Continuing our look at the new changes introduced in ET101 the 4th edition … In the last issue of VoltiTECH, we finished with a brief look at chapter 523 Current-carrying capacity of conductors. Before we carry on one important note to make on your own copy of ET101 is to update Rule 523.6.3, third line, delete “ten per cent,” insert “fifteen percent”.
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Chapter 524 Cross-sectional area of conductors |
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There have been no changes made to Table 52D. In 524.2 the treatment of the neutral is mentioned and the reader is referred back to 523. It is worth mentioning again that one should be aware when sizing the neutral conductor that factors such as the harmonic content could have the capacity to cause serious problems if the neutral conductor is under sized please see 431.2.3. The bottom line is the Rules must be observed in full. There are no changes in section 525 i.e. Voltage drop in consumer’s installations where I.S. EN 50160 is the relevant standard. |
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Chapter 53: Equipment for protection, isolation, switching, control and monitoring
There are a number of important changes contained within this section and as always it is useful for the reader to understand the background to the introduction of the new requirement.
ETCI often receive requests for the clarification of particular rules. One common question asked by electrical contractors is; What are the maximum height requirements for distribution boards? This question arises in most instances because of customer demand’s to fit the main distribution board above a false ceiling in an area such as a shop unit. The customer of course would have different priorities such as saving valuable display space etc. The electrical contractor would correctly be concerned about the potential risks associated with complying with the customer’s request. In situations where the customer was adamant that the electrical contractor should comply with their demand the argument nearly always resulted in the clarification question arriving at ETCI. The present Rules make it clear in clause 530.5.3 that placing the distribution board at a height above 2.25m is not permitted. Unfortunately this new clause has itself caused some additional queries in a number of cases. As a result of these queries it has been decided to replace the entire clause in order to avoid further confusion. The new clause should read as follows:
“530.5.3: A distribution board shall be located in a location where it is readily accessible. A distribution board located in a switch room shall comply with 539. A wall-mounted distribution board shall be mounted at a height not greater than 2.25m measured from the floor to the top surface of the board. In addition, where a wall-mounted distribution board is mounted at a height less than 1.4m measured from the floor to the bottom surface of the distribution board, it shall be accessible only by authorized persons.
Note: The intention of the third paragraph is to prevent ready access by young children (i.e. in areas with External Influence Classification BA2 in accordance with Annex 51D.
In clause 531.2 there are expanded requirements for Residual Current Devices (RCD) used for protection in the case of a fault (indirect contact). In addition there is a new annexe (53A) summarising the RCD requirements. Also included in this annexe is some useful information concerning the different types of RCD that are required by the rules for differing situations. Covering information such as the “source of energy for operation”, the effects of d.c. components in the supply, selectivity between RCD’s and the avoidance of nuisance tripping. Some of the main changes regarding RCD’s include the following: On construction and demolition sites socket outlets above 32A rating must be protected by an RCD with a residual current sensitivity rating of not more than 500mA. The RCD selected must be type A or B depending on the characteristics of the d.c. component present. In agricultural and horticultural installations socket outlets above 32A rating must be protected by an RCD with a residual current sensitivity rating of not more than 100mA in addition all other circuits require an RCD with a residual current sensitivity rating of not more than 300mA. Where continuity of service is “desired” an RCD incorporating a tripping time delay is required. There are additional RCD requirements in the 4th edition of ET 101 but in order to avoid confusion we will cover these when we discuss the relevant section in future issues of VoltiTECH.