Who owns what - your guide on cut outs, meters, fuses and who is responsible

Who owns what - your guide on cut outs, meters, fuses and who is responsible
Userlevel 7
Badge +5

Updated on 16/09/21 by Jess_OVO


We’ve got an introductory guide on whose responsible for what with your meter and related equipment, for gas and electricity supplies here - for a more technical breakdown check out the user guide below:



The Meter Operation Code of Practice Agreement (MOCOPA) is between the UK’s Energy Suppliers and the Distribution Network Operators (DNOs).

The Agreement includes a document which classifies the way in which faults and non-compliances can be identified. It is well written, with numerous photographs.

It includes this excellent diagram, showing who is responsible for what in the area of your electricity meter:

The Agreement identifies faults with the Distribution Board (DB) equipment, which are the responsibility of the DNO. These are divided into three broad categories:

A: Emergency. A life threatening situation and requiring immediate action.

B: Remedial work required. Serious, requiring attention for safety reasons, but unlikely to cause a threat until it can be resolved.

C: Asset Condition; Requiring attention because it isn’t to the current standards.


Thus, by way of example, Code B11 Flow is a reporting category which prevents a Meter Installer from undertaking the work because there is a fuse on the Neutral supply as well as the Live.


Old Distribution Board equipment.

Sometimes there isn’t actually a fault, but your house appears to have old-style devices belonging to the DNO.

The Energy Networks Association publishes another guide with similar format, which enables such items to be identified. The Cut-out Types and Ratings Guidance  has full colour photographs and the date range when that equipment was fitted.


When viewing items of electrical equipment in your home, it is important not to tamper with it. If in doubt, take a photograph and post it here on the Forum for us to see.

42 replies

Userlevel 7
Badge +5

Any update on this please @Adiavel ?

Userlevel 6

You’re welcome, @Adiavel, please keep us updated, the outcome of this may be very handy to other members.

There’s a post here that you and @Transparent might be able to shed some light on. 



Userlevel 1

Hi Amy, thank you for your reply. 

I will see what UK Power Network will do, maybe will cancel my appointment too or maybe they will be able to fit only a 80 Amps fuse on the current existing meter tails (16mm) which is still a great achievement for my property.

My electrician will install indeed 2 x  100Amp isolation switches, one for each CU, in order to allow trouble free maintenance in the future.

Thank you very much for your help.



Userlevel 6

Hey @Adiavel, I’ve been in touch with our operations team to ensure the information I give is fully accurate.

It’s a shame to hear the appointment has been delayed, but the DNO won’t touch the meter tails at all, it will be in your best interest to wait for the appointment. It's best practice that we upgrade the tails before the fuse is changed. 

I'd also recommend having an isolation switch installed if you don't already have one, if you’re planning on having two consumer units.  It'll make it easier for the electrician to wire. We can do meter tail upgrade and isolation switch fitting in one job, no problem, please reach out to the team, you’ll find our contact details in the post earlier by @Tim_OVO

I hope this helps! 

Userlevel 1

He will split the meter tails and from the splitter he will feed both the house CU and the summerhouse CU. For summerhouse, a 16mm armoured SWA cable will leave the splitter, running on the ground along the garden fence towards the summerhouse to its CU.

Hopefully it is ok.

While the main fuse will be 100Amps and the meter tails need to be upgraded  to 25mm, I hope the 16mm Cable going to the summerhouse it is ok too, even if those kind of cables can carry maximum of 80amps, much more than the summerhouse will ever need at one time.

By my calculation both CU's added will never draw more than 80Amps at one time from the main cut out fuse. 

So if they got one and they agree to fit it than I will be very happy indeed.

But maybe they will see that my fuse box needs replacing so there is a chance to have actually the meter tails changed by them along with a 100Amp fuse, which will set the house ready for charging an EV vehicle in the future too.

They are UK Power Network, maybe different from DNO, hopefully everything will go as planned.

I will keep you updated.

Thank you for your reply, Transparent.

And finally, I received the appointment email from OVO for upgrading  the meter tails which now is 3 weeks later than the initial one...I lost faith they will do it, so I am trying to go ahead with the UK Power Network appointment if they will allow it.

Thank you again.


Userlevel 7
Badge +5

Well I think @Adiavel ‘s idea of requesting an 80A fuse is a masterstroke. I doubt that the DNO holds many of those in the stores. So there’s a fair chance they’ll turn up with a standard 100A fuse anyway!

Just returning for a moment to the additional Consumer Unit you want to put into the summerhouse, I’m unsure how your local electrician might wish to link that to your existing Distribution Board. There are a number of alternatives, dependent on the type of cable (Steel Wire Armoured underground?) and what mechanical space there is in your existing CU.

When I started a house renovation about 5 years ago, I had the DNO relocate my meter into a new box built into the external wall. The existing arrangement was a mess of three CU’s, two with re-wireable fuses. So my friendly electrician placed a new 100A Switch Disconnector in a separate box screwed to the internal wall just behind the meter enclosure.

The DNO engineer arrived mid-morning, fitted the Service Fuse and meter, which had short tails running through the wall to the new Switch. He performed the required tests and left site.

