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On the subject of pulling the DNO fuse.
alanblaby 1100240690
Joined 21/10/2013 - 46 Posts
Question
There have been a couple of reports here of the DNO confronting electricians who have pulled their fuse.

It's getting closer to home, a work colleague was doing a CU change on a domestic house last week, no isolator fitted, so he pulled the fuse (no seals present).
South Nottinghamshire.

Around 90 minutes later there was a knock on the door, a guy from Western Power was investigating a power loss at the property, reported by the Smart Meter phoning home.
He gave the sparky a talking to, and warned they are getting strict in pursuing people who do it, he said meter fiddling was rife, so any loss of power is checked out asap.
110 Replies
crossy 11001208723
Joined 01/12/2018 - 14 Posts

Arran Cameron:
What is the situation like in other countries? Are electricians and homeowners allowed to remove the DNO fuse?

Has anybody actually seen an arc flash caused by shorting out a service head?

Here in sunny Thailand there's no such animal as a DNO fuse, the wires in your incoming MCB (or fused knife switch) go directly to the meter (on a pole in the street) and thence to the local transformer.

Want to work dead on your installation? Pull the live tail out of the meter (seals? what seals?) and do the deed. When done poke the wires back in and you're good to go.

 
davidwalker2 11856795
Joined 29/04/2009 - 125 Posts
With all this talk about protective equipment, I had a smart meter fitted a couple of weeks ago (1960's property, WPD is the DNO).  No sign of PPE to pull the fuses, not even gloves.

David
Alan Capon 20740443
Joined 27/12/2005 - 347 Posts
Indeed. An aluminium conductor will burn back down into the insulation until it goes out (which could be a long way from what is believed to be the cable end). A copper conductor is likely to just burn until hopefully a fuse operates, as copper has a much higher melting point. 

Regards,

Alan. 
Jam 1100158471
Joined 25/11/2009 - 40 Posts

Have you ever seen a faulty cutout “let go” whilst being fairly near it? It is incredibly frightening, and surprising how long it will burn for, throwing molten metal at anyone in range. An electrical arc flash has a temperature hotter than the surface of the sun, and an explosive force of several sticks of dynamite. You really don’t want to discover it in the cupboard under the stairs, or anywhere else for that matter. . . 

It's not my field but I was told by a lecturer on protection course last year that DNO disconnection times are rather longer than BS7671 and indeed the design of some LV distribution systems is intended to have the cable burn back within the insulation/sheath and extinguish itself before the substation fuse operates, meaning other customers remain connected. Which is fine buried underground well away from people, but means the risk assessment for a live cutout in a building is a bit different to pulling a fuse in "normal circumstances"
Zoomup 1100345625
Joined 23/10/2014 - 1751 Posts

geoffsd:
Perhaps such dangerous equipment in people's homes should have been maintained properly and replaced by the 'owners' before getting into that condition.

Well said Sir, well said.

Z.
geoffsd 1100177619
Joined 29/03/2015 - 118 Posts
Perhaps such dangerous equipment in people's homes should have been maintained properly and replaced by the 'owners' before getting into that condition.
Alan Capon 20740443
Joined 27/12/2005 - 347 Posts

Chris Pearson:
. . . Almost new fuse holder secured to a board which is in good condition and is easily accessible. Not a lot of danger. . . 

Have you ever seen a faulty cutout “let go” whilst being fairly near it? It is incredibly frightening, and surprising how long it will burn for, throwing molten metal at anyone in range. An electrical arc flash has a temperature hotter than the surface of the sun, and an explosive force of several sticks of dynamite. You really don’t want to discover it in the cupboard under the stairs, or anywhere else for that matter. . . 

Regards,

Alan. 
Alan Capon 20740443
Joined 27/12/2005 - 347 Posts

Kelly Marie:
I think we are all agreed pulling DNO fuses is not a good idea I think that we need for them to understand that sometimes it's unavoidable due to circumstances. . . 

There are virtually no circumstances when it is allowable. The fuse belongs to neither the electrician nor the householder and it should not be touched. All DNOs have a procedure for them to temporarily isolate the supply, and the HSE believe that this method of working - arranging for the DNO / Meter Operator to draw the fuse is acceptable. It is good that companies like WPD are able to spot tampers with the new smart meters, as well as being able to investigate them immediately. 

