The kitchen in my newly-(almost) completed extension has a (professionally
installed) 45A radial cooker circuit which currently terminates in a
junction box. I don't intend to install a cooker but I do need to power an
electric domino hob and a fridge-freezer close to where the box is situated.
Is there any reason why I can't take two 2.5mm cables from the junction box
via two switches to two sockets, to do so?

Many thanks.

On Friday, 20 January 2017 11:05:16 UTC, Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a (professionally
installed) 45A radial cooker circuit which currently terminates in a
junction box. I don't intend to install a cooker but I do need to power an
electric domino hob and a fridge-freezer close to where the box is situated.
Is there any reason why I can't take two 2.5mm cables from the junction box
via two switches to two sockets, to do so?

If the junction box is before/instead of a cooker control unit, no.

If the jb is downstream of a cooker control unit, when someone switches the cooker control unit off, they'll turn the fridge off.

If the cooker circuit trips, you might not notice as quickly as loss of a general power circuit.

This is useful for splitting cooker cables

https://www.tlc-direct.co.uk/Products/AA45DCOP.html

Owain

Owain,

If the junction box is before/instead of a cooker control unit, no.

Thanks for that; there is no cooker control unit, just the junction box.

Bert Coules wrote:

Owain,

If the junction box is before/instead of a cooker control unit, no.

Thanks for that; there is no cooker control unit, just the junction box.

The fridge should certainly have its own fused spur, with a proper
isolating switch, e.g.:

https://www.tlc-direct.co.uk/Products/MKK1040.html

If the hob is wired with suitable cable/flex for 45A *and* the makers
of the hob specify that a 45A supply is ok you could use a standard
cooker switch (which would be useful if you ever put an oven in),
otherwise same as above.

The main criteria are to protect the cable to the appliance by limiting
fault current and to make servicing easy and safe by having separate
isolation switches for the two appliances. Just having a standard plug
would appear to work for the above, but a suitable socket to both
accommodate 45A wire and safely switch 45A does not exist.





--

Roger Hayter

Roger Hayter wrote:

If the hob is wired with suitable cable/flex for 45A *and* the makers
of the hob specify that a 45A supply is ok you could use a standard
cooker switch (which would be useful if you ever put an oven in),
otherwise same as above.

The hob is specified as 230V 2900W and is fitted with what appears to be a
standard flexible 3-core cable. It came from a previous kitchen where, as I
recall, it was plugged into an ordinary 32A socket located behind the
cabinet. I was intending to use a conventional cooker switch with 2.5mm
cable to a cooker connector and the hob's own cable thereafter.

In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.

--
*Husbands should come with instructions

Dave Plowman London SW
To e-mail, change noise into sound.

On 20/01/2017 11:12, wrote:
On Friday, 20 January 2017 11:05:16 UTC, Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a (professionally
installed) 45A radial cooker circuit which currently terminates in a
junction box. I don't intend to install a cooker but I do need to power an
electric domino hob and a fridge-freezer close to where the box is situated.
Is there any reason why I can't take two 2.5mm cables from the junction box
via two switches to two sockets, to do so?

If the junction box is before/instead of a cooker control unit, no.


2.5mm2 is not rated for a 45A circuit!

It would be fine if he de-rated the breaker.

2.5mm2 is not rated for a 45A circuit!

It would be fine if he de-rated the breaker.

I just checked. Despite the fact that the circuit is labelled "cooker" and
wired with what I think is 6mm cable, the breaker installed is a 32A model
identical with those on the ring circuits.

On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

--
Robin
reply-to address is (intended to be) valid

Bert Coules wrote:

Roger Hayter wrote:

If the hob is wired with suitable cable/flex for 45A *and* the makers
of the hob specify that a 45A supply is ok you could use a standard
cooker switch (which would be useful if you ever put an oven in),
otherwise same as above.

The hob is specified as 230V 2900W and is fitted with what appears to be a
standard flexible 3-core cable. It came from a previous kitchen where, as I
recall, it was plugged into an ordinary 32A socket located behind the
cabinet. I was intending to use a conventional cooker switch with 2.5mm
cable to a cooker connector and the hob's own cable thereafter.

You shouldn't do that. The 2.5mm^2 cable, the flex and the hob will
then only be protected by a 45A MCB. If you don't want to plug the hob
into the socket on the cooker switch (and you probably don't as it would
look untidy) it needs it's own 13A spur. How you actually connect the
isolating switch to the 45A circuit is a mystery to me, as you probably
can't connect sufficiently big cable into the switch input - perhaps
someone will tell us.
--

Roger Hayter

Robin wrote:

On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

But if is going to wire in the hob directly without a plug he needs
either a 10A MCB, which probably woudln't be enough, or at most a 16A
MCB, which might well be bigger then the hob is rated for; a 13A fused
spur would be desirable.

--

Roger Hayter

Roger Hayter wrote:

But if is going to wire in the hob directly without a plug he needs
either a 10A MCB, which probably woudln't be enough, or at most a 16A
MCB, which might well be bigger then the hob is rated for; a 13A fused
spur would be desirable.

What if I did use a plug and socket for the hob connection? That's what was
done (not by me) in my old kitchen.

Bert Coules wrote:

Roger Hayter wrote:

If the hob is wired with suitable cable/flex for 45A *and* the makers
of the hob specify that a 45A supply is ok you could use a standard
cooker switch (which would be useful if you ever put an oven in),
otherwise same as above.

The hob is specified as 230V 2900W and is fitted with what appears to be a
standard flexible 3-core cable. It came from a previous kitchen where, as I
recall, it was plugged into an ordinary 32A socket located behind the
cabinet. I was intending to use a conventional cooker switch with 2.5mm
cable to a cooker connector and the hob's own cable thereafter.


On reflection, if you want to connect this circuit to a cooker switch it
would be a lot better to leave it otherwise unused and take a spur off
an adjacent ring main to a socket for the fridge and a fused spur switch
for the hob. Ideally these should be two separate spurs, but one might
do if they are not too long.

If you are going to use the original circuit you probably need to use a
smaller MCB (absolute minimum 32A) and a plug for the fridge and
definitely a fused 13A spur for the hob if you don't want it on a plug.
The danger it seems to me is someone in the future changes it back to a
45A MCB for a cooker without removing these spurs they will not be
properly protected.

--

Roger Hayter

On 20/01/2017 11:12, wrote:


If the cooker circuit trips, you might not notice as quickly as loss of a general power circuit.

How often do cooker circuits trip?

And what are you probably doing if it does trip?

I'll bet it's something that you would notice:-)




--
Adam

On 20/01/2017 19:43, Roger Hayter wrote:

The danger it seems to me is someone in the future changes it back to a
45A MCB for a cooker without removing these spurs they will not be
properly protected.


That's their problem.

If they cannot spot a couple of 2.5mm T&E cables from the junction box
they connect the cooker into then they should not be doing the job.

--
Adam

On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!


There are no equations if it was changed to a 20A or 32A MCB:-)


--
Adam

In article ,
ARW wrote:
On 20/01/2017 11:12, wrote:


If the cooker circuit trips, you might not notice as quickly as loss of
a general power circuit.

How often do cooker circuits trip?

oven elements can short to their sheath

And what are you probably doing if it does trip?

I'll bet it's something that you would notice:-)

--
from KT24 in Surrey, England

Bert Coules wrote:

Roger Hayter wrote:

But if is going to wire in the hob directly without a plug he needs
either a 10A MCB, which probably woudln't be enough, or at most a 16A
MCB, which might well be bigger then the hob is rated for; a 13A fused
spur would be desirable.

What if I did use a plug and socket for the hob connection? That's what was
done (not by me) in my old kitchen.

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

--

Roger Hayter

Roger Hayter wrote:

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

I checked back through the thread and found that, just after I posted the
question. Thanks for reinforcing it, and to Robin and all the others who
responded. Much appreciated.

On 20/01/2017 20:16, Roger Hayter wrote:
Bert Coules wrote:

Roger Hayter wrote:

But if is going to wire in the hob directly without a plug he needs
either a 10A MCB, which probably woudln't be enough, or at most a 16A
MCB, which might well be bigger then the hob is rated for; a 13A fused
spur would be desirable.

What if I did use a plug and socket for the hob connection? That's what was
done (not by me) in my old kitchen.

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.


No reckon, it's a fact.


--
Adam

charles wrote:

In article ,
ARW wrote:
On 20/01/2017 11:12, wrote:


If the cooker circuit trips, you might not notice as quickly as loss of
a general power circuit.

How often do cooker circuits trip?

oven elements can short to their sheath

And in the common domestic arrangements it is an RCD covering more than
the cooker circuit that will trip rather than the MCB. Not if you have
RCBOs though.



And what are you probably doing if it does trip?

I'll bet it's something that you would notice:-)


--

Roger Hayter

ARW wrote:

On 20/01/2017 20:16, Roger Hayter wrote:
Bert Coules wrote:

Roger Hayter wrote:

But if is going to wire in the hob directly without a plug he needs
either a 10A MCB, which probably woudln't be enough, or at most a 16A
MCB, which might well be bigger then the hob is rated for; a 13A
fused spur would be desirable.

What if I did use a plug and socket for the hob connection? That's
what was done (not by me) in my old kitchen.

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.


No reckon, it's a fact.

I reckon it's an acceptable wiring practice under some conditions in the
UK rather than a "fact", but fair enough.

--

Roger Hayter

ARW wrote:

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

No reckon, it's a fact.

And what constitutes "short" in this instance?

Bert Coules wrote:

ARW wrote:

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

No reckon, it's a fact.

And what constitutes "short" in this instance?

I'll leave others to give a definitive answer, but if all the
connections are on the same or adjacent walls I doubt there will be a
problem. Especially given the junction box is supplied with 6 or
10mm^2.

--

Roger Hayter

Roger Hayter wrote:

I'll leave others to give a definitive answer,
but if all the connections are on the same
or adjacent walls I doubt there will be a
problem.

Thanks for that. The longest spur will in fact be about three feet, so I
should be OK.

On 20/01/2017 21:37, Bert Coules wrote:
ARW wrote:

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

No reckon, it's a fact.

And what constitutes "short" in this instance?



A live to either neutral or earth

--
Adam

Boom, boom.

On 21/01/2017 12:42, ARW wrote:
On 20/01/2017 21:37, Bert Coules wrote:
ARW wrote:

Then the experts (see Robin's post in this thread) reckon a short spur
of 2.5mm^2 from your cooker switch or the junction box to a socket will
be ok provided you have no bigger than a 32A MCB.

No reckon, it's a fact.

And what constitutes "short" in this instance?



A live to either neutral or earth


Or a live/neutral to a live/neutral on a different circuit.
Won't always trip RCDs but will trip RCBOs, sometimes.
Quite a lot of DIYers understand borrowed neutrals causing trips but are
completely flummoxed when there is a live/live short.

On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.




--
Adam

ARW wrote:

On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.

Did you mean 16mm? I would have thought that would have been ok until
someone rested on a spade on it. But it looks somewhat smaller.


--

Roger Hayter

Roger Hayter wrote:

ARW wrote:

On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.

Did you mean 16mm? I would have thought that would have been ok until
someone rested on a spade on it. But it looks somewhat smaller.

(FAOD I am not asserting that 16mm^2 *would* be adequate without further
information. It was a joke. Alright?)

--

Roger Hayter

On 21/01/2017 16:21, Roger Hayter wrote:
Roger Hayter wrote:

ARW wrote:

On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.

Did you mean 16mm? I would have thought that would have been ok until
someone rested on a spade on it. But it looks somewhat smaller.

(FAOD I am not asserting that 16mm^2 *would* be adequate without further
information. It was a joke. Alright?)


The 16mm T&E installation is the joke:-)


It's a real installation.

If you ever needed an adiabatic equation then that's the time to use
one. As you said "rest a spade on it".

It will end in tears and they will not be mine.


--
Adam

On 21/01/2017 13:57, ARW wrote:
On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.


I enjoyed that, thanks. Really sloppy work. I like to think I would at
least have taken the time to drill a few holes in the board below the
meter so I could say "Blow me, some bugger's nicked the CU & meter tails!"

--
Robin
reply-to address is (intended to be) valid

On 21/01/2017 17:56, Robin wrote:
On 21/01/2017 13:57, ARW wrote:
On 20/01/2017 16:33, Robin wrote:
On 20/01/2017 14:09, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
The kitchen in my newly-(almost) completed extension has a
(professionally installed) 45A radial cooker circuit which currently
terminates in a junction box. I don't intend to install a cooker
but I
do need to power an electric domino hob and a fridge-freezer close to
where the box is situated. Is there any reason why I can't take two
2.5mm cables from the junction box via two switches to two sockets, to
do so?

Yes. But change the MCB to a 20 amp one.


A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur
running to a single socket or twin socket. (It's even shown in Appendix
15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

What do think of this one?

16mm T&E straight into the meter with a 100A 1361 type II fuse for
protection.

http://wiki.diyfaq.org.uk/index.php/File:Equation.jpg

It's about a 20m run of cable mostly just thrown across the floor of a
building site with no mechanical protection to power the site cabin.
It's only mostly because there is the bit where it is just suspended
with a couple of cable ties at each end at just above head height
between the house and the site cabin with no catenary wire.


I enjoyed that, thanks. Really sloppy work. I like to think I would at
least have taken the time to drill a few holes in the board below the
meter so I could say "Blow me, some bugger's nicked the CU & meter tails!"

Oddly enough there was not a meter there last week!


--
Adam