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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
Contributed by Grant Laidlaw
Many people ask for assistance in the understanding of 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 .
Robyn asks : Dear Grant , in air-conditioning a lot is said about cooling , but heating is not spoken much about . I ran into open elements which I found strange .
Could you please give us some insight on this topic , thanks .
Hi Robyn , thanks for the question . Heating , even in South Africa , is necessary and can be diverse . I will look at heating mostly as it is applied by our industry and will focus on elements .
In order to overcome heat loss , heating is provided to the space by means of supplying air which is hotter than the required room air temperature . This air can be heated in various ways and in various positions in the system . The position where the air is heated depends mainly on the air-conditioning or heating system selected .
In the case of a central plant the air is usually heated in the central air handling equipment . In the case of smaller individual units , the heating is also done in these units . Occasionally when the window surface in a space is large down draughts could be experienced at these windows during winter – skirting board heaters are recommended . Gas heating equipment is available which we do not generally deal with .
Robyn , the four main methods used to heat the air in airconditioning equipment are :
1 . By means of electric heating elements 2 . By means of hot water coils 3 . By means of steam heating coils 4 . By means of heat pumps
The choice of method depends on the advantages and disadvantages of each , as detailed below .
1 . Electric heating elements
Advantages :
• Standard equipment being used
• Low capital cost
• Easy to control
• Low maintenance requirements
• Reticulation of electricity is both easy and cheap
Disadvantages :
• Running cost could be high ( maximum demand )
• Fire risk
2 . Hot water coils
Advantages :
• Extremely fine control is possible
• Simple installation
• Hot water can be produced centrally
• Alternative fuels such as oil and coal can be used
• Water can be heated by reclaimed heat
• Off-peak electricity can be used
• Heat can be stored
Disadvantages :
• Much higher capital cost
• Higher maintenance cost
• Trained supervisory personnel required
• Reticulation pipe work required
• Central plant-room required
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RACA Journal I February 2024 www . refrigerationandaircon . co . za