Yes, we know that.
My point is that either MCBs do trip instantly and something goes bang so the faults must be near negligible - or, if as you say, carcasses are live for a long time.
or
such faults never happen.
Safety issue with domestic appliance
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My point is that either MCBs do trip instantly and something goes bang so the faults must be near negligible - or, if as you say, carcasses are live for a long time.
or
such faults never happen.
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I have been asking him repeatedly, from early on, about details of the perceived problem, how he has detected a 'live' casing and how 'live' it was - and he appears to have some reason for not wanting gto divulge that information.
Indeed - but, as often discussed here, I think it arguable that they should not have the option of passing the buck to 'the installation'. As often said, if a manufacturer feels that their equipment requires over-current protection, they should provide it internally and not rely on (and impose requirement regarding) the OPDs of the installation (which, after all, are there to protect the installation, not equipment connected to it.
Kind Regards, John
I would say that we often don't know. Unless it is due to an observed event (like your touching an MCB onto a Main Switch terminal, or at the instant one switches on an appliance) it will often be the case that all one knows is that the supply has suddenly been disconnected at some point in time. However, one will quite often not know whether the responsible fault showed itself 40ms, 10 secs, 10 minutes or 2 hours previously.that point in time.
Of course, RCDs are being increasingly ubiquitous and, with them, operation is usually going to be either 'immediate' or 'never'.
Kind Regards, John
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Had a look at hob instructions it tells you to use H05RR-F3G-1,5 which is rated 15 amp and it is 2.9 kW a Gorenje EC310AC domino hob it is supplied from a FCU so would assume fused to 13A. A useless hob I used a free standing Lidi induction hob sitting on top of it with the Gorenje hob isolated at the consumer unit as it is so useless.
The Beko induction hob which it replaced HII 64401T says in the instructions maximum 32 amp single phase and 2 x 16 amp when using 2 phases. It was removed by the council who installed the disabled kitchen for my mother as it had a warning about pace makers and my mother had a pace maker also she could not use the controls due to angle of view when sitting in a wheel chair, the touch controls could not be seen. Two months after it was ripped out, my mother had a new pace maker which complied with the standards so she could have then used the induction hob.
At home I use a stand alone cooker load 10466 - 12455 W it states minimum 32A supply it does not state the maximum. Since it can use over 50 amp I would not see any problem with a 45A supply, it is actually supplied with a 32A MCB which has never tripped. Very few consumer units could house a MCB over 50A and there is a Warning: This appliance must be earthed.
The Lidi induction hob does not really count as it is a portable appliance so supplied with a 13A plug. Oh and it is class II.
So it seems instructions do vary, so before using a twin outlet cooker connection unit we should read the instructions, I suppose I am guilty in the past for installing equipment without reading the instructions, simply as not there, some one else has unpacked the device and installed it and I have only been required to connect it. It is some thing which I have commented on before, all well and good swapping a 45A MCB for a 32A MCB but unless there is paperwork to say how installed swapping a 32A for 45A is not so easy, if a smaller overload is required with commercial premises we would use a fuse box at the cooker end. But with domestic there is no FCU which can take 16A or 20A fuses.
One of these in the kitchen is not really what we want to see.
The Beko induction hob which it replaced HII 64401T says in the instructions maximum 32 amp single phase and 2 x 16 amp when using 2 phases. It was removed by the council who installed the disabled kitchen for my mother as it had a warning about pace makers and my mother had a pace maker also she could not use the controls due to angle of view when sitting in a wheel chair, the touch controls could not be seen. Two months after it was ripped out, my mother had a new pace maker which complied with the standards so she could have then used the induction hob.
At home I use a stand alone cooker load 10466 - 12455 W it states minimum 32A supply it does not state the maximum. Since it can use over 50 amp I would not see any problem with a 45A supply, it is actually supplied with a 32A MCB which has never tripped. Very few consumer units could house a MCB over 50A and there is a Warning: This appliance must be earthed.
