UK Old rewireable fuse boards, alterations and additions

[Rhino-Spark]

Hi all, I am looking for some advice regarding old rewireable (3036) fuse boards in regards to additions and alterations. I am an electrician and have a relatively good understanding of the regulations, that said I have been working for myself until recently and now work for a company that completes disability adaptions including bathrooms, stairlifts, hoists etc. Previously when I encountered old rewireable fuse boards and the clients requirements were additional circuits or alterations to special locations I would either upgrade the existing system or turn the work away. My reasoning for this is adding separate consumer units for a kitchen, bathroom, outside lighting etc is nothing more than a "work around" to the installation and increased risk of customers or future electricians interconnecting between, complicated isolation of circuits/ areas within the property, any existing faults not rectified and so on. This is a personal preference only and I understand that not all would agree with me and some may even claim I am scare mongering clients into unnecessary work and cost, but this is not the case.

I have encountered some existing rewireable fuse boards that in reality are in desperate need of updating and possibly a partial or full rewire in my opinion. I have attached 2 images that I hope will help.

• Example 1 -- TT arrangement, no main earth, no bonding on water (well, there is a 4mm cpc connected in board to a pipe upstairs under the boiler, but not what id consider suitable at all), no bonding to gas, charring/ blackening of cables, no 100ma rcd, sockets on lighting circuit with no cpc (old rubber singles) amongst other issues.

I am tasked with installing a switched fused spur for stairlift only

• Example 2 -- TT arrangement, incoming tails are different csa, enter the board at 3 separate places, no 100ma rcd, warning label from British Gas, upon arrival I noticed 3 x 2.5mm radial circuits supplied by 30A cartridges (I exchanged these to 15A and 20A), external lights that have the glass bezels open and damaged etc.

I am tasked with installing new 9.5kw electric shower, bathroom light, extractor fan

I have to arrange for the DNO to remove the main fuse at both properties including installation of new 100A main isolator. My question is, to my understanding a new CU woth spd and 30ma rcds do not require a 100ma rcd provided the incoming tails are secured to minimise them becoming loose, an 100ma time delay rcd would be needed if installed in front of the sub board (though a new CU with 30ma does not require this). If I install new main earthing to existing board it may create a "circuit" to earth if there are faults to the existing installation, any rcd installed in front of the existing installation will likely trip due to existing faults, should the existing tails (different csa) be replaced.

To what extent am I responsible for responsible to the existing installation?

Personally I wouldn't feel comfortable re connection of installations that I know have these issues, even though technically as I'm only working on the new sub boards and no alterations are made to the existing installation.

Any help or advice would be appreciated, thanks in advance

 

[Dustydazzler]

Having worked for several companies and for myself in near every situation we would avoid extending or adding anything on a really old installs.this was because we didn't want to be the last person to mess about with 40 or 50 year old wiring and risk any come backs being the ' last person to touch it '

 

[ipf]

I would stay clear of any additions to such installations. The last person working on an installation is responsible and that lot looks deadly.

 

[timhoward]

Wow! To answer the questions:

My question is, to my understanding a new CU woth spd and 30ma rcds do not require a 100ma rcd provided the incoming tails are secured to minimise them becoming loose

Yes. There's a note in the On Site Guide to this effect.

If I install new main earthing to existing board it may create a "circuit" to earth if there are faults to the existing installation, any rcd installed in front of the existing installation will likely trip due to existing faults, should the existing tails (different csa) be replaced.

There's obviously going to have be be a main earth whatever happens, so I'd instead focus on finding the scale of the problem. A global L+N to CPC bar IR test will show up leakage on the installation side and whether there's an issue or not even with no main earth connected.
If by some miracle this is over 2 Mohms then you may have some options to just replace tails and fit your own new board, making it very clear on the certificate what you are taking responsibility for.
Otherwise really it's a case of running for the hills...it's not safe to extend and unless the scope can increase to a full EICR, fault finding, and maybe even a partial or complete rewire I wouldn't want to be the last one touching that (as others have said).

(Just wondering, what makes example 1 TT if there is no main earth and no RCD?)

