Isolator between meter and CU

[vargen]

Guys - what kind of isolator switch will I need to fit between the meter and CU so I can work on the CU in safety without having to pull the main fuse?

Presumably, an electrician is authorised to pull the main supply fuse for this purpose, wire in new meter tails and then reseal it? Or could I do it myself? - not that I ever would of course!

 

[ColJack]

no, an electrician is NOT authorised to pull the main fuse, it should only be touched by the suppliers people..

most will come and fit an isolator for you if you contact them and say you are going to have some work done in a few weeks / months..

 

[RF Lighting]

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[Steve]

Only DNO electricians are authorised to pull the fuse - these people have the appropriate PPE to do the, sometimes risky, job, and they only work for the DNO. The DNO is the regional company that looks after your power supply and the power infrastructure in their region (not the people you pay for the electric).

However, it is commonplace for electricians to pull the fuse when they need to.

If you wish to install an isolator, you hang it on the wall, fit the incoming tails long enough to reach the main fuse, then call the DNO to come and isolate - while they are there, wire in your tails to the meter, and jobs a good un - they can restore power on the same visit. Subject to getting a decent guy. He may just leave you without power for a few hours while he does anotehr job. There may be a charge for this visit, or they may do it free.

I presume you know your earthing arrangements and that they are up to scratch - while the DNO is out they could also provide a better earth terminal for you if applicable. But you'll know about your earth if your working on the CU.

 

[ColJack]

i need a better earth.. mines a bit rubbish at the moment...


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[vargen]

Thanks for replies everyone. Unexpectedly quick! I'd gone to catch up on the news over a coffee. Here's the full monty:-

My former council flat was rewired about 8-10 years ago (i think) with a brand new x3 earth supply cable by EDF. EDF will be coming to move the meter board (main fuse box & meter) for me in a couple of weeks - already arranged and in the pipeline - £102. The meter board's moving onto a new partition (to replace existing between kitchen & bathroom) and go inside a kitchen cupboard about 0.5 metre from existing site (and up a bit). The CU will need to follow the meter board shortly afterwards (somehow!). Most cables are long enough to cope.

I asked Eon, my supplier, to fit an isolator but they won't do it, saying I have to get an electrician to do it but that they could cooperate by arranging for EDF to switch power off for a while whilst the work is done.

I can't find an electrician who isn't already booked for the next month. I thought I'd found one but after waiting 2 weeks for an estimate, when I chased him he said he was too busy and couldn't help after all. Thanks mate, I'll remember you! So I thought s*d it, I may as well do it myself - hence info re isolator requested. Nothing is going to be changed, circuits wise, really, apart from the addition of an electric shower and replacing storage heaters with u/f electric heating. Ratings are unaffected. I'm removing dot & dab plaster board, chasing out brickwork and re-using (mostly) existing cables in top hat capping and steel conduit. There are, however, a few changes supply-wise.

I did have off-peak and standard rate feeding separately via 2 meters to the CU. Off-peak for storage heaters & h/w cylinder - std for everything else. I now have Economy 7 but it's only connected to the std side of the CU at the mo as I want everything available 24/7. The CU needs to be reorganised to be fed accordingly and, of course, moving to its new location next to the meter board.

Whilst EDF is moving the meter board the isolator could be fitted. Can I get away with DIY with EDF present?

PS I've already broken the tag on the main fuse to pull it while I removed some 'superfluous' cable to remove some partitioning. Am I in stuck with anyone?

 

[sijaysee]

half the places i work in dont have a tag on the main fuse so i wouldnt worry. and i dont personally do any major work eg new CU's without pulling the main fuse

 

[sparkyspike]

Just wondering why you need a separate isolator. Will the CU isolator not suffice? It's only live up to the top of the isolator until it's turned on.

 

[RF Lighting]

I still wouldn't advise it.

Yes I do it, and appreciate the risks.

I have pulled a new style fuse which was missing the screw which holds the shell together. The shell came away leaving an uncovered live fuse still sat in the cutout within a few mm of my fingertips.

I have also come across a broken ceramic main fuse which became two halves as I tried to remove it. That is an interesting call to the DNO.

 

[securespark]

The shell came away leaving an uncovered live fuse still sat in the cutout within a few mm of my fingertips.

Please tell me you were wearing gloves????

 

[ColJack]

EON aren't the ones you need to ask for an isolator.. they are just paper pushers..
it's your DNO that you contact and ask.. that's EDF in your case is it?

All of this work is major and definitely comes under Part P of the building regs... since you don't mention it.....

I'd also highly recomed getting your Eco7 meter taken out and replaced with a single tarrif one ( or can they just dissable the off peak somehow? never had to deal with one.. )
you'll be paying a premium on your peak electric on a dual tarrif bill..

 

[vargen]

Thanks again for contributions.

I've got a big red fuse in a grey box with "Henley" on it. EDF said the main fuse is at the bottom of the service shaft the supply cable comes up to enter my flat.

I'd have to be crazy not to pull the fuse to work on the CU. The CU input (via grey fuse box to meter and small black box) is right next to the outputs, so it's a bit dodgy to have fingers in the forest of spaghetti in there even when switched off at CU. The inputs are threaded up through the back of the CU and back down the front onto the input connectors. The ouputs are right next to those connections. I could try to hold my breath, I suppose............ An isolator would help me keep breathing whilst I'm working and make sure I don't stop altogether!

Re-reading an earlier reply, it sounds like the isolator would go between the main fuse and meter rather than between meter and CU as I had assumed would be easier. Or is it optional? Which route should I go for and can someone tell me precisely what to order in the way of the isolator, please?

 

[vargen]

Cross-posted there Col Jack. Yep, EDF is the DNO. Their guy is very helpful. I'll call him tomorrow and try to get it organised with the meter board move.

My reading of the 17th Edn gives me the impression the work's excluded from Building Regs and Part P except for the CU, the shower and the underfloor heating (and maybe one or two other little bits. But essentially little or nothing is changing circuits-wise. Everything is mostly "mechanical protection to existing..." as far as I can see..... and I'm re-using red and black twin core. Would anybody find out if I don't mention it?

 

[GaryMo]

Re-reading an earlier reply, it sounds like the isolator would go between the main fuse and meter rather than between meter and CU as I had assumed would be easier.

The isolator goes on the consumers side (your side), between the meter and consumer unit.

You just need a 2 module enclosure with din rail and a 100A switch.
Make sure you have room for four 25mm2 DI tails.

 

[TicklyT]

If you have everything prepared, and boil your kettle ready for when the DNO arrive to pull the fuse, you will be ready for them to replace and reseal it by the time they've finished drinking their tea.

If you think you will need a bit longer to do the job, invest in a packet of chocolate biscuits.