We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.

The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:

9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall.

Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs? And if I did, any
idea what it would cost? We're at the east end of Berkshire.

Thanks

Andy

On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density


How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall.

http://wiki.diyfaq.org.uk/index.php?title=Cable


Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs?

Is someone forcing you to do it? Lots of diyers just replace their fuseboxes when necessary.


And if I did, any
idea what it would cost?

You can get populated CUs for £100 or less.


NT

On 16/12/2012 19:44, wrote:
On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density


I was hoping someone would say "Oh, that's the standard xxxx cable"

As I said it's a little over 9/64ths.


How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall.

http://wiki.diyfaq.org.uk/index.php?title=Cable

doh



Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs?

Is someone forcing you to do it? Lots of diyers just replace their fuseboxes when necessary.


If I can get a bigger fuse (or if 30 is enough) that's not a problem. As
I understand the regs though I won't be allowed to replace the box.


And if I did, any
idea what it would cost?

You can get populated CUs for £100 or less.


That won't be the half of upgrading a 30yo house especially as part P
etc. means I'll be forced to contract it out. Or am I wrong there too?

Andy

On 16/12/2012 22:27, Andy Champ wrote:
On 16/12/2012 19:44, wrote:
On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density


I was hoping someone would say "Oh, that's the standard xxxx cable"

We would if we knew what you were talking about...

As I said it's a little over 9/64ths.

What is? The diameter of one strand, of all the strands, all the strands
and the inner insulation, or the whole cable including outer insulation?

Chances are its adequate for the size of fuse protecting it.

That won't be the half of upgrading a 30yo house especially as part P
etc. means I'll be forced to contract it out. Or am I wrong there too?

Part P does not force you to contract it out, you could DIY. If you DIY
then you should submit a building notice to cover the work. Needless to
say the number of people who actually do that is a nice round number!

If you change a CU there is no requirement to upgrade the whole house to
the 17th edition. Any new work you do would need to comply with it. So
the CU itself, and the main equipotential bonding as a minimum. There
may be additional work to do if the inclusion of RCDs on circuits
previously unprotected shows up long standing faults that had previously
not been visible.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 16/12/2012 23:33, John Rumm wrote:
On 16/12/2012 22:27, Andy Champ wrote:
On 16/12/2012 19:44, wrote:
On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density


I was hoping someone would say "Oh, that's the standard xxxx cable"

We would if we knew what you were talking about...

As I said it's a little over 9/64ths.

What is? The diameter of one strand, of all the strands, all the strands
and the inner insulation, or the whole cable including outer insulation?


The strands as a bunch.

Chances are its adequate for the size of fuse protecting it.


Well, the fuse is 30A, and the cooker... oh. Right. You covered that
one already

That won't be the half of upgrading a 30yo house especially as part P
etc. means I'll be forced to contract it out. Or am I wrong there too?

Part P does not force you to contract it out, you could DIY. If you DIY
then you should submit a building notice to cover the work. Needless to
say the number of people who actually do that is a nice round number!




I must admit the 100A feed into the box with no switch does make me a
little nervous. I like to turn these things off.

If you change a CU there is no requirement to upgrade the whole house to
the 17th edition. Any new work you do would need to comply with it. So
the CU itself, and the main equipotential bonding as a minimum. There
may be additional work to do if the inclusion of RCDs on circuits
previously unprotected shows up long standing faults that had previously
not been visible.


I'm pretty sure there are no odd earth leaks, nor on the live side. I
don't of course know whether there are cross links on neutral - in fact,
I wouldn't be at all surprised to fine one in the lighting which has a
3-way switch controlling the outside light, hall light and landing light.

Thanks again

Andy

On 17/12/2012 20:34, Andy Champ wrote:
On 16/12/2012 23:33, John Rumm wrote:
On 16/12/2012 22:27, Andy Champ wrote:
On 16/12/2012 19:44, wrote:
On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density


I was hoping someone would say "Oh, that's the standard xxxx cable"

We would if we knew what you were talking about...

As I said it's a little over 9/64ths.

What is? The diameter of one strand, of all the strands, all the strands
and the inner insulation, or the whole cable including outer insulation?


The strands as a bunch.

Be easier to measure one strand, work out its area and then multiply up.
Saves guessing on the wasted space in the bundle.


Chances are its adequate for the size of fuse protecting it.


Well, the fuse is 30A, and the cooker... oh. Right. You covered that
one already

That won't be the half of upgrading a 30yo house especially as part P
etc. means I'll be forced to contract it out. Or am I wrong there too?