 

[Rhino-Spark]

Wow! To answer the questions:

Yes. There's a note in the On Site Guide to this effect.

There's obviously going to have be be a main earth whatever happens, so I'd instead focus on finding the scale of the problem. A global L+N to CPC bar IR test will show up leakage on the installation side and whether there's an issue or not even with no main earth connected.
If by some miracle this is over 2 Mohms then you may have some options to just replace tails and fit your own new board, making it very clear on the certificate what you are taking responsibility for.
Otherwise really it's a case of running for the hills...it's not safe to extend and unless the scope can increase to a full EICR, fault finding, and maybe even a partial or complete rewire I wouldn't want to be the last one touching that (as others have said).

(Just wondering, what makes example 1 TT if there is no main earth and no RCD?)

There is overhead supply from dno, I created 2 pdf docs with all the images but couldn't upload them due to the file size. I've attached a picture showing the supply and CU if that helps. ..... if you zoom in on the incoming tails there is also copper visible too.


I 100% agree with not touching it unless the issues are rectified buy I'm getting push back from both the company and the council that is supplying the grant. I almost quit the job over this the other day whilst explaining to the boss but now I'm waiting for them to come back to me. I need both the work and money but I'd rather be broke and have a clear conscious.

 

[littlespark]

In an ideal world, yes, it all gets replaced…. But that would mean spending a lot of time and money sorting underlying faults.

As far as company is concerned, adding a new CU “in parallel” so to speak is within regs… and they will have financial constraints to think about.
Supposedly all agreed beforehand.

Unfortunately, there are many electricians who will gladly just tow the company line and do what they’re told.


As soon as a Henley block is introduced to split the tails, to me, you would be responsible for everything downstream. That includes the original install, as well as the new work.


Even if you make pages and pages of notes to accompany the test certificate…. That could either get lost, altered or deleted before it gets to the customer….. depending how devious the company wants to be.

 

[Mike Johnson]

(Just wondering, what makes example 1 TT if there is no main earth and no RCD?)

I was wondering the same thing?

 

[LeeH]

Glad to see I’m not the only one hanging onto their mechanical meter.

 

[timhoward]

As soon as a Henley block is introduced to split the tails, to me, you would be responsible for everything downstream. That includes the original install, as well as the new work.

I'd have said there is a way to accept partial responsibility.
The EIC has a box to say the extent of the installation you are certifying. It would be completely fine in my view to say "Supply, tails to original consumer unit (untested), consumer unit 2 and it's final circuits"

Just as a smart meter installer doesn't assume responsibility for an installation by reconnecting meter tails, as long as good connections are made I don't consider that I take responsibility for everything by installing some new tails or reconnecting old ones if they are in acceptable condition. Maybe my view is wrong and this is a point to discuss!

 

[Dustydazzler]

Blimey , If we were responsible for every 50 year old install we ever worked on or did an EICR on then we are assuming one heck of a lot of liability.
For me the responsibility starts and stops on the circuit or circuits we worked on and that is it , not the entire electrical installation/
If I split the tails to add a single consumer unit for say a garage circuit then that is the extent of my work. The fact I worked in the house doesn't me I am guaranteeing the entire houses electrical installation for the next 5 years. Only the circuit I installed.

 

[bennie]

As soon as a Henley block is introduced to split the tails, to me, you would be responsible for everything downstream. That includes the original install, as well as the new work.

If you install a sub board and don't touch alter or add to the main board then the only part of the original installation you are liable for is making sure the main earth and bonding comply with the current regs.

 

[timhoward]

If you install a sub board and don't touch alter or add to the main board then the only part of the original installation you are liable for is making sure the main earth and bonding comply with the current regs.

I'd generally agree. In addition there are two issues that I wouldn't feel I could walk away from on this one.
1 - no main earth. I wouldn't ever leave any consumer unit without a main earth even if that meant doing some uncertificated work (i.e. not including it on the EIC)
2 - no fault protection. If I was aware that a fault to earth wouldn't clear I wouldn't feel able to ignore that. This one is harder.

