www . refrigerationandaircon . co . za RACA Journal I June 2023 37
Support
GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy ( ACRA ) in Edenvale . He holds a Bachelor of Business Administration and an associate degree in educational administration . He has a National Technical Diploma and completed an apprenticeship with Transnet . He has dual-trades status : refrigeration and electrical . He has been involved with SAIRAC for over two decades and served on the Johannesburg committee as chairman and was also president between 2015 and 2018 . Currently he is the SAIRAC national treasurer .
WELCOME TO THE
SOLUTIONS PAGE
By Grant Laidlaw
Many people ask for assistance in the understanding of theoretical and practical aspects of the industry . I will endeavour to enlighten . I am going back to basics as I have questions coming in which indicate that the basic understanding necessary to work in industry is not in place .
Margaret asks : I am an apprentice , and our company does fridge repair . Could you please explain the service and repair issues when working with hydrocarbon R600a . I have seen people taking out R600a and simply replacing it with R134a where I work , they say it is safer .
Hi Margaret , I would imagine that you work in the smaller capacity domestic refrigeration market where you are running into R600a . Continuing from last month ’ s feature , we will now look at service procedures beginning with pressure testing .
SERVICING PROCEDURES WITH HYDROCARBON REFRIGERANTS Servicing procedures for hydrocarbon ( HC ) refrigerants are similar to those for R134a , except for the additional precautions needed for working with flammable refrigerants .
We will look at :
• Pressure testing
• Leak testing
• Evacuation
• Charging
• Sealing the process tube
• Leak testing of process tube
SERVICE PRACTICE Remember that HC refrigerants ( R600a ) are flammable and can be ignited by any ignition source . It is best to work in a well-ventilated area or , if possible , outdoors . When venting , an HC refrigerant should be vented to an area away from ignition sources ( flames and sparks ), preferably outside . The best tools to open a system that does not have service valves is by using piercing pliers or a piercing valve , with a long hose connected and vented outside .
1 . Pressure testing The HC system can be pressure tested in a similar way to R134a systems . It is preferable to use dry , oxygen free nitrogen for pressure testing . Note – dry , oxygen free nitrogen is 99.997 % nitrogen . Testing pressure should be 1.3 times the working pressure , as used previously .
NB : You must use a pressure regulator when working with nitrogen , we see many accidents and even deaths resulting from technical people working with nitrogen cylinders without a regulator .
2 . Leak Testing The refrigeration system must be tested for leaks when fault finding and before charging the system . The safest and most accurate method for leak testing is with an electronic leak tester but one can use soapy water while the system is still pressurised with dry nitrogen .
On a system charged with refrigerant each joint should be checked with the system at the highest practical pressure . What do we mean ? The low side of the system should be leak tested when the system is not running ; and the high side should be tested when the system is running as this gives the highest pressures in the system under these conditions and gives the best results for leak testing .
www . refrigerationandaircon . co . za RACA Journal I June 2023 37