Kitchen Wiring

[ScottInnesx]

I have recently bought a run down house and I need to run in all my cables for the Kitchen. I was wondering if people could confirm the below is suitable and correct for my kitchen and if they suggest any other way.

2.5mm2 ring circuit 20A (could be 32A)
two double sockets on worktops (kettle 3000W, toaster 1800W)
kitchen extractor 200W

2.5mm2 ring circuit 20A (could be 32A)
washing machine 1200-2400W
tumble dryer 2000-3000W
double socket outside

10mm2 radial circuit 32A
to 45A dp cooker switch then
to CCU then
to double oven (5.8kW)

10mm2 radial circuit 32A
to 45A dp cooker switch then
to CCU then
to induction hob (max power 12kW)

2.5mm2 radial circuit 16A
to 3 gang plate grid switches (20A rated)
to microwave 1000W
to fridge-freezer 500W
to dishwasher 1600-2400W

I have not decided on some of my kitchen appliances so I would like the cable to be suited for the highest rating.

Thanks for any of your help/advice in advance.

 

[James]

Nothing fundamentally wrong there.
10mm might be a bit big to get in terminals of 45A switches, will need deep boxes and some careful forming of conductors.
I understand the idea of over spec is better than under spec but depending on the length of run and insulation it might be a bit excessive.

What does the electrician who will be installing say, or is this a DIY kitchen fit?

 

[radiohead]

Ring circuits are required to be protected by a 32a device, the last circuit will overload a 16a device at the load you have given and should be protected by a 20a device, and 2'5mm may be inadequate depending of the length of run, this needs to be calculated.
I trust you are aware that this comes under Part P, and therefore must comply with Bs7671, including certification, and must be registered with building control

 

[James]

Ps. It would be good to get an electrician on board early rather than late.
It can save you some expensive mistakes, the first mornings labour could almost be paid for in the savings you make by correctly rating the cables instead of going for worst case and adding some “just in case”

 

[telectrix]

way overkill, IMO.
6mm cable (32A MCB) is more than adequate for cooking appliances. think diversity.
and i'd ditch the last circuit and share the load between the other 2 rings. diversity again.

 

[ScottInnesx]

Nothing fundamentally wrong there.
10mm might be a bit big to get in terminals of 45A switches, will need deep boxes and some careful forming of conductors.
I understand the idea of over spec is better than under spec but depending on the length of run and insulation it might be a bit excessive.

What does the electrician who will be installing say, or is this a DIY kitchen fit?

For installation it will be Method 100.
1st circuit will be approx. 20meters
2nd circuit approx. 25meters
3rd circuit approx. 8meters
4th circuit approx. 8 meters
5th circuit will be approx. 8meters to grid plate then 7meters to microwave, 3meters to fridge/freezer and 10meters to dishwasher.

Can change mcb to 32A for circuit 1 & 2 as 2.5mm2 in ring circuit.
Can change cable to 6mm2 for double oven
Can change mcb to 20A for circuit 5 as 2.5mm2 in radial.

Would this be ok? any suggestions
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way overkill, IMO.
6mm cable (32A MCB) is more than adequate for cooking appliances. think diversity.
and i'd ditch the last circuit and share the load between the other 2 rings. diversity again.

Please see my reply above regarding method of installatuon and the cable lengths.
Due to my appliances being built in then i would like a local isolation point for them hence the reason for the last circuit.

Could you suggest the circuits I could do with the above information and appliances?

 

[pc1966]

Personally I would put the outside socket on to either a separate breaker, or at least a double-pole isolator, so if anything goes wrong with it you won't keep getting trips on the other circuits.

A single 32A ring would do for the first two sets of equipment, but I would make sure that either your washing machine & tumble dryer sockets are above the appliances, or you use unswitched sockets and a 20A DP isolator switch above them (or in a grid switch as for your built-in stuff).

The Sottish building regulations require "white goods" power points to have accessible means of isolation, something that is good advice for all of the UK.

Other advice is use single socket outlets for them - double sockets are typically 20A for both, so show thermal stress if you have two 2-3kW loads on them simultaneously.

If as your profile says you are in Buckie then you don't have the Part P requirements of England & Wales, but for goodness sake make sure you are able to properly test the installation if doing it yourself. Unless you already posses a MFT it will be a lot cheaper to get a sparky in for that, and you can probable come to an agreement of what you do and what they need to check for a proper sign-off in order to keep the total cost down.

 

[Dustydazzler]

I would use 6mm cable , I hate trying to terminate 10mm it’s a pig and total overkill imo...
don’t bother fitting 20a for the rings , use 32a breakers...
the rest looks fine

 

[ScottInnesx]

Personally I would put the outside socket on to either a separate breaker, or at least a double-pole isolator, so if anything goes wrong with it you won't keep getting trips on the other circuits.

A single 32A ring would do for the first two sets of equipment, but I would make sure that either your washing machine & tumble dryer sockets are above the appliances, or you use unswitched sockets and a 20A DP isolator switch above them (or in a grid switch as for your built-in stuff).

The Sottish building regulations require "white goods" power points to have accessible means of isolation, something that is good advice for all of the UK.

Other advice is use single socket outlets for them - double sockets are typically 20A for both, so show thermal stress if you have two 2-3kW loads on them simultaneously.

If as your profile says you are in Buckie then you don't have the Part P requirements of England & Wales, but for goodness sake make sure you are able to properly test the installation if doing it yourself. Unless you already posses a MFT it will be a lot cheaper to get a sparky in for that, and you can probable come to an agreement of what you do and what they need to check for a proper sign-off in order to keep the total cost down.

