Kitchen - rewire help required

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Hello

I have just had a new consumer unit fitted and all existing wiring connected by the electrician. Now i need to rewire the kitchen and would be grateful of any advice.

1. I understand that appliances under worktops need an FCU connected above the worktop to isolate the appliances. Can i use one FCU for both the washer and dishwasher?

2. Do the FCU's need to be a specified distance above worktops, away from hobs, cooker hoods etc?

3. Are FCU's ok to be spured from the new ring?

4. Where should i ideally take the power feeds from for:
a) cooker hood
b) extractor fan
c) outside light
d) underfloor heating

Many thanks
 
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get the sparky back as it's going to cost you about £100 to notify the LABC that you are doing the work and you also need to be able to produce test results for the altered circuits.

it'll be cheaper in the long run to get the pro's in to do it..
 
supermoto1962 said:
I have just had a new consumer unit fitted and all existing wiring connected by the electrician. Now i need to rewire the kitchen and would be grateful of any advice.

Why didn't you get the electrician to do the kitchen wiring and then change over CU and test the whole lot? Work in the kitchen is notifiable, so you'll probably end up spending more than you would have if you had the electrician do it.

First bit of advice: notify your BCO BEFORE you start work or get the sparky back.

supermoto1962 said:
1. I understand that appliances under worktops need an FCU connected above the worktop to isolate the appliances. Can i use one FCU for both the washer and dishwasher?

They don't need an FCU, they can be plugged into sockets above the worktop if you don't mind the cables/plugs being on show...

If you go down the FCU route then you need one FCU per appliance.

supermoto1962 said:
2. Do the FCU's need to be a specified distance above worktops, away from hobs, cooker hoods etc?

There are no set requirements, just that they are in suitable positions so that they do not get splashed and the flex doesn't get damaged.

supermoto1962 said:
3. Are FCU's ok to be spured from the new ring?

Connect the FCU's to the ring, don't spur them from sockets if you are re-wiring.

supermoto1962 said:
4. Where should i ideally take the power feeds from for:
a) cooker hood
b) extractor fan
c) outside light
d) underfloor heating

a) Ring main - 3A fuse most probably.
b) Lighting circuit - remember to fit a fan isolator.
c) Lighting circuit
d) Own circuit from CU.
 
There are no set requirements, just that they are in suitable positions so that they do not get splashed and the flex doesn't get damaged.

yes there are specific requirements..

I believe that it's 300mm from the edge of any sink or hob.. someone will undoubtedly confirm or correct this..
 
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Appliances under the worktop:

An even more beautiful way to do it is to run the kitchen ring cable horizontally 150mm or more above worktop height, with numerous sockets on it, and a 20A DP switch in the same row at every position where you have, or might one day want, an appliance below.

The switch feeds an unswitched 13A single socket below

This layout is very economical in labour and materials, and allows you to use the supplied appliance fused plugs (easy to pull out when they are removed for cleaning, maintenance or replacement). As you are using switches not FCUs there is just one fuse, and one switch, per appliance. And one appliance per switch and per fuse.

One is the ideal number.
 
you forgot to mention that you need to wire the link from the "20A" DP switch to the 13A socket with 4mm² cable.. ( otherwise you are potentially putting 32A down a 2.5mm²)

also, do you feel happy using a 20A DP switch on a circuit capable of providing 32A?

I know that in theory you can only draw 13A from a single socket but the fault potential of more than that still exists..

the first time that the dishwasher goes on the fritz and trips the 32A breaker it means that more than 32A went down that cable and through that switch and indeed through that socket for however short a period of time..
 
ColJack said:
I know that in theory you can only draw 13A from a single socket but the fault potential of more than that still exists..

As it does with every single circuit... During a fault any circuit is going be put under conditions that they are not rated for - that's when automatic disconnection comes in to prevent damage/fire etc.

I understand what you are getting at but you don't size cables/switches on the potential fault current, otherwise we'd be wiring sockets with massive cables and using switches rated in kA's just incase...
 
i'm aware of that,

but what i'm getting at is that possibly under some strange series of events the socket could in theory draw a sustained current of up to 32A for whatever reason ( maybe some idiot puts a double off it and plugs in a dishwasher, dryer and washing machine.... or a fitter changes the socket outlet to a flex outlet and hard wires in a larger double oven etc.. )

then the cable would be damaged as well as the switch..

the cable on a circuit and any switch gear should be able to at least take the rated current of the OCPD that is protecting it..
 