My electrician called by a couple of hours later, made safe the loose cable-ends around the consumer units and ran an overly-long pair of new tails to the other side of the same 100A switch.

Each party had completed the work for which they had responsibility. But the arrangement allowed us several months to gradually run new cables through the house as the renovation work continued. Whenever we had a new circuit ready we could isolate everything without needing to call the DNO to pull their Service Fuse.

Anyone considering future changes to consumer units (perhaps for an EV charger) should ask their electrician for the same arrangement. It’s cheap, practical and safe.

Userlevel 7

Yep some more really interesting questions about who should be doing what and when here. It’s clearly a grey area so I have a feeling this topic might be getting A LOT of action!


Thank you for sharing, @Adiavel - if you have any doubt as to what the next steps are from OVO’s side, we’re on FacebookTwitter and our Help centre has online chat! It would be really handy to hear back from you when you notify the DNO, so we know what next steps they’ve advised…?


Nice advice once again, @Transparent - you’re the most knowledgeable non-engineer we have as part of this community! 



Userlevel 3

Hi @Adiavel, I think @Transparent is correct when referring to this particular topic when discussing your query.


I’ve moved all of your comments over to this existing topic to keep everything in one easy to find place, which will mean other users will be able to get their hands (and eyes) on it.


Some great back and forth information here, and it would be extremely beneficial for us to hear more about your journey. Please continue to update this thread if and when you learn more about the process.


Have a great day,

Userlevel 1

Thank you, Transparent.

The bitumen drippings looked solidified not liquid. So it happened some time in the past.

Thank you for this reply too. I will let them know so they can decide the apropiate action to be taken.


Userlevel 7
Badge +5

That bitumen leak might be the clinch argument, @Adiavel

Have a look at page 47 of the Faults and non-Compliances document. Category C-02 non-compliance is where bitumen has leaked but is not currently doing so. But there’s a particular note to say if the leak is still occurring, then the fault category gets raised to A-01 (the highest safety alert).

By all means post a photo here, but you’ll have to decide if you think the leak is happening now by seeing if the bitumen is soft/tacky. It’s indicative of the fuse getting too hot. There’s a good description on page 13, where A01 is described.

Userlevel 1

Hi thank you for your reply.

Reason for fuse upgrade is that I need more Amps available for house as I will have a summerhouse CU installed soon, so more power demand overall.

Yes you are correct, the OVO engineers can change meter tails as Ovo owns the meter.

On UK Power Network it is clearly stated that the meter tails must be upgraded by the energy supplier BEFORE they can upgrade the fuse.

However because OVO it seems to be useless, I have contacted UK Power Network again and asked for a revised upgrade to 80 Amps only. This will be possible on the current meter tails size of 16mm hopefully. It is still a step forward for me.

Yes if the UK Power Network will decide that the whole fuse box needs to be changed because of visible damage or overheating, then probably they will break the seal on the top part of the fuse box where meters tails are fitted and be able to put new meter tails too at the same time with replacing the entire fuse box. It makes sense to me and hopefully this will be the case as I noticed some kind of black asphalt kind of leakeage along the fuse box, God knows from when, as the house electrics have been done in 1976 and I bought it as it is in 2012.


Thank you for your reply.






Userlevel 7
Badge +5

Sorry to hear this @Adiavel

I have been present at three meter installations by OVO engineers when they broke the seal on the Service Fuse and changed the tails. They are permitted to do so under the MOCOPA Agreement.

I’ve also discussed the situation with my own DNO, with whom I enjoy good communications on technical issues. They said that they commonly change the tails to the meter when upgrading the Service Fuse… unless it’s obvious that the tails have recently been changed, as would be the case if a Smart Meter had been installed.

In either case, the tails themselves are simply regarded as the “side issue” to the change of meter or fuse. That makes sense, and errs on the side of safety.

This topic is primarily concerned with safety issues. If the DNO changes the Service Fuse for any of the 33 categories listed in the Faults and non-Compliances document then it also most likely that tails would be changed too.

You haven’t given a reason as to why you want the Service Fuse changed to 100A, so I don’t know if this is related to a “non-compliance”, or merely that you’d like more amps available.

I’m not in SE England, so I don’t often get to speak with UK Power Networks. Their policy may well be different. But it seems overly pedantic that they will not change the tails when they’re booked on-site to attend to their fuse.

Userlevel 1

Hi Transparent, thank you for your reply.

But I think you are very mistaken.

OVO MUST change the meter tails BEFORE the fuse is changed by UK Power Networks (DNO equivalent in my area). It is a common sense procedure. You can't let more power into the house by changing fuse when tails size might not cope with it. 

Also stating that DNO (or UK Power Networks in my case) might change the tails, it is again a HUGE untrue statement.

For DNO to change tails will need to break seals into the meter and the meter belongs to my Ovo energy supplier, so they will not do it.

Why are you providing false and misleading information?!

I was hoping on this forum I can find good answer.

My problem was related only to OVO handling very badly the meter tails upgrade appointment, blaming it on lack of engineers in my area. 

