HELP...Kitchen wiring inadequacies??.

[Ceekay]

Sorry guys I'm sure these points have been raised before but been busy searching.

I have been sent a diagram by the shop where we purchased our kitchen for the electrical wiring requirements and positions. I am a electrician to the 17th edition by trade but it's not my every day job nowadays so I'm questioning myself and require some confirmation.

One of the items is a 7KW induction hob for the island and the drawing states a 2.5mm cable to the cuboard under the hob??. This is scary to me as I work this out at around 28A which I believe is around the max the cable could carry even without any factoring taken into consideration? There is some led lighting also on the island which I take they will supply from this cable but obviously that will be minimal (I take it this would need to be fused down?) but more importantly a 13A pop up socket has also been added to the island and therefore had just put this part of the installation well beyond what they have originally stated.

The second major point is the ovens and two of them. One is a standard fan oven rated at 3.45Kw and the other is a smaller microwave combination oven rated at 3.6KW so if im correct both together are roughly 7KW and therefore roughly 28A? On the drawing they are showing 1 standard 13A double socket outlet! Surely just one of these item exceeds the maximum as even a double outlet its max load is still 13A or 3KW there abouts no matter how many outlets you have as far as I'm aware they are still only rated 13A. So my point is that one oven is slightly over but the two ovens are definitely a no no even if they were to have plug tops on which as suggested by the shop may be the case? Not sure how an oven rated at 3.6KW can possibly have a plug on?

Thirdly the drawing states a 2.5mm cable to be left in cupboard below sink for both a 2.5Kw dishwasher and also a instant hot water tap which states it needs a 10A supply but is rated at 1.5Kw? These two items should be fine if they are using say a 20A putlet plate but I have been told to leave a cable as on the island so not sure?

Normally I would place a double pole switch for the dishwasher above the worktop and not sure where the local cooker point isolators will be for the ovens and hob? Is it ok to place these within a cupboard especially the under sink position? I also take it they will tap off at various points for the led lighting but as far as I'm aware this would need to be a fused spur downrated to 3A?

Anyway I have added the so called plans below and would really appreciate your help as I think it must be me going insane?

Many thanks, Keith

 

[telectrix]

what you could do is fit a 45A isolator for each cooking appliance and wire from that to a sinle 35mm back box. wago the cable ends, then fit either a cooker outlet or a single socket, as the case may be when the appliances arrive.

 

[Midwest]

Thanks again chaps much appreciated but I think you will find that the whole purpose of this post was because I disagreed with the drawings that were sent to me and wanted to confirm this so I could wire this as per most of the advice so the general confirmation is what I was after although if I place 2 45A isolators in for the ovens and the fitter turns up with plug tops on them it may void the warranty to cut them off?

Also not had any reply's really about any of the other problems mentioned as it seems to be all concentrated around the ovens? Any advice re the hob/socket on the island or the other points?

Many thanks

I did a rather comprehensive (if I say so myself ) poll of manufactures about cutting off their moulded plugs. There was only one (unfortunately can't remember who!) of several manufactures who said cutting off the plug would void the warranty. It's generally the 'fitters' aren't electricians, so are not 'qualified' to connect cables to FCU etc, only plug a cable into a socket (if that is what is supplied).

As per the induction hob, you've been shown the diversity calculus and made your own design calculations and don't appear to be happy with the suggested cable size, then your should decide the cable size, not the kitchen company?

PS, don't have a pop up socket, there're pants!

 

[telectrix]

+ 1 for pop-up sockets being crap.

 

[Ceekay]

Thanks again.

Good idea with the 45A connection points then a back box for either connecting a socket face or an fcu but another slight problem is that there is nowhere to put any switched items as the cupboards are boxed in floor to ceiling so only option would be to place inside the top cupboard above the ovens or quite a distance away else where in the kitchen. What do you think?

