VoltiTECH Part 5: Jim Keogh discusses the changes in the 4th edition, including section 539, Chapter 54 and 55 and Part 6.

This is a very important requirement which if observed by the user could reduce the incidence of “stiction” in RCD’s. The word stiction was coined by RCD manufacturers during the early stages of their development. It described a problem that resulted in the RCD tripping mechanism not reacting immediately when it received an “instruction” to trip. This delay or in some cases inaction has resulted in a number of serious and in some cases fatal consequences. With a maximum allowable tripping time of 300ms for a 30mA sensitivity any delay is unacceptable and in order to attempt to keep the mechanism working properly regular operation of the device is necessary. Labels are available from the Electro Technical Council of Ireland free of charge.

In section 539: Isolation of premises in an emergency a number of measures which were originally introduced in Amendment No. 2 of 2005 appear to many readers of the 4th edition of ET101  as “new requirements”. This of course is not the case`, but due to this incorrect perception it may be necessary to spend a little extra time discussing the key points. This section of the rules has important implications for every location that has more than one electricity supply. The technical intention of the requirement is to provide a switching facility at ground level intended to operate in the case of a fire or other emergency, using a main isolation device that interrupts all electrical supplies in a defined electrical installation. There are of course many different scenarios but the fundamental principle always remains the same i.e. the Distribution System Operators network service cables must be interrupted at the perimeter wall of the building. The objective of this requirement is twofold: (1) the main electricity isolator when in the “open” position has a cable that always remains “live” connected to the incoming terminals. The location of the isolating device determines the length of this cable that remains “live”. As you might expect the prospective short circuit current levels will always be at the highest level in this particular part of the electrical installation. Therefore the intention is to keep the “length” of this “uncontrolled” cable to the minimum. (2) Another reason for locating the main isolating switch in this specific location is to make it easily accessible to emergency personnel without them having to “go deep” into (for example) a burning building in order to isolate the electrical installation. Some of the requirements listed in 539 also appear in the technical guidance document “B” (Building Regulations 2006) in section 1.4.10. which states:

“Where an electrical transformer or substation room and any associated main switch room are to be provided in a building, they should be located on the perimeter of the building with an external access door. The location on the perimeter of the building including external access to the relevant room to be discussed with the electricity distribution system operator.”

Moving on to Chapter 54: Earthing, Protective conductors and Equipotential Bonding  in this section there are no major changes except in 544.1.3 where in the requirement concerning main bonding conductors there is a statement which says “Notwithstanding these requirements in general, the cross-sectional area need not exceed 70mm2 copper or the equivalent values for other materials.” This is a change from 25mm2 which was the figure quoted in the third edition.

Chapter 55: Other Equipment. There are a number of changes in this chapter. A reference in 551.1.2 refers to I.S.EN50438 This European Norm covers the agreed standards for the interface between a micro-generator and the fixed electrical installation. With the focus on green energy now and into the future you can expect further additional information / requirements in this section in the future. Section 552 now contains all the requirements for electric motors. Section 554 Plugs, sockets, cable couplers contains new requirements for the height of socket outlet heights. These particular requirements were driven by changes that were made in the Building Regulations Technical Guidance Document M published recently by the Department of the Environment. Other changes include rule 554.3.5 where the electrical contractor must ensure that he / she installs an accessible means of isolation for a socket outlet that is not readily accessible. This requirement will result in some important changes in the approach to wiring socket outlets under counter tops etc and should be welcomed by the end user. Section 555 Electrical Appliances has a requirement that all circuits supplying water heating appliances must be protected by an RCD having a rated residual operating current not exceeding 30mA. This requirement does not apply to water heaters used for industrial or similar purposes. Section 559 Luminaires and Lighting has a number of new requirements covering the subject including new requirements for connections, fixing, temperature limits, and the through wiring of luminaires.

Part 6. The section that deals with Verification and Certification has a number of important changes included in it. One such change is the formal recognition of a test that has been done by every experienced electrical contractor down through the years, yet this test was not specifically mentioned in previous rules. The test in question is the detection of erroneous connections between circuits. The test is meant to reveal a phase to (same) phase fault which could remain undetected if the “detection of erroneous connections between circuits” test was not performed. Technical committee no. 2 ETCI decided to formally incorporate this test into the routine tests, Rule 613.4 is where you can find the “new” requirement.

Next time we will conclude our look at the new rules with a quick look at the rest of the changes in Part 6 and the new and changed special sections in part 7. Finally we will wrap up proceedings with a look at the new annexes that are contained in the 4th edition of ET101.

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