Post
by ericmark »
Sat Dec 13, 2014 9:35 am
Job one is to find where supplied from. Start at fuse box / consumer unit and see the size of fuse or MCB feeding it. Also if RCD protected or not.
The standard cable used for sockets is 2.5mm which is good for around 20A but a ring final is often supplied with 32A and relies on the 13A fuse in plug to stop over loading. But you can have radials and these may use 4mm cable instead so can't really give a solid answer without being sure what you already have.
Likely method is to find the socket on the ring final which supplies the socket you have found and swap the socket on the ring final for a RCD FCU which since it has a 13A fuse built in and RCD protection will allow you to then fit a string of sockets from this which if any one tries to overload them will simply blow fuse and fail safe. And all new sockets must be RCD protected and using one of these they would be.
Every time the occupant changes in a house changes you should get an EICR done or old name PIR. This electrical installation condition report will detail what has been found. The major problem is before 1960 often no earths on lights and before 2008 often no RCD protection on cables and sockets so near every house has some codes raised.
These do tell you however what you have to do. i.e. if no earth on lights then must buy only class II lights or switches. If no RCD (30 mA type) then you know one must be added before you can extend and circuit.
Under 13A then the RCD FCU is the easy way out. But over 13A then often only real way is to change the consumer unit first. Once the consumer unit contains the RCD protection then no need for the RCD FCU or RCD sockets.
So you need to decide what you want to do? If answer is add a couple of sockets then RCD FCU but if you decide you want 3 sockets here and 2 sockets there and another socket up there then it will work out cheaper to change the consumer unit first.
It was called a fuse box but when we got rid of fuses then we wanted a group name so we have the distribution unit however in a domestic house we want a type tested unit and when type tested we call it a consumer unit.
Often old houses end up with an array of fuse boxes where items are added over the years. Old houses may have a ELCB-v which were used with earth rods but are now banned and have been replaced with the ELCB-c or RCD as it's better known. These were normally around the 100 mA mark delayed (S type) which allowed for the bad earth of the earth rod but does not really protect people for the latter we need a 30 mA unit.
All this should be on the EICR but just in case it has not been done yet I am warning you.
I remember an old farmer who always used his hat to switch lights on and off as so many switches would give you a shock. Today we tend to expect safe electrics.
