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| Bluest Member Since: 23 Apr 2016 Location: Lancashire Posts: 4209   
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Each appliance should have an input power in Watts marked on it. Yiy can just add everything up and speak to Electrician about what's needed. Will she be using all those things at once? That's potentially quite a hefty power supply for shed. 2007 110 TDCi Station Wagon XS
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30th Aug 2018 6:56pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1423 
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I would say straight away
You need a proper designated armored supply wired back to you consumer unit, fitted and certified by a qualified competent person. Its just not worth bodging it a s your house insurers will have a field day |
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30th Aug 2018 6:58pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20347
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An extension cord is also really only a temporary fitting and max load 13A.
I'd echo what Jim said above, but unfortunately comes at a cost! $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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30th Aug 2018 7:01pm |
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| AndyT66 Member Since: 19 Sep 2016 Location: Bedford Posts: 148  
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Hello Rocco, as Jim says ideally you should run a new cable from your main consumer unit to something like this https://www.screwfix.com/p/british-general...unit/1926g mounted in your workshop. You can then have separate lighting and appliance circuits from this unit.. The new supply cable would need a part p qualified electrician to fit it. Cheers Andy
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30th Aug 2018 7:38pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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Rosco, simple advice is get a qualified electrician in to do the work as that amount of work needs certifying to part 17 or even part 18 Regulations these days.
As pointed out an extension lead is 13 amp or 3 kW Now 3 kW is say an electric kettle. 8 electric hob rings at say 1 kW each or 8 kW in total will fry your extension cable. If possible get steel sheathed cable underground at correct rating. Overhead used to be possible on a properly tensioned gantry wire. Not sure if still allowed. So get a proper qualified sparky in and work out current max total load and then allowed another 50% for those extra toys your wife will need. Brendan |
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30th Aug 2018 7:42pm |
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| Rosco Member Since: 03 Dec 2010 Location: Burntwood Posts: 1833 
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Thanks for the quick respknses all and confirms my suspicions.
I know the current mains board is dated, so I can see this little venture getting expensive  2007 - Stornoway Grey 90 XS SW - Gone
2002 - Black Discovery II - Gone 2014 - Montalcino Red 110 XS SW |
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30th Aug 2018 7:48pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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Better expensive and safe rather then cheap and new shed/house burning down due to an electrical fault!
Brendan |
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30th Aug 2018 7:57pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1423
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Not necessarily........
The outdoor cable will have to be protected itself, so tacking onto an old consumer unit might not be such an issue. My workshop was less than £400 , 50 meter run of 16mm armored socket ring main and lighting. I did all the work and sparky tested and certified  |
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30th Aug 2018 8:03pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3497 
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Good advice from Brendan.
For information and interest to all (this isn't suppose to be instructions on how to do it), if your main supply (electricity board supply to use a better phrase) is what is known as a TN-C-S or PME supply (the main electricity supply fuse will usually have a label, but not always) you don't want to be exporting your earth from the house to an external building unless you know what you are doing. Another way of discovering whether your supply is PME, an earth wire will be connected from the neutral terminal of the main fuse block to the consumers main earth terminal. Most (but not all) properties these days have this kind of electricity supply. Two options. 1. Send a supply cable out to the shed with an earth cable the same size or larger than the main bonding conductor in the house (this is what as known as extending the equipotential bonded zone and it will usually require installing a 16mm2 or 25mm2 earth cable) 2. Isolate the earth as it enters the external building, protect the cable at the source with an RCD (Earth Leakage Circuit Breaker) and provide a point of earth adjacent to the external building using an earth electrode(s). It's not quite a simple as the above, and you need to be making sure the earth electrode has a low enough resistance and the RCD is the correct mA rating. Oh, and the cable if buried should be armoured with steel and ideally buried in a bit of ducting and not a hose pipe, please 
Yes, there are hundreds if not thousands of external buildings out and about that do not have any of the above done, but that's what should be happening. And just because it works, sadly does not mean it is safe. Doing the above is not cheap I'm afraid. Again, as Brendan says, talk to a good electrician. |
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30th Aug 2018 8:24pm |
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| Bluest Member Since: 23 Apr 2016 Location: Lancashire Posts: 4209
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I had a new consumer unit for my garage, two seperate circuits for sockets and one for lights. It wasn’t that expensive, maybe a few hundred. I saved a bit of money by running the cables and conduit, mounting the sockets etc myself once the sparky had specified it. He did all the actual connections and signed it off. 2007 110 TDCi Station Wagon XS
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30th Aug 2018 8:31pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6298 
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in this crazy world there's not point employing a fantastic electrician who may have recently finished re-wiring the Shard in London....he needs to be part P certified ie for domestic installations. commercial electricians don't need to be part P
your best option is likely the RCD route. you'll likely find that'll be the only option in all honesty and 30mA at that. I might be right in saying no one has been killed with an electrical supply protected by an operational 30mA RCD. at a guess from what you've said you're possibly looking at a 10kW supply which if you know anything about electric showers and the cables associated with them you're gonna be looking at a fairly hefty supply cable (by domestic standards). without looking at any books and assuming you'll be looking about a 50 mtr run of cable I'm going to guess you'll be looking about a 16 -25 mm cable (armoured as mentioned above) to ensure correct / minimal volt drop. Also look at a 3 core cable which will hopefully avoid the need for a separate earth / CPC as noted above. good luck. |
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30th Aug 2018 8:53pm |
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| v8bob Member Since: 14 Mar 2018 Location: Midlands Posts: 317 
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Well how much is this really going to be used?
How about using a petrol generator? As a quick fix to get things up and running this could be an option. Bob |
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30th Aug 2018 9:08pm |
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| miker Member Since: 13 Sep 2015 Location: Surrey Posts: 1763 
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Gas hobs and a couple of calor bottles would be the way I'd look. Runnin upwards of 8kw into a she's becomes a pain!
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30th Aug 2018 9:16pm |
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| apt100 Member Since: 05 Mar 2015 Location: Derbyshire Posts: 1547 
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I was going to mention not exporting PME, but you have summarised it well already
Just to add about 30mA RCD... Many people call the green/yellow wire "earth", but there is usually a voltage difference between it and true earth. Inside a building it doesn't usually matter. When you take it outside it can be dangerous. If you have a PME supply, and there is a broken neutral in the supply network, then the green/yellow wire (and anything metal connected to it) can be close to the full 230V supply voltage above true ground. And an RCD won't be any help at all. Hence it is illegal to have PME supply at eg caravan parks and marinas. And usually not recommended for supplies to outdoor buildings. |
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30th Aug 2018 11:02pm |
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