Regulation 421.1.7 Arc Fault Protection The AFDD Arc Fault Detection Device
This is a new regulation added to the 18th, it is not mandatory that they are installed, but asks the installer to think about the application and If an AFDD installed in the circuit would improve protection of persons and building. If not the case, then installation of an AFDD would not be necessary, but for further information on AFDDs, please contact us.
RCD Types and Applications
Selecting the devices and consumer unit type has to be thought through carefully, as not all consumer units are equal. The most commonly supplied consumer unit is the dual RCD with main incoming 100A switch, or the 100A main switch with all RCBO’s.
Regulation 531.3.2 Unwanted tripping
This regulation should also be looked at in conjunction with regulations for division of circuits and RCDs used for a given circuit. It states that in order to avoid unwanted tripping, accumulation of earth leakage currents downstream of an RCD shall not be more than 30% of the rated residual operating current. This could be anywhere between 15mA and 30mA, based on the standard for an RCD used for additional protection. If a ramp test is performed on an RCD installed, this will provide the tripping point of that RCD, 30% of this would be the appropriate value to use.
So how do we choose the assembly and devices we require for a given residential or commercial property?
Step 1: Identify the number and type of circuits required.
Step 2: Identify the type of load on each circuit. Will a type AC or type A RCD be required.
Step 3: This selection will be driven by the type of circuits required. The most common selection is a dual RCD board followed closely by an RCBO board where all circuits are protected by its own RCD. The latter option also leads to the probability of meeting regulation 531.3.2 without the need for calculations or testing for the amount of earth leakage as regulation 531.3.2 requires the installer to comply with.
Step 4 – Select BG as the preferred supplier. Why BG?
1. Availability – BG has an extensive supply chain network, built over years of successful distribution of quality products with stock readily in place locally
2. Quality – BG operates a BSI approved ISO 9001:2015 accredited quality management system and our product ranges have been tested and approved by many recognised accreditation authorities.
3. Confidence – we consistently meet product standard requirements and will always be on hand to help installers meet BS7671 18th edition compliance.
Email:
sales@bgelectrical.co.uk
www.bgelectrical.uk
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