Regards,

Alan. 
Chris Pearson 11001208764
Joined 05/12/2018 - 1367 Posts
Just a random thought ...

Almost new fuse holder secured to a board which is in good condition and is easily accessible. Not a lot of danger.

Old service head on a tatty old board with multiple redundant screw holes in a damp poorly lit cellar. That's when you need to get out your arc shield and marigolds.

I think that you have to have one clear rule and "don't touch" is easiest. Or you could, like SSE, trust properly credentialed electricians.
Kelly Marie 11001211805
Joined 18/07/2019 - 274 Posts
I think we are all agreed pulling DNO fuses is not a good idea I think that we need for them to understand that sometimes it's unavoidable due to circumstances  I get why it's not allowed  I think the main concern is if its done to enable someone to steel electricity. But I understand that in some substations there are KWh meters which record the consumption of all the customers on it  so if they suspect steeling surely they can add up all the meter readings for a given area subtract that from the subs meter and after allowing for street furniture use if it don't add up correctly they know someone's on the fiddle then you hey can look more closely instead of being on our backs every time we pull a fuse
davidwalker2 11856795
Joined 29/04/2009 - 125 Posts
Andy - that is interesting, because at my Spanish apartment fed by a smart meter there is a load limiting MCB, also inaccessible in a locked cabinet (as is the meter) but it will automatically reset after 1 or 2 minutes I think twice, and then has to be reset by the DNO

David
AJJewsbury 77361768
Joined 13/08/2003 - 1441 Posts
If this proposal goes ahead then the big MCB will effectively double as an isolator switch.
 
only if it's not sealed ... from what I've heard from Spain if the 'load limiting' MCB trips than the householder is obliged to call out the supplier to re-set and re-seal (and pay a penalty charge) - it's not user (or elecctrician) accessible.

   - Andy.
Arran Cameron 1100402286
Joined 31/03/2015 - 415 Posts
Sparkingchip mentioned in a previous discussion that he thinks houses in the future will have a big MCB instead of a DNO fuse as a maximum current trip, similar to the arrangement in France. He also thinks that the standing charge will increase with the maximum available current of the trip. If this proposal goes ahead then the big MCB will effectively double as an isolator switch.
UKPN 1100233915
Joined 17/12/2014 - 87 Posts
"I was called out on Friday to a report of a switch burning

The local fire brigade too busy again!

Regards, UKPN.🎅
Dreckly 16257685
Joined 09/10/2015 - 10 Posts
I was called out on Friday to a report of a switch burning. The KMF type fused switch and nearby neutral meter tail had overheated due to a loose connection. The cut-out was less than 10 years old and in good order. I turned off at the CU, cut the seals, gave the fuse holder a bit of a wiggle to check that it would move, then pulled it. No problem. A smart meter had been fitted so I rang the DNO (WPD). I explained what I had done and their operator said they would send someone to put the fuse back in and re-seal. They turned up four hours later, which was plenty of time for me to fit a new switch. I also had an isolator of the type that WPD use ready for when WPD attended. They were more than happy to fit the isolator and said every thing I had done was the correct action in the circumstances.

I would willing attend a training course on assessing the risk of pulling a fuse, correct PPE, etc. if such a thing was on offer.

Tomorrow, I have another customer who is having a smart meter fitted. I told him to ask for an isolator because I need replace his CU next year, but apparently he is with a small supplier who says they can't. WPD quoted £220. I'm going to give my customer an isolator and ask him to get the meter man to connect his new smart meter to it rather than the existing tails.

Eventually, every supply will have an isolator. It didn't need to be made so difficult getting to that point, did it!

Dave
Chris Pearson 11001208764
Joined 05/12/2018 - 1367 Posts

Alan Capon:

Chris Pearson:
. . . Funny old thing, nowadays DNOs and meter installers take pictures of their completed work.

It shows that on a certain date and time, the installation was correctly sealed. 
Precisely. If anybody interpreted my comment as being critical of the DNOs (and suppliers) that was not my intention. They have every reason to do so, and the means.

When my own meter was fitted, the fitter sealed my switch isolator in the off position. He also gave me some paperwork about who would be authorised to cut the seal. We both knew that it would be cut before he reached his van. So be it. Mind you, he was having his six-monthly assessment. 🙂
Alan Capon 20740443
Joined 27/12/2005 - 347 Posts

Chris Pearson:
. . . Funny old thing, nowadays DNOs and meter installers take pictures of their completed work.

