Hi all

I need some advice on a supply for a new oven.

The oven that I'm looking at buying states that it needs a 30amp supply.
I'm proposing to add a 32amp MCB in a spare slot on the RCD side of a split
load CU and run a radial circuit in 6mm cable from the CU to kitchen, approx
15m allowing for routing. Does this sound OK (understand this should be done
by electrician, Part P etc etc)

Thanks

Jim

Jim wrote:

The oven that I'm looking at buying states that it needs a 30amp supply.
I'm proposing to add a 32amp MCB in a spare slot on the RCD side of a split
load CU and run a radial circuit in 6mm cable from the CU to kitchen, approx
15m allowing for routing. Does this sound OK (understand this should be done
by electrician, Part P etc etc)

Sounds ok in principle. No need for this to be on the RCD side of the CU
(in fact there are disadvantages in doing so). You could use 4mm^2 in
this circumstance, although you may as well use 6mm^2 since the price is
not much different, and it gives you the option of running a full
electric cooker off it later should you need.

--
Cheers,

John.

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

"John Rumm" wrote in message
news:Os6dnYKRPulFJWranZ2dnUVZ8tWvnZ2d@plusnet...
Jim wrote:

The oven that I'm looking at buying states that it needs a 30amp supply.
I'm proposing to add a 32amp MCB in a spare slot on the RCD side of a
split load CU and run a radial circuit in 6mm cable from the CU to
kitchen, approx 15m allowing for routing. Does this sound OK (understand
this should be done by electrician, Part P etc etc)

Sounds ok in principle. No need for this to be on the RCD side of the CU
(in fact there are disadvantages in doing so). You could use 4mm^2 in this
circumstance, although you may as well use 6mm^2 since the price is not
much different, and it gives you the option of running a full electric
cooker off it later should you need.

--
Cheers,

John.

Thanks for the reply John. What are the problems with putting the cooker on
the RCD side of the CU ??

Will defintely go with 6mm as have a reel of this sitting in the garage.

Cheers

Jim

"John Rumm" wrote in message
news:Os6dnYKRPulFJWranZ2dnUVZ8tWvnZ2d@plusnet...
Jim wrote:

The oven that I'm looking at buying states that it needs a 30amp supply.
I'm proposing to add a 32amp MCB in a spare slot on the RCD side of a
split load CU and run a radial circuit in 6mm cable from the CU to
kitchen, approx 15m allowing for routing. Does this sound OK (understand
this should be done by electrician, Part P etc etc)

Sounds ok in principle. No need for this to be on the RCD side of the CU
(in fact there are disadvantages in doing so). You could use 4mm^2 in this
circumstance, although you may as well use 6mm^2 since the price is not
much different, and it gives you the option of running a full electric
cooker off it later should you need.

Any reason not to use 6 mm SWA?
Its cheaper than 6 mm T&E on tlc.

I need a 40A cable for a job. 8-)

In an earlier contribution to this discussion,
Jim wrote:

What are the problems with putting the
cooker on the RCD side of the CU ??


It means that if the RCD trips - maybe because of an earth fault in an
external device like a pond pump - you'll loose the supply to the cooker and
may come home to an uncooked Sunday lunch!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Jim wrote:

Thanks for the reply John. What are the problems with putting the cooker on
the RCD side of the CU ??

A cooker is not a portable appliance and hence does not really need RCD
protection - there are not really any fault scenarios (assuming your
house earthing and main equipotential bonds are ok) that could result in
it posing any real shock risk to you that would not be adequately dealt
with via the normal MCB or fused protection.

The oven however will have mineral insulated heating elements. These are
common culprits for causing some earth leakage even when working
correctly. Hence placing one on the RCD side of the CU will just eat
into your leakage budget with no real benefit in return. The worst case
being that it sensitises the RCD enough to cause nuisance tripping
problems.

Will defintely go with 6mm as have a reel of this sitting in the garage.

Good enough ;-)



--
Cheers,

John.

