Four electrical jobs in a kitchen - am I right?

[SUNRAY]

To return to the real world, are you really suggesting that an oven such as you mentioned can only be installed on its own dedicated 16A circuit?

Yes if MI makes that statement.

The trouble is I work in the real world where things do go wrong, my avatar is just one of those situations. In that situation a 16mm² tri-rated 3 phase circuit in packed management trunking protected by 80A MCB.

A second example of real world incorrect circuit design in this thread.

 

[JohnW2]

Yes if MI makes that statement.

OK, that's your view, but I'm not sure how widely held that view will be.

I've seen many an appliance in a kitchen whose MIs 'call for'a 16A OPD, but I don't think I've yet seen one fed by its dedicated 16A circuit. Indeed, I'm not sure that I've ever seen (in the UK) a 16A circuit serving a kitchen at all.

What one needs to remember is that many of these calls for '16A circuits'relate to products sold in many countries outside of the UK where 16A circuits are 'the norm',and those who write the MIs do not necessarily understand what happens in the UK.

 

[EFLImpudence]

There is of course the situation where the same cooker may be connected to two or three 16A circuits in other places but in the UK it will be on one 32A circuit.

The internal wiring being the same for a cooker or separate oven.

I know SUNRAY does not think other places worthy of consideration but the physics is the same.

 

[SUNRAY]

OK, that's your view, but I'm not sure how widely held that view will be.

I've seen many an appliance in a kitchen whose MIs 'call for'a 16A OPD, but I don't think I've yet seen one fed by its dedicated 16A circuit. Indeed, I'm not sure that I've ever seen (in the UK) a 16A circuit serving a kitchen at all.

What one needs to remember is that many of these calls for '16A circuits'relate to products sold in many countries outside of the UK where 16A circuits are 'the norm',and those who write the MIs do not necessarily understand what happens in the UK.

But I have seen many of them served by a 13A FCU or 13A plug which is suitable for <3KW units

In a commercial situation (which has always been my main situation) it would be unlikely to find an oven on anything bigger than 16A unless it required bigger. Commercial electricians (proper commercial electricians) will be far stricter with such things.

What happens in other countries is irrelevant in a forum called 'Electrics UK'

 

[JohnW2]

But I have seen many of them served by a 13A FCU or 13A plug which is suitable for <3KW units

That's different. If they represent a low enough load for a 13A OPD to be adequate,then there is no problem in the UK. The problem(in the UK) is with those which draw a little more than 13A (no problem in most non-UK countries) and for which the MIs call for a 16A OPD (which is what they would naturally be on in many other countries) - since,in the UK,the only practical way of providing 16A protection would be to supply the oven with its own 16A dedicated circuit - which,as I said,I don't recall ever having seen done (in the UK).

 

[SUNRAY]

That's different. If they represent a low enough load for a 13A OPD to be adequate,then there is no problem in the UK. The problem(in the UK) is with those which draw a little more than 13A (no problem in most non-UK countries) and for which the MIs call for a 16A OPD (which is what they would naturally be on in many other countries) - since,in the

Sorry, what problem?

Providing 16A OCP is no more dificult than providing 32A OCP or 6A OCP or 45A OCP

UK,the only practical way of providing 16A protection would be to supply the oven with its own 16A dedicated circuit - which,as I said,I don't recall ever having seen done (in the UK).

Or a local 16A OCPD which is not difficult.

The fact that domestic installers are so lazy is rediculous. It doesn't usually happen in commercial premises.

 

[JohnW2]

Sorry, what problem?

Having to have a dedicated circuit for a small oven

Providing 16A OCP is no more dificult than providing 32A OCP or 6A OCP or 45A OCP

Indeed, but we rarely install 16A circuits (other than for immersions),in kitchens or anywhere else - so, as above, it would usually be an extra circuit 'just for a small oven.

Or a local 16A OCPD which is not difficult.

Not difficult, but there is no particularly 'compact' way of doing it, and many/most people would regard it as unnecessary.

The fact that domestic installers are so lazy is rediculous. It doesn't usually happen in commercial premises.

