I need some advice from the above. At the moment I have an electric
cooker/oven and thus the 32amp MCB and radial circuit. I've changing
this to a full gas version and would like to convert the radial to a
socket circuit (plug for cooker ignition, cooker hood and possibly
another a doubel socket).
I have read diy books and posting here but there are areas I am not
1. Do I need to change reduce the MCB to a lower ampage. For example,
to 20amp (and how is this done?). If I do change it to 20amp is the
6mm cable (I think) still suitable?
2. I'm likely to place a junction box or my first socket at the end of
the circuit. To extend the circuit do I need to use 6mm or is a lower
rated cable OK (for 2.5).
3. Is their a rule on how many sockets I can add and how far apart
they need to be.
4. Anything else I need to think about?
Thanks in advance.
You have two choices for a 'conventional' radial circuit for sockets as
specified in the IEE On-site Guide :-
20 Amp MCB and wire the rest of the circuit in 2.5sq mm T&E
32 Amp MCB and wire the rest of the circuit in 4sq mm T&E
Personally I'd go for the 20 amp MCB even though it involves changing
the MCB as wiring with 4sq mm will be a pain. The existing length of
6sq mm is fine. To change the MCB you are best getting an MCB of the
same type (i.e. manufacturer) as your existing CU. It should then be
fairly straightforward to change it (with the power off obviously).
The exact method for removing and installing MCBs can vary with
See above, depends on the MCB in the CU. With a radial circuit you
can branch it as much as you like which makes wiring very easy.
A radial circuit wired with 2.5sq mm T&E can supply up to 50 square
metres floor area and there's no limit on the number of sockets. A
radial wired in 4sq mm can supply up to 75 sqare metres floor area.
There's no rules about how far apart sockets have to be.
Not really, except to label clearly on the CU that this is now a
radial circuit supplying sockets. A similar note inside the box in
the kitchen would be a good idea too.
You can keep the 32A MCB. I would, especially for a kitchen, where there are
many power hungry appliances. You can spread the load by taking something
big (i.e. washing machine) off the old ring and sticking it on the new
If you do change to 20A MCB, there are no problems with the 6mm cable. You
are allowed to use bigger cable than necessary, if convenient.
This depends on installation details. 6mm (or even 10mm in some rare cases)
may be required, but calculations will probably allow 4mm, depending on
installation details. (i.e. a short distance clipped direct is allowed, but
buried in insulation or in conduit may not be).
There are some limits to do with floor space, but they simply wouldn't apply
for a kitchen. You'd have to be covering the area of a small size house to
run into them, not a single room.
You can have as many sockets as you wish. Indeed, the latest on site guide
gives guidance on how many sockets might be considered reasonable and you
need quite a lot to meet their suggestions. The IEE are on a mission to
reduce the number of multiway extension leads.
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