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Earth Continuity Test and Polarity Test following when replacing low voltage single phase fixed electrical equipment

Hi all,

Would appreciate your thoughts on the need to undertake Earth Continuity tests and Polarity tests following replacement of single phase low voltage fixed electrical equipment such as tea boilers / heating pumps / immersion heaters etc, that are supplied either from a switched and/or fused connection unit or an isolator. The existing electrical supply cable is going to be re-used as the equipment being replaced will be like for like, so there is no increase in load, no requirement to undertake a design.

This enquiry has been put forward as it is anticipated that (some) engineers, who have a mechanical background but with limited electrical knowledge (safe isolation), would be able to carry out the replacement of certain items of plant once they have completed some competency training followed by assessment and sign off by the company's NIC EIC QS. 


Thanks in advance.

Rob
  • If you've got a human terminating individual wires (rather than inserting a plug into a socket) then I reckon you need to consider the possibility of that human making mistakes with those connections - both not terminating properly (e.g. wire over-inserted so that the screw bites down on the insulation rather than the conductor) or into the wrong terminal are easy mistakes to make. Lack of earthing is certainly potentially dangerous - possibly immediately dangerous if the appliance has high leakage currents - so I certainly wouldn't skip an eatth continuity test. Polarity (i.e. L-N reversal) perhaps isn't quite such a safety issue - especially for modern CE marked appliances.

      - Andy.
  • Thanks, that's a good point. Like you say the polarity on a single phase supply (inadvertently swapping L and N) might not be so damaging but having the engineer sign to say he has tested the polarity (and earth continuity) would be belt and braces as well as providing some form of evidence that the installation was sound at the time of the work being undertaken.
  • The  absolute minimum, a quick buzz test for continuity from the case to a nearby socket or similar. There is a slight risk the nearby socket has no earth when you start of course !

    If it is earthed, then at least all the other bad faults would be  self-revealing on energising.


    If these folk are only doing occasional wiring, then a reminder mechanism for where to check and what to do if you are out of your depth needs to be part of this - a "what to do if" reminder ending in  'phone a friend' for the 'any other case' as a laminated pocket flash card or similar may be an idea, - much as if you have trainees doing stuff, and they get stuck, they know to stop and call, rather than to try and wing it.
  • It's an interesting question, but to my mind it is more about the competence of the maintenance engineers (and how to demonstrate it) than about the testing.


    Never in my life would I have thought about continuity and polarity testing after putting on a plug and this seems very similar.


    If you are going to test, that means having the machinery to do so. Inspection achieves the same result. All of us do it, perhaps without thinking. It's just looking at the job and checking before putting on the lid.
  • Forgetting anything else, the HSE Guidance (e.g. EIS 35, EIS 36) for appliance repair engineers includes for consideration that the installation is safe for the appliance (depending on what you're doing) - and Zs test is recommended.


    Suitable checks of the appliance to ensure it's safe after repair, even as simple as replacing or fitting a plug (minimum earth continuity here) is necessary. This is part of either consumer protection legislation (domestic customers) or Electricity at Work Regulations (absolute duty of Regulation 8 puts you in a difficult position if a simple test could have shown up an issue with the protective earthing)


  • Also, simple things that we do automatically others may miss. Electricians try to "fill" terminals with the copper conductor by either doubling over the solid copper wire or twisting and doubling over strands of flex before inserting into electrical terminals. I have seen others just push wire flex strands into terminals parallel, some strands just find themselves not securely gripped by the screw as they are positioned either side of it, others break off and serve no purpose. The terminal can then run hot. Simple fails often cause trouble for the partially experienced.


    Z.
  • Also, simple things that we do automatically others may miss. Electricians try to "fill" terminals with the copper conductor by either doubling over the solid copper wire or twisting and doubling over strands of flex before inserting into electrical terminals. I have seen others just push wire flex strands into terminals parallel, some strands just find themselves not securely gripped by the screw as they are positioned either side of it, others break off and serve no purpose. The terminal can then run hot. Simple fails often cause trouble for the partially experienced.


    Z.
  • It seemed an odd question on first reading it.


    A firm that is an NICEIC registered electrical contractor wants to get some of the non-electricians it employs to do minor electrical work, presumably for paying customers, on the basis that the QS and the firm will take responsibility for ensuring the work completed by these people who are not formally qualified as electricians is satisfactory.


    Then there is the question as to what testing should be carried out and certification produced.


    Both of these matters are something that should be asked of the QS, is the QS going to accept the responsibility of supervising these non-electricians when they are undertaking electrical work for customers and being qualified in design, erection and verification the QS should know the answer as to what testing and paperwork will be required for the company’s and customers records.


    So perhaps the question should be, what testing and certification to the firms electricians do when they undertake such work should be asked?


    Given the list of appliances given as an example perhaps it would be better to get the electricians to do the plumbing, rather than the plumbers do do the electrical work?


     Andy Betteridge

  • Zoomup:

    Also, simple things that we do automatically others may miss. Electricians try to "fill" terminals with the copper conductor by either doubling over the solid copper wire or twisting and doubling over strands of flex before inserting into electrical terminals. I have seen others just push wire flex strands into terminals parallel, some strands just find themselves not securely gripped by the screw as they are positioned either side of it, others break off and serve no purpose. The terminal can then run hot. Simple fails often cause trouble for the partially experienced.




    Back in the day (1980s) it probably was considered good practice to twist the ends of a ring together (and the whole CPC in one sheath). I distinctly remember raising this point during my training and the response was that twisting the ends (particularly with a pair of pliers) could fracture them.


    I can see the sense of that, but I have also experienced CPCs failing to be gripped by an accessory (or at least a poor quality one). The solution, if that is the householder's choice, is IMHO to make a lazy twist.


    Personally, at home, I'd stick with the known reputable brands.

  • This is the old chestnut that gets roasted on the forum every so often.


    If a customer uses the services of a NICEIC registered contractor it seems reasonable that they will expect the electrical work to be carried out by a trained and competent electrician with appropriate qualifications for the level they are working at.


    At the very least they need to be able to assess the existing electrical fittings and circuit to ensure it is actually safe to work on and connect new equipment to, then be able to check their own work is satisfactory before restoring the electrical supply.


    Andy Betteridge