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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> consumer unit/garage/shed/greenhouse https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1091321184 Message started by Captslogg on Aug 1^st, 2004, 1:46am

Title: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 1:46am

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

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 1^st, 2004, 1:50am

Hey Richard, sounds like you have it all pretty much worked out, however 2.5mm cable for the outside buildings is unlikely to be enough for what you want to run and also the distance the cable will run.

il work out a suitable size cable for you for the Garage, Shed & Greenhouse

Title: Re: consumer unit/garage/shed/greenhouse
Post by plugwash on Aug 1^st, 2004, 1:57am

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

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 1^st, 2004, 2:02am

I will try and set down some soloutions tommorow if i get time, but PG is right in saying flexability but depends on what scale

I would suggest 32A or 40A at House to run the first cable

Garage should have 16A for sockets, 16A for greenhouse+shed & 6A for lights

Shed could have 16A for sockets and lights run off the ring fused via a Fused Connection Unit (FCU)

greenhouse 16A available to run the heater via FCU and lights via FCU

I would suggest 4mm sq 3-core SWA cable for this, or better would be 6mm 3-core

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 5:47pm

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.

Title: Re: consumer unit/garage/shed/greenhouse
Post by rabbit_rabbit on Aug 1^st, 2004, 5:50pm

Aint 10mm a bit OTT Plug? Where did the 43 metres come from and if it comes to that the 40A? I agree its good to be flexible but 10mm can be a bit of B to install.

What is being proposed to run in shed and garage (in sockets) i.e. what sort of loading anticipated?

Greenhouse heater probably 1kW? or is a hot house type of thing? I can't see you needing some 9kW.

Still you have an 30mA RCD in split MK CU so no need for further RCD at house but do suggest RCD's at garage, shed and greenhouse.

I would have suggested 4mm but Plug has the calcs I just question the distance versus volt drop and need to 40A+

RR

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 5:56pm

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

Title: Re: consumer unit/garage/shed/greenhouse
Post by rabbit_rabbit on Aug 1^st, 2004, 6:02pm

But what sort of demand are you expacting to need at each location. I mean in the garage say you may need sockets for electril drill, maybe a heater for winter working on car etc. But were you to say "Oh no I have an electric hoist for the car and arc welding kit.." then the stroy is very different indeed. If youi get my drift.

I would ALWAYS fit 30mA RCD's at user side of garage, sheds and greenhouses without thinking twice about it.

RR

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 6:18pm

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

Title: Re: consumer unit/garage/shed/greenhouse
Post by rabbit_rabbit on Aug 1^st, 2004, 7:41pm

So say 3kW in greenhouse, shed say 1kW at most, garage another kW = 5kW or 21 Amps. With a max distance of some 30 mtrs.

I would use 4 mm swa BUT old Plug has the expensive cable calculator and I am sure he will respond soon.

By the way DO put in RCD's at all locations please especially if machinery is being used. The cost of a life os considerably less than cost of some tacky old RCD.

RR

Title: Re: consumer unit/garage/shed/greenhouse
Post by plugwash on Aug 1^st, 2004, 8:01pm

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:

I was told 2.5 SWA was good for 21amps at even 50m.

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

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 1^st, 2004, 8:07pm

im afriad without casuing offence, thats pretty poor using the TLC calculator, ive personaly tried it and it does not give adequate resuslts, I use a proper calculator and regulations book.

10mm is way too extreme for this, and the first cable should be run from the RCD protected side of the board, then the cable is protected aswel.

finnaly using anticapted loading 16A for sockets is reasonable, no 32A rings, and dont worry too much about small loads, after all your 58W light takes more than the 58W, you are only counting the lamp.

What you have asked for is not unreasonable, just needs carefull consideration, the 2.5mm cable you have id say will come in nicely at the later stage, but somthing a tad bigger e.g 4mm will be more appropriate at the house

Title: Re: consumer unit/garage/shed/greenhouse
Post by rabbit_rabbit on Aug 1^st, 2004, 9:37pm

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.

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 10:35pm

I have just looked at the tlc calculator.

surely it is flawed?

giving load of 2700 watts over 50 metres

using basic pvc swa it recommends 2.5mm
using xple swa it recommends 4mm

I thought Xple was better and gave a lower votage drop.

Quoting TLC Description for 2.5mm Xple SWA
Current Rating: 31 Amps
The Max current rating above is for XLPE insulated cables ( TLC standard cable ) and not for just Pvc insulated SWA

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 1^st, 2004, 10:41pm

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.

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 1^st, 2004, 10:43pm

oh and finnaly unless its all they sell, you need PVC SWA which runs at a lower temperature, XLPE takes more current and therefor looses more volts, however all of your wiring accesories wont be up to the high current. PVC SWA is you ticket :)

Title: Re: consumer unit/garage/shed/greenhouse
Post by plugwash on Aug 1^st, 2004, 10:50pm

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?

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 10:57pm

OK my first distances were guesstimates

Ive now measured it properly

1st run House to Garage 12 metres will use 4mm SWA XPLE
2nd run Garage to shed 25 metres will use 2.5mm SWA XPLE
3rd run Shed to greenhouse 10 metres will use 2.5mm SWA XPLE

Total Distance 47 metres

Max use will be 2500 watts only over winter

normally max will be 1000 watts

Please can I use my reel of 2.5mm SWA now.

P.S Seeings how we are all confessing for the last 2 years the greenhouse and the mowing has been run off a 50m extension lead plugged into my conservatory spur. And it doesnt even get warm. lol :-)

re cheaper swa try http://www.electricalshop.net

Title: Re: consumer unit/garage/shed/greenhouse
Post by Logic_Plus on Aug 1^st, 2004, 11:03pm

wrote on Aug 1^st, 2004, 10:50pm:

Try these Plug

http://www.essexelectricalwholesalers.co.uk/acatalog/3Core_SWA.html

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 11:15pm

http://www.electricalshop.net all prices include vat

Title: Re: consumer unit/garage/shed/greenhouse
Post by Captslogg on Aug 1^st, 2004, 11:35pm

Well guys, thanks for all your well thought out, well debated descriptive answers. You really really all have been a great help.

I thought you would like to see what answer another forum gave me.

Hager. Spl;it load and get the cabling and connections tested. Armoured cable to green house with MCB's

Sparky

Not quite the same eh?

Title: Re: consumer unit/garage/shed/greenhouse
Post by L.Spark on Aug 2^nd, 2004, 12:20am

nope it's not, were all pro's here :)

however if your basing any of your calculations on XLPE you making a mistake, you cannot run the current ratings of XLPE with out the correct acceories, stick to PVC, or use XLPE with PVC ratings 70oC which will solve your problems, and yes use 2.5mm for your last couple of runs, fused appropriatly

good luck and take care with the work.