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

On Sat, 05 Apr 2008 19:21:37 +0100, dennis@home wrote:

"John Rumm" wrote in message
news:Os6dnYKRPulFJWranZ2dnUVZ8tWvnZ2d@plusnet...
Jim wrote:

The oven that I'm looking at buying states that it needs a 30amp
supply. I'm proposing to add a 32amp MCB in a spare slot on the RCD
side of a split load CU and run a radial circuit in 6mm cable from the
CU to kitchen, approx 15m allowing for routing. Does this sound OK
(understand this should be done by electrician, Part P etc etc)

Sounds ok in principle. No need for this to be on the RCD side of the
CU (in fact there are disadvantages in doing so). You could use 4mm^2
in this circumstance, although you may as well use 6mm^2 since the
price is not much different, and it gives you the option of running a
full electric cooker off it later should you need.

Any reason not to use 6 mm SWA?
Its cheaper than 6 mm T&E on tlc.

I need a 40A cable for a job. 8-)

By the time you have added the cost of the glands, perhaps also
enclosures for the glands, and short length of 6mm² T&E for connection to
the appliance. The cost saving may well have disappeared.

Then there is the fact that you have to route a fat round cable as
opposed to a medium size flat one which fits in 16x25 trucking.


--
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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

"Ed Sirett" wrote in message
...
On Sat, 05 Apr 2008 19:21:37 +0100, dennis@home wrote:

"John Rumm" wrote in message
news:Os6dnYKRPulFJWranZ2dnUVZ8tWvnZ2d@plusnet...
Jim wrote:

The oven that I'm looking at buying states that it needs a 30amp
supply. I'm proposing to add a 32amp MCB in a spare slot on the RCD
side of a split load CU and run a radial circuit in 6mm cable from the
CU to kitchen, approx 15m allowing for routing. Does this sound OK
(understand this should be done by electrician, Part P etc etc)

Sounds ok in principle. No need for this to be on the RCD side of the
CU (in fact there are disadvantages in doing so). You could use 4mm^2
in this circumstance, although you may as well use 6mm^2 since the
price is not much different, and it gives you the option of running a
full electric cooker off it later should you need.

Any reason not to use 6 mm SWA?
Its cheaper than 6 mm T&E on tlc.

I need a 40A cable for a job. 8-)

By the time you have added the cost of the glands, perhaps also
enclosures for the glands, and short length of 6mm² T&E for connection to
the appliance. The cost saving may well have disappeared.

I wouldn't have thought glands were needed for an internal run where the
earth is the third conductor.
I don't like using the armor as earth as I see corrosion as a problem.
I was just planning on stripping back the armor and shrink wrapping it and
terminating the inner as for T&E.



Then there is the fact that you have to route a fat round cable as
opposed to a medium size flat one which fits in 16x25 trucking.

I did wonder.. I haven't used 6 mm SWA but its only 18 mm dia.
I would have to go somewhere and bend a bit to see.

dennis@home wrote:

I wouldn't have thought glands were needed for an internal run where the
earth is the third conductor.

The proper type of glands must always be used with SWA ("proper
materials and good workmanship by competent persons"). Type BW glands
for indoor work and CW for outdoor terminations exposed to the elements.

I don't like using the armor as earth as I see corrosion as a problem.
I was just planning on stripping back the armor and shrink wrapping it
and terminating the inner as for T&E.

Use of the armour as the CPC (earth) is perfectly satisfactory (subject
to design calculations). If a separate or 3rd-core CPC is used the
armour should still be earthed; it's classed as an
exposed-conductive-part and could become live in the event of a fault
(cable damage) unless earthed.

No glands, armour floating = DIY bodge job = failed Part P inspection =
more ammunition to those who'd like to see DIY-everything banned. Tut tut.

--
Andy

"Andy Wade" wrote in message
...
dennis@home wrote:

I wouldn't have thought glands were needed for an internal run where the
earth is the third conductor.

The proper type of glands must always be used with SWA ("proper materials
and good workmanship by competent persons"). Type BW glands for indoor
work and CW for outdoor terminations exposed to the elements.

I don't like using the armor as earth as I see corrosion as a problem.
I was just planning on stripping back the armor and shrink wrapping it
and terminating the inner as for T&E.

Use of the armour as the CPC (earth) is perfectly satisfactory (subject to
design calculations).

It may be acceptable to the standards but not to me, I have seen what
corrosion does to SWA and I don't want to have to inspect it every year.

If a separate or 3rd-core CPC is used the armour should still be earthed;
it's classed as an exposed-conductive-part and could become live in the
event of a fault (cable damage) unless earthed.

