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Outstandng 18th Oddities

As far as I recall, we still have some unanswered questions about some of the changes in the 18th. Does anyone have any further information about these? (If not at least this post should ensure the issues aren't forgotten with the demise of the old Forum.)


From memory there was at least:


461.2
  1. The intended meaning of the phrase "neutral conductor is reliably connected to Earth by a low resistance to meet the disconnection times of the protective devices" (given that the Part 2 definition of "Earth" is conductive mass of the Earth rather than any protective conductor or MET; and which protective devices are we talking about anyway?)

  • Also "protective equipotential bonding is installed" - is this intended to mean it actually is installed, or is installed where it is required? (Otherwise new installations with plastic pipes would need N isolation everywhere)


531.3.6 - if it the intention to prohibit the use of Socket RCDs and similar (e.g. FCU RCDs) for additional protection? (being that the generally comply with BS 7288 etc which appears to have a slightly different set of technical requirements to the standards listed)


537.3.2 - Switching off for mechanical maintenance. Although the definition of mechanical maintenance remains unchanged - so continues to include simple relamping - the requirements have changed considerably to the point they just about require complete electrical isolation. Thus a common lightswitch is no longer suitable for switching off for replacing a domestic lamp. Was this really the intention? Or are the changes aimed more at rotating machinery? Given that most householders would prefer not to plunge and entire floor let alone the complete installation into darkness to replace a simple lamp, should we be installing switches rated for isolation in every room?


any others?


   - Andy.
Parents

  • kfh:

    Having a general anaesthetic alone carries a 1:100,000 risk of death irrespective of the risks associated with a particular operation.



    How many custommers, sorry, patients, are told that? In fact that's the risk of an unpredictable anaesthetic event and equates to about once in a career for an anaesthetist. The point in relation to electrical installations is that it is difficult to put a number to various risks (we have discussed the risk of lost neutrals/PME/EVCPs for example) and even when we can, customers don't understand the numbers.
Reply

  • kfh:

    Having a general anaesthetic alone carries a 1:100,000 risk of death irrespective of the risks associated with a particular operation.



    How many custommers, sorry, patients, are told that? In fact that's the risk of an unpredictable anaesthetic event and equates to about once in a career for an anaesthetist. The point in relation to electrical installations is that it is difficult to put a number to various risks (we have discussed the risk of lost neutrals/PME/EVCPs for example) and even when we can, customers don't understand the numbers.
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