The Lidi induction hob does not really count as it is a portable appliance so supplied with a 13A plug. Oh and it is class II.
So it seems instructions do vary, so before using a twin outlet cooker connection unit we should read the instructions, I suppose I am guilty in the past for installing equipment without reading the instructions, simply as not there, some one else has unpacked the device and installed it and I have only been required to connect it. It is some thing which I have commented on before, all well and good swapping a 45A MCB for a 32A MCB but unless there is paperwork to say how installed swapping a 32A for 45A is not so easy, if a smaller overload is required with commercial premises we would use a fuse box at the cooker end. But with domestic there is no FCU which can take 16A or 20A fuses.
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In the instructions I have found, it actually says -
"Fuse - Min 16Ax2/32A"
http://be.beko.com/urun_detay.aspx?urn=15686&kat=4533&lang=en-US
Although after diversity, one 16A would theoretically be sufficient.
So, perhaps the so-called instructions are not written by someone who actually knows what they are doing, but merely adding up numbers.
The same, then, in different words.
23A after diversity so quite understandable.
Hager and CED do.
They do indeed - some are wrong (as Winston tells us).
I must say that I would be more inclined to say that one should do some thinking and apply one's knowledge and common sense.
Assuming it is properly designed and installed, the circuit's protective devices should provide adequate overload protection to the circuit (cables, with the possible exception of any flex supplied by the appliance) and adequate fault protection for both the circuit and the appliance.
That only leaves overload protection for the appliance itself and as many of us have said many times, and you yourself said recently, if that is deemed to be necessary, then the manufacturer should provide it internally. ... and, in any event, I doubt that the rating of the circuit's OPD will have much bearing on the amount of damage to the appliance, or to the fire risk, should a fault within the appliance result in an excessive overload current. However, that's all just 'my opinion'.
Kind Regards, John
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With portable appliances I understand there is a directive meaning if it needs a overload or fuse this must be included within the appliance, so if a British appliance is used in mainland Europe and the plug is changed, it is still protected.
However with a fixed appliance we have a different set of rules, I have commissioned many items of plant where the manufacturer has instructed we should use a selected protection device, it does make some sense having it external to the machine as it can be placed where it can be accessed. I have had special instructions as to what fuse to use, be it a semi-conductor fuse or a machine rated.
However where I worked with had a competent person as he was called then in charge, where with domestic we only have an ordinary person in charge. So domestic has some special rules, like using of type tested distribution units called consumer units. So it is open for debate as to if a manufacturer of domestic appliances which are not portable should expect the installer to select the correct over current protection device?
Where the fixed appliance is supplied with a 13A plug, is it permitted to remove that protection? OK swap from plug to FCU, but if you hard wire an oven which came with a plug into a cooker connection unit with a 32A overload in the case of something going wrong what would the court say?
If we can show we have followed BS7671 then in the main the court we say we did everything expected, however the reverse is also true. In the main it is unlikely anything will go wrong, so we are unlikely to see a court case. But I am sure you can see line of questioning, what size cable was recommended for the appliance, what is the published current carrying capacity of that cable, did you fit a protective device appropriate to that cable size?
I have looked inside an oven, and the wiring is not that thick, I don't care if you can terminate a 10mm cable onto the oven terminal block, it is clear the wires inside an oven will not take 45 amp. Technically you may be able to say I followed BS7671 to the letter, there is nothing wrong with me using 10 mm cables and a 45A overload. However if it all goes wrong, do you think the court will pat you on the back and say yes you did nothing wrong, or will they say in your opinion did you really think a 45A supply was appropriate for a 16A appliance? If not then whatever BS7671 says why do it.
The simple question I am asking is with an oven over 13A but under 16A if you supply it from a 45A MCB and some one dies with the court find the manufacturer or the installer at fault, if shown that the accident would not have happened with a 16A supply?
However with a fixed appliance we have a different set of rules, I have commissioned many items of plant where the manufacturer has instructed we should use