mitigate them. This is achieved by adding a supplementary bond to the system, the course became known as ‘Making the Bond (MTB)’. In addition to MTB, other content included: n Regulations regarding earthing and bonding. n Be able to decide if a single dwelling system (SDU) requires earthing. n Perform the
via conductive cables such as Coax, HDMI, Screened Network, the currents ‘add up’ and could pose a significant reaction under certain circumstances. The following table indicates the effect and the human body of various levels of current.
Current Level
Effect
1 – 2mA Perception, tingling feeling 5mA Pain, muscle activation 10 – 15mA Muscle contraction 20 – 30mA Impaired breathing 50mA Ventricular Fibrillation, DEATH IEC 60479-1:2018-TC (Effects of current on human beings and livestock) has determined that for a current of 3.5mA some people may not be able to let go of a conductor, known as “can’t let go” (threshold of let go). This considers things like body composition, skin moisture, skin damage, contact area and contact pressure. CAI has adopted the upper limit of 0.5mA for each piece of interconnected device which means there can be a MAXIMUM of 6 devices before the dangerous current of 3.5mA is reached. The CAI Electrical Safety Course was developed to teach the understanding of the presence of ‘dangerous voltages’ and how to
necessary tests and checks that ensure a system is safe. n Be able to measure the
Earth Fault Loop Impedance and make sure it is compliant. n Multiple Dwelling Unit (MDU) and commercial Premise requirements. n An understanding of different lightning protection devices (LPD). n Understand the different types of Surge Protection Devices and where and when they should be fitted. As part of the requirements for completion of the CAI Diploma and contribution towards ECS cards, this course is essential for anyone involved in signal reception systems.
Why we may need to earth?
Seven Class 11 devices will need mitigation.
49 CAI Feedback Winter 2025
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