Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 26 replies
  • Subscribers 32 subscribers
  • Views 4267 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

EICR Certification DNO Fuse

Chivers
What are peoples thoughts on completing Certificates with regards to DNO fuses.


When you complete a Certificate Technically you do not remove the DNO Cut out fuse so you do not know 100% what the Fuse size is so would you personally put the fuse down as a 1362 type 2 and note down the rating advised by the Supplier or put this down as a Limitation? Up to this week I had normally put the rating as Written on the Fuse carrier by the DNO so 100A = 100A , 80a = 80a etc... I test the ZE/ZS at the closest place to the Suppliers cut out & note this down as the EFLI.


A colleague of mine has recently been "critical" of this stating we should be putting it down as a limitation as we can not guarantee the fuse is exactly what it says on the carrier.
  • 0
    It is very difficult to get the fuse rating of the cut out fuse. Whilst the DNOs have a Statutory Duty to keep records on fuse ratings they do not. Before forum member UKPN says otherwise I have a copy of an email from UKPN that says they do not keep records.


    You cannot remove the company fuse unless you are an approved person in the SSE DNO area. So on the basis you cannot write down anything you have not checked so it has to be a LIM or N/V.
  • 0
    Western Power don’t have records either, they have to send someone to pull the fuse and have a look at it.
  • 0
    Ditto Norweb too (OK the Eon and the like or United Utilities)
  • 0
    So on the basis you cannot write down anything you have not checked so it has to be a LIM or N/V.

    So how can you verify disconnection time for ADS on the supply side of your steel clad CU? Or say that the PFC that's a little over the breaking capacity of the MCBs is adequate? Or will many EICR have to have an FI on those points - and thus be unsatisfactory?


    Is it not a reasonable assumption that the fuse type matches the carrier and it's rating won't exceed the carrier's rating (typically marked as 100A) - often that would provide sufficient information to answer the above points.


       - Andy.
  • 0
    You cannot verify that anyway Andy. Measurements of PSCC are not accuraate on a MFT. Unless it is very low the error band is at least +- 25%, In any domestic you don't care anyway as the ultimate current limiter is the DNO fuse, and the whole CU rating thing is based on that fuse. If you did (very unlikely) measure 8kA, how can the problem be fixed, as generally CUs are not type tested or rated with 10kA breakers? You would therefore have to change to industrial encloseures, and life gets expensive for a consumer who probably does not need that rating anyway. Disconnection of a tails short, or busbar or similar is down to the DNO fuse. The normal 6kA breakers should cope with anything else, although they may be damaged. Once you have gone a few metres the problem has gone anyway. Perhaps this is a way to get an "up front" MCCB into all domestic instaallations...........
  • 0
    In any domestic you don't care anyway as the ultimate current limiter is the DNO fuse, and the whole CU rating thing is based on that fuse.

    Yes - that's exactly my point (if not well expressed). If the DNO's fuse is "dunno" you can't then say that the conditional rating of the CU is acceptable - whereas if you can at least say it's a BS 1361 (or equivalent) rated at no more than 100A (based on the label on the carrier) then you can reasonably claim that it is. If it turns out to be a 80A or 60A then it doesn't matter.


       - Andy.
  • 0
    whereas if you can at least say it's a BS 1361 (or equivalent) 


       - Andy.




    Maybe it should be pointed out that the BS1361 for fuses was withdrawn thirteen years ago and the BS EN 1361 is for rubber hoses and the BS ISO 1361 is for tin cans, which are not much use in a fuse holder.


    So if the fuse has been installed or replaced since 2007 and is not very likely that it is to BS1361 but will be BS88-3.


    Also some of the DNO fuse holders I see are so old I question if they contain double pole fuses, I have have found some DNO intakes with double pole fuses in the last few years, one was easily identifiable because the lid had fell off,  to be fair Western Power replaced it within two hours of my call to them.


    Andy Betteridge.


  • 0
    I'm sure we could come up with a rating for a strip cut from a tin can... to some of us 13 years is practically new -  I cannot imagine many houses have a post 2007 cut-out, that were built before that, there is not much of a programme of network replacement after all.
  • 0
    From the first of January 2021 all the BS88-3 will presumably have a UKCA mark on them as well ?


    (That's a wry or pained smile rather than a smirk!).
  • 0
    Yep plugtop fuses of fag paper (silver foil) and paperclips and DNO fuses of 6" nails or a bit of 2.5 or indeed a screw bolt all have BS fuse ratings - they must have cos you find em so often! ?

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines