Plug sockets and exposed wires

Engineer Judgement – What does that mean?

There are so many comments floating around about the level of skill and experience of those working in our industry today. It would be easy to state that this is not the case and that it’s a select few who are unhappy about the shift in work ethics and training which has ultimately led to reduced costs and less money in the pockets of vocal sparks. Truth be told, it would be impossible to pinpoint the exact cause but I’ll share the theories I’ve been told over the last few months (I may miss some, please add at the bottom if you’ve heard more).


1.        Some required competencies have been removed from the apprenticeship programme.


I’ve been told that the major players in the industry have dumbed down the competency requirements to be able to outsource certain jobs and reduce electrician’s wages. If we don’t teach sparks how to use Cat5 cables etc. we can use external TV and data engineers and drive costs down for the organisation. Same applies to MICC (Pyro).


If this was true we would be able to see this very clearly in the work carried out before with the National Occupational Standards (NOS) and then the changes. Surely this would be challenged. Of course, if the people who wrote it are the people who would normally challenge it….. we have a flaw.


2.        The introduction of short courses or training courses outside of national apprenticeships.


Yes, this is a problem. Why? Because we are giving people a little knowledge and then they’re earning money which is the same as those who have a lot of knowledge. The issue here is the perception from the client ordering the work and not an electrical industry problem, as such. Instead of moaning about reduce competency we should be educating the consumer, we don’t do that enough. If you use someone with very little experience over someone with a lot…. The life of the installation may be significantly reduced.


3.        The Competent Person Schemes are reducing entry requirements to get more members – thus increase profit.


I would be amazed if this was actually true. Although it has legs. As with the first theory, I can’t see how this would be true as they all have to monitor and manage members the same way. Yeah, CertSure has this QS model which needs to change but all in all the model they all work towards is the same. There is actually a specification which is developed to enforce how a Ukas accredited Competent Person Scheme must perform (let’s ignore the fact they write the standard themselves).


Whichever theory you back I would like to take you back to the title of this article, engineering judgment. I regularly see people shooting electricians down for calling themselves engineers yet the guidance notes we use state the need for engineering judgement. Does this mean an electrician has to employ an engineer to determine deterioration or risk when carrying out testing on properties?


The truth is that judgement sits with the tester and inspector. Whether you call this engineering judgement or electrician judgement, it means the same thing when considering competence. If you have only done part of the qualifications needed to be a fully qualified spark then your judgement is less worthy than someone with 20 years experience and all the qualifications needed to be an electrician.


I recently spoke to an electrician who challenged me on the following.


Circuit supplying a ring final circuit had a Zs of 0.67 ohms. The r1+r2 was 0.23 ohms and the Ze was 0.07ohms.


(R1+R2)+Ze = 0.30 ohms (Zs)


I was told that because it was within the parameters of the Max permitted Zs it was fine and that it was probably a spur causing the increase. Which I agreed but disagreed in terms of frequencies of inspection and determining the deterioration factor. Let me explain.


The reading the electrician got was 0.67ohms but the assumed calculation reading should have been 0.30ohms. That’s 123% difference from calculated to actual. If this was a spur it would be around 19 meters long.


19.51 / 1000 * 19 = 0.37ohms (this is the calculation you could use to validate cable length resistance and is a good guide if you take into account connections etc. which are minimal).


Anyway, the spur is 19 meters long????? Really?


What about the previous result? What if the property was tested 3 weeks or 6 months ago and the reading then was as expected (0.30ohm ish). That means over 3 weeks say, the deterioration factor is 0.02 ohms per day. That means in 35 days the system could potentially fail because the Zs would reach the max permitted.


If you are a sparky and you’re not following this…. think about it.


So now you’ve just tested an installation and got a reading of 0.67Ohms and told someone it’s fine because it’s within the parameters. You’ve put your signature on the document and signed it off for 5 years because you follow one rule and not the whole picture. You’ve actually just put the person ordering the work at risk for potentially for 1790 days. Fingers crossed nothing happens in that time.


Engineering Judgment in our sector is knowing your regs, knowing your calculations and understanding what you’re doing. It also means understanding the other requirements your clients need. Say the above was a Local Authority or Housing Association, they are required to manage properties in accordance with a handful of regulations that all say the property has to be safe throughout any tenancy. If you’re the electrician above, you’ve just put them at risk and they (or you) don’t know it.


It’s extremely important for risk management and technical management of electrical systems to use competent people. It’s even more important to stand up and shout to our industry that its time for Individual Accountability.


Let me know if any of this doesn’t make sense. Happy to sit down with anyone who wants to understand this but is not at that level yet.

