( SARACCA ) and sits on various other boards within the HVAC industry , including the South African Qualifications and Certifications Committee for Gas ( SAQCC ) Gas .
PRACTITIONERS MUST STAY UP TO DATE
Practitioners must be aware of safety and changes in design concepts and the phase-out of HCFC and HFC refrigerants and use of new refrigerants in refrigeration .
The requirements of the SAQCC Gas registration revolve around the safe handling of refrigerant gases by practitioners . The training being followed with the new SARACCA training manual provides an understanding of the Pressure Equipment Regulations , SABS standards and good engineering practice in refrigeration .
There is also continuing training and education in new design concepts , the phase out of HCFCs and HFCs and the procedures for natural refrigerants such as hydrocarbon , carbon dioxide and ammonia refrigerants .
The handling of refrigerants includes the proper pressure testing and leak detection procedures to safely be followed . The training not only gives a basic understanding of refrigeration and refrigerants but also the procedures for recovery of refrigerant , leak detection , repair , pressure testing and charging of the system .
For existing refrigeration systems where a leak is suspected this is usually indicated by lower system pressures and poor performance . The leak must be found and pinpointed . The common methods used would be a visual check first then to use a soap solution to see if any bubbles come up on joints etc . A halogen or electronic detector can also be used .
To repair a leak or the replacement of a faulty component the remaining refrigerant must be recovered into a service cylinder . It is important to avoid leaking refrigerant into the atmosphere . The refrigerant must be recovered into an approved service cylinder with indication of the recommended capacities for common refrigerants in kilograms .
Cylinders have different capacities for refrigerants , for example a cylinder rated for R134a at a capacity of 12.6 Kg will be rated at 9.8Kg for R404 . The cylinder must be empty and free of other refrigerant types . Use an accurate scale and fill to the capacity shown . Do not over fill . It is advised to fill only to 80 % of the capacity – this allows for expansion if the temperature rises for any reason .
The recovered refrigerant should be tested for contaminants and purity . Always avoid mixing refrigerants . There are several substances that could contaminate the recovered refrigerant . These could be water vapour , acid or metal particles from the moving parts of the compressor left over from installation activity .
There could also be non-condensable gases like nitrogen , carbon dioxide and air that may have been introduced during installation or previous service work . Remember that if the refrigerant was such as a Zeotropic blend , the leak could have resulted in a loss of one of components in the blend in which case new refrigerant will have to be used .
Refrigerants can be recycled after the contaminants are filtered out and removed . This may be difficult to do on site unless a specialist is brought in to do this . In most cases it is advised that the gas is sent to a supplier who has the laboratory facilities to do this . These specialist suppliers can analyse and process a used refrigerant through a reclamation procedure .
This process usually applies to larger capacity systems . The smaller recovered quantities would need to be checked for contamination before being accumulated and recycled through the reclamation process .
Pressure testing after a new installation or repair is always undertaken using dry Nitrogen before pulling a vacuum . Evacuation is an important part of the refrigeration system commissioning process . The pulling of a vacuum lowers the boiling point of water , which if present will evaporate and can then be extracted through the vacuum pump . The lower the pressure in the system , the lower to boiling point it will be .
Therefore , it is advisable that the evacuation should be to an absolute pressure of 5000 microns . An electronic pressure monitoring device should be used to ensure a complete evacuation and removal of moisture . Great care must be taken when connecting and disconnecting the vacuum pump and hoses to avoid losing the vacuum . This procedure is explained in the SARACCA training manual .
When it come to charging , accuracy is important . If oil is to be charged this must be done first and be warm to avoid the refrigerant combining with the oil . Some refrigerants should be charged in liquid form e . g . the 400 group of refrigerants known a Zeotropic refrigerant .
Charging can be done preferably by weighing using an electronic scale for accuracy or by sight glass as a reference until it shows a clear flow of refrigerant . The temperature and pressures need to be monitored carefully until the system is running satisfactorily and to specification . RACA
www . refrigerationandaircon . co . za RACA Journal I August 2022 45