Cooker circuit

maxamillius

Am I correct in thinking an 11.2kw cooker circuit will require a 45amp breaker and a 10mm cable instead of 6?
Cooker is approx 25mtrs from board.
There is a 6mm already installed on a 32a breaker

https://www.currys.ie/ieen/household-appliances/cooking/cookers/kenwood-ck418sl-90-cm-electric-ceramic-range-cooker-slate-grey-chrome-10194261-pdt.html

Thanks

2011

Are you sure about the 25m? That seems very long.
Off the top of my head: I would be think that a 40A MCB would make more sense due to diversity, but if the run is long I would expect you will need a 10 mm sq.

maxamillius

2011 wrote: »

Are you sure about the 25m? That seems very long.
Off the top of my head: I would be think that a 40A MCB would make more sense due to diversity, but if the run is long I would expect you will need a 10 mm sq.

Ye your right it’s probably more like 15mtrs, 3 bed semi, board at front door and cooker switch at back of house. If I was to apply the diversity of 10 A plus 30% of the remainder of the total connected load, it brings it down to approx 25amps, but does that diversity rule still apply?

Risteard81

maxamillius wrote: »

Ye your right it’s probably more like 15mtrs, 3 bed semi, board at front door and cooker switch at back of house. If I was to apply the diversity of 10 A plus 30% of the remainder of the total connected load, it brings it down to approx 25amps, but does that diversity rule still apply?

Yes. The reality is that for up to 15kW of cooking loads a 32A device on 6mm^2 cable is fine. The total connected load (TCL) quoted for cookers is pretty meaningless, as often multiple elements cannot be simultaneously energised, even leaving aside the fact that they will cycle on and off as they reach temperature. People sometimes have a habit of getting carried away with cooking loads.

maxamillius

Thanks lads, was just thinking about the likes of Christmas where someone might have both ovens on and all the hobs, but the likelihood of them all being on full whack is slim.

Appreciate the input,

2011

maxamillius wrote: »

If I was to apply the diversity of 10 A plus 30% of the remainder of the total connected load, it brings it down to approx 25amps, but does that diversity rule still apply?

This diversity calculation was removed from the rules a very long time ago and it wasn’t by accident.

Risteard81 wrote: »

The total connected load (TCL) quoted for cookers is pretty meaningless, as often multiple elements cannot be simultaneously energised

That is not the case with this cooker in the link provided. That is why the manual for this cooker states “No diversity can be applied to this control unit.”

even leaving aside the fact that they will cycle on and off as they reach temperature.

For the elements to cycle on and off they must first heat up to the desired temperature. Therefore the loading is at 100% when switched on cold. This makes it possible to overload a 6mm sq. cable. How much this happens depends on how the cooler is used but over a protracted period of time excessive thermal cycling of the cable can damage the insulation making it brittle and can result in cracking. I would think it likely that someone buying a substantial cooker such as this plans to do some serious cooking.

maxamillius

2011 wrote: »

This diversity calculation was removed from the rules a very long time ago and it wasn’t by accident.



That is not the case with this cooker in the link provided. That is why the manual for this cooker states “No diversity can be applied to this control unit.”



For the elements to cycle on and off they must first heat up to the desired temperature. Therefore the loading is at 100% when switched on cold. This makes it possible to overload a 6mm sq. cable. How much this happens depends on how the cooler is used but over a protracted period of time excessive thermal cycling of the cable can damage the insulation making it brittle and can result in cracking. I would think it likely that someone buying a substantial cooker such as this plans to do some serious cooking.

It’s actually my brother in law that bought it just because it looked nice and shiny and was expensive so therefore must be the best!!!!!!

The floor is lifted upstairs and a new kitchen being fitted so if I need to pull in a 10mm now is the time to do it!!

He is the type to have everything on at once just because he can.

So are we thinking 10mm with a 40amp breaker?

2011

maxamillius wrote: »

The floor is lifted upstairs and a new kitchen being fitted so if I need to pull in a 10mm now is the time to do it!!

If it was my house I would grasp this opportunity and install the 10 sq.

The rules state "555.1.4 Appliances shall be installed in accordance with this Standard, taking into consideration manufacturer's instructions"

He is the type to have everything on at once just because he can.

Enough said, from cold everything on presents a substantial load.

iwillhtfu

maxamillius wrote: »

Thanks lads, was just thinking about the likes of Christmas where someone might have both ovens on and all the hobs, but the likelihood of them all being on full whack is slim.

Appreciate the input,

Even in that scenario it would be unlikely everything would be operating at max demand.

The 6sqmm you have in situ will be fine.

2011

iwillhtfu wrote: »

Even in that scenario it would be unlikely everything would be operating at max demand.

....unless it is cold. Cooker elements will be 100% on until the set point is achieved.

The 6sqmm you have in situ will be fine.

Most likely you would get away with a 6 mm sq.
Personally I wouldn't take the chance with an 11.2 kW cooker.

As the floor is lifted upstairs I would recommend installing the larger cable.

Other factors can derate the current carrying capacity of the cable such as the method of installation which may change at a future date due the the addition of thermal insulation.

See page 17 of the manual for this cooker.

iwillhtfu

2011 wrote: »

....unless it is cold. Cooker elements will be 100% on until the set point is achieved.

The hobs will be heaviest draw in that oven and who runs all of the hobs at once. The oven itself will likely be a pittance of the overall load.

You make a valid point though if the floor is up and the cable is cheaply found then why not. Just an FYI op 10sq is a pig to make off into a cooker switch.

2011

iwillhtfu wrote: »

The hobs will be heaviest draw in that oven

Yes, I agree.

who runs all of the hobs at once.

Some people do just that, see extract from post 7 above: "He is the type to have everything on at once just because he can"

The oven itself will likely be a pittance of the overall load.