Just wanted assuring about the induction hob really as they have stated a 2.5mm cable but at 7Kw then adding a treble socket outlet (pop up socket) if this was used at 3Kw that's 10Kw minus any diversity so in excess of 40A as you said I suppose I've answered my own question. Oh the pop up is a good quality one at £165 trade but only using this as the island unit has nowhere to put any other socket outlets unless it's in a cupboard again as its Quartz stone straight on top of units unless anyone has alternative suggestions I'm screwed really.?

Many thanks

 

[Wilko]

Hi - re the pop-up, can you not use the ends of the island bench to mount sockets (just below the bench top) instead? At my place a pop-up would need to be IPmillion to cope with life. But I am clumsy. Cheers.

 

[Midwest]

Thanks again.

Good idea with the 45A connection points then a back box for either connecting a socket face or an fcu but another slight problem is that there is nowhere to put any switched items as the cupboards are boxed in floor to ceiling so only option would be to place inside the top cupboard above the ovens or quite a distance away else where in the kitchen. What do you think?

Just wanted assuring about the induction hob really as they have stated a 2.5mm cable but at 7Kw then adding a treble socket outlet (pop up socket) if this was used at 3Kw that's 10Kw minus any diversity so in excess of 40A as you said I suppose I've answered my own question. Oh the pop up is a good quality one at £165 trade but only using this as the island unit has nowhere to put any other socket outlets unless it's in a cupboard again as its Quartz stone straight on top of units unless anyone has alternative suggestions I'm screwed really.?

Many thanks

The regs require clearly identifiable and accessible. But then the IET don't design kitchens. Sometimes you have to put the isolators in the best place possible but not ideal. So with some kitchen designs that sometimes has to be in a cupboard. Just make sure it's accessible by people other than giants, and not behind wall unit
accessories. Think it would be better closer to an appliances in a cupboard, rather than 6 metres away in another room IMO.

Ditch the pop up and have some sockets on the floor units, just below the worktop. Pops up just get in the way, when 'popped up', and don't think they look particular nice IMO.

PS don't put the isolator above the appliance, not useful if it starts to catch fire, and adjacent cupboard is better IMO.

 

[Midwest]

PPS, the OSG has some guides for isolators, switches and the like. Only guides though.

 

[Midwest]

Just wanted assuring about the induction hob really as they have stated a 2.5mm cable but at 7Kw then adding a treble socket outlet (pop up socket) if this was used at 3Kw that's 10Kw minus any diversity so in excess of 40A as you said I suppose I've answered my own question.

Think you have your cals wrong. telectrix gave you a figure of 16amp, diversity cals suggest 5amp for single socket, so your pop up adds 15amps (if your using industrial kitchen appliances!). So that's 31amps? So 32 amp supply would be suitable, not allowing for route & vd if any.

 

[R G]

I'd be checking with the manufacturer's connection data regarding all the appliances. They know what diversity, and how they have built that diversity into their appliances, and what size cable they require for safe operation. It is invariably always smaller cable than required for the stated FLC, but do check. I have connected full electric hobs with 1.5mm, 2.5mm, and 4.0mm cable. I have also connected appliances that have no built in diversity as confirmed through current measurement.

Which is why I always like to see the appliances on site and get the info from them rather than go on a kitchen plan or even brochures as they are sometimes not forthcoming with the correct info , don't go on what kitchen fitter tells you ....

 

[telectrix]

if a kitchen fitter told me the sun rise in the east, i'd check before accepting it.

 

[Ceekay]

Thanks for the reply's again all very much appreciated.

I appreciate what you have said about the 2.5mm cable to the hob and 13A socket for the island but even with that diversity applied it would still be around the max carrying capacity and my mrs will have all 4 plates of that hob at full all at once on a regular occasion but in any case I'm sure not many of you would go for that size cable running at its max when you could just install a 4 or 6mm whilst undertaking the install and balls to the kitchen fitters drawing?

In ref to doing away with the pop up socket I'm screwed again really as the ends of the island are fitted with a cloaking panel which is the same high gloss finish as the cupboard doors so can't really make holes in it hence the pop up.

Would you all be happy with running the led cupboard lights off the appliance wiring say on a fused spur or whilst it's being wired just throw in a dedicated lighting supply?