I don't think it's laziness but, rather, as above, that they don't think that there is a need.

We happily have equipment which draws only an amp or two protected 'only'by a 13A OPD, and equipment which draws only a handful of mA protected 'only' by a 6A OPD, so why is it such a big deal having equipment which draws 13A-14A or so protected 'only''by a 32A OPD?

Your whole approach seems to be dictated by the MIs, but what they say will often be there only 'to protect ther backsides' and/or to provide them with opportunities to try to wriggle out of warranty claims.

 

[EFLImpudence]

Your whole approach seems to be dictated by the MIs, but what they say will often be there only 'to protect ther backsides' and/or to provide them with opportunities to try to wriggle out of warranty claims.

...and because someone thinks it is the regulation in the UK - as with extractor fan isolator and 3A fuse.

 

[SUNRAY]

Having to have a dedicated circuit for a small oven

Indeed, but we rarely install 16A circuits (other than for immersions),in kitchens or anywhere else - so, as above, it would usually be an extra circuit 'just for a small oven.

Not difficult, but there is no particularly 'compact' way of doing it, and many/most people would regard it as unnecessary.

I don't think it's laziness but, rather, as above, that they don't think that there is a need.

We happily have equipment which draws only an amp or two protected 'only'by a 13A OPD, and equipment which draws only a handful of mA protected 'only' by a 6A OPD, so why is it such a big deal having equipment which draws 13A-14A or so protected 'only''by a 32A OPD?

Your whole approach seems to be dictated by the MIs, but what they say will often be there only 'to protect ther backsides' and/or to provide them with opportunities to try to wriggle out of warranty claims.

My approach is simply based on safety and good practice.
13 a rated cable only protected by 32a ocpd not good.
Risk of fire not good.
When it goes wrong someone will (and does) say 'why didn't...' and all due to a simple omission.

 

[Murdochcat]

Meanwhile in the real world the OP hasn’t come back …..

 

[SUNRAY]

And probably took the advice of the first reply and possibly made some botch together 4 different size cables into a joint and won't look at it again.

Chances are it will only looked at again IF and I emphasise IF something goes wrong and then the repair man refuses the repair due to way it's installed it could also possibly be fire brigade doing the looking.

And all for the sake of a fuse...

 

[JohnW2]

My approach is simply based on safety and good practice. 13 a rated cable only protected by 32a ocpd not good. Risk of fire not good.

Does that mean that you think that complying with the requirements of BS7671 is not enough to be good practice?

As you are aware, it is compliant with BS7671 for a "13A cable" (or any other cable) to have no overload protection at all, if the designer believes that the nature of the load is such that it is "not likely" to result in an overload current - and many would probably say that such is the case with an oven - and,before you start scraping barrels and producing anecdotes "not likely" means "not likely" and does not mean "will never happen".

In a situation in which it would be compliant with BS7671 for the cable to have no overload protection at all, why does it matter whether an OPD which does exist is 16A or 32A (or, come to that, 80A!) ?

The requirements of BS7671 are,of course, only 'minimum' ones, and there is no reason why one should not exceed them - but I can but presume that you do not feel that compliance with BS7671 is enough to even represent "good practice". Is that the case?

 

[JohnW2]

...and because someone thinks it is the regulation in the UK - as with extractor fan isolator and 3A fuse.

I'm not convinced that those who write MIs necessarily have thee ability to think and/or enough knowledge of electric principles and regulations on which to base useful thinking!

 

[SUNRAY]

Does that mean that you think that complying with the requirements of BS7671 is not enough to be good practice?

As you are aware, it is compliant with BS7671 for a "13A cable" (or any other cable) to have no overload protection at all, if the designer believes that the nature of the load is such that it is "not likely" to result in an overload current - and many would probably say that such is the case with an oven - and,before you start scraping barrels and producing anecdotes "not likely" means "not likely" and does not mean "will never happen".

In a situation in which it would be compliant with BS7671 for the cable to have no overload protection at all, why does it matter whether an OPD which does exist is 16A or 32A (or, come to that, 80A!) ?

