www . refrigerationandaircon . co . za RACA Journal I April 2025 39
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 understanding theoretical and practical aspects of the industry . I will endeavour to enlighten . We are going back to basics as I have questions coming in that indicate that the basic understanding necessary to work in industry is not in place .
Riaan asks : Hi Grant . Can you please explain the use of R744 and give some indication as to the use of safety devices and sensors that are applicable . Thank you .
Hi Riaan . I have looked at R744 previously but let us investigate
R744 in more detail . As you are aware refrigeration has many applications in the industrial , commercial and domestic sectors . With a rising increase in global temperatures , one must consider the impact that refrigerants have on the environment . According to the IIR , refrigeration systems represent a major challenge to sustainable development . The approximately three billion refrigeration systems worldwide consume 17 % of global electricity .
There is concern as both the increased energy consumption and the current use of refrigerants have led to environmental problems .
An efficient use of more environmentally friendly natural refrigerants , such as CO2 ( R744 ) as a refrigerant provides an approach that meets the challenge of a growing demand for air conditioning and refrigeration and the urgent need to limit its impact on the environment . There has been considerable change of late introducing new refrigerants as a replacement for HCFCs : a third class of fluorinated chemicals was introduced , hydrofluorocarbons ( HFCs ). These have no ozone depletion potential ( ODP ), but GWP ( global warming potential ) still up to several thousand times higher than CO2 . The latest amendment to the Montreal Protocol , the Kigali Amendment ( 2016 ), requires the phase-down of this group of chemicals .
It is important to note that South Africa as a signatory to the Montreal Protocol and subsequent amendment has now entered the first phase of the phase down process with regard to HFC refrigerants . There is no doubt that the phasing down of CFC refrigerant usage will have considerable impact on the industry . Consider the extensive use of HFC refrigerants in unitary air conditioning systems ( R410a / R32 ):
ULTRA-LOW GWP NATURAL REFRIGERANTS Focus has now switched from ozone depleting refrigerants to those causing global warming and there is movement towards natural refrigerants .
Natural refrigerants are substances that occur naturally in the environment . Natural refrigerants are composed of the elements
hydrogen , oxygen , carbon and nitrogen and include hydrocarbons , carbon dioxide , ammonia , water and air – ‘ the natural five ’.
The strong advantages of natural refrigerants are that they have zero ODP , and a zero or negligible GWP . As part of the natural biogeochemical cycles , natural refrigerants do not form persistent substances in the atmosphere , water or biosphere .
Carbon dioxide or CO2 , can be used as the refrigerant in the vapour compression refrigeration cycle as well as in direct refrigeration in its ‘ dry ice ’ form . CO2 , when used as refrigerant is also called R744 .
The GWP of CO2 is defined as the reference value 1 for a period of 100 years . The GWP is calculated for a specific time horizon , arbitrarily over 100 years . In some contexts , other periods are chosen , i . e . 5 , 20 or 100 years .
The diagram below illustrates the GWP values for natural refrigerants :
Refrigerant
Chemical structure
Refrigerant nomenclature
Hydrocarbons propane C3H8 R290 3 propene C3H6 R1270 3 isobutane C4H12 R600a 3 Carbon dioxide CO2 R744 1 Ammonia NH3 R717 0 Water H2O R718 0
Air N2 , O2 , Ar , CO2 , others
R729 0
GWP
www . refrigerationandaircon . co . za RACA Journal I April 2025 39