Hi Group

Can anyone advise me on the correct type of cable and the size to wire
a cooker 6Kw and a hob 6Kw to the cooker isolating switch. Should this
be some kind of flexable cable? Does part P allow me to connect
directly from the switch to the appliance?
All help greatly appreciated.

Graham

wrote:

Can anyone advise me on the correct type of cable and the size to wire
a cooker 6Kw and a hob 6Kw to the cooker isolating switch. Should this
be some kind of flexable cable? Does part P allow me to connect
directly from the switch to the appliance?
All help greatly appreciated.

Quick answer: 6mmsq cable; no, not flex. Ass-U-ming your cooker
isolating switch is fed by a dedicated circuit from the consumer unit,
with its own MCB/fuse rated at 30A/32A/40A.

Both the hob and the cooker (I ass-U-me you mean oven?) ought to be
within 2m of the cooker switch - the idea being that you (and anyone
else, even Just Passing Through the kitchen) can readily see and operate
the isolator quickly in the event of a cooking fire or other fault. If
significantly beyond that distance, put another isolator closer to the
one that's far away, wired either in series with the 'main' cooker
switch, or with its feed run from the incoming (permanantly live) side
of the cooker isolator.

Let us know if you need more detail - Stefek

if the total load is 12kw should a new seperate cooker circuit be put in for
either the hob or oven or at anyrate the whole lot i would have thought
should be upgraded to 10mm t&e and this might still not be enough depending
on voltage drop over distance from the main cu please correct me if i am
wrong
"Stefek Zaba" wrote in message
.. .
wrote:

Can anyone advise me on the correct type of cable and the size to wire
a cooker 6Kw and a hob 6Kw to the cooker isolating switch. Should this
be some kind of flexable cable? Does part P allow me to connect
directly from the switch to the appliance?
All help greatly appreciated.

Quick answer: 6mmsq cable; no, not flex. Ass-U-ming your cooker isolating
switch is fed by a dedicated circuit from the consumer unit, with its own
MCB/fuse rated at 30A/32A/40A.

Both the hob and the cooker (I ass-U-me you mean oven?) ought to be within
2m of the cooker switch - the idea being that you (and anyone else, even
Just Passing Through the kitchen) can readily see and operate the isolator
quickly in the event of a cooking fire or other fault. If significantly
beyond that distance, put another isolator closer to the one that's far
away, wired either in series with the 'main' cooker switch, or with its
feed run from the incoming (permanantly live) side of the cooker isolator.

Let us know if you need more detail - Stefek

dale hammond wrote:
if the total load is 12kw should a new seperate cooker circuit be put in for
either the hob or oven or at anyrate the whole lot i would have thought
should be upgraded to 10mm t&e and this might still not be enough depending
on voltage drop over distance from the main cu please correct me if i am
wrong

With all the authority of one who's recently been corrected by Andy Wade
- you're wrong ;-) For *domestic* use it's sanctioned by the Regs to
treat the *design* current as the 'diversified' figure of 10A +
30%-of-the-rest; so your 12kW of cooking appliances - which the OSG
specifically says is OK to treat as one appliance - will pull 52A using
the fiction of a 230V supply, which we downrate to 10 + (42*0.3) =
22.6A. You'd be 'allowed' to use 4mmsq (hell, even 2.5mmsq with
charitable assumptions about cable routing!), but the 6mmsq I suggested
is the 'usual' answer, which allows for the peak loads without even
warming noticeably (since they don't last for more than a couple of
minutes).

HTH - Stefek

I wrote:
For *domestic* use it's sanctioned by the Regs to treat the *design*
current as the 'diversified' figure of 10A + 30%-of-the-rest...
... so your 12kW of cooking appliances - which the OSG
specifically says is OK to treat as one appliance

I follow up my own posting (tsk, tsk) to stress again that this
application of diversity is appropriate ONLY for 'domestic' usage, or
wot the OSG heading calls 'household or similar premises'. It's based
upon normal home cooking practice, and would NOT be sensible if you were
regularly cooking up batches of [marmalade, soup-run soup, bike chain
grease].oneof() making heavier-than-usual use of all the cooking elements.

i stand corrected thank you
"Stefek Zaba" wrote in message
.. .
I wrote:
For *domestic* use it's sanctioned by the Regs to treat the *design*
current as the 'diversified' figure of 10A + 30%-of-the-rest...
... so your 12kW of cooking appliances - which the OSG specifically says
is OK to treat as one appliance
I follow up my own posting (tsk, tsk) to stress again that this
application of diversity is appropriate ONLY for 'domestic' usage, or wot
the OSG heading calls 'household or similar premises'. It's based upon
normal home cooking practice, and would NOT be sensible if you were
regularly cooking up batches of [marmalade, soup-run soup, bike chain
grease].oneof() making heavier-than-usual use of all the cooking elements.

Stefek and Dale

Many thanks. Just to be sure the current configuration is 6mmsq TE from
consumer unit (fused 40A) which is 2Mtrs away from cooker switch. From
cooker switch to oven and hob I have 2 separate 4mmsq TE each 1.5 Mtrs
long. Can I ask one final time should the cable to the oven and hob be
the same stuff I wire my ring main with? Sorry to labour this point but
someone told me this stretch of cable should be flexable i.e. a
stranded make up.