No glands, armour floating = DIY bodge job = failed Part P inspection =
more ammunition to those who'd like to see DIY-everything banned. Tut
tut.

No different to any other bit of metal floating, there are plenty of them in
every house, even those done by experts.
All the metal channel covers in walls to start with. Floating metal work is
not actually dangerous anyway, especially when its insulated as with the
armor.

The design of SWA is such that it is double insulated within the armor just
like T&E is double insulated.
The only problem I can see is if the core isn't restrained at the ends it
could chafe the cores insulation, suitable glued shrink wrap should stop
that.

"dennis@home" wrote in message
...


I need a 40A cable for a job. 8-)

I no longer need a 40A supply.. the appliance has just been delivered and it
doesn't fit!

It doesn't tell you that it needs about 5 inches of space above it in the
loft.. shame really as I want it on the ground floor and I am not getting
the floor up to fit it.

dennis@home wrote:

[SWA armour as CPC]
It may be acceptable to the standards but not to me, I have seen what
corrosion does to SWA and I don't want to have to inspect it every year.

The armour is zinc plated steel and the glands are brass, so there's
certainly scope for electrolytic corrosion if damp gets in. Correct
gland selection and installation should prevent this though. What sort
of severe corrosion have you seen, and in what circumstances?

[Armour not earthed!]
No different to any other bit of metal floating, there are plenty of
them in every house, even those done by experts.
All the metal channel covers in walls to start with.

It is different. The other metalwork you refer to doesn't form part of
a cable. There's specific provision in BS 7671 that allows cable with a
_non-metallic_ sheath to provide fault (formerly indirect contact)
protection - see Reg. 471-09-04 in the 16th ed. or 412.2.4.1 in the
17th. I don't see that this can be applied to SWA where the
supplementary insulation is provided by the bedding layer.

The design of SWA is such that it is double insulated within the armor
just like T&E is double insulated.

Again, BS 7671 is quite clear that T&E cable should not be described as
being of Class 2 (double-insulated) construction or marked with the
double-square symbol. The regs I mentioned above merely state that when
correctly installed it is deemed to satisfy the requirements for
indirect contact / fault protection by Class 2 construction. You can
call that a semantic argument if you like, but the fact is that SWA with
the armour left floating will not pass muster.

--
Andy

"Andy Wade" wrote in message
...
dennis@home wrote:

[SWA armour as CPC]
It may be acceptable to the standards but not to me, I have seen what
corrosion does to SWA and I don't want to have to inspect it every year.

The armour is zinc plated steel and the glands are brass, so there's
certainly scope for electrolytic corrosion if damp gets in. Correct gland
selection and installation should prevent this though. What sort of
severe corrosion have you seen, and in what circumstances?

Rust. The boot was damaged though.
I didn't measure the earth resistance but I don't like rust on contacts.
If you use three core and use one core for earth it doesn't matter if the
armour is earthed from a practical point of view.


[Armour not earthed!]
No different to any other bit of metal floating, there are plenty of them
in every house, even those done by experts.
All the metal channel covers in walls to start with.

It is different. The other metalwork you refer to doesn't form part of a
cable. There's specific provision in BS 7671 that allows cable with a
_non-metallic_ sheath to provide fault (formerly indirect contact)
protection - see Reg. 471-09-04 in the 16th ed. or 412.2.4.1 in the 17th.
I don't see that this can be applied to SWA where the supplementary
insulation is provided by the bedding layer.

The design of SWA is such that it is double insulated within the armor
just like T&E is double insulated.

Again, BS 7671 is quite clear that T&E cable should not be described as
being of Class 2 (double-insulated) construction or marked with the
double-square symbol. The regs I mentioned above merely state that when
correctly installed it is deemed to satisfy the requirements for indirect
contact / fault protection by Class 2 construction. You can call that a
semantic argument if you like, but the fact is that SWA with the armour
left floating will not pass muster.

Passing muster and being safe aren't necessarily the same thing,
unfortunately.

Anyway it doesn't matter now, I can't fit the appliance where I wanted it.
It would have been helpful if the screwfix catalogue had been a bit more
informative.

It was a body drier if anyone is interested.
A 9kw fan heater that you can wire in series with the shower to prevent them
both being on together.