Part P does not force you to contract it out, you could DIY. If you DIY
then you should submit a building notice to cover the work. Needless to
say the number of people who actually do that is a nice round number!




I must admit the 100A feed into the box with no switch does make me a
little nervous. I like to turn these things off.

The normal solution is to pull the main fuse.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sunday, December 16, 2012 10:27:44 PM UTC, Andy Champ wrote:
On 16/12/2012 19:44, wrote:
On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:

We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.
The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:
9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Less if its stranded, you don't get 100% packing density

I was hoping someone would say "Oh, that's the standard xxxx cable"
As I said it's a little over 9/64ths.

How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall..

http://wiki.diyfaq.org.uk/index.php?title=Cable

doh

Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs?

Is someone forcing you to do it? Lots of diyers just replace their fuseboxes when necessary.

If I can get a bigger fuse (or if 30 is enough) that's not a problem. As
I understand the regs though I won't be allowed to replace the box.

And if I did, any
idea what it would cost?

You can get populated CUs for �100 or less.

That won't be the half of upgrading a 30yo house especially as part P
etc. means I'll be forced to contract it out. Or am I wrong there too?
Andy

I think you've missed the point.

But unless you're installing something commercial its moot anyway, you shouldnt need more than a 30A circuit.


NT

Andy Champ wrote:
We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.

The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:

9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered
wall.
Will I be able to get bigger fuses for my old Wylex 8104 box, or will
I be forced to upgrade the whole house to 17th regs? And if I did, any
idea what it would cost? We're at the east end of Berkshire.

A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(



--
Adam

On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

Andy

On 16/12/2012 22:24, Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

Andy

IMHO you'd be a complete idiot to install any electric hob other than
induction. So chuck that "probably" out. Decision made.

--
Rod

On 16/12/2012 22:27, polygonum wrote:
IMHO you'd be a complete idiot to install any electric hob other than
induction. So chuck that "probably" out. Decision made.

If the cables won't take it we stay with gas.

Andy

On Sun, 16 Dec 2012 23:18:16 +0000, Andy Champ wrote:

IMHO you'd be a complete idiot to install any electric hob other than
induction. So chuck that "probably" out. Decision made.

If the cables won't take it we stay with gas.

Good grief you have gas and want to change to electric, why FFS?

Electric hobs are terrible things to cook on and I've cooked on open
ring, ceramic and solid hot plate. Of all of them open ring is probably
the best but it's not as good as gas, next is ceramic (just don't spill
*anything*), bottom is solid hot plate more thermal inertia than the QE2.

We don't have mains gas here so torn between getting propane and a gas
hob or sticking with lecky in the form of an induction hob. But I've only
heard (glowing) reports about induction, and of course showrooms etc
don't have induction hobs wired in, a pan and half a pint of milk to play
with or a thick sweet sauce that needs gently reducing over 20 mins not
caramelising on the bottom of the pan the moment you stop stiring it...

--
Cheers
Dave.

On 16/12/2012 22:24, Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

http://wiki.diyfaq.org.uk/index.php?title=Diversity




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 16/12/2012 23:27, John Rumm wrote:
On 16/12/2012 22:24, Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

http://wiki.diyfaq.org.uk/index.php?title=Diversity


:O

So no-one ever puts all the rings on at once? 30% seems remarkably low.
(The idea of diversity on a ring main, which might have one heater, and
angle grinder, and a dozen assorted chargers makes more sense)

However... if that's what they say, that's what we can do. I assume that
a hob-and-oven is treated as one unit? It will certainly be used as one.

Thanks everyone

Andy

On 17/12/2012 20:30, Andy Champ wrote:
On 16/12/2012 23:27, John Rumm wrote:
On 16/12/2012 22:24, Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

http://wiki.diyfaq.org.uk/index.php?title=Diversity


:O

So no-one ever puts all the rings on at once? 30% seems remarkably low.

The rings are thermostatically controlled though - so even with
everything on at once, you won't be drawing the peak current - or at
least not for long enough to trip the MCB (and you already know the MCB
will protect the cable).

(The idea of diversity on a ring main, which might have one heater, and
angle grinder, and a dozen assorted chargers makes more sense)

However... if that's what they say, that's what we can do. I assume that
a hob-and-oven is treated as one unit? It will certainly be used as one.

