CU features

[deuceofsome]

Gents
In tandem with revising most of my lighting circuits I plan to have the existing consumer units replaced. There are currently 2 boxes with cartridge-type carriers (second one originally had 6 fuses for storage heaters).
Given the expense of all the other work I do not intend to skimp on the CU, but what features/specification (mandatory or nice-to-have) should I be looking for (board split, RCD protection, case type, recommended manufacturers, etc.) ?
In addition to the existing assignments on the main board I plan to add the storage heater circuits (already converted to regular power sockets) in 2 groups, bring in the new power and lighting circuits, plus add dedicated breakers for computer and alarm feeds.
This will provide a lot of flexibility but if all are kept separate this will be 12 or 13 assignments – is that excessive in a 3-bed property ?
Most of the walls and floors/ceilings are concrete so I want to make this project a one-off, to be good for 30 years.
My role is limited to the new wiring and CU supply. The live stuff is for a.n.other.
Your advice, please.

[Steve]

Quote:

most of my lighting circuits

how many do you have? You lighting a football stadium?

Quote:

but what features/specification (mandatory or nice-to-have) should I be looking for (board split, RCD protection, case type, recommended manufacturers, etc.)

Nowadays it is normal for houses to have split load consumer units with one side protected by a 30mA RCD unit, usually downstairs sockets, shower, any outdoor electrickery, high-risk circuits. (regs state sockets likely to feed power tools and outdoor electrics need RCD protection)

Quote:

I plan to add the storage heater circuits (already converted to regular power sockets)

as single radial feeds? If this is the case, buy a cheap second consumer unit and fill it with 16 or 20A MCBs, run off a 40 or 45A MCB in the RCD side of the main CU. Neater and saves space in the main CU.

normal in a house that size is probably 6-8 circuits, getting those seperate radial socket circuits into a seperate box (as they were with the old storage heaters) will achieve this.

computer and alarm feeds should go on non-RCD side afaik

[andy]

crafty1289 wrote:

computer and alarm feeds should go on non-RCD side afaik

yes, unless you plan to use the computer outside

[deuceofsome]

Thanks for the comments.
As you note the storage heater sockets are on separate radials – of the 6 originals, 2 have been/will be deleted by building works and 1 is now dedicated to IT kit. I had planned for the other 3 to be pulled together into a single RCD, cable length permitting. Can you see any problem with this ? (I too appreciate neat work).
A bit more scene setting: the property was originally 2 maisonettes. All power cables (ring & radial) are buried somewhere in the floor. Original lighting circuit is MICC are buried in the walls and ceiling. Most of the structure is reinforced concrete and I’ve never had much luck using cable finders, even when I know where the cable must run. The MICC circuits emerge out of the concrete behind the CU.
I’ve no idea why the place was built so, I’m just trying to deal with the consequences and am now no fan of domestic MICC.
I am fixing up false ceilings to enable recessed LV lighting fittings to be installed and am taking the opportunity to run new cables from each area (L & R, up & down) back to the CU – hence 4 separate runs.
The outside (roof terrace) electrics are fed from a ring main spur (with fused RCD unit).

As it stands, assuming I amalgamate the radials, I will end up with 10 assignments, with those marked * on the RCD side.
*Cooker
*Ring Main (org.)
*Radials
*IT
*Ring Main (short new)
Lights (4)
Alarm

Hence leaning towards a 6+6 insulated unit.

[Gary0]

crafty1289 wrote:

computer and alarm feeds should go on non-RCD side afaik

That sounds a good idea. Hmmm PCs and alarms from this thread, fridge/freezers from another. I'm beginning to get the impression that every room on the house needs to be on 2 separate rings, RCD and non-RCD !

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[Steve]

Gary0 wrote:

crafty1289 wrote: computer and alarm feeds should go on non-RCD side afaik That sounds a good idea. Hmmm PCs and alarms from this thread, fridge/freezers from another. I'm beginning to get the impression that every room on the house needs to be on 2 separate rings, RCD and non-RCD !

no but seperate radials for things like fridges and freezers - and other things for which RCD tripping would be a problem - are a good idea.

[ban-all-sheds]

The items on the list below may not all apply to you, but they are worth looking at to get you thinking:

1. Upstairs sockets
   
2. Downstairs sockets
   
3. Kitchen sockets
   
4. Circuit for appliances
   
5. Cooker circuit
   
6. Non-RCD circuit for F/F
   
7. Non-RCD circuit for CH boiler
   
8. Dedicated circuit for hifi
   
9. Dedicated circuit for IT equipment
   
10. Upstairs lights
    
11. Downstairs lights
    
12. Immersion heater
    
13. Shower
    
14. Alarm
    
15. Supply for outside lights
    
16. Supply for garden electrics
    
17. Supply for shed/garage
    

Plus any peculiarities brought about by your house layout & construction - e.g. in mine because of solid floors and where the rest of the sockets are, I have a radial just for one socket in the hall, the doorbell and the porch lights.

Plus a few spares on RCD & non-RCD sides for expansion beyond that for future unforeseen needs.

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