Questions about replacing CU

nerd8192 · 11 Jun 2011

My folks live in a house that was re-wired in the 80's with PVC cables but has an old Wylex rewirable fuse CU. Recently they have had issues with rat infestation leading to replacement of nearly all the upstairs lighting circuit as rats had chewed through the cables! The electrician that did the work commented to my folks: "amazing you didn't have a fire". I am clearly a bit concerned by this and consider myself to be competent on electrics but not formally trained. In the past I have replaced two similar CU's with a friend, and we just removed the DNO fuse to do the work.

I wonder if you folks can confirm somethings for me:

- Is it actually illegal to remove the DNO fuse and are many people fined/prosecuted for this?

- Any idea how much a DNO would charge to come and fit an Isolator, the DNO in question is Scottish and Southern Energy (Southampton area).

- When considering a new CU to 17th ed regs, how would you normally split the circuits up on the 2 loads: is it best to have all lights on one and then ring main, cooker, etc on the other?

- With economy 7 heaters (house has 7), Is it best to have a CU with a 100A incomer then 80A RCD followed by MCB's for each heater?

- If I was to do the work, but then get a spark to check it and sign off on it, would this be OK for Part P?

Thanks for your help.

Seth

riveralt · 11 Jun 2011

nerd8192 said:
My folks live in a house that was re-wired in the 80's with PVC cables but has an old Wylex rewirable fuse CU. Recently they have had issues with rat infestation leading to replacement of nearly all the upstairs lighting circuit as rats had chewed through the cables! The electrician that did the work commented to my folks: "amazing you didn't have a fire". I am clearly a bit concerned by this and consider myself to be competent on electrics but not formally trained. In the past I have replaced two similar CU's with a friend, and we just removed the DNO fuse to do the work.

I wonder if you folks can confirm somethings for me:

- Is it actually illegal to remove the DNO fuse and are many people fined/prosecuted for this?

Yes it is and no I am not aware of any - however the contract for the supply is with your folks so they will be in breach of the contract not you.

-

Any idea how much a DNO would charge to come and fit an Isolator, the DNO in question is Scottish and Southern Energy (Southampton area).

Normally it is free but the isolator is supplied by the people your folks pay the bill to not the DNO.

When considering a new CU to 17th ed regs, how would you normally split the circuits up on the 2 loads: is it best to have all lights on one and then ring main, cooker, etc on the other?

You would be best reading the regs first to understand why.

With economy 7 heaters (house has 7), Is it best to have a CU with a 100A incomer then 80A RCD followed by MCB's for each heater?

Not 100% sure but it might be best to put those circuits on a separate CU.

If I was to do the work, but then get a spark to check it and sign off on it, would this be OK for Part P?

No.

And no self respecting spark would fit a new consumer unit without first of all doing a PIR on the installation.

bernardgreen · 11 Jun 2011

nerd8192 said:
Is it actually illegal to remove the DNO fuse and are many people fined/prosecuted for this?

Not always illegal as in criminal but it does break your contract with the supplier and they could sue you for damages and /or dis-connect you.

But that is the trivial part. If the fuse holder falls apart you might end up with a very badly burnt hand and face, maybe blinded. The incoming cable might burn long enough to set the house on fire. Oh and you will put out the power to at least one third of the street when the fuse in the substation ( 200 amps or more ) finally pops. This blackout will not be short as the damage you caused to the network has to be repaired.

And the supplier has every right to pass on your details so people can sue you for loss of thier power.

Of course this might not bother you at all as you may already be dead from your injuries.

Now the next question. ?

holmslaw · 11 Jun 2011

nerd8192 · 11 Jun 2011

nerd8192 said:
Any idea how much a DNO would charge to come and fit an Isolator, the DNO in question is Scottish and Southern Energy (Southampton area).

holmslaw said:
About £100, but why do you want one? its just something else to go wrong.

I have read quite a lot of posts on here about the ins and outs of Isolators and DNO fuses - but the only thing I can really see that you can agree on is that you don't want to do the work live - which is of course very sensible. I can see that in some cases DNO fuses/connections could be very old and therefore you might have problems if you tried to remove the fuse - but in the vast majority of cases I don't see what difference it makes - the work needs to be done and you need the power off to that part to do it.

nerd8192 said:
When considering a new CU to 17th ed regs, how would you normally split the circuits up on the 2 loads: is it best to have all lights on one and then ring main, cooker, etc on the other?

holmslaw said:
Its best to have individual rcbo's for each circuit. If you opt for two main rcd's, then you would split the circuits across them both.

So RCBO's are the best way to go these days?

nerd8192 said:
With economy 7 heaters (house has 7), Is it best to have a CU with a 100A incomer then 80A RCD followed by MCB's for each heater?

holmslaw said:
See above.

I understand and to the person who said about a different CU for this - they are currently in different fuse boxes - which I would intend to keep as the Economy 7 has different tails.

nerd8192 said:
If I was to do the work, but then get a spark to check it and sign off on it, would this be OK for Part P?

holmslaw said:
No it won't be ok, your spark will advise what you can or cannot do.

In 'your' (I say this because its part of the site rather than anyone person having written it), guide to Part P, you say that DIY work isn't outlawed, but needs to be signed off by local council, have any DIY'ers actually got this done?

Thanks.

riveralt · 11 Jun 2011

nerd8192 said:
I have read quite a lot of posts on here about the ins and outs of Isolators and DNO fuses - but the only thing I can really see that you can agree on is that you don't want to do the work live - which is of course very sensible. I can see that in some cases DNO fuses/connections could be very old and therefore you might have problems if you tried to remove the fuse - but in the vast majority of cases I don't see what difference it makes - the work needs to be done and you need the power off to that part to do it.