Ryan Dempsey - CEO
Ryan Dempsey

Over the last few years I have found myself in a very fortunate position where I can implement and promote change in the Social Housing sector. My passion and drive to improve Electrical Safety continually fuels my motivation to implement slight changes to engineer and industry work patterns in the hope the mentality currently sitting in the engineering industry can change. We need to ensure the right people with the right skills and experience are working in and around the properties we provide. Not only that, we need to ensure the workforce are the people talking and helping develop the standards we work towards. Improved quality assurance and the avoidance of the 'status quo' should be a starting point in any organisations route to complete compliance. Improved compliance at all levels will improve the safety and sustainability of the properties we provide and manage. The key to improve risk management is to pinpoint the areas of risk and manage these individually. Don't over complicate a simple process. We also need to ensure those with a similar passion speak up and be counted for. It's time for change and that means moving out the old and replacing with the new. All the views and opinions on here are my own and not that of any company I am associated with.

  • Avatar
    William Bruce
    Posted at 11:36 am, 5th December 2017

    I’ve never used a meter, that you can trust the calibration on for taking a Zs. Easy test is, to take 2 readings at the same point on high on low trip and compare. I’ve never had acreading anywhere close.
    If the Ze is taking at the incoming terminals of the DB the R1+R2 then done on the outgoing terminals, we miss out on all the DB connections through busbars and mcb’s and rcbos. Ze = Zs + (R1 + R2) is therefore not intirely true but a useful guide.
    You can only log what the meter reads, but who can ever guarantee results?

  • Avatar
    Richard Llewellyn
    Posted at 11:37 am, 5th December 2017

    I would also add that a Ze of 0.07 suggests the installation is very close to the supply transformer, such that a standard multi function tester is unlikely to be accurate. Unfortunately I can’t explain why, but do know there is a problem when close to the supply transformer from conversations with people far cleverer than me. I remember being flummoxed by reactance vs resistance among other things.

    What your post shows is the difference between people who can write a number in a box, and people who can understand the numbers and what they mean. A result as wildly different as the one mentioned should definitely be looked at closer, to try and decipher what is going on. It could be due to spurs, unusual meter readings, external influences etc, the trick then is that the tester needs to be able to think about it rather than to just say the number is within requirements so just be alright.

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    Christopher Mckay
    Posted at 11:37 am, 5th December 2017

    Rcbo it 👍🏻

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    Daniel Wise
    Posted at 11:38 am, 5th December 2017

    In my experience…. anti trip Zs testers are wildly inaccurate, calibrated or otherwise. I hste the things…. anything such as noise on the circuit can cause the tester to send limited currents into the installtion and likely this would give you unreliable readings. Also the 5year interval is a guide and not set in stone. The inspecting engineer can recommend a further inspection at an interval he or she feels is appropriate. Also in the summary section of the report you can always advise of any specific recommendations so you could recommend that this particular circuit be retested in say a month or 2 and the readings taken on the same meter this might give a better idea of the deterioration of ghe circuit if there is one. My instinctive guess is that the anti trip on the Zs tester is the reason behind the high reading

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    tony Meehan
    Posted at 11:39 am, 5th December 2017

    Sometimes a socket will give you a higher Zs value. The Circuit can be fine but the socket would need replacing. Should have been tested for on the day.

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    Keith Jones
    Posted at 11:40 am, 5th December 2017

    The 0.67 loop impedance could have resulted due to the instrument being set on the 15mA rcd no trip setting which will generally provide an artificially high value of loop impedance.

    The question we must ask ourselves is ” do we test for goodness or badness when taking readings and measurements during EICR’S”?

    Is a £400 instrument accurate enough to provide the best reading? I honesty don’t think so.

    If the reading recorded during the EICR is compliant with the maximum loop impedance values detailed in BS7671 then it up to the competent person undertaking the test to use his/her judgement to decide whether it requires further investigation.

    Just my humble contribution. 😆

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    Ryan Dempsey
    Posted at 11:41 am, 5th December 2017

    Or”testing and then inspection”!! 😜

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    Paul Skyrme
    Posted at 11:42 am, 5th December 2017

    Isn’t the process, Inspection & Testing, not Testing and Inspection?
    IMHO the clue is in the name…

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    David Watts
    Posted at 11:43 am, 5th December 2017

    I often say that even an idiot can press a button and write down a number.

    With software ‘checking’ our values for us and testers flashing green lights or big ticks on the screen to say ‘Yes, this is acceptable’ it is no wonder many disconnect their brain from their work.

    My interpretation of engineering judgement is for example where you choose to overrule your test instrument – they are just a tool anyways, no more important than your screwdrivers.
    You may measure a resistance and choose not to accept the value. It could be too low from an undetected parallel, or too high maybe from contact resistance within a switching arrangement.
    If we don’t apply our engineering judgement (applying our knowledge of conductor resistances according to length etc) then what’s the point in measuring in the first place? Just turn it on and do the loop at the end!! – Which unfortunately is what many are doing. 🙁

    That is my opinion on electricians applying engineering judgement, being able to strip the system down in their head and redesign it on the fly.

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