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EICR Certification DNO Fuse
Chivers
27 Posts
Question
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.    
24 Replies
You shouldn't be asked to put down a value at all. You cannot know, even if the label says 60A or whatever. Put N/A, as you cannot legally find out. If asked the DNO will probably say 60A, as this seems to be the current fitment. Does it matter? The answer is no.
AJJewsbury
1881 Posts
Couldn't you just write "≤100A" - we should be able to deduce that much at least (and you probably do need that much if you're relying on Annexe ZB of BS EN 61439).

(BTW an EICR isn't a certificate)

   - Andy.
 
wallywombat
288 Posts
You could always ask the DNO for the fuse rating, as they are legally obliged to tell you under ESQCR. (Excuse me while I stop giggling.)
jcm
173 Posts

I got a letter from the DNO that said (Urgent action required) we are going to change your electric meter, in order to maintain a safe and reliable electricity supply to your property.   ( We are not installing a smart meter). If the meter is fitted is stutated outside we will endeavor to change it and an appoitment is not always necessary. Anyhow they came at the appointed time, and I bounced the meter changer about this safe and reliable supply.

I took this letter the wrong way ,he said they have a program of changing all meters over 20 years old, and part of their job was to tighten the supply cables inside the cut-out as over time the copper conductors can soften and become loose, he did get a turn because I was looking , and also opened the HRC cover to check the mains fuse. So best to do a visual inspection of the cut in as with BS7671 that recommends this to be carried out.

On a different note, if you had arcing in the cut out or sometimes called a cut in would the  small rated AFDDs detect arcing downstream and trip (don't think so really) but it is going to be Hell to find the cause in the upstream circuits. Can you even use a pulsating Loop tester, or just tell another lie as with MCBs that all is well in your report without testing.

jcm
Alcomax
231 Posts

BTW an EICR isn't a certificate


Thanks AJ , but with your permission I repeat it in big bold type for the benefit of the hard of thinking "satisfactory EICR" brigade.
Sparkingchip
3167 Posts
I normally put “NK” for not known or “NC” for not confirmed.

It can matter what the rating is, for example a 100 amp fuse does not provide overload protection for a 63 or 80 amp RCD in a consumer unit, also a 60 amp fuse may be rated at less than the maximum demand of the installation.

Andy B.
Sparkingchip
3167 Posts
I say normally, because if it’s a 60 amp fuse holder I assume that’s what it is fused at or occasionally it will have a label on it stating the size of the fuse.

Andy B.
UKPN
169 Posts
Thank you Chivers for asking this question. The BS7671, Requirements for electrical installations, as its name suggests has no bearing on ESQCR Distribution/Suppliers works. For some years now the guide book has tried to associate itself with the legal paper but of course any reports/certificates (EICR/EIC) can only ever be of a visual nature. If by chance you through your experience you notice exposed terminations, overheated wiring, tampering, its best to contact the local DNO who will attend as an emergency, or ask your customer to make the call. In answer to your question the term N/V (not verified) is suitable.

Regards, UKPN
lyledunn
393 Posts
NV is fine for an EICR, however correct details are required for an EIC, see 313.1(vi). 
Timeserved
88 Posts
NV over here
John Peckham
494 Posts
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.
Sparkingchip
3167 Posts
Western Power don’t have records either, they have to send someone to pull the fuse and have a look at it.
ebee
830 Posts
Ditto Norweb too (OK the Eon and the like or United Utilities)
AJJewsbury
1881 Posts
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.
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...........
AJJewsbury
1881 Posts
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.
Sparkingchip
3167 Posts
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.

mapj1
2467 Posts
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.
Sparkingchip
3167 Posts
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!).
ebee
830 Posts
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! 😬
Paperclips certainly must have a BS fuse rating since A COUPLE OF YEARS AGO I found one in parallel with an open circuit 60A fuse in a SEALED cutout. (The meter was being changed and the fuse carrier was already out and I asked the meter fitter what fuse was fitted.) He fitted a 63A fuse before he left.
Going by the discolouration of the paperclip, there must have been some high power loads at some time following the "upgrade". http://ancient-mariner.co.uk/public/IMG_1024.JPG
Clive
Sparkingchip
3167 Posts
Now you have confused things, how many people would have a guess at the fuse rating being 63 amps?
ebee
830 Posts
I think that 60A fuses and 63A paperclips were pretty much interchangeable for a while as were the 80A or 100A  fuses and 4" or 6" nails
Johno12345
85 Posts
AncientMariner:
Paperclips certainly must have a BS fuse rating since A COUPLE OF YEARS AGO I found one in parallel with an open circuit 60A fuse in a SEALED cutout. (The meter was being changed and the fuse carrier was already out and I asked the meter fitter what fuse was fitted.) He fitted a 63A fuse before he left.
Going by the discolouration of the paperclip, there must have been some high power loads at some time following the "upgrade". http://ancient-mariner.co.uk/public/IMG_1024.JPG
Clive

that was our on-site electricians trick, bits of armouring wedged in behind a blown fuse, carefully done so it couldn't be seen without taking the fuse out, right up to 630a fuses were found like that

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