They booked me, they took my money  then a week later they cancelled my appointment.

Now they are playing the very hard to reach to try to book another appointment.

I just wanted to hear of similar experiences with other forum members.




Userlevel 7
Badge +5

Hi @Adiavel - we’ve just started this Topic to discuss these issues.

There are several parties responsible for different parts of your electricity supply. Customers find it tricky to work out who needs to do what and in what order.

In your case OVO are correct. The Service Fuse upgrade comes first. As you say, it’s the responsibility of your Distribution System Operator, UK Power Networks.

It’s possible that the DNO will also change/upgrade the meter tails at the same time. That depends on their engineer’s assessment whilst he’s on site. These decisions are made primarily on safety grounds. Even if you posted a photo here, I doubt that Forum Members could adequately evaluate the construction of the tails and their condition without handling them.

Please post again if you’d like to make further comment. That’s what the Forum is for!

Userlevel 1

Hi there,

I have just been canceled  by OVo the appointment with the engineer on 6th of August to upgrade my meter tails as I am looking to upgrade the main fuse from 60 to 100Amps with UK Power Network. 

Because of that I had to cancel their appointment too.

Very upsetting all this.

Anybody had recently any similar experience of upgrading meter tails with OVO or they are just pretending to do it but never actually getting it done?

Userlevel 1

Hi @Tim_OVO ,  I didn’t get any call from you or Ovo generally as yet with any kind of solution. This leaves me with reporting this to the HSE tomorrow as previously advised.

Userlevel 7

Please keep us updated after we reach out to you and get things resolved. It would be great to hear from you about this, so there’s a conclusion to this topic. 

Userlevel 1

Thanks for this @Transparent ! If categories were collectible it seems like I’d be close to the full set.

I do have a feeling that my sparky may well have mentioned earthing with regard to the incomer but couldn’t swear to it, and that this would normally be dealt with in the head replacement. In any case, he said the B11 was the most important issue to highlight and that it would get the issue dealt with promptly. Lol.

Userlevel 7
Badge +5

That’s just what we need to see @killicrankie 

So that looks to me as if it’s a cast-metal box containing the cut-out fuses. That’s an asset failure with Category C06.

I’m not entirely sure of the earthing wires in the photo and whether your house has a PME supply (earth provided via the Neutral). But it’s possible there’s also a Category B10 fault present if the metal casing isn’t earthed!

As an aside, DNOs also think differently about what you fix to “their” back-board. You’ve actually got your PV isolator on the DB Board!

Having once had my knuckles rapped for fitting an extra 100A switch disconnector next to my meter, I now tend to keep all “my” hardware away from the board to which the DNO’s equipment is fixed.

In this case I think they’ll ignore it. There’s plenty of actual fault-codes to keep them entertained. :wink:

Userlevel 1

Here's a more complete shot of the board.


Userlevel 1

Ok, I'll see if I can get s good clear shot and upload it.

Userlevel 7
Badge +5

Well I’m imagining that your fuses are sited within an old cast-iron box with an interlocked switch. If so, then there’s still value in uploading a photo of that enclosure on the back-board.

Then in months to come, if another end-user has a similar box, they’ll have an idea of whether it needs to be reported to their DNO for possible investigation and replacement.

Userlevel 1

Hi @Transparent , yes indeed. I can only apologise for the limited and poor photo. I expect my electrician wasn't expecting to have to prove himself. I'm reluctant to pay for an extra visit.

Perhaps the Ovo engineer has better documentation of the visit and if there are photos of the installation proving their opinion we could get copies. All I have see to date from them is a screenshot of the "report" with about 6 or 7 fields and no images.

As you'd expect the fuse enclosure is now sealed and I can't get a picture of the parallel fuses, nor prove they are fuses over links. That being the case, is there any value to a wider picture of the whole board?

Userlevel 7

As always you have my contact details on file if you have any solutions to propose.


I’m arranging a call to you, @killicrankie 



So that still means the highest priority is the Category-B11 (fused neutral)…. for which I’d like to see a photo of the Service Fuse carrier in the context of the whole board if possible.

And that would be the most instructive/helpful upload to this Forum thread. I think we’d like customers to become more aware of the ownership and condition of their board using their eyes (no tools!). So pics uploaded to this Topic will help steer us in the right direction.


:point_up:  :ok_hand:  :spy:  :nerd:  this would be handy! 

Userlevel 7
Badge +5

Well I was actually expecting a photo of the entire Distribution Board @killicrankie !

But I think we’ll agree that the word “asbestos” is printed on your fuse. At this stage, that’s not a safety issue of any great priority @Tim_OVO. The asbestos isn’t fractured and is sealed within the carrier. Also the fuse is operational.

So that still means the highest priority is the Category-B11 (fused neutral)…. for which I’d like to see a photo of the Service Fuse carrier in the context of the whole board if possible.

And that would be the most instructive/helpful upload to this Forum thread. I think we’d like customers to become more aware of the ownership and condition of their board using their eyes (no tools!). So pics uploaded to this Topic will help steer us in the right direction.