Failure of professional installation of immersion heater in unvented tank

Discussion in 'Electricians' Talk' started by VicS, Sep 18, 2018.

  1. VicS

    VicS New Member

    Firstly here is a copy of my email (in italic font) of thanks to Screwfix for a prompt refund and the helpful advice from this community.

    "We do not now need this thermostat and so will not be collecting it from Worthing

    Ordered the new immersion heater thermostat as our failed immersion heater, in an unvented tank, was installed professionally about a year ago .

    I thought the problem might have been overheating or reset problems as described on your community pages.

    Was disgusted to find that the “professional” installation had failed because the neutral wire had come out its terminal – there was scorching of the heat resistant sheath and the blue wire insulation was brittle and cracked. Again your community pages were helpful in describing the effects of temperature fluctuations on terminal tension!

    Cut out the faulty end of the wiring and reconnected all wiring tightly and all is now working well.

    Sorry for any inconvenience but would appreciate a refund for the uncollected thermostat.

    Thanks for all the support on your web pages dealing with immersion heater wiring and thermostats!

    Obviously our professional plumber was an amateur electrician! Like me he did not have the correct small size spanners to tighten the nuts on the terminals or the outer cover. Fortunately I have a needle nosed mole wrench that has done the job adequately without damaging the nuts.

    Do others agree that the design of our traditional immersion heater terminals could and should reduce the area of uinsulated wiring or posts and not rely on a somewhat flimsy over cover?

    My feeling is that it would be safer to have terminal blocks of adequate size to take the more substantial heat insulated wires needed for powerful immersion heaters. Provided the right size spanners are available is there an advantage to using nuts rather than screw down terminals?

    If we had experienced a fire and damage to property or injury to people would what appears to be an awful product design be responsible? Sadly the product seems so badly designed that it needs a professional electrician to complete a safe installaton.

  2. CGN

    CGN Screwfix Select

    Installation error. Granted they're a bit fiddly, but a competent person can do the job just fine.
    Heat and Allsorts like this.
  3. unphased

    unphased Screwfix Select

    Vic there is nothing complicated about installing an immersion heater element and thermostat. It is a matter of having the correct tools for the job. Thousands of these things are installed every week. It is unfortunate that in your case the tradesman didn't check the terminations were sufficently tight. There is no point ranting about this its poor installation that caused the issue.

    As an aside this is an example of how customers get really over the top about something quite simple. "Obviously our plumber was an amateur electrician". he made a mistake. Did you not think to get him back and ask for his help? No you just went off on one!
  4. MGW

    MGW Screwfix Select

    If there is a fault, first thing is if within warranty, call back the installer, if I as an installer return an item to my supplier they will normally replace FOC, if however I return items which on investigation it shows it was my fault, this privilege is soon removed. So I have to be satisfied it is as I left it, as soon as I see some one else has worked on the system, then I would not chance my reputation with whole sale outlet by returning anything, as soon as you touch it warranty is void from installer.

    OK a little give and take, but there was a case where Henley blocks were faulty, what had happened was the screw thread was slightly tapered, so unless the electrician tried screwing the screw in to start with, he would be unaware, this is why they normally supplied with screw already home so electrician has to unscrew them first.
    There was a second problem, the electrician had been given a torque screwdriver to ensure screws were tight enough, this removed the feel you normally get. So a number of these units failed because the cable was not tight, as the screw became bound in the thread, once heated the brass expands so inspection will show a loose screw, however it was not loose on fitting, where the originally electrician was called back, he knew he had used a torque screwdriver so sent the screw driver to be tested, when that was found not faulty he looked else where and found other Henley blocks with binding screws, so the real fault was found, however where a different electrician was sent then he wrongly assumed the other guy had not used the torque screw driver. So it took a lot longer to find the real fault.

    It could well be the guy who did your job had been supplied with a faulty batch, however your actions in not calling him back will have cost you more money and put other people in danger as he will be unaware of the faulty batch for longer.

    Yes we should always screw the terminal home before putting in wires to ensure threads don't bind, and we should always use ferrules on stranded cable where the screw is direct on cable, but I have simply twisted the strands, and I am sure most electricians do, not many carry a box of ferrules and crimp pliers. However we know the risk, and we give the wire a good tug. Some times going by the book simply does not work, I am sure if the electrician had not used a torque screwdriver he would have felt the screw bind or at least tugged on the wire. But that is experience, that's why we serve an apprenticeship, so we are warned about these problems, if you should use a ferrule and a calibrated set of crimp pliers and a calibrated torque screwdriver and test the screw first, then you don't need to tug on wires, but few will ever comply with all that, so we give the wires a tug, which could in its self cause problems, but we are aware of them, that's where the skill comes in, and every so often some one misses a check.
    VicS likes this.
  5. VicS

    VicS New Member

    Our local respected and long established plumber had unfortunately failed in his attempt to remove a failed immersion heater from a hot water cylinder of 1974 vintage. We were warned this might happen. Sadly the somewhat higher estimate from our local plumber with added VAT made the job considerably more expensive for us than the average. We discussed this and the work seems to have been subcontracted to minimize the VAT element With the work in progress we were held to ransom my what we regarded as an unreasonable extra cost of £150 to replace a faulty flow diversion valve (parts and labour).

