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Topic Title: am i wrong ??
Topic Summary: connecting an oven
Created On: 16 May 2018 01:22 PM
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 16 May 2018 01:22 PM
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garywwess

Posts: 60
Joined: 03 April 2017

We have recently had a customer complaint, an electrician had informed them that we had "incorrectly" connected the built in oven, (2.2kw fan assisted) this was on a new build, our std practice is --- 6mm circuit to 45a switch, 6mm to cooker outlet, as some of the offered ovens are 2.2kw, others heavier duty drawing more current, we use a 16a mcb at the consumer unit but leave a 32a alongside for future upgrading.. his problem was "it should have been connected via a 13a fcu" we purposely don't do this as we have a stock of "melted fcu`s" that have had to have the fuses chiselled out.. also whereas a cooker outlet is surface mounted a fcu is recessed and the cables are more likely to sustain damadge due to compression... but in the instruction booklet it does show a fcu.. firstly, can we be forced to adopt this method because it has been asked for by the manufactures? second, is a fcu even designed to accept a cable as large as 6mm ? ..
gary
 16 May 2018 01:32 PM
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broadgage

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On strictly electrical grounds, I would say that a 2.2KW oven on a 16 amp MCB is just fine.
The oversized cable and switch though not required, are good practice to cater for changing needs.

The only possible pitfall would be suppliers instructions, If these state that connection is to be made in a certain way, then these instructions should be followed*.
Seems an unlikely instruction though, remembering that these ovens are presumably sold in countries that don't use UK style fused connection units.


*It is IMHO acceptable to ignore instructions if they are clearly daft, mistranslated, or not applicable to UK conditions. In general however such instructions should be followed.
 16 May 2018 01:37 PM
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Zoomup

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Surely a 2.2kW oven does not need a 6.0mm2 cable. A 1.25 or 1.5mm2 flex would serve. I have in the past hidden a non switched fused connection unit at low level behind an oven in a kitchen unit. But some will say that overload protection is not required as the load is fixed. Just fault protection is required. Good quality switched fused connection units should not melt if loaded at 2.2kw. I have a 13 Amp switch fused connection unit supplying my 3kW immersion heater (I know, I know).

Z.
 16 May 2018 02:03 PM
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AJJewsbury

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second, is a fcu even designed to accept a cable as large as 6mm ?

BS 1363 sockets are I think required to accept 3off 2.5mm2 or 2off 4mm2 conductors as a minimum, so presuming that the requirement for FCUs is the same, they should be fine with a single 6mm2 (on the incoming side at least).

but in the instruction booklet it does show a fcu.. firstly, can we be forced to adopt this method because it has been asked for by the manufactures?

I'd contact the manufacturer from advise - it seems very unlikely that any CE marked appliance would in any way be unsafe on a C16 MCB or smaller - I'd expect them to be able to confirm your approach as being an acceptable alternative. But the bottom line is that BS 7671 does require us to take account of manufacturer's instructions.
- Andy.
 16 May 2018 02:10 PM
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mikejumper

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I think the 13A FCU thing has probably more to do with catering for the possibility that an oven of this rating may be connected to a RFC.

What you have done in my view is sensible because it allows for a range of appliance ratings. Also, it complies with guidance that ovens rated over 2kW should be on their own radial circuit.
 16 May 2018 02:14 PM
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chrispearson

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Perhaps the concern is that anything heavier than a 13A fuse would not adequately protect the oven's flex?
 16 May 2018 02:15 PM
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garywwess

Posts: 60
Joined: 03 April 2017

Originally posted by: Zoomup

Surely a 2.2kW oven does not need a 6.0mm2 cable. A 1.25 or 1.5mm2 flex would serve. I have in the past hidden a non switched fused connection unit at low level behind an oven in a kitchen unit. But some will say that overload protection is not required as the load is fixed. Just fault protection is required. Good quality switched fused connection units should not melt if loaded at 2.2kw. I have a 13 Amp switch fused connection unit supplying my 3kW immersion heater (I know, I know).

Hi Zoomup..
the 6mm supply is as std on all our houses, this is just the final connection depending on which type of oven they use.. it is the requirment to change the std cooker outlet and do a "bodge job" of trying to fit the 6mm into the exsisting metal box & fcu that is irking me, and if we do fit one.. and somone puts a larger oven in later.. "ohhh missus, those cowboys have fitted a likle connection thing instead of an outlet like wot us proper sparkies doos"

Z.
 16 May 2018 02:22 PM
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dustydazzler

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Plug and socket
 16 May 2018 03:02 PM
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Zoomup

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Originally posted by: garywwess

Originally posted by: Zoomup



Surely a 2.2kW oven does not need a 6.0mm2 cable. A 1.25 or 1.5mm2 flex would serve. I have in the past hidden a non switched fused connection unit at low level behind an oven in a kitchen unit. But some will say that overload protection is not required as the load is fixed. Just fault protection is required. Good quality switched fused connection units should not melt if loaded at 2.2kw. I have a 13 Amp switch fused connection unit supplying my 3kW immersion heater (I know, I know).



