Residual Current Device or more commonly known as Safety Switches

Do I need to have my safety switch tested by a compatent person!

The simple answers is YES, Here at All States Safety services we perfom under AS/NZS 3760:2003 Manual and Trip time test under the required service intervals. In most cases a manual trip test must be perfomed every 6 months followed up with a Trip Time test every 12 months. Like Electrical test and tagging All States Safety Serivces provide a PDF documented report on all test on completion of job.

Different Styles of Portable and fixed RCD Safety Switches to look out for in your workplace -

              

How does a Safety Switch work and what it will not stop!

RCD is a generic term which embraces the various forms such as RCCB, RCBO, etc. Residual Current Devices are now firmly established around the world as a primary means of providing protection against electrocution and fires caused by electrical faults. Less than one quarter of an amp (250mA) leaking from a faulty installation can generate sufficient heat to start a fire (the heating effect is proportional to the current squared), or if leaking through a human body for only 200mS can cause heart fibrillation and subsequent death.
An RCD protects by constantly monitoring the current flowing in the live and neutral wires supplying a circuit or an individual item of equipment. Under normal circumstances, the current flowing in the two wires is equal. When an earth leakage occurs due to a fault in the circuit or an accident with the equipment, an imbalance occurs and this is detected by the RCD, which automatically cuts off the power before injury or damage can result.

What an RCD will not protect;

If a user was to touch both active and neutral at the same time, then current flow would be even through both circuits. RCD WON’T TRIP

 
Scenario #1  A carpenter using a tool with an internal fault, can be electrocuted from a positive to neutral connection, because both positive  and neutral would be feeding electricity evenly into the body, hence the RCD wouldn’t trip.

Scenario #2 An ice machine with a faulty earth and a positive short to it metal frame is touched by a user; positive could flow into the users hands join the neutral side within a fan or compressor. This would happen because an earth wasn’t present. Electrons always take the path of least resistance. If a good earth contact was present then as soon as a positive short was made to the frame positive would have gone to earth and its amperage would have been higher than the negative, therefore the RCD would have tripped.

In basic terms if you short;

• Positive to earth – RCD Trips
• Positive to negative with a good earth – RCD Trips
• Positive to negative – RCD wont trip
• Positive to a metal frame with no earth – RCD wont trip

The milliamp table below shows a potential result, taking in consideration an average drill uses 3 – 10 amps.

• 0 -0.5mA   Generally this current is below the level of perception, resulting in no reaction.
• 0.5 - 5mA  Although no dangerous physiological effects, this current may produce a startle effect that results in injury due to falling etc.
• 5mA - 10mA  Same effect as above but in addition muscular reaction may cause inability to let go of equipment. Once current flow ceases letting go is then possible.
• 10mA - 40mA  Severe pain and shock as current value increases. At currents over 20mA the victim may experience breathing difficulties with asphyxia if current flow is uninterrupted. Reversible disturbance to heart rhythm and even cardiac arrest is possible at higher values of current and time.
• 40mA - 250mA  Severe shock and possibility of non-reversible disturbances to the normal cardiac cycle, referred to as ventricular fibrillation. The possibility of fibrillation increases as current and time increase. It is also possible to experience heavy burns at higher currents in addition to full cardiac arrest.

In short why test RCD Safety Switches

RCD Safety Switches form part of the overall requirements under the “Duty of Care” and the responsibility under the Occupational Health Safety laws and yes Safety Switches do perform part of the safety requirements. However without regular maintenance they may not trip in time and or worse not work at all. So get your Safety Switches tested today. What is stopping you! 

  

Contact us now -

Ph. 1300 255 777 or Email. admin@allstatesafety.com.au