running a heavy load on a fused spur

Hi,

I am installing a washing machine and dryer with an occasional iron in the basement and need to install the sockets for these. I want to run a 3metre spur from the existing socket ring system on the ground floor. The appliances all used to be plugged into this ring system but now will run from the spur in the basement.

As the appliances are heavy load, I intend to use 2.5mm2 cable for the spur and to fuse the spur with a 13amp fuse. The cable will be clipped to the wall rather than running through plaster.


Is my proposed wiring safe? Will the fuse constantly blow? Should I just get a dedicated circuit installed for the basement?


thanks!

 

What's the point of that?

Not really.

It might.

If you're unlucky the FCU might catch fire through being subjected to a load so high that it overheats but not high enough to rupture the fuse - check the time/current curves for BS 1362 fuses: http://www.diynot.com/wiki/electrics:bs1362

Yes.

 

run 2 cables and extend the ring.

It's not actually that much more work.

 

Thanks for the advice.

The spur is already in place, but is single socket with no fuse. My 'work' would be to install the FCU and a double socket.

So the option of extending the ring from the ground floor involves removing floorboards/walls etc. and is not practicable.

My consumer unit is in the basement right next to the appliances so it would be very easy to wire a new ring circuit for the appliances, but the problem is there is no spare space for a new circuit.

Is there anyway (apart from buying a new CU) of installing the new ring using existing setup?

 

If the CU is in the basement then could you not break into the ring at that point? Add a socket next to the CU - one leg of your new ring to the CU & other to the socket.

 

Never thought of that. Seems obvious really.



tks

 

you also not advisable to have a washer & dryer plugged into the same double socket (unless it's an MK). So 3 sockets would be best.
Probably the least of your worries though.

 

You should also do some design calculations to check that you won't be overloading one leg of the ring if you have sockets that close to the origin which you use for appliances like that.

 

thanks. This has occurred to me as well.

As the appliances are right next to the CU, is it advisable to use considerably more cable than the distance requires, just so the ring is balanced and doesn't just draw on one leg?

 

Or use 4 mm for the leg from the CU to the new sockets. Then however "un-balanced" the load was that leg would not be over loaded by a load to the maximum of the MCB.

Considerable care will be needed in the terminals where the 4 mm meets the 2.5 mm to ensure the joint is secure.

 

Not sure whether an unbalanced ring is something that causes problems in the real world but I found http://www.diynot.com/forums/viewtopic.php?t=43604 which might be useful.

 

A 4mm spur from a 2.5mm standard ring final? I'm not sure if that is best practise. Better to provide a separate 32A MCB and create a new 4mm radial circuit.

 

Or perhaps he should just break into both legs of his existing ring and put a socket on each to split the washing machine & drier. Still not sure whether this problem is real enough to be worried.

 

I can't even draw on one leg, never mind two.

 

Ok, I had a look a the CU and there is one 32A 2.5mm radial circuit that supplies one double socket at the other end of the basement.

My new plan is to replace this radial with a 32A 2.5mm ring that supplies this socket, the washer dryer and a freezer. The washer dryer will be moved so that they aren't too close to the CU.

Will a straight swap for a radial to a ring cause any issues on my CU?