DIY Doctor

can i run a spur

Postby giblets » Fri Dec 09, 2011 3:52 pm

Hello, I'm after some advice.
In my downstairs toilet/washing machine room I have 63amp 3 way consumer unit which is powered by a spur from the household socket ring which is from 30amp fuse in an old fusebox.
Firstly is this ok.
There are 2 mcb's in the consumer unit one going to a fused switch then to a double socket in the shed the other to a double socket for washer and drier.
Assuming the above is ok could I take a spur off the internal double socket to power another double socket.
Many Thanks
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Postby ericmark » Sat Dec 10, 2011 4:07 am

The UK ring main has some strict rules as it is easy if not followed to overload one leg of the ring. Although a single double socket is allowed as a spur, it is considered unlikely it will even have the max of 26A and depending on installation method the 2.5mm cable would likely be overloaded at 26A so when one want's more than a single double socket the method is to use a fused connection unit FCU which will then limit the max on the spur to 13A.
Even at 13A one does have to be careful overload is still possible. But by using only portable equipment again the likelihood of an overload is reduced to a minimum.
So any fixed appliance over 2kW should have a dedicated supply. This is in the main as items like an immersion heater will run a lot longer than a kettle.
The regulations don't list what is fixed but items like Ovens, Tumble Driers, Washing Machines, Dishwashers, and Immersion Heaters should all have a dedicated supply. Often one finds that builders have not quite followed the regulations to letter but have installed a ring dedicated for the kitchen only with a grid switch supplying each item.
What you talk about seems to be well over the top. A washer drier should not come off the ring main even in the house it should have a dedicated supply although often they do come off ring main.
If you use a fused connection unit (FCU) at 13A likely you will get fuses blowing which would be a sure sign of overload.
So what you have is rather dangerous. As to how to rectify it hard without seeing what you have. Although one can still use an existing rewire-able fuse one can't fit new ones. So likely you would be looking at a new consumer unit with RCD's and MCB's or RCBO's before you can add any sockets.
Using Ali-tube cable and RCD Sockets in theroy could be done but in practice to buy short lengths of Ali-tube cable is hard and a whole role is expensive.
What you have from your description would if you took some photos go well in the rouges gallery showing what not to do.
The problem is what damage has it already caused? I had one in my dad's house where he had spurred off a spur and I had to ripe the whole lot out as it had melted the cable in the wall and it would not pass an insulation test.
It will need minimum of testing with a 500 volt insulation tester likely it will have degraded the cable.
It's not electric shock I worry about at least if it kills you that way it's quick. It's the fire risk. Likely the ring will be OK and only the spur will need replacing and correct FCU fitted. But it will need testing.
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Postby giblets » Sun Dec 18, 2011 6:40 pm

Many thanks for your indepth advice. Sorry for delay in replying.
I am going to get old fusebox replaced and will get electrician to change whatever needs changing.
(Better safe than sorry)
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