Thanks again
Graham

Stefek Zaba wrote:

For *domestic* use it's sanctioned by the Regs to treat the *design*
current as the 'diversified' figure of 10A + 30%-of-the-rest; so your
12kW of cooking appliances - which the OSG specifically says is OK to
treat as one appliance - will pull 52A using the fiction of a 230V
supply, which we downrate to 10 + (42*0.3) = 22.6A.

In fact the OSG (not BS7671) says this [p.154]:

"A 30 or 32 A circuit is *usually* appropriate for household or similar
cookers of rating up to 15 kW."

I've emphasised the "usually" - for (hopefully) obvious reasons.

--
Andy

On Thu, 07 Jul 2005 02:13:19 -0700, graham.else wrote:

Stefek and Dale

Many thanks. Just to be sure the current configuration is 6mmsq TE from
consumer unit (fused 40A) which is 2Mtrs away from cooker switch. From
cooker switch to oven and hob I have 2 separate 4mmsq TE each 1.5 Mtrs
long. Can I ask one final time should the cable to the oven and hob be
the same stuff I wire my ring main with? Sorry to labour this point but
someone told me this stretch of cable should be flexable i.e. a
stranded make up.
=

The stuff from the switch to the oven and hob should be 6mm. Because that
is the conductor size for this 40A circuit.
Even if the circuit has a 32A MCB then by the book the cables would have
to be 6mm as there should be protection wherever a cable changes size.

Both 4mm2 and 6mm2 cable have stranded conductors although the earth wire
in the 4mm2 is usually a single solid wire.

It is quite wrong to use ring main cable 2.5mm2 in this case.

If I've got something wrong someone will tell me I hope.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

wrote in message
oups.com...
Stefek and Dale



Can I ask one final time should the cable to the oven and hob be
the same stuff I wire my ring main with? Sorry to labour this point but
someone told me this stretch of cable should be flexable i.e. a
stranded make up.


The manufacturers installation instructions should tell you what cable to
use.
I had to use http://www.tlc-direct.co.uk/Products/CA4TQ3slash50.html
on an install last week as that is what was specified.

Adam

Hi Stefek , Dale and ARWadsworth

Well it appears this was not to be my last request for clarification as
the cable shown in the above link is a flexable cable with many thin
strands of copper in each wire. The wire I currently have to the oven
and hob is the same as used for the connection from the consumer fuse
box to the isolating switch. This has only 7 very thick copper strands
in each wire and is very difficult to bend for the connection to the
appliances. Sorry guys but could you please clarify.

Regards
Graham

wrote in message
ups.com...
Hi Stefek , Dale and ARWadsworth

Well it appears this was not to be my last request for clarification as
the cable shown in the above link is a flexable cable with many thin
strands of copper in each wire. The wire I currently have to the oven
and hob is the same as used for the connection from the consumer fuse
box to the isolating switch. This has only 7 very thick copper strands
in each wire and is very difficult to bend for the connection to the
appliances. Sorry guys but could you please clarify.

Regards
Graham

The protection at the consumer dictates the gauge of cable used. If the
fuse in the fuse box is 32 Amps rated, then the cable from that supply must
be able to take 32 Amps current along its full length. If you reduce the
gauge of cable being supplied from the fuse in the fuse box, then you also
have to reduce the rating of fuse to suit the cable.

When you need to reduce the gauge of cable being supplied from a larger
gauge, then you need to install a protective device that is able to
withstand the heavier current, but can be fused to suit the lower gauge
cable paths spurred from it. Something like a Fused Connector Unit that can
easily withstand the 32 Amps current rating, but can fitted with a 13 Amps
rated fuse for the loads taken from it.

The fuse or safety breaker device in the consumer unit protects the cable,
not the appliance if the appliance is a lower rated current device.

Get it?

"BigWallop" wrote in message
. uk...

wrote in message
ups.com...
Hi Stefek , Dale and ARWadsworth

Well it appears this was not to be my last request for clarification as
the cable shown in the above link is a flexable cable with many thin
strands of copper in each wire. The wire I currently have to the oven
and hob is the same as used for the connection from the consumer fuse
box to the isolating switch. This has only 7 very thick copper strands
in each wire and is very difficult to bend for the connection to the
appliances. Sorry guys but could you please clarify.

Regards
Graham

The protection at the consumer dictates the gauge of cable used. If the
fuse in the fuse box is 32 Amps rated, then the cable from that supply
must
be able to take 32 Amps current along its full length. If you reduce the
gauge of cable being supplied from the fuse in the fuse box, then you also
have to reduce the rating of fuse to suit the cable.

When you need to reduce the gauge of cable being supplied from a larger
gauge, then you need to install a protective device that is able to
withstand the heavier current, but can be fused to suit the lower gauge
cable paths spurred from it. Something like a Fused Connector Unit that
can
easily withstand the 32 Amps current rating, but can fitted with a 13 Amps
rated fuse for the loads taken from it.

The fuse or safety breaker device in the consumer unit protects the cable,
not the appliance if the appliance is a lower rated current device.


Having said all that, the number of strands in the cable only really affects
the flexibility of it. The cross sectional area affects the current handling
capacity.

I'd choose the more flexible cable when running to a free standing cooker,
or to something like an industrial dishwasher that may well move about a
fair bit.

Solid core (in practice often a-few-strands) like you have is often used for
cookers. As long as the rating is right either should be OK for a built in
oven/hob. Solid is cheaper than flexible stranded stuff.