I Want to replace ancient 6 way fuse box to a new Consumer Unit with RCD

Existing configuration is:-
1. Downstairs Ring Main
2. Downstairs Lights
3. Upstairs Ring Main
4. Upstairs Lights
5. Spur to Conservatory
6. Spare

Need to Put Electricity to Garage (8 metres) then on to Shed (30 Metres away) and then on to Greenhouse (5 Metres)

Garage will run couple of sockets, couple of lights, transformer for Low voltage garden lights, and a Pump for a water feature

Shed will run couple of sockets, couple of lights, transformer for Low voltage garden lights, and a Pump for a Pond and Waterfall

Greenhouse will run 1 flourescent Tube and one electric fan greenhouse heater

Will have separate Consumer unit in Garage do I need separate one in Shed and Greenhouse

I have already got a new MK split load 12 ways Consumer unit.

I am going to use SWA cable 3 core 2.5mm  

Thanks

2.5mm is far too small for this

i advise 40A rating for feeds to outbuildings to give flexbility in future (do you really wan't to dig those trenches twice)

there should be DP isolation in each building and a small CU is generally the best way to get that along with suitable breakers for sockets and lights

at 43m and 40A the tlc calculator says 10mm would be appropriate

at each outbuilding i would connect both armoured cables to the inputs of the small CU and then run the cuircuits in that building from the outputs

with this setup you have 3 main options for rcd protection
1: rcd side of CU
2: seperate rcd or rcbo at start of outdoor wiring
3: rcd CUs in outbuildings

personally i would advise the third option on the grounds of the distances involved if you trip it by mistake

Thanks for your advice so far.

I was going to run 4mm swa to the Garage CU conected to the non rcd side of the main cu on a 40a MCB then I was going to run 2.5 swa to the shed CU. the permanant power use in the garage is only at most Low voltage garden lights and a pond pump and occasional Lawnmower or strimmer use. I will not be Welding or using and large equipment. The greenhouse heater is only 10 amp and will only be used in the spring when nothing else will. The lighting is only 96watt Transformer to 12v bulbs. I already have 50m of 2.5mm SWA. I was told 2.5 SWA was good for 21amps at even 50m.

The garage Consumer unit was going to be a 4 Way - 100A SW non rcd and the shed a 2way with 32A, 30mA RCD

Greenhouse max use 10a heater over winter early spring only and Fluorescent Fitting 58w

Shed only flymo or strimmer and one Fluorescent Fitting 58w and 96w Transformer for garden lighting only at night when I wont be mowing and a 85w pond pump

Garage possibly Circular saw (drill is battery) one Fluorescent Fitting 58w and 96w Transformer for garden lighting only at night when I wont be mowing and a 40w water feature pump

i just use the cable calculator on tlc directs website

the sizing i gave was corerct for the plan i gave (ie keep full rating to the end of the cuircuit)

Quote:


then you were told some bullshit
i put that into the cable calculator and it came out with 6mm

so your plan is an 8m 40A submain (house to garage)
followed by a 35m 16A? submain (garage to shed to greenhouse)

with this setup you should wire the 40A bit in 6mm giving a volt drop of 0.9% over that bit

and wire the 16A bit in 4mm giving a volt drop of 2.3% over that bit

this gives a total volt drop of 3.2% which is under the 4% maximum by enough to alow for volt drop in final cuircuits

PLUG! I thought you had a copy of the program that cost some £6K ya mean ya using the TLC web site calculator!

4.00 mm csa xple swa it is. Just make sure ya have RCD's on EVERYTING ya likely to plug (no pun) into.

PS. No I should not say this BUT I have an SWA to garage here to garage run is 50 metres and there is a freezer in the garage and 2 x lights. 2.5 mm swa xple with RCD at source and garage unit with RCD works fine.

no offence intended to TLC obviously, but there calculator sucks, it doesnt give the correct awnsers end of, gives you some ott awnser

nope, work it out with regs book for him Ray, dont have my calcs with me atm

4mm or 6mm would suit no problems for first run, 2.5mm for others, make sure all has rcd, and house at minimum, must put it on rcd at house.

yeah volt drop is almost always the first issue you hit on such jobs so xple is fairly pointless

i did use some xple myself but that was because it was all tlc sold (and the local wholesaler i spoke to wanted nearly twice the price and non of the diy type places do 6mm)

anyone know any cheap(er than tlc) online suppliers for swa?