It shows that on a certain date and time, the installation was correctly sealed. 

Regards,

Alan. 
UKPN 1100233915
Joined 17/12/2014 - 87 Posts
"and new to DNO stuff" 
Perhaps you should stick to restorations, Building restorations?⛑

Regards, UKPN.
Typiod 70746608
Joined 21/10/2013 - 49 Posts
What I can't understand is that if you try to book an appiontment with either the DNO or the supplier to disconnect/reconnect a supply it is at least a 2 week wait, however if you remove a cutout fuse on a "smart" meter then as if by magic they arrive within the hour.
MHRestorations 11001209997
Joined 03/03/2019 - 252 Posts
Honestly I am not finding the thread boring. I think I have learned a lot regarding the dangers and a lot regarding the (il)egality of removing the DNO fuse.

What I am absolutely sure of, is the current system is a ****dy shambles, and given that lives are at risk, that's a pretty poor state of affairs.

I agree the cable tie comment was flippant but if it would fit, it would prevent people removing the fuse without a tool (the safety aspect?)

I am new here on the forum, and new to DNO stuff, having been trained on a university site under the 16th edition, (no seals, we just turned off the feeder switch..., and the electricity board turned up on one substation, monthly, to read the bill) then working for 6 yrs in the USA, where their power system is even more convoluted than here. So who has the authority to do what, and who pays for the expense when the SEB... sorry, SSE take 3 hrs to arrive to do something I could do in 10 seconds.... and the customer is paying by the hour?... this interests me
 
UKPN 1100233915
Joined 17/12/2014 - 87 Posts
Verging on boring now.

Regards, UKPN.🎅
Chris Pearson 11001208764
Joined 05/12/2018 - 1367 Posts

AJJewsbury:

it could be reasonably replaced by a cable tie?  Same means of removal, i.e. by wire snips...

I guess in theory yes - in practice though a reasonbly robust nylon tie probably isn't going to fit though the little holes they provide. Maybe it could go around the whole thing, but it then gets difficult to ensure it can't be slid off.
It's about intent isn't it? If you are very agile, you could probably bite it off. (When I was a very small boy, I could bite not just my finger nails, but also my toe nails; nowadays I do well to kiss my knees.)

Isn't it like those hopeless dolly locks? Yes, you have demonstrated safe isolation, but one good tug and the lock comes off. However, should there be any difficulty, you can still demonstrate that the padlock was secure.

Funny old thing, nowadays DNOs and meter installers take pictures of their completed work.
AJJewsbury 77361768
Joined 13/08/2003 - 1441 Posts

it could be reasonably replaced by a cable tie?  Same means of removal, i.e. by wire snips...

I guess in theory yes - in practice though a reasonbly robust nylon tie probably isn't going to fit though the little holes they provide. Maybe it could go around the whole thing, but it then gets difficult to ensure it can't be slid off.

  - Andy.
Dutch of the Elm 11001201698
Joined 03/10/2017 - 27 Posts

AJJewsbury:

On a directly-related topic, what is the point of a seal on a head that is installed after the meter?  I have seen this and can't understand what it is there for.  No abstraction is possible even if you remove it and make any changes.

Do you think its there as the DNO just always put one on any red-head?

It's probably from an electric shock point of view - preventing someone pulling the fuse or otherwise removing covers to expose live parts - which if it were not for the seal could be accessed without the use of a tool.

  - Andy.

 

Aha!  Good point.  So on that basis (and I'm probably being an ar$e here...) it could be reasonably replaced by a cable tie?  Same means of removal, i.e. by wire snips...

Thanks,
AJJewsbury 77361768
Joined 13/08/2003 - 1441 Posts

On a directly-related topic, what is the point of a seal on a head that is installed after the meter?  I have seen this and can't understand what it is there for.  No abstraction is possible even if you remove it and make any changes.

Do you think its there as the DNO just always put one on any red-head?

It's probably from an electric shock point of view - preventing someone pulling the fuse or otherwise removing covers to expose live parts - which if it were not for the seal could be accessed without the use of a tool.

  - Andy.

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