Cheers Keith

 

[Midwest]

Thanks for the reply's again all very much appreciated.

I appreciate what you have said about the 2.5mm cable to the hob and 13A socket for the island but even with that diversity applied it would still be around the max carrying capacity and my mrs will have all 4 plates of that hob at full all at once on a regular occasion but in any case I'm sure not many of you would go for that size cable running at its max when you could just install a 4 or 6mm whilst undertaking the install and balls to the kitchen fitters drawing?

In ref to doing away with the pop up socket I'm screwed again really as the ends of the island are fitted with a cloaking panel which is the same high gloss finish as the cupboard doors so can't really make holes in it hence the pop up.

Would you all be happy with running the led cupboard lights off the appliance wiring say on a fused spur or whilst it's being wired just throw in a dedicated lighting supply?

Cheers Keith

I don't think anyone has suggested using a 2.5mm cable for your hob? You should calculate the design current, using diversity and other correction factors, then select an appropriate sized cable & ocpd.

The suggestion of putting sockets on the floor units, just below worktops, is nothing new. Any decent kitchen fitter or electrician would be able to cut an aperture in high gloss décor panel for a back box? If there is insufficient room for a back box, I've used Click Mode 1G To 2G 16mm Deep Converter Pattress (CMA091) - https://www.electrical2go.co.uk/mode-1-gang-to-2-gang-16mm-deep-converter-pattress.html. However not designed for this purpose there is only sufficient space to terminate one cable.

In a new install, I prefer to switch lights from a light switch not an FCU. Don't know how many led lights you are installing, but you may need to consider in-rush current, if controlled by one switch.

From your replies, I'm wondering if you are competent enough to carry out this work and you suggest you are going to use a 3rd party to certify & notify this installation, no offence. You may wish to peruse this thread; Diy wiring extension - http://www.electriciansforums.co.uk/threads/diy-wiring-extension.113214/

 

[Ceekay]

Thanks for your reply Midwest.

I appreciate that no one suggested keeping the 2.5mm cable to the island to run the hob and socket but at the same time whilst advising me it was viable with diversity I was expecting some responses being alarmed like myself that they wanted me to install a cable from new that was going to run towards its maximum capacity on a daily basis. All I was after was after was reassurance I was correct in thinking the drawing was indeed inadequate or was at best not what professional electricians would recommend in their daily practice. As I undertaken my qualifications 30 years ago and then ending up working within the industry again a few years back and went and did all my C & G again and also did my 17th edition at the same time. We were an NICEIC registered company and I was the qualifying manager so I appreciate its not what I do day in and day out and I may of forgot some of the terminology but when I'm first fixing my own home I think my competence which is all that is required plus proof the installation meets part P (which 5 day sparks/ kitchen fitters can obtain) and because of these reasons I was simply asking people much more in the know than I am if it was in fact not recommended to wire in the way the kitchen company had recommended in their drawing. As for certificates and notification I am known by all my friends and family as the King of overkill and trust me this will be wired well in excess of what time and money normally allow, and will be certified and approved accordingly. Sorry if I worried or offended you or anyone else in asking for advice as I'm just second guessing myself when a company currently in business (although a kitchen company) are telling me this is how it's done everyday nowadays and it's my very incompetent self that immediately thinks this is inadequate.

I do really appreciate what you have said and have even swatted up on my onsite guide since receiving many of your reply's.

Many thanks again, Keith

 

[Midwest]

Thanks for your reply Midwest.

As for certificates and notification I am known by all my friends and family as the King of overkill and trust me this will be wired well in excess of what time and money normally allow, and will be certified and approved accordingly. Sorry if I worried or offended you or anyone else in asking for advice as I'm just second guessing myself when a company currently in business (although a kitchen company) are telling me this is how it's done everyday nowadays and it's my very incompetent self that immediately thinks this is inadequate.

No offence meant, if your suitably qualified, then that's that.

As regards certification, I note that this work is being done as part of an approved planning application or Building Regs. You may wish to read the link I posted on a similar thread, about certification & notification. The subject comes up many times, and can cause complications, even for qualified electricians.