The requirements of BS7671 are,of course, only 'minimum' ones, and there is no reason why one should not exceed them - but I can but presume that you do not feel that compliance with BS7671 is enough to even represent "good practice". Is that the case?

I have no specific issues with BS7671 althought to be fair I don't agree with all of it. You have described the situation I am talking about quite well, One of the areas I'm not fully in favour of is unprotected cables but I do accept downstream protection with caveats. For example in control panels and switchgear there is often a large supply on a bussbar and small taps are made protected by a downstream OCPD. It would be crazy to provide a 5000A wire to a 6A fuse, but of course not impossible to attach the fuse directly to the bussbar.

Who makes the decision that the overload is unlikely? The appliance manufacturer or the lad who has learnt to house bash on a 2 week special training course? My guess is the appliance manufacturer who have put many hours of research and developement including overload testing and risk assessment will come up with their percentages and include in their instructions the requirements for installation based on their rigorous testing procedures based on standards possibly set by outside bodies.
These instructions will include, but not restricted to: ventilation, heat loss, physical dimensions and clearances (such as to be able to open a door), gas flow and pressure limits, and electrical connexion. All of that to ensure their product operates in a correct and safe manner.

So I assume you would not encase a product in a chip board enclosure if the air coming out of the exhaust vent is at 1000º and I assume you wouldn't ignore the requirement to allow space for the door to open and I assume you wouldn't ignore the electrical requirements that they deem to be required? Oh actually silly me, actually yes you do ignore all of that infact I dare say you don't even read it because another risk assessment elsewhere says you can.

Yes I agree most of the contents of MI's include an element of arse protection. If that appliance were to catch fire and destroy the house, who do you believe will be liable for recompense? The manufacturer, the installer (carpenter electrician etc), the insurance company, the customer? sure the insurance company may payout if the unprotected appliance caught fire but they will then try for recompense from the party they deem to be responsible, the manufacturer will quickly be able to provide sloping shoulders if their conditions/instructions are not met, the installer may not.

Now if the electrician has installed that little ol' fuse thingy... bingo.

 

[JohnW2]

I have no specific issues with BS7671 althought to be fair I don't agree with all of it.

I doubt whether any of us who are capable of some thought agree with all of it, so you're not alone.

You have described the situation I am talking about quite well, One of the areas I'm not fully in favour of is unprotected cables ...

You may not be "fully in favour of it", but you presumably accept that, in the situation I described (when it is considered "not likely" that the load would result in an overload current), omission of overload protection is compliant with BS7671? However,as you go on to ask ...

Who makes the decision that the overload is unlikely? The appliance manufacturer or the lad who has learnt to house bash on a 2 week special training course?

I would say 'neither of those'. As with many things, the decision needs to be made by someone who has adequate knowledge and thinking power and who also does not have the sort of potential 'vested interests' that I mentioned in relation to the manufacturer.

My guess is the appliance manufacturer who have put many hours of research and developement including overload testing and risk assessment will come up with their percentages and include in their instructions the requirements for installation based on their rigorous testing procedures based on standards possibly set by outside bodies.

No matter what the manufacturer may know and/or believe (on the basis of testing or anything else),I think one nevertheless has to suspect that what iswritten in MI's may relate to(or be influenced by) those 'vested interests' rather than anything 'technical'. Don't forget what the Technical Dept guy at MK told me - that he could not answer for (and did not even fully understand) what was written in "Technical Data Sheets" or MIs, since they were written primarily by the marketing and legal departments, not the Technical Dept !

I'm not sure what you mean by "overload testing" but if a manufacturer really believed (on the basis of testing or anything else) that their product was "likely" to result in an overload current (the only situation in which BS7671 would require overload protection) I think it would be questionable as to whether they should be selling the product, wouldn't it?

Of course,if the flex supplying the oven were large enough to be adequately protected by a 32A OPD, then the situation would become even more straightforward, since BS7671 would then be satisfied by that protection even if the oven were considered to be "likely to result in overload current", and regardless of anything the MIs might say!