Help needed to feel right instalation is going to be done

[russells]

Hi all,

Have posted this on another forum but seem to just be getting slated, not given advice.

I am not going through a design Consultancy, and seem to be getting a conflict of what is most suitabl (it seems there are many ways) trying to get my topic thrashed out so that when i have the work undertaken I will be able to be confident it is fit for purpose.
I might add that i work as construction manager, and even as I type a colleague is thrashing out with a contractor issues over a faulty or wrongly designed installation.

Ok so this is what ive got

25mm tails through 100amp fuse to meter to Main CU.

Main CU = RCD split consumer unit in house with plenty of spare ways.

Want to add sub Main CU 12 Meters away in house, cables to be within joists more than 50mm from any surface (above/Below).

New sub main to be a 10 way split board, this will eventually supply a kitchen, a bedroom, 2 different heatmat underfloor heating, A garage by way of 10mm SWA, and stables By way of 16mmSWA.

Garage will have a small board for lights and possibly 2-3 sockets on a ring.

Stables will have another submain.
Submain will have 5 ways

1 for 10mm SWA cable to static caravan (caravan as submain with RCB etc so basically powering up)

1 for Lights circuit to stables

1 for 2 sockets max on ring for stables

1 for 10mm overhead cable (Not SWA, but twin and earth in grey sheaving) this is temporary little workshop, in workshop is a standard Garage kit with 40amp x 30ma rcd with a 6a for lights and 32 amp for sockets..proposing 2 sets sockets on a ring also.

OK so that seems like a lot going on, but the reality it seems simple.

Some of the things i am querying.

1. The CU submain in the house will be on a 40a MCB not rcd protected the cable will be 16mm twin and earth.

2. The 16mm SWA to stables will be on 63a MCB not RCD protected.

3. The 10mm SWA to the garage will be on 40a Mcb Not RCD protected

4. The kitchen and bedroom and heatmat at this submain will be RCD protected

5. The fridge/Freezer, and a dedicated strategic radial of lights will not be RCD protected .


Can somebody let me know if this seems ok, I am looking for constructive critisism, or possibly a more suitable approach.

 

[telectrix]

a schematic would help. are you saying that the plan is to daisy chain all these sub-mains?

 

[IQ Electrical]

Hi Russels, you say your colleague is already "thrashing out issues with a contractor over a faulty or wrongly designed installation" does this not encourage you to get the design verified and hence indemnified by a legitimate contractor (who will possibly charge a small design fee)?

There are many compliant designs for what you've described but there are also many many variables to consider and I'd be rather wary of 'crystal ball forum design'.

 

[russells]

Yes and No
Diagram below gives a rough overvie to layout of buildings etc

 

[russells]

Some of the text missing on drawing having another go

 

[ackbarthestar]

IMO, 30mA RCDs protect final circuits.

If you want RCD protection due to high impedance fault fault paths then use a 'S' type 100mA for the sub main circuits. Personally, I wouldn't bother if you are supplied via a TN system, just use SWA bonded at either the supply or both supply and load.

A diagram of the layout might determine how the sub-main cables are run. - diagram now seen, thank you

My main concern would be this 'temporary' installation supplied via an overhead cable, I can just imagine going back to this type of installation in a couple of years to fault find an intermittent fault knocking out the shed electrics.

Now that I've seen the diagram, other things to consider would be the volt drop due to length of cable runs, this appears to be taken care of by the size of cable conductors. I personally would use 4 or 6mm2 since the loading to the shed, garage, caravan is unlikely to more than 10A each and unlikely to be on at the same time unless you've got mates coming over from Ireland for a racing weekend

 

[russells]

Thanks for the help so far
(some of this infrastructure i have already put in place)
Just a few notes
The temporary overhead is to be there for approx six months, Its by way of 10mm twin and earth on catinery wire, distance 10M new cable (too good not to use somewere).

I suppose the one big thing I am sort of questioning is the 40a MBC from the Main CU to The sub CU, been told this does not need RCD protection as cable is in joists and 50mm from floor or ceiling and thus no risk to being damaged. Likewise the 16mm SWA on a 63a mcb heading out to the stables No RCD required.
10mm SWA on a 40a Mcb Going from stables to caravan no RCD required.


The 10mm SWA to the caravan i have put in place, distance 22M
the 16mm SWA I have put in place distance 35M

 

[telectrix]

looks odd to be feeding the first 1 in 10mm then increasing to 16mm. i would up the first SWA to 16mm. i assume the 16mm in the diagram has been selected to overcome volt drop, not CCC.

 

[russells]

Thanks for help
Telectrix
Confused by what you say as 10mm 1st one

Basically its Main CU to sub CU in 16mm t& E 12 Metres

Sub CU to stable cu in 16mm SWA 35 Metres

Stable cu to caravan in 10mm SWA 22 Meters

Stable cu to tin shed 10mm T&E 10 Meters

Sub CU in house to garage 10MM SWA 15 Meters

Hope this makes sence