"Man at B&Q" wrote in message
...
On Apr 8, 9:44 am, "dennis@home"
wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to prevent
them
both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

Its OK the council will pay for someone to drive there and help him to dry
himself and then pop the towels in the tumble drier before they drive to the
next person on their list. I am sure that is greener than making it possible
to do it himself.

"PCPaul" wrote in message
. ..
On Tue, 08 Apr 2008 04:27:59 -0700, Man at B&Q wrote:

On Apr 8, 9:44 am, "dennis@home" wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to prevent
them both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

I'd go along with that.

You won't after you read my previous reply. But then its always easy to
speak before thinking.


Have you tried the Dyson 'Airblade' hand driers though? They run on cold
air and create a very high speed, very thin (sub millimetre) plane of air
that you just pull your hands through slowly, once. It sort of scrapes
the water off in one go. Their website (www.dysonairblade.co.uk) says it
uses 1600W for 10s instead of 2400W for 35s+.

That's a big saving!
Probably pay for itself in 10 years or so.

Can't quite imagine what a full body one would feel like, though... the
hand one is somewhere between a tickle and a sting..



It would probably rip the oxygen tubes off. ;-)

"Owain" wrote in message
news:hJSdnav3wsSd92banZ2dnUVZ8tSdnZ2d@plusnet...
dennis@home wrote:
It doesn't tell you that it needs about 5 inches of space above it in the
loft.. shame really as I want it on the ground floor and I am not getting
the floor up to fit it.

Leave it in the back garden and build a shed round it

I would need SWA then. 8-)

On Apr 8, 1:33*pm, "dennis@home"
wrote:
"Man at B&Q" wrote in ...

On Apr 8, 9:44 am, "dennis@home"
wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to prevent
them
both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

Its OK the council will pay for someone to drive there and help him to dry
himself and then pop the towels in the tumble drier before they drive to the
next person on their list. I am sure that is greener than making it possible
to do it himself.

How did he manage before? How will he manage now you've realised the
heater doesn't fit?

MBQ

"Man at B&Q" wrote in message
...
On Apr 8, 1:33 pm, "dennis@home"
wrote:
"Man at B&Q" wrote in
...

On Apr 8, 9:44 am, "dennis@home"
wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to
prevent
them
both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

Its OK the council will pay for someone to drive there and help him to
dry
himself and then pop the towels in the tumble drier before they drive to
the
next person on their list. I am sure that is greener than making it
possible
to do it himself.

How did he manage before?

By having a nurse help him, how do you think?

How will he manage now you've realised the
heater doesn't fit?

By having a council worker drive around.

On 2008-04-08 12:27:59 +0100, "Man at B&Q" said:

On Apr 8, 9:44*am, "dennis@home"
wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to prevent th
em
both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

MBQ

Patio heaters are an absolute requirement for modern day living.
Apparently one can buy diesel ones.

On Apr 8, 7:06*pm, "dennis@home"
wrote:
"Man at B&Q" wrote in ...





On Apr 8, 1:33 pm, "dennis@home"
wrote:
"Man at B&Q" wrote in
...

On Apr 8, 9:44 am, "dennis@home"
wrote:

It was a body drier if anyone is interested.

What's wrong with a towel FFS?

A 9kw fan heater that you can wire in series with the shower to
prevent
them
both being on together.

If ever there was a case for "green" taxes, then this must be high in
the running, just behind patio heaters.

Its OK the council will pay for someone to drive there and help him to
dry
himself and then pop the towels in the tumble drier before they drive to
the
next person on their list. I am sure that is greener than making it
possible
to do it himself.

How did he manage before?

By having a nurse help him, how do you think?

I didn't know, that's why I asked. For all I knew it may have been a
sudden change in his abilities.


How will he manage now you've realised the
heater doesn't fit?

Fair enough.

Having all the facts still doesn't change my attitide towards the
things. I can see thay have a place in a limited set of sircumstances.

MBQ

"Man at B&Q" wrote in message
...


Having all the facts still doesn't change my attitide towards the
things. I can see thay have a place in a limited set of sircumstances.

Well you haven't seen all the facts yet.

How does using 9kw for 3 minutes compare with laundering the towels you
would use instead?
I suspect that the dryer may be greener.