Installing a hob but no oven
 

I've searched around but can't find a clear answer to this; apologies
if the subject is covered somewhere.

In my new kitchen I'm thinking of having a built-in hob but no oven.
The hob will be a small two-ring model, probably ceramic: the specs of
a typical example (by Siemens) are given as Total load 2.9, Maximum
current draw 12kw.

Does a hob like that require its own dedicated circuit? I assume it
can't (or shouldn't) simply be connected into a general ring circuit.
Does the hob have to be connected via a "proper" cooker point, or will
a fused isolating switch leading to a cooker connecting plate be
acceptable?

Many thanks,

Bert
http://www.bertcoules.co.uk

On Sun, 24 Apr 2005 10:25:33 +0100, "Bert Coules"
wrote:

I've searched around but can't find a clear answer to this; apologies
if the subject is covered somewhere.

In my new kitchen I'm thinking of having a built-in hob but no oven.
The hob will be a small two-ring model, probably ceramic: the specs of
a typical example (by Siemens) are given as Total load 2.9, Maximum
current draw 12kw.

Does a hob like that require its own dedicated circuit? I assume it
can't (or shouldn't) simply be connected into a general ring circuit.
Does the hob have to be connected via a "proper" cooker point, or will
a fused isolating switch leading to a cooker connecting plate be
acceptable?

Many thanks,

Bert
http://www.bertcoules.co.uk


hi Bert,
the specs you gave dont add up ? read them again.
2.9 what ? apples oranges
12kW sounds wrong to, is that supposed to be 1 . 2 kW ?
regards
bob

Bert Coules wrote:
In my new kitchen I'm thinking of having a built-in hob but no oven.
The hob will be a small two-ring model, probably ceramic: the specs of
a typical example (by Siemens) are given as Total load 2.9, Maximum
current draw 12kw.

Are you *sure* you've got that right?

Total load 2.9 kW, Max current draw 12 A would be more reasonable.

A 12 kW load would require 50A circuit. Such a hob would be very
unlikely to be found in a domestic kitchen, especially a small one.

Does a hob like that require its own dedicated circuit? I assume it
can't (or shouldn't) simply be connected into a general ring circuit.

It should really have its own circuit, and you might as well install a
30A cooker circuit to allow for a future upgrade to a 4-ring hob at a
later date.

Does the hob have to be connected via a "proper" cooker point, or will
a fused isolating switch leading to a cooker connecting plate be
acceptable?

It requires a double pole isolator within 2m of the hob. A FCU would be
acceptable, but I think it would be better to use a 20A switch on a
16/20A MCB, or a 30A cooker switch on a 30A MCB. You can get 30A
switches the same size as a double socket.

The cooker instructions might state a 16A circuit is required - that's
common amongst European appliances. I'd suggest using a 16A MCB in that
case, but using heavier cable to allow upgrade to a 30A circuit nonetheless.

Owain

In article ,
Bert Coules wrote:
In my new kitchen I'm thinking of having a built-in hob but no oven.
The hob will be a small two-ring model, probably ceramic: the specs of
a typical example (by Siemens) are given as Total load 2.9, Maximum
current draw 12kw.

Does a hob like that require its own dedicated circuit? I assume it
can't (or shouldn't) simply be connected into a general ring circuit.
Does the hob have to be connected via a "proper" cooker point, or will
a fused isolating switch leading to a cooker connecting plate be
acceptable?

The limit for connection to a ring is 13 amps. So multiply volts by amps
for watts. 13 x 230 gives 2990 - let's say 3 Kw.

12Kw will draw - watts divided by volts - so 12,0000
------- = 52 amps
230

That would suggest using 10mm cable.

--
*A closed mouth gathers no feet.*

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

Thanks to everyone for the replies.

Here are the specs, taken directly from the Siemens brochu

Zone rating (kW): Front: 1.2 Back 0.7 - 1.2
Total connected load: 2.9 (obviously kW, though it doesn't
actually say so)
Maximum current draw (kW): 12

On re-reading it, I think there's a misprint in the brochu it seems
pretty obvious that the "kW" designation should appear at the head of
the column for total load, not in the one for maximum current draw.

That makes the two-ring hob, as Owain suggested:

Total load 2.9 kW, Max current draw 12 A

With that rather less scary rating, could the hob be connected into an
existing 30A ring circuit, as long as it was via a properly rated
isolating switch unit?

Thanks again,

Bert
http://www.bertcoules.co.uk

Owain,

Are you *sure* you've got that right?

As you might have seen from my earlier reply, I suspected that there
was a misprint in the Siemens brochure. I think this is now pretty
much confirmed: I just noticed that in the next column the weight of
the hob is given as 5 Amps!

Bert
http://www.bertcoules.co.uk

Bert Coules wrote:
That makes the two-ring hob, as Owain suggested:
Total load 2.9 kW, Max current draw 12 A
With that rather less scary rating, could the hob be connected into an
existing 30A ring circuit, as long as it was via a properly rated
isolating switch unit?

If the hob is connected to a 30A ring circuit, it *must* be connected by
a *Fused* Connection Unit with a 13A fuse.

However the loading on the ring circuit must be considered -- if the
ring is already heavily loaded (kitchen rings usually are, with washing
machine, tumble, dishwasher, kettle etc), it would be wiser to install a
dedicated circuit.

Owain

Owain,

However the loading on the ring circuit must be considered -- if the
ring is already heavily loaded (kitchen rings usually are, with
washing
machine, tumble, dishwasher, kettle etc), it would be wiser to
install a
dedicated circuit.

Clearly, that's good advice. Thanks very much.

Bert
http://www.bertcoules.co.uk

In article ,
Bert Coules wrote:
Are you *sure* you've got that right?

As you might have seen from my earlier reply, I suspected that there
was a misprint in the Siemens brochure. I think this is now pretty
much confirmed: I just noticed that in the next column the weight of
the hob is given as 5 Amps!

IIRC, any appliance designed to be plugged into a normal 13 amp socket
comes with a fitted lead and plug.

But I'd say a two ring hob will be ok to be plugged in.

2.9 kW equates to 12.6 amps at 230 volts, or 12 amps at 240 volts.

--
*I'm not your type. I'm not inflatable.

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

Dave,

But I'd say a two ring hob will be ok to be plugged in.

It seems that way to me. I do take Owain's point about the total
loading of the complete circuit, but I can't see many instances
arising when I'd have both rings going full blast while simultaneously
using a load of other relatively high-rated appliances (which I don't
have room for anyway - which is why I'm installing only a two-ring
hob...)

I'm not your type. I'm not inflatable.

Oh, blow.

Bert
http://www.bertcoules.co.uk