That makes sense about the outside socket, I could put it on the same circuit as the two double sockets for kettle & toaster because outside socket for a power washer only.

A few people have said I could get the first 2 circuits in a single 2.5mm2 ring circuit so think I will go for this. For washing machine and tumble dryer it will be 2 single sockets. I was thinking about doing 2 grid switches for washing machine and tumble dryer because just now the utility is just bricks but I am planning plasterboarding walls and ceiling. Would that not be more than 1 spur of a ring circuit though? a spur from grid switch to washing machine and a spur from grid switch to tumble dryer?

Thank you for your advice.

 

[telectrix]

seen so many grid switches burnt out. although they are rated 20A, these have failed when only loaded to 10A (ish) for washers and dryers.

 

[Dustydazzler]

I personally don’t like grid switches , I would rather just a few swi spurs / cooker switches to control the appliances...
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Kitchen I rewired a few years ago , put a new dedicated ring in and new cooker circuit. No need for a grid imo.
spur next to a socket looks fine imo

 

[telectrix]

20A D/P switch (with or without neon) above w/top. single socket for appliance below. that way you don't have 2 x 13A fuses in series. as Punch used to say (before he was declared a non-PC wife-beating sexist)That's the way to do it.

edit: to the pc brigade... i should have said "genderist".

 

[ipf]

One big question.
Qualified to design, install, test and commission or DIY?

 

[ScottInnesx]

20A D/P switch (with or without neon) above w/top. single socket for appliance below. that way you don't have 2 x 13A fuses in series. as Punch used to say (before he was declared a non-PC wife-beating sexist)That's the way to do it.

edit: to the pc brigade... i should have said "genderist".

Where would I have 2 x 13A fuses in series?

 

[James]

One in the fuse connection unit
One in the plug of the appliance

 

[ipf]

Where would I have 2 x 13A fuses in series?

Hence my question.

 

[ScottInnesx]

One in the fuse connection unit
One in the plug of the appliance

What appliance is this for?

 

[pc1966]

What appliance is this for?

If using a FCU to control/isolate an unswitched outlet behind a washing machine, etc.

 

[ScottInnesx]

If using a FCU to control/isolate an unswitched outlet behind a washing machine, etc.

Was just gonna use a switch not a fused switch

 

[pc1966]

Was just gonna use a switch not a fused switch

That was exactly @telectrix suggestion.

 

[ScottInnesx]

That was exactly @telectrix suggestion.

Sorry I’m confused. not sure where I said I am using a FCU at?
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Hence my question.

mate, I’m just gonna run in the cables. need to know what I need. Thats all, not claiming to be an expert

 

[pc1966]

Sorry I’m confused. not sure where I said I am using a FCU at?

You didn't, but Dustydazzler's example had them.

 

[ScottInnesx]

You didn't, but Dustydazzler's example had them.

Thats make sense, I was getting confused. Thanks for clearing that up

 

[nicebutdim]

20A D/P switch (with or without neon) above w/top. single socket for appliance below. that way you don't have 2 x 13A fuses in series. as Punch used to say (before he was declared a non-PC wife-beating sexist)That's the way to do it.

edit: to the pc brigade... i should have said "genderist".

Some more learning for me here.

House is under 3 years old and all appliances in kitchen & utility are controlled by a switched FCU (not cooker obviously) above single unswitched sockets.

What problems could this cause where both fuses are of equal rating or is this just bad practise?

 

[pc1966]

What problems could this cause where both fuses are of equal rating or is this just bad practise?

It is bad practice as in the event of a fault you might have one, the other, or both fuses blow. And if one survives it is probably so weakened that it might blow on small overloads / switch-on surges in the near future.

When cascading protective devices you want to have selectivity - so the one closest to the fault goes and those upstream survive intact. For fuses of the same general family then you typically get that for a 1:2 ratio (and in some cases with a 1:1.6 ratio).

So if you have a 13A fused outlet then really the downstream fuse ought to be 5A or less, so you get reliable disconnection of the closest OCPD.

For MCB in cascade it is hard to be much selectivity when you hit the instantaneous magnetic trip region, hence for an out building the preference for a fused-switch feeding the garage CU sort of thing. Similarly for fuse/MCB/fuse combinations it is complicated as to quite what will happen as the trip curves typically intersect at two fault currents. Whole books have been written on it!

 

[nicebutdim]

It's not something I'd encountered before (other than in extension leads), nor thought much about. It hadn't even occured to me that the situation existed in my kitchen until reading this thread.

Will have to learn more on the subject, but I'm a bit surprised that a practicing electrician would have fitted these. Must have been the only in-stock option at the cheapest of cheap accessory supplier on that day

 

[James]

It's not something I'd encountered before (other than in extension leads), nor thought much about. It hadn't even occured to me that the situation existed in my kitchen until reading this thread.

Will have to learn more on the subject, but I'm a bit surprised that a practicing electrician would have fitted these. Must have been the only in-stock option at the cheapest of cheap accessory supplier on that day

To be fair, it is a fairly common practice.
And let’s face it, if the washing machine blows a fuse, it has to be pulled out to investigate the fault.
At that time, change both fuses when it is repaired or replaced.

More often than not, a 32A B type breaker will trip before a 13A fuse anyway.

 

[nicebutdim]

At that time, change both fuses when it is repaired or replaced.

This is exactly the thought that occured to me, should a fuse ever blow.

I like information and learn a lot from this forum, but this was one of those occasions were the information had immediate relevance.

Back to reading again...

 

[richy3333]

Jesus, are we now teaching DIY-Dave’s For free ?