Our cooker control unit incorporates a 13A socket but is too high (and directly
above the cooker) to be of much use. I can access the cable under the floor and
wonder if I could insert a 30A junction box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more convenient
position. I cannot run from the existing kitchen sockets since they are both
spurs from upstairs (1969 house).
The CCU has a 30A fuse for this radial - and no spare positions.

Geo

On Tue, 09 Jan 2007 19:51:07 GMT, Geo
wrote:

Our cooker control unit incorporates a 13A socket but is too high (and directly
above the cooker) to be of much use. I can access the cable under the floor and
wonder if I could insert a 30A junction box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more convenient
position. I cannot run from the existing kitchen sockets since they are both
spurs from upstairs (1969 house).
The CCU has a 30A fuse for this radial - and no spare positions.

Geo

I do not know the regulations on this but it would be dodgy from a
safety point of view. I had one of these here and turned the socket
ring off at the CU and opened the "dead" socket to work on it, not
realising it was still live on the cooker circuit. You know the
combined cooker switch/socket is on the cooker circuit, but not an
anonymous socket near to it.

On Tue, 09 Jan 2007 19:51:07 GMT someone who may be Geo
wrote this:-

Our cooker control unit incorporates a 13A socket but is too high (and directly
above the cooker) to be of much use. I can access the cable under the floor and
wonder if I could insert a 30A junction box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more convenient
position.

The protective device for this circuit is 30A. What size is the
cable?

In theory you could insert a joint of a suitable rating into the
cable and run a socket from that, via cable the same size as that of
the existing cable. Alternatively, in theory, a fused connection
unit or circuit breaker could be inserted and smaller cable run to
the socket.

However, cocker control switches above cookers are not a good idea,
for obvious reasons. Far better to move it and at the same time add
sockets as necessary into the existing ring main.

If you have the misfortune to live in England or Wales beware of the
idiot John Prescott and his gold plated idea for incorporating the
Wiring Regulations into law.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Tue, 9 Jan 2007 19:51:07 UTC, Geo
wrote:

Our cooker control unit incorporates a 13A socket but is too high (and directly
above the cooker) to be of much use. I can access the cable under the floor and
wonder if I could insert a 30A junction box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more convenient
position. I cannot run from the existing kitchen sockets since they are both
spurs from upstairs (1969 house).
The CCU has a 30A fuse for this radial - and no spare positions.

Even under absolutely ideal conditions, 2.5mm2 cable is rated at less
than 30A. So there is no proper overcurrent for that cable (which in
this situation is probably rated only at around 20A). A 30A fuse is thus
not good enough.

Either use cable rated at a higher current (e.g. 4mm2) or use a fused
spur connection. Problem is that even then the connection from the JB to
the fuse unit needs to be rated at 30A, at least in theory.

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

Bob Eager wrote:
On Tue, 9 Jan 2007 19:51:07 UTC, Geo
wrote:

Our cooker control unit incorporates a 13A socket but is too high
(and directly above the cooker) to be of much use. I can access the
cable under the floor and wonder if I could insert a 30A junction
box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more
convenient position. I cannot run from the existing kitchen sockets
since they are both spurs from upstairs (1969 house).
The CCU has a 30A fuse for this radial - and no spare positions.

Even under absolutely ideal conditions, 2.5mm2 cable is rated at less
than 30A. So there is no proper overcurrent for that cable (which in
this situation is probably rated only at around 20A). A 30A fuse is
thus not good enough.

Either use cable rated at a higher current (e.g. 4mm2) or use a fused
spur connection. Problem is that even then the connection from the JB
to the fuse unit needs to be rated at 30A, at least in theory.

But (subject to earth-loop and 0.4s disconnecton calculations being
satisfactory
which if they are for the existing arrangement, are likely to also be with a
short
length of 2.5mm" to the socket)
the 30-A fuse is only serving for short-circuit protection, and the load is
limited
by feeding a 13-A socket, and 2.5mm2 cable is adequate for a spur from a
ring
under similar conditions.It is non-standard, but more better than, say,
shoving an
unfused 2-way adaptor in the existing CCU.

Geo wrote:

Our cooker control unit incorporates a 13A socket but is too high (and directly
above the cooker) to be of much use. I can access the cable under the floor and
wonder if I could insert a 30A junction box (without cutting the cable) and run
2.5mm cable from there to a new 13A socket in a slightly more convenient
position. I cannot run from the existing kitchen sockets since they are both
spurs from upstairs (1969 house).
The CCU has a 30A fuse for this radial - and no spare positions.

It might be neater to replace the cooker point with a switch only type
(i.e. no socket) and then run an additional cable from the switch
position to the new single socket (following the allowable cable routing
zones).

You would also need to check the loading imposed by the cooker to see if
you have "spare" capacity. When doing these calculations for a domestic
cooker you normally include diversity such that you assume a load for
the cooker equal to 10A + 30% of its actual full load in excess of 10A.
You also allow a further 5A for the socket if fitted to the cooker point.

(Also remember to place a label on the CU indicating that the circuit
feeds both cooker and socket).


--
Cheers,

John.

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On Wed, 10 Jan 2007 04:04:06 +0000, John Rumm
wrote:

You would also need to check the loading imposed by the cooker to see if
you have "spare" capacity. When doing these calculations for a domestic
cooker you normally include diversity such that you assume a load for
the cooker equal to 10A + 30% of its actual full load in excess of 10A.
You also allow a further 5A for the socket if fitted to the cooker point.

OK - thanks for all the replies and sorry for the delay in responding. This
final point prompted me to check the plate on the back of the cooker where it
states 11.25kW at 240V (nearly 47A) so the theory says - I think - about 3A left
to play with. In practice, I asked the cook and she said that the oven, grill
and one ring are often used together so initially about 7kW (29A).
I take the point about using 6mm cable to the socket and this would have been
quite convenient since I still have some 7/.044.
Anyway I am now trawling ebay for a decent length of 2.5mm to extend the ring
from a back-to-back pair of sockets between the kitchen and hall. This will give
me more flexibility than the initial proposal.

Part P does not reach this far North - but we have to maintain an additional
bunch of waffling looneys in their ivory tower.

Geo