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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 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 ).
ACS POWER SUPPLY ,
AND FAULT-FINDING ON ELECTRICAL MOTORS
By Grant Laidlaw
To address these topics , we need to consider the SANS and a logical approach .
Jaco asks : Hi Grant , is it okay to plug an air conditioner into a wall plug , and is this even legal ? Also , we struggle with electrical fault-finding with electrical motors , any help will be appreciated .
Hello Jaco , let us begin with the first question , here we need to look at regulations – namely SANS 10142 . Item 6.16.4.1.1 , which states : “ Dedicated circuits shall be provided for fixed space heating and cooling ( air-conditioning units ) that are rated more than 16 Amps . There may be more than one unit on each circuit and the power supply to each unit shall be controlled by a switch disconnector .”
So , in essence if your unit ( s ) draw more than 16 Amps , then you have to run a dedicated circuit with an isolator to each unit . If your air conditioning unit is rated at less than 16 Amps , then you can use a wall plug . Take note : some users may prefer a dedicated circuit with isolator even on units rated lower than 16 Amps .
LOOKING AT FAULT FINDING IN GENERAL When approaching a fault , the first step is to ask questions . We need to refer our questions around our knowledge of symptoms . Questions need to be asked around how the fault occurred . It is important to be logical in your approach . There are seven-basic steps to fault-finding :
• Gather information
• Understand the fault
• Identify the parameters to be evaluated
• Identify the source of the problem
• Correct / repair the fault
• Verify the repair
ACRA
An example of a motor that was faulty with burnt out windings .
• Perform root cause analysis . These seven steps may be applied to any fault condition and could lead to a corrective action
LOOKING MORE CLOSELY AT THE STEPS IN FAULT- FINDING :
• Gathering information We need to ask questions about the symptoms of the fault . Gather any documentation , for example : technical manuals , service or fault reports , wiring diagrams , plant logbooks , operational manuals , maintenance history .
• We need the necessary knowledge to understand the fault In what way is there a fault , how does the fault present itself ? Analysis of the symptoms , what component would give these symptoms ? What particular component or module could be faulty ?
Continued on page 39
www . hvacronline . co . za RACA Journal I November 2020 37