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Earth Continuity Test and Polarity Test following when replacing low voltage single phase fixed electrical equipment
Rob Bain
6 Posts
Question
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
18 Replies
AJJewsbury
1764 Posts
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.
Rob Bain
6 Posts
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.
mapj1
2348 Posts
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.
Chris Pearson
1659 Posts
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.
gkenyon
1164 Posts
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)

 
Zoomup
1760 Posts
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.
Zoomup
1760 Posts
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.
Sparkingchip
2928 Posts
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 
Chris Pearson
1659 Posts

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.
Sparkingchip
2928 Posts
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 
mapj1
2348 Posts


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.

Maybe in an ideal world, but it is not the case in practice. It is equally likely that the cable will be pulled in and the screws  hammered home by someone 'in training'  following long distance instructions, and supervised by no-one especially closely. The give away is when a different person comes along to 'do the inspection for the certificate'  for a really trivial job . This tells you the installer was not able to test their own work.
And that is before we note that there are those who are indeed trained and really by all measures should be competent, who can still create some remarkably poor installations.

Rob Bain
6 Posts

Sparkingchip:
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 

 
Sparkingchip
2928 Posts
Have a look at the EAS document.

Jump to the last page which is 36.

The work is medium risk, being Electrical work defined as Minor Works in an occupied building – subject to safe isolation procedures documented and implemented.

The person who carries out the electrical work should be a Level 2 Operative (instructed person: experienced, trusted) with periodic involvement of the QS/RP on site.

So to comply with the requirements placed on your firm as a NICEIC registered contractor it seems that the guys doing the minor electrical works should be qualified with an electrical level 2 qualification if they are working without constant supervision.

Andy Betteridge 



 
Rob Bain
6 Posts
Hi Andy,
I appreciate your reply and the information provided, be rest assured that I have also reviewed the NICEIC process, to ensure that we are not going outside of the registration requirements. Also to double check I have looked at the interpretation of minor works in an occupied building, which BS7671 states is "additions and alterations to an installation that do not extend to the provision of a new circuit". All this is good information for me to collate a reply to my Senior Authorising Engineer before the business actually go down the road of instructing the mechanical engineers to complete any electrical works which they feel is outside of their competency limits .

Thanks again 
Rob
DjOhms
1 Posts
there right or wrong when it comes to that?
I think (I've seen) 90% of  electricians won't bend or twist a single stranded cable before introducing it inside terminal..
 
Hi.

After reading some of these posts it seems most are making the assumption, that the installation was correct before you started with your minor works,

But once you have fitted something new to an old circuit, you become responsible for it.  As for polarity we all check we have connected every thing as it should be.  But a polarity check makes sure everything in the circuit  before our work was correct. Without a polarity check a switch or MCB could be in the neutral and all we have done is added a little flex. but would leave you responsible for any problems in the future.

as for the ZS reading just this Friday, I was tasked with fitting a switch fuse spur for a garage door my R1 + R2 was just 0.11 ohms, but ZS was 1.74 ohms too high for the protective device.  When I checked the supply cable to garage the sub main protective device, was all ready compromised. so the protective device would not operate in time. so left my work disconnected even though I had a lot of pressure from my line manager to connect it,

so I see testing firstly protecting you from prosecution, then the customer who is the final user from harm. so my thoughts are its extremely important to do tests regardless on how small an input you have made to a circuit.
This is a description of what is wrong with the whole QS system employed by the NICEIC. In fact, there is no quality checking at all, and the person issuing the certificate will have to "make up" the test numbers on the minor works form unless your "non-electrician" can measure them correctly with the appropriate test equipment. A Zs measurement and a polarity check really are the minimum even for this kind of job, along with a proper inspection of the existing circuit.

believe that there are no untrained people carrying out electrical works any more since BS 7671:2018 only recognises three type of people skilled, instructed and ordinary. They’re no longer accepting competent as enough knowledge.

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