Sounds like you see what you want to see and hear what you want hear. The illegal element comes from the Criminal Damage Act and the Health & Safety Act.

nerd8192 said:
In 'your' (I say this because its part of the site rather than anyone person having written it), guide to Part P, you say that DIY work isn't outlawed, but needs to be signed off by local council, have any DIY'ers actually got this done?
Thanks.

DIY work is not outlawed provided you go through your Local Authority Building control - they will want to see evidence of your competence.

But for a start, and before you consider fitting the CU yourself, you should conduct a Periodic Inspection on the installation - this will give you the opportunity to identify any issues with the current wiring and therefore minimise any issues after the CU has been fitted.
For this you should purchase a copy of the IET guidance note three and hire a multimeter. You should also have access to BS 7671 and probably the OSG.

nerd8192 · 11 Jun 2011

riveralt said:
But for a start, and before you consider fitting the CU yourself, you should conduct a Periodic Inspection on the installation - this will give you the opportunity to identify any issues with the current wiring and therefore minimise any issues after the CU has been fitted.
For this you should purchase a copy of the IET guidance note three and hire a multimeter. You should also have access to BS 7671 and probably the OSG.

OK, I will go out now and buy a copy of Guidance Note 3 and read it.

Taylortwocities · 11 Jun 2011

bernardgreen said:
nerd8192 said:

Is it actually illegal to remove the DNO fuse and are many people fined/prosecuted for this?

Click to expand...

Not always illegal as in criminal but it does break your contract with the supplier and they could sue you for damages and /or dis-connect you.

But that is the trivial part. If the fuse holder falls apart you might end up with a very badly burnt hand and face, maybe blinded. The incoming cable might burn long enough to set the house on fire. Oh and you will put out the power to at least one third of the street when the fuse in the substation ( 200 amps or more ) finally pops. This blackout will not be short as the damage you caused to the network has to be repaired.

And the supplier has every right to pass on your details so people can sue you for loss of thier power.

Of course this might not bother you at all as you may already be dead from your injuries.

Now the next question. ?

Please see the following picture. This shows the PPE employed by a trained engineer to "just" remove a domestic supply fuse.

Untitled

Taylortwocities
11 Jun 2011
8

ban-all-sheds · 11 Jun 2011

riveralt said:
The illegal element comes from the Criminal Damage Act and the Health & Safety Act.

I doubt that a prosecution for criminal damage of a fuse seal would be regarded as in the public interest, and I don't think that H&S legislation applies.

The Electricity Act also makes it illegal

.... hire a multimeter.

Not adequate - need a set of installation testers (or a multifunction tester).

Different kettle of fish.

nerd - you can also read about testing here: http://www.tlc-direct.co.uk/Book/8.1.1.htm

Plus you will need to be able to do proper circuit sizing calculations, test what's installed before you start, understand installation methods etc. You can't assume that what's already installed is OK, or just copy it if you're replacing, because because it's going to become your responsibility and what's there might be wrong.

jozeffo · 11 Jun 2011

If you want to do the work yourself, you have to submit an application to building control who should oversee the work and arrange for a test and inspection when it is complete.

You would be wise to have a copy of the IEE onsite guide 17th Edition to hand as this would ensure that you comply with current regs. An Isolator can be reassuring and I have had a couple fitted in the past when chatting to the Engineers when they are changing old meters for new ones. Very helpful of them.

Riveralt has offered the most practical advice thus far.

Stoday · 12 Jun 2011

ban-all-sheds said:
The Electricity Act also makes it illegal

Really? I didn't know that. Electricity Act 1989? Or an amendment of it? Or anoher electricity-related Act?

Would you kindly be a bit more definite clause no. etc. please?

If it is illegal, there are many electricians who must be criminals since pulling the cutout fuse without permission to do so is common. DNOs will not give permission because they lay themselves open to unknown risks if they do, so why should they? Many DNOs publish a leaflet saying that they don't allow anyone except their staff to pull the fuse.

If, as I think, it's not illegal, and, as BAS says, calling the breaking of the seal criminal damage is de minimis, it's difficult to see what DNOs should do about it. Seek an injunction? That'll cost £150 just for the court fee. Sue you? You can only sue for damages. A seal.

securespark · 12 Jun 2011

I only break a seal in an emergency. Imminent fire risk etc...

Otherwise I get the customer fitted with an isolation switch before I do the work.

ban-all-sheds · 12 Jun 2011

Stoday said:
Really? I didn't know that. Electricity Act 1989? Or an amendment of it? Or anoher electricity-related Act?

Would you kindly be a bit more definite clause no. etc. please?

//www.diynot.com/forums/viewtopic.php?t=257575&start=0

If it is illegal, there are many electricians who must be criminals since pulling the cutout fuse without permission to do so is common.

Even more common I imagine is breaking the speed limit going to or from the job.

OK - not a criminal offence, but still an offence. You can't use the fact that all the electricians in the country haven't been banned from driving to indicate that speeding is not an offence.

holmslaw · 12 Jun 2011

ebee · 12 Jun 2011

Ban,
I thought speeding was a criminal offence?

In fact I thought that all driving offences were criminal offences with the fairly recent exception of the last few years that most parking offences have been de-criminalised.

Have I been wrong all this time?

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Sorry, not trying to detract from the valid point you made though about criminal acts/wrong doing

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Questions about replacing CU

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