4 consumer units in one house Help

[James Warren]

I have just installed 4 new split consumer units in an old edwarian house. The boards are not in the same place and are being fed by the meter in a barn about 60 meters away. Very unconventional setup. The tails (25mm) come into the kitchen and I have put the feeds for 3 of the boards through a 300ma rcd to protect the cable but this is making it impossible to test with my KT65 as it sometimes trips the 30ma rcd on the CU and sometimes the 300ma on the incomming board. Would I be better ommiting the 300ma rcd and just putting 100A incommers on ? The wiring is a mixture of 16 mm twin with a seperate earth (that seems ok) And the feed for the upstairs consumer unit is 16mm twin and earth (but has very little load. ) Hence the reason for the 300ma rcd in the main board. Obviously if that trips most of the house is in darkness so not good. I have told them that in my opinion it's much safer than the old fuses it had but obviously falls short of modern 17th regs. The small earth is an issue going to the upstairs. When I try a loop test with both rcds inline it just says no. (But I know it's intact) Other times it just trips the 300ma rcd (which I'm beginning to suspect is faulty). If I do the same test on a downstairs circuit it just gives me a correct reading (0.60 ohms which is ok considering the distances And 0.86 at the furthest socket) Replacing the cables is out of the question at the moment and I'm just trying to make it safe.
Anybody got a better sugestion ? I'm veering toward taking out the 300ma rcd ?
My first post so be gentle.

 

[Guitarist]

I admire you for tackling this. It is impossible for us to really comment on what you are up against, but from what you have described so far I think I would have offered 2 options regarding this setup.

1) New install to my design
2) Walk away.

Best of luck

 

[Engineer54]

One of the cables is a 2 core with a brass sheath used as a neutral.

Brass sheath?? Never seen or heard of such a cable system!!! Going purely on what you have written it sounds more like MICC, but illegally having the sheath used as the neutral conductor!! Almost like concentric wiring, but with a twist!! lol!! I would look into this cable configuration a lot deeper than you have, this sounds like a potential major cock-up waiting quietly to Bite!!!

 

[londonlec]

Ive only skimmed over this but it looks like a bad design by someone.

 

[Dan the spark]

Are these 25mm tails your describing coming into the house double insulated tails or are they an swa?

 

[James Warren]

The tails (4 in total ) are in swa. This part look like it was done by the distributor but why they put the meters in an out house god only knows. Like I said it looks like it has been there at least 30-40 years.
It has to be the most bizare set up around.

 

[RISElectrical]

The brass sheath you spoke about does sound like pyro (micc) which if it is an the sheath is used as a neutral then that is a problem which needs addressing. Can you post a picture up of this cable? I assume this then has a separate cpc wired with it? Good luck. Sounds as though you'll need it. Personally I'd have insisted a full EICR be carried out prior to any work and then quoted accordingly. As said in a previous post, certain items would need upgrading to my design or I'd also walk away.