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

 

[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?

 

[Mike Johnson]

In Rural France I would say that nearly all the installations are TT with an up front S type RCD, the supply is such that if you try to draw more than your allowed A the RCD will trip out, so it gets tested every-time you put on all your white goods at once, seems washing day is always associated with putting on the dishwasher as well.

 

[Dustydazzler]

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

Oh and I should add all of these old houses are old 3036 re-wirable boards no Rcds what so ever.
The most recent I got around 35-36 ohms on Zdb

 

[ipf]

Oh and I should add all of these old houses are old 3036 re-wirable boards no Rcds what so ever.
The most recent I got around 35-36 ohms on Zdb

Been acting as a rod for years, then?

 

[timhoward]

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

Hitting services is the main thing spoken about.
I also know it was a controversial addition and some on the committee were opposed to it. I didn't get to hear exactly why.

 

[ipf]

Hitting services is the main thing spoken about.
I also know it was a controversial addition and some on the committee were opposed to it. I didn't get to hear exactly why.

An insurance issue, maybe?

 

[pc1966]

Hitting services is the main thing spoken about.
I also know it was a controversial addition and some on the committee were opposed to it. I didn't get to hear exactly why.

There is always someone opposed to any change, what would be nice (but unlikely to happen) would be the BSI committees providing a written rational for the decisions for or against any given proposal.

I can see a real risk from proposing adding rods to existing properties due to service pipes and cables, etc, but where they really dropped the ball was not mandating a decent earth to be incorporated in any new builds. I think for years the USA has required bonded rebar in concrete foundations and aspects like that would not have been difficult to do at the build stage, could have provided fairly good Ra values, and over time made a big difference to the safety of PME systems.

 

[Dustydazzler]

Been acting as a rod for years, then?

absolutely fine until they change the supply pipes to plastic : )

 

[Mike Johnson]

Long time since I had any dealings with the Institute of Structural Engineers but bonding of reinforcement was being advocated as far back as the 1970's.

 

[ipf]

absolutely fine until they change the supply pipes to plastic : )

Absolutely, yes.
It was just a bit of a joke, looking at your quoted Z values.

edit. Oh, joking too!.....I see your attempted smile didn't work : ).......