    Perhaps some elderly wealthy people would have paid £150 without question but I was aware of the actual cost of the standard diversion valve! Our final settlement left a sour taste for both parties and that is the reason we did not go back.

    I regard myself as an amateur electrician yet always double check that wiring is secure and screws and nuts are properly tightened. Failing to do so is not an acceptable "mistake" especially if it could lead to death, injury or fire.

    Good product design would minimise the risk of "mistakes" and I am sorry you regard this serious discussion as a "rant"
  6. VicS

    VicS New Member

    Thanks for this insight and perhaps others like me are not fully aware where an unqualified electrician is permitted to complete electrical works. If I recall correctly the problem was not associated with a Henley block screwed connections but the uninsulated post with a nut and crimp plate.

    As you rightly say experience counts! After seeing the disaster on my system I tried to do better!

    After reading Screwfix I found my crimp pliers and box of connectors and ferrules but all of the correct size had been used.

    On reflection I am wondering if a wee drop of solder has added to security. The small half loop I made was tinned before putting on the post. After securing the wire solder was applied to the outside of the loop and good flow made through the wire. Don't think there was sufficient heat for the solder to have made strong bond with the terminal.

    All seems well with my finger and thumb torque tested pull rather than a violent tug :)
  7. Coloumb

    Coloumb Screwfix Select

    I use bootlace crimps on flex these days. Regs should be updated to not allow bare flex on terminals without a crimp imo.

    Stands back having lit touch paper.
    MGW likes this.
  8. Bazza-spark

    Bazza-spark Screwfix Select

    Solder should only be used on terminals designed for it. Tinning connections where screw terminals of any type are concerned is not good. If the connection starts to heat up for any reason the flux starts to collapse and makes the connection worse, leading to more overheating and more collapse.

    Cut the soldered bit off and use proper connection methods for the terminals involved.

    Kind regards
  9. HappyHacker

    HappyHacker Active Member

    While I prefer to crimp flex connections I also prefer to use heat resistant 2.5mm flex on immersion heaters. When i look at the number of 13A plugs I have wired over the years without using crimps and no problems I am not sure screwing to flex without a crimp it is a major problem but most plugs do not take 12A for long periods of time as with an immersion. I do see quite a few immersion installations that have not used heat resistant cable which may be a cause of issues.

    I agree that the terminations on immersion heaters and thermostats are very small but for the majority of people they work well with no problems, however the majority of installations I see rarely use the immersion.
  10. MGW

    MGW Screwfix Select

    I did like solder, however not lead free, two reasons, one it may not have flowed correct, but more to the point the fumes from the flux used for lead free are extremely bad for your health. You need extractors to use it.

    I did have a bad job, we got some one to fit a wet room, the electrician promised to return but was never seen, however I have that feeling the main contractor may have failed to pay him. And so it was reasonable that he cut his losses.

    We saw the father of the guy who ran the firm trying to fix it all, it was a right mess, he was completely out of his depth. His real problem was out of date tile cement. This turned a 2 week job into 5 weeks and not finished, my son and I took over the job when they walked off site, and I informed LABC we were taking over the work, only to find he had not told them in the first place.

    I think that caused him to go bankrupt. The big issue was not electrics but he moved a door opening without altering the lintel so lintel only held on one side, lucky we found it.

    LABC were also a problem, they did not want to accept my signature to start with, however my son stated that if we were to pay for a third party inspector of course he will need to be higher qualified than my dad, and he has a degree in electrical and electronic engineering. Only then did they back down and decide my signature would be adequate. I would have never stuck my neck out like that, even if it was true. The LABC inspector seemed to have no idea what a C&G2391 was, both my son and I held one.

    To be frank I was not happy, I did not really know what the electrician had done, so I wrote to that effect on the installation certificate, so expected it to be kicked back, however the completion certificate arrived in due course in the post.

    Although Part P only requires registering for certain work, which varies England and Wales, it still covers all domestic work, it states if it complies with BS7671 the year varies England to Wales then it is considered OK. It can also be considered OK if it complies with any EU countries regulations, it does not need to be British. As to how LABC inspectors would read a German document is another question.

    But clearly for any installation you need either an installation certificate which would normally also have a completion or compliant certificate as well, or a minor works certificate. Not issuing these leaves a tradesman wide open. They in real terms protect him more than you.

    So what did it say on the Minor Works? Go on give us a peep.

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