Hi Zoomup..

the 6mm supply is as std on all our houses, this is just the final connection depending on which type of oven they use.. it is the requirment to change the std cooker outlet and do a "bodge job" of trying to fit the 6mm into the exsisting metal box & fcu that is irking me, and if we do fit one.. and somone puts a larger oven in later.. "ohhh missus, those cowboys have fitted a likle connection thing instead of an outlet like wot us proper sparkies doos"



Z.


The Zoom solution. Have the 6.0mm2 T&E terminating in a deep dual outlet metal box behind the oven position. One half has a standard cooker connection unit fed by the 6.0mm2, the other half has a fused connection unit or 13 Amp socket, both linked together with a bit of 2.5mm2. Sorted, all possibilities covered.

Z.
 16 May 2018 03:19 PM
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Zoomup

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This is not the first time that installers have wondered about oven installation. http://www.youtube.com/watch?v=6yurCsLnbXI

Z.
 16 May 2018 03:35 PM
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mapj1

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What you have done is not wrong - 'take account of makers instructions' is not the same as 'follow blindly without understanding'.
I suspect you are meeting someone who likes to be given a recipe, instead of having to plan.
It may be cost effective for you to demur, but there is no technical reason to do so.
Perhaps they'd like to overlay the breaking curves for a 16a MCB and a 13A fuse, and tell you which they think goes first.
Fuses here
MCB here

by my reckoning the MCB line fits between the go and no-go lines of the 13A fuse for sensible fault levels.

-------------------------
regards Mike
 16 May 2018 03:44 PM
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garywwess

Posts: 60
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Hi Z.. If it was just the odd house it would be no problem.. but over hundreds of houses thats a big hit to my profit margin..
 16 May 2018 03:53 PM
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dustydazzler

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Originally posted by: Zoomup

This is not the first time that installers have wondered about oven installation. http://www.youtube.com/watch?v=6yurCsLnbXI



Z.


Plug top ..... ??
 16 May 2018 04:36 PM
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garywwess

Posts: 60
Joined: 03 April 2017

. I have since had an independent electrician look at the situation and he has confirmed what the Currys electrician said that yes by law you should have a fused spit for a 2.3 kilowatt oven and connecting straight into the mains is dangerous and should a fire have occurred I have confirmed with my Insurance Company that my house insurance would have in fact been void. As you can imagine I am furious and would like to give you the opportunity of sorting this out before I take matters further. Not only am I hundreds of pounds out of pocket but I am concerned that the electrician who fitted our oven has said that all the others on Site have been wired into the mains also thus making this a huge problem for everyone else. I would very much appreciate an explanation from yourselves and not the electrician. hmmmm, not sure if he thinks im a trustworthy person..
 16 May 2018 04:43 PM
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dustydazzler

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Give em what they want

If it's a swi fused sour then so be it
 16 May 2018 04:49 PM
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garywwess

Posts: 60
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if only it was that easy, he is insisting that his first oven had broken down " because it was wired into the cooker outlet instead of a fused spur ??"
 16 May 2018 06:10 PM
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ArduinoXR

Posts: 101
Joined: 16 August 2017

Originally posted by: garywwess

if only it was that easy, he is insisting that his first oven had broken down " because it was wired into the cooker outlet instead of a fused spur ??"


Tell him he's wrong then.

Christ, every day there's always at least one thing to remind myself of how happy I am to be off my tools.
 16 May 2018 06:12 PM
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mapj1

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I have since had an independent electrician look at the situation and he has confirmed what the Currys electrician said that yes by law you should have a fused spit for a 2.3 kilowatt oven and connecting straight into the mains is dangerous and should a fire have occurred I have confirmed with my Insurance Company that my house insurance would have in fact been void.

As I understand it the customer is mistaken, and you have not connected direct to the mains, but rather via a 16A MCB, and some generously oversized cable
Is this correct?

If so I am not aware of any law or statutory instrument, or indeed any wiring regulation that is breached by using an MCB in place of a fuse in this way, and you can have that from a consultant electrical and electronic engineer, albeit one who does not go near domestic these days, except his own.

Do you belong to a trade organisation (Niciec /Napit) ? if you can get their technical folk on-side their opinion may hold more weight than the shop assistant at Currys or whatever.
What went wrong with the oven may quite possibly be due to poor handling or installation, we cant see it, but not the ADS aspect.

-------------------------
regards Mike
 16 May 2018 06:23 PM
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colinhaggett

Posts: 499
Joined: 08 July 2004

Your oven installation is extactly the same as mine. I've yet to see oven instructions that ask for a switched fuse spur. So your best bet is to download the oven instructions of the one you fitted highlight the connection requirements and send it to them.
To be honest your going to get these complaints it's just the way the world is now.
 16 May 2018 06:29 PM
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dustydazzler

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Some people get all confused about integrated appliance wiring ...

They don't see a plug socket or switched spur and they suddenly get all anal saying it shouldn't be wired 'directly' into the mains

My intergrardd oven asks for a 230 volt 16 amp supply and shows a little picture of the oven plugged into a wall socket
IET » Wiring and the regulations » am i wrong ??

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