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 17 years and has been a Johannesburg committee member for the past eight ( chairman in 2011 and 2012 ). Currently he is the treasurer ( Johannesburg council ) as well as president ( national council ).
ELECTRICITY AND
ELECTRICAL SAFETY
By Grant Laidlaw
It ’ s seemingly a basic skill , however the dangers are real .
Johann asks : Grant , many refrigeration people work on or near electrical power without any idea to the hazards . I realise that this is the basics , but it should be important . What about electrical safety using arc welders ? Any advice ?
Hi , Johann . Many refrigeration / air conditioning people do work with electricity as it forms part of the required skills set . But , unfortunately many working in our field do so without any formal training . This then creates a problem as understanding the dangers one is exposed to when working with electricity , is only theoretical in nature . One cannot just learn about the associated dangers from experience .
shock .
Let us begin with what happens when you get an electrical
Electric shock occurs when the body becomes part of an electrical circuit . Electrical shock can occur in several ways :
• A person may come in contact with conductors , live and neutral in a single phase circuit , or between lives in a three phase circuit .
• A person may provide a path between a conductor and earth .
• A person may provide a path between earth and a conducting material that is in contact with a live circuit . ( For example : A live wire is in contact with a metal casing and you touch the casing .)
We use the terms high and low voltage but the terms high voltage and low voltage are relative .
Typically , we call a circuit low voltage for any circuit below 600 volts . Our colleagues working at the power stations work with 20 000 volts and on the transmission lines South Africa uses 132 000 , 275 000 and up to 765 000 volts . Yes , we then work with the relatively low voltages of 230 volts and 400 volts .
Creative Commons
Do not be deceived , low voltage does not necessarily mean low hazard . The potential difference is only one factor making up the dangerous effects of electricity .
When applied to 230 and 400 volt circuits , the extent of injury accompanying electric shock depends on several factors .
• The amount of current conducted through the body .
• The path of the current through the body .
• The length of time a person is subjected to the current .
Do not be deceived . Low voltage does not necessarily mean low hazard .
The amount of the current depends on the potential difference and the resistance . The effects of low current on the human body range from a temporary mild tingling sensation to death . An electric shock can injure you in either or both of the following .
• A severe shock can stop the heart or the breathing muscles , or both .
• The heating effect of the current can cause severe burns , especially at points where the electricity enters and leaves the body .
• Other effects include severe bleeding , breathing difficulty , and ventricular fibrillation . In addition , you may fall , or have some other accident as a result of your response to the shock .
www . hvacronline . co . za RACA Journal I January 2021 57