If the DNO can't provide PME, it will have to be TT. Therefore by stealth I'm slowly getting my paws on more and more of this. If lucky, leakage will be tolerable and an up front RCD could be added, split the tails and do the necessary.
But if leakage is down to RCD tripping levels then the only way to add compliant fault protection is to fix the original install and at that point I would dig my heels in and say "it needs fault protection and I'm not working on this unless this can be rectified".

I'd add that I'm generally pragmatic - in the past I've added smoke alarms to a similarly bad install (wasn't TT) that had no CPC on lighting circuit, as it felt crazy to be saying "this wiring is dangerous and could start a fire" at the same time as saying "I can't fit smoke alarms because the wiring is dangerous".
But for me, no main earth, and no fault protection are both too significant to simply ignore and claim "that bit isn't my responsibility"

 

[pc1966]

Seeing no main earth really is a serious risk to those using the installation and to you further down the line should the worst happen and we see another case like the poor boy killed due to well-dodgy pub wiring a couple of years back.

Sadly it is more common then you might think as often very old installations used the water pipe bond as an earth which was low enough to achieve ADS (against rewireable fuses of the day). Of course that has not been allowed for many decades due to the obvious issue of old lead pipe, etc, being replaced with plastic and/or joints that have no need to be conductive, but still you see systems than have been untouched, or maybe updated 'a bit' and nobody has addressed it.

As @timhoward says, it opens a major can of worms (DNO earth available, or TT otherwise plus checks and certification for it) and at that point it really should be a proper EICR to determin how much other trouble is lurking and ultimately costing for corrective action.

Probably the best action is to tell the client in writing (and keep a copy obviously!) about the serious risk it presents and what is likely involved in fixing it. If they turn your offer down then at least you are not the patsy for anything that happens, but if it is an installation placing others at risk (rented property, public access like pub, etc) and you suspect they will do sod-all then it might be worth informing the relevant authorities of the problem you found and they hopefully* can follow up with an inspection to see if they got someone else in to fix it, etc.

[*] yes I know that is optimistic...

 

[Mike Johnson]

The recurring theme of DNO earthing seems to be posted often on this Forum, the old use of metal water pipes not now available due to plastic being used (used to be acceptable), and not all properties have gas, it would seem that the DMO don't really care/interested in providing a usable earth to domestic properties, is it time for legislation for new builds to all have a TT supply, discuss?

 

[DPG]

The recurring theme of DNO earthing seems to be posted often on this Forum, the old use of metal water pipes not now available due to plastic being used (used to be acceptable), and not all properties have gas, it would seem that the DMO don't really care/interested in providing a usable earth to domestic properties, is it time for legislation for new builds to all have a TT supply, discuss?

But it's not normally new builds that have the waterpipe earth issue, it's older ones. Doesn't seem a good idea compromising all new builds by not providing good solid TN earths.

 

[Mike Johnson]

The original point of my post is that the DNO don't seem to be supplying an adequate/maintainable earth to any dwelling, old or new, it just seems a recurring theme on this Forum.

 

[DPG]

The original point of my post is that the DNO don't seem to be supplying an adequate/maintainable earth to any dwelling, old or new, it just seems a recurring theme on this Forum.

What percentage of UK new build houses in recent years have had no earth supplied?

 

[timhoward]

is it time for legislation for new builds to all have a TT supply, discuss?

In general, new builds are PME from the get-go, so it's not totally fair to say the DNO don't care about providing an earth. The argument is usually over old service heads where for them to take responsibility could be economically costly.

AM2 does add a recommendation to add a backup earth rod to TN systems. New builds actually would be ideal candidates for following this. At the moment NAPIT are advising members not to try and add rods to existing TN properties for fear of hitting services.

I don't think I'll ever regard TT as anything other than 2nd choice. I don't particularly trust RCDs that have sat their for years, wouldn't like to be relying on them for fault protection in ideal circumstances.

 

[Dustydazzler]

I still come across old council houses which sole means of earthing is an old water pipe bond or old gas pipe bond.

 

[Mike Johnson]

@timhoward Is the NAPIT advice only due to the fact you may hit service's or is there a more sinister/sound reason?