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Topic Title: Domestic ovens
Topic Summary: Diversity/manufacturers instructions/regs
Created On: 09 April 2014 06:43 PM
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 09 April 2014 06:43 PM
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ady1

Posts: 766
Joined: 19 April 2005

Kitchen refurb.
Kitchen company supplies 2 x 16A single ovens and one combi 20A
So how's about a 32A breaker, a 6mm cable, a 45a adjacent switch and 3 x 2.5 T&E's ready to connect to the appliaces ??
Yes i'm playing devils advocate here

Regards
Ady

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Resistance is futile.
 09 April 2014 07:08 PM
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OMS

Posts: 19592
Joined: 23 March 2004

Well, it's up to the designer to make an assessment of the load and select cables accordingly.

Personally speaking, I wouldn't be overly concerned with the approach

If memory serves, a 45A DP switch in accordance with BS EN 60669 will accept 3 x 2.5mm2 conductors although that specific grouping isn't listed within the product standard.

A singe point of isolation is acceptable for more than one appliance.

Ideally, I might be tempted to put in 2 x 32A circuits (one for the two ovens and the other for the hob)

A check on each appliance to see the manufacturers recommendations on protection might be worthwhile - but in principle I don't see a real problem

Regards

OMS

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Failure is always an option
 09 April 2014 07:25 PM
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alanblaby

Posts: 356
Joined: 09 March 2012

I've done similar twice recently.
Something like a 39 Amp total rating for 2 cooking appliances - oven and separate hob, I put them on a single 32A circuit.

I put one query on here about the Manufacturers instructions, 'MUST be connected with a 6mm T+E cable' was the instruction IIRC.

I asked at the next NAPIT Trade Assn. meeting, all agreed the Manufacturers Instructions would not take preference when it could be shown that the method you did use was as safe, in my case using a 4mm T+E cable, instead of the required 6mm.
 09 April 2014 07:28 PM
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geoffsd

Posts: 338
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Originally posted by: ady1
Yes i'm playing devils advocate here

Why have they used 6mm² cable ?
 09 April 2014 07:30 PM
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perspicacious

Posts: 7199
Joined: 18 April 2006

"using a 4mm T+E"

Lucky to find a customer who doesn't mind seeing it clipped to the surface

Regards

BOD
 13 April 2014 09:12 PM
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antric2

Posts: 1052
Joined: 20 October 2006

Click do a great multi connection box for cookers rated at 50A.
It has two outlet connections that both take upto 10mm if you wanted to allow multiple appliance connection.
Regards
Antric
 13 April 2014 09:26 PM
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daveparry1

Posts: 6162
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I agree Antric, they are very good, I just wish I could get my local supplier to stock them, I usually have to get them on-line.
 13 April 2014 09:38 PM
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antric2

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Originally posted by: daveparry1

I agree Antric, they are very good, I just wish I could get my local supplier to stock them, I usually have to get them on-line.


Evening Dave,
Some of my main suppliers have had a bit of trouble with supplies from Scolmore who brand Click.
They are apparently raising the minimum order value and are being a bit picky who they supply which is a shame cos they have agreat 50A shower pull switch which I have had to order myself on line for my last batch because of local supply probs.
Regards
Antric
 02 May 2014 08:34 PM
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ady1

Posts: 766
Joined: 19 April 2005

Just to pick this one up again....
The manufacturers stated the appliances fuse ratings at 16, 16 and 20A, but in this scenario it's 32A ???

Regards
Ady

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Resistance is futile.
 02 May 2014 08:53 PM
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daveparry1

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Well 32 amp is a standard cooker circuit isn't it Ady so I can't see what else you could do unless you put dedicated circuit's in for each appliance!
I've wired plenty of ovens into 32 amp cooker circuit's where the recommended fuse size is 16 amps.
That doesn't make it right of course but I can't see it's practicable to do it any other way, unless of course it's just the one appliance in which case the breaker could be changed for a 16 amp one.
 02 May 2014 09:13 PM
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ady1

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Thanks Dave
I agree, yet still I wonder if it would be deemed compliant. Particularly as a standard cooker circuit is 6mm all the way, although nowadays the appliances often have a 1.5 HOV flex fitted. Is it adhering to manufacturers specifications (and again they also gave the connected load 3k, 3K and 3.5K).
All a bit heavy for a Friday night

Regards
Ady

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 02 May 2014 09:15 PM
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sparkingchip

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" Ideally, I might be tempted to put in 2 x 32A circuits (one for the two ovens and the other for the hob) "

Two single ovens and hob, if it's a Siemens induction hob three 1.5mm T&E cicuits with a B16 upfront of each would possibly be sufficent.