Good point, when I wrote my response I must have had my blonde hat on because I totally skipped that scenario. A point to consider thought is that nothing is safe from the hands of DIY'ers and incompetent fitters etc. anything you can wire safely a DIY'er can turn into a death trap but assuming* everyone follows the rules regarding notifying jobs within the kitchen or getting a certified sparky in to do it, there shouldn't ever be an issue with those DP switches taking more than 13A except during fault conditions.

*Try to be optimistic :LOL:
 
Hi Lads
Thanks for all the replies - and the speed of them.
I might add that the house is an ongoing project and the company who installed the consumer unit have advised on cable and connector types and will come in to check how all wiring has been installed prior to fixing any boxes/faceplates etc. If i make a mistake i will have to correct at that point.

Once they are happy all cables are correctly pulled and fastened then i can complete the first fix ready for them to come in and test.

I am just doing the 'monkey' part of the job and i'm fully aware of my limitations (in many ways!).

Thanks again and anymore advise will be appreciated.
 
ColJack said:
i'm aware of that,

but what i'm getting at is that possibly under some strange series of events the socket could in theory draw a sustained current of up to 32A for whatever reason ( maybe some idiot puts a double off it and plugs in a dishwasher, dryer and washing machine.... or a fitter changes the socket outlet to a flex outlet and hard wires in a larger double oven etc.. )

then the cable would be damaged as well as the switch..

the cable on a circuit and any switch gear should be able to at least take the rated current of the OCPD that is protecting it..

If this was the case, wouldn't the regs state that any spur taken off a socket should be done with 4mm cable?
 
ColJack said:
...but what i'm getting at is that possibly under some strange series of events the socket could in theory draw a sustained current of up to 32A for whatever reason ( maybe some idiot puts a double off it and plugs in a dishwasher, dryer and washing machine.... or a fitter changes the socket outlet to a flex outlet and hard wires in a larger double oven etc..

You can't design for what some idiot may do in the future. On the other hand, it is never wrong to increase cable size (just impractical and confusing).

Have a gander at the following:
433-01-01
433-02-04
434-01-01
And then read Appendix 8 of the OSG.

Enjoy. ;)
 
twocom said:
ColJack said:
If this was the case, wouldn't the regs state that any spur taken off a socket should be done with 4mm cable?

No, because the MCB/fuse is 30A/32A and the spur is 13A, the 2.5mmsq T&E can take 13A with no problem but cannot take 32A.

I agree that the best way to connect the appliences is by using SFCU's and single sockets under the work top. But when the kitchen is very small it will create a situation were the walls will be loaded with sockets and spurs. As far as I know the regs do not require a spur for the appliences (although I do it whenever I can), this is required when the applience can not be pulled out.

And there is a recommended distance for sockets/spurs etc. from a sink or hob and as mentioned it is 300mm.
 
There is a reg that states the the OCD in some circumstances does not have to be at the origin of the circuit. In this case the OCD for the cable from the DP iso to the socket will be in the plug top. IMO putting a switched fused spur and then leaving a plug top on the appliance is bad practice, so you could use flex outlets - but that would create problems when you move the appliances!!

What are you doing designing for what might be?? You design the circuit for how you are going to leave it and if someone alters it in the future then that's their look out.... I'm sure ost of you have seen lights powered from socket rings with no fused spurs present, so how would you stop that from hapening??
 
ColJack said:
you forgot to mention that you need to wire the link from the "20A" DP switch to the 13A socket with 4mm² cable.. ( otherwise you are potentially putting 32A down a 2.5mm²)
No you don't, load is limited to 13A by the virtue of the fuse in the plugtop, same as it is for any other spur

also, do you feel happy using a 20A DP switch on a circuit capable of providing 32A?

That is the important issue, if you intend to put the rfc conductors in the supply terminals, have you checked with the maker that it is suitable for this, afterall you wouldn't use a 20A JB on a rfc (AFAIK BS1363 and FCUs are required to be suitable for connecting in this way by BS1363, DP switches don't come under this british standard).

If of course you were to take the spur from a socket and put the switch along the length of the spur cable, then I cant see an issue

I know that in theory you can only draw 13A from a single socket but the fault potential of more than that still exists..
As it does for any spur

the first time that the dishwasher goes on the fritz and trips the 32A breaker it means that more than 32A went down that cable and through that switch and indeed through that socket for however short a period of time..

Indeed, and there are calculations for it ;) (but it can be accepted that protection against fault current exists when the circuit is protected against overload and the OPD has sufficent breaking capacity for where it is installed - and as for a spur, thats a standard circuit in the OSG and no further calculations are necessary :) )
 

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