Most circuits within a modern electrical installation are protected by an RCD or Residual Current Device. RCDs offer protection against electrical faults and electric shock. However, as electrical installations and connected appliances become more complicated, this places additional requirements on the designer to ensure the RCDs are matched and offer the correct levels of protection. In this free accredited CPD training module, we explore using RCDs as defined in BS7671 UK wiring regulations.

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00:00 Introduction to RCDs
01;20 What protection do RCDs provide?
03:40 How do RCDs work?
08:40 DC leakage currents & non-linear electrical loads
12:30 Different types of RCD
13:00 Type AC – RCD
14:10 Type A – RCD
15:30 Type F – RCD
17:10 Type B – RCD
18:40 Installing the correct type of RCD
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Types of Residual Current Devices, Type AC, A, F, B and B+. What each type is intended for and what fault currents they will work with.

Effective September 2022, BS7671 requires a minimum of Type A for the majority of installations.
However some devices are not suitable for use with Type A and require others such as Type F or B.

One of the most interesting things about this RCD/GFCI is that it is a type-A designed to detect pulsing DC from a mains voltage rectifier. Something that can defeat standard AC RCD’s/GFI’s in some fault scenarios.
It appears that Rolec have had quite a lot of these breakers fail in the same way, including the single phase ones, and usually on the same terminal.

. The device can be employed for earth leakage currents of up to 1A and can efficiently compensate leakage currents over a broad spectral range from 150Hz to approximately 30kHz.

The device couples a 180-degree phase-shifted current with the same amplitude to the leakage current to the respective phases and feeds it backwards to the source. This stops the leakage currents from flowing through the RCD and tripping it inadvertently, thus enhancing plant availability.

In this video we show how to set up a Megger 1741 MFT tester so we can test AC RCD’s, A Type RCD’s and B Type RCD’s. We also discuss the application for AC, A type and B type RCD’s

Demonstration of a Ground Fault Circuit interrupter (GFCI). Home Inspection Tips

In this simple demo conducted at Eaton Corp.’s Power Systems Experience Center, Dan Carnovale explains what an arc fault is and why there is such a big deal made about detecting arc faults in circuits. Also explained are the components added to an ordinary circuit breaker that go into detecting both arc faults and ground faults.