Andy
 02 May 2014 09:41 PM
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geoffsd

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If the manufacturer specifies a 16A fuse that will be because that's what they use in Europe and that's what the flex rating is.

If they specify a 16A supply that's what it requires to work properly.


32A MCB and 4mm cable (method C) is good for up to 15kW with diversity and integral socket in the switch.

6mm is/was only used because of 30A 3036 derating factor.
 03 May 2014 03:49 PM
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broadgage

Posts: 1282
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IMO, if the supplier says to use a 16 amp circuit then that is what you should do.
I would not normally connect an appliance to an OCPD of twice the recomended value.
Any internal fault or failure of the appliance will "make a bigger bang" with greater risk of fire, property damage or injury.

Would you consider it correct to connect say a washing machine directly into a 32 amp ring or radial circuit ?
Or how about two washing machines and a dryer on a 40 amp circuit ?

Surely not ! presuming standard type domestic appliances intended for use on 13/15/16 amp circuits.
 03 May 2014 08:52 PM
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geoffsd

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Originally posted by: broadgage
IMO, if the supplier says to use a 16 amp circuit then that is what you should do.

If they state that they mean a minimum supply for operation of the appliance.

I would not normally connect an appliance to an OCPD of twice the recommended value.

The 'OC' in your statement is the relevant part. Cookers do not require OC protection.

Any internal fault or failure of the appliance will "make a bigger bang" with greater risk of fire, property damage or injury.

That will be fault current and the internal wiring will be its own fuse.

Would you consider it correct to connect say a washing machine directly into a 32 amp ring or radial circuit ?

A washing machine may cause OC so it has a 13A fuse in the plug to protect the flex and likely a fuse inside if required.

Or how about two washing machines and a dryer on a 40 amp circuit ?

Your questions are not relevant to cookers and the thread.

Would you connect a 20W lamp directly to a 6A circuit - or a 16A circuit as with the oven lamp?

OCPD devices are for the protection of the cable.
If the appliance requires specific OC protection the manufacturer will have fitted internal fuses.

Nearly every cooker in the country will be on 30/32A circuit.
 04 May 2014 10:34 AM
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broadgage

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I can not agree, in general that it is acceptable to connect an oven or other appliance to a larger than recomended OCPD.

If the supplier states that a 16 amp OCPD should be used, then IMO the instruction should be followed.
If however the instructions state that 16 amps is the MINIMUM, then of course larger is fine.

Many cookers are on 30/32 amp circuits and this is fine and normal practice provided that it was designed for such use. Most full size cookers are intended for 32 amp circuits and this is reflected in the instructions.

I would have no concerns connecting a 20 watt lamp to a standard lighting circuit of 6 amps, this is normal practice.
Neither would I be worried about a lamp built into an oven or other appliance, provided that the appliance was CE marked and was installed as instructed.
 04 May 2014 03:26 PM
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geoffsd

Posts: 338
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Originally posted by: broadgage
I can not agree, in general that it is acceptable to connect an oven or other appliance to a larger than recomended OCPD.
If the supplier states that a 16 amp OCPD should be used, then IMO the instruction should be followed.

In that case it will be because the flex is rated for 16A and because in Europe they have 16A circuits.
If you account for fault current or, if necessary, replace with larger flex it will be fine.

If however the instructions state that 16 amps is the MINIMUM, then of course larger is fine.

It is unlikely they will include the word minimum.

Many cookers are on 30/32 amp circuits and this is fine and normal practice provided that it was designed for such use. Most full size cookers are intended for 32 amp circuits and this is reflected in the instructions.

It is because they have more elements.
You will find no difference in the internal wiring.
An oven is just a cooker without a hob.

I would have no concerns connecting a 20 watt lamp to a standard lighting circuit of 6 amps, this is normal practice.

Why is that with the reservations you have?

Neither would I be worried about a lamp built into an oven or other appliance, provided that the appliance was CE marked and was installed as instructed.

It will not be wired with 4mm conductors.


What about a 7kW shower on a 50A circuit?
 04 May 2014 03:54 PM
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daveparry1

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I think one of the problems here Geoff is that many people don't understand the difference between short circuit protection and over current protection!
 04 May 2014 04:55 PM
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phantom9

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Joined: 16 December 2002

Scolmore head office is about 2 miles down the road from me but makes no difference, they won't serve personal customers, only wholesalers.
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