Yes, I agree.

You make a valid point though if the floor is up and the cable is cheaply found then why not.

Exactly.

Just an FYI op 10sq is a pig to make off into a cooker switch.

It has been a while since I did this (yes I am old) but I do remember

I used the larger MK or Crabtree cooker switches which had larger terminals to make life easier.

liveandnetural

https://www.youtube.com/watch?v=QQduU8RkjD8 https://www.tlc-direct.co.uk/Book/6.5.2.htm

useful on the subject

maxamillius

liveandnetural wrote: »

https://www.youtube.com/watch?v=QQduU8RkjD8 https://www.tlc-direct.co.uk/Book/6.5.2.htm

useful on the subject

Interesting that he uses that diversity, can’t find anything in the Irish regs that says diversity on cooker circuit is allowed?

maxamillius

2011 wrote: »

....unless it is cold. Cooker elements will be 100% on until the set point is achieved.



Most likely you would get away with a 6 mm sq.
Personally I wouldn't take the chance with an 11.2 kW cooker.

As the floor is lifted upstairs I would recommend installing the larger cable.

Other factors can derate the current carrying capacity of the cable such as the method of installation which may change at a future date due the the addition of thermal insulation.

See page 17 of the manual for this cooker.

Thanks for that, pg18 actually states that a diversity factor can be applied, so the manual actually contradicts itself

2011

maxamillius wrote: »

Thanks for that, pg18 actually states that a diversity factor can be applied, so the manual actually contradicts itself

That statement refers to the feeder cable which has a specific insulation.
But yes it is a bit of a contradiction.

I agree that diversity can be applied but for the situation you have described I would upgrade the cable. I acknowledge that a 6 mm sq. would most likely be ok, but personally I just wouldn’t chance it.

Risteard81

2011 wrote: »

If it was my house I would grasp this opportunity and install the 10 sq.

The rules state "555.1.4 Appliances shall be installed in accordance with this Standard, taking into consideration manufacturer's instructions"



Enough said, from cold everything on presents a substantial load.

The load is only of short duration though.

maxamillius

Interesting debate, might just tell him his brand new shiny cooker can’t be used all at once!!!

2011

Risteard81 wrote: »

The load is only of short duration though.

Yes, that is true.

.....and I know that in the UK you would generally use a 32A MCB and a 6mm sq. cable. I also admit that I would be the first to say that the same laws of physics apply in the UK as in the ROI But, I don't agree with a number of the rules they have in the UK (such as rewireable fuses). I prefer the approach that we have here and our rules include 555.1.4 (quoted in my earlier post). I would recommend complying with this clause.

We both know that it is good to take advantage of the fact that the floor is lifted upstairs

maxamillius wrote: »

Interesting debate, might just tell him his brand new shiny cooker can’t be used all at once!!!

Yeah, but you know what he is like :D

Risteard81

2011 wrote: »

Yes, that is true.

.....and I know that in the UK you would generally use a 32A MCB and a 6mm sq. cable. I also admit that I would be the first to say that the same laws of physics apply in the UK as in the ROI But, I don't agree with a number of the rules they have in the UK (such as rewireable fuses). I prefer the approach that we have here and our rules include 555.1.4 (quoted in my earlier post). I would recommend complying with this clause.

We both know that it is good to take advantage of the fact that the floor is lifted upstairs



Yeah, but you know what he is like :D

Certainly if floors are up and you're starting from new then your options are much greater and this may influence your approach.

maxamillius

Thanks gents some good information here none the less, appreciate the input!! Looking forward to cramming a 10mm into a 47mm back box. Can’t be much worse then a 10mm to a shower pull cord!!

Emptur.

maxamillius wrote: »

Thanks gents some good information here none the less, appreciate the input!! Looking forward to cramming a 10mm into a 47mm back box. Can’t be much worse then a 10mm to a shower pull cord!!

Should be no problem, use a full-length quality isolator obviously

John.G

maxamillius wrote: »

Interesting debate, might just tell him his brand new shiny cooker can’t be used all at once!!!

Is the (cooker) diversity rule still law here?, often wondered how it worked in my house at Christmas with all plates + oven in use.

Emptur.

John.G wrote: »

Is the (cooker) diversity rule still law here?, often wondered how it worked in my house at Christmas with all plates + oven in use.

Not sure if it's there

Diversity is a guide anyhow, if you apply diversity to the total load it's up to you to get it right.

John.G

I have a 16485W (16.485kw) cooker, if diversity is not applied then I need a cable/MCB sufficient to carry 72 amps??.

Emptur.

John.G wrote: »

I have a 16485W (16.485kw) cooker, if diversity is not applied then I need a cable/MCB sufficient to carry 72 amps??.

You can apply diversity but the question is the amount

The formula is not set in stone

John.G

Mine is the original 6MM2/35A fuse which has never blown so maybe indicative of load never > say 50A or 11.5kw, if using diversity calc....= 10+30%*(71.7-10), or 28.5A, might be interesting to see how often a 20/25A fuse would blow.

Emptur.

I can't find it in ET101

I'd be surprised if they reference a calculation for cookers in the new rules

John.G

From post#4 "The total connected load (TCL) quoted for cookers is pretty meaningless, as often multiple elements cannot be simultaneously energised" what does this mean?.

Emptur.

John.G wrote: »

From post#4 "The total connected load (TCL) quoted for cookers is pretty meaningless, as often multiple elements cannot be simultaneously energised" what does this mean?.

It refers to "changeover" where heating elements are wired so they can't come on together

You see it with the oven/grill selector switches

2011

Diversity can be applied. The point is that the rules no longer provide a calculation for this. How much diversity should be applied depends on many factors but it mainly depends on the end user.