Well I have measured my (all electric) hob and oven running under "heavy
load", and the reality is it rarely gets above 20A in use.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Dec 16, 10:24*pm, Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:

A 30A or 32 A circuit is usually appropiate for household or similiar
cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

Andy

What you have missed is diversity factor, ie an assumption is made
that not all the hotplates/ovens are in simultaneous use. Even when
on they only run intermittantly.

Diversity factor is applied at many points in an electrical supply
system.

In the UK (230v) every Kw needs 4.3 amps.
So your 30a supply is good for 7Kw continuous.
30a is the norm for a domestic cooker,

Andy Champ wrote:
On 16/12/2012 20:20, ARW wrote:
A 30A or 32 A circuit is usually appropiate for household or
similiar cookers of rating up to 15kW - unless your name is Mr B:-(

We're looking at a dual-oven under hob unit, and a separate hob,
probably induction.

But 15Kw at 30A needs 500 volts in my book... looks to me as if I need
60. What have I missed?

As John Rumm said - diversity. For a cooker the fuse you need is = 10A +
((full load of cooker - 10A) x 0.3).

So a 12kW cooker can draw 12000/230 = 52.17 Amps. And 10 + ((52.17 - 10) x
0.3)) = 22.65 Amps. And you have to add another 5 amps if the cooker switch
has a socket.

--
Adam

On 16/12/2012 18:45, Andy Champ wrote:
We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.

The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:

9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Per strand?

How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall.

Installation method C mostly by the sounds of it. 6mm^2 ought to be
adequate for a 30A circuit.

Remember you can apply diversity to the cooker load when sizing the
supply. Use 10A + 30% of remaining full load current + 5A if a socket is
fitted to the cooker point.

So say the total cooker is 12kW, that gives you 12,000/230 = 52A peak
load. 10 + 0.3 x (52 - 10) = 26.6A diverse load.

Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs? And if I did, any
idea what it would cost? We're at the east end of Berkshire.

Unless you are fitting a seriously commercial sized cooker, you are
unlikely to need it.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , John
Rumm writes
On 16/12/2012 18:45, Andy Champ wrote:
We're looking at replacing out gas hob with an electric one. Obviously
the supply is a question. It's got a 30 amp fuse (yes, fuse!), and
probably has had since the house was built; I wonder whether the cable
can stand an upgrade.

The cable feeding the cooker point has 5 strands and I measure it as a
little over 9/64ths diameter (I have some old tools!) which would seem
to indicate 10mm^2 cable:

9/64ths - 3.6mm diameter - 1.8mm radius - 10mm^2 area.

Per strand?

How much power can I push through it? AFAIK it's either in free air
(it's on top of insulation in one place) or buried in a plastered wall.

Installation method C mostly by the sounds of it. 6mm^2 ought to be
adequate for a 30A circuit.

Remember you can apply diversity to the cooker load when sizing the
supply. Use 10A + 30% of remaining full load current + 5A if a socket
is fitted to the cooker point.

So say the total cooker is 12kW, that gives you 12,000/230 = 52A peak
load. 10 + 0.3 x (52 - 10) = 26.6A diverse load.

Will I be able to get bigger fuses for my old Wylex 8104 box, or will I
be forced to upgrade the whole house to 17th regs? And if I did, any
idea what it would cost? We're at the east end of Berkshire.

Unless you are fitting a seriously commercial sized cooker, you are
unlikely to need it.

5 strands would be a very odd cable. Are you sure somebody has not
clipped out two strands to get it to fit a terminal?

From a 1967 diary... 0.0145"2 is 7/.052" and the current rating (13th.
edition) was 43 amps for twin cable.

Next size down was 0.01"2 (7/.044") and 36 amps.


--
Tim Lamb

On 16/12/2012 22:59, Tim Lamb wrote:
5 strands would be a very odd cable. Are you sure somebody has not
clipped out two strands to get it to fit a terminal?

Good thought, I'll double check that. Seven bundle so much nicer.

Andy

On Sunday, December 16, 2012 6:45:07 PM UTC, Andy Champ wrote:
We're looking at replacing out gas hob with an electric one.

You do not say if a re-wireable fuse, although if a 10mm cable should still be fine. Measure the width of the cable sheath, or the diameter of the insulated core - you can tell if something is say 6.8mm v 8.6mm as it were.

6mm cable for 32A RCBO/MCB for 15.7kW cooker (2 oven, silly power grill, 4 hob with 2 high kW high speed elements... and an oven light).

You do not need to upgrade your cable or fuse from 30A even for an electric cooker, which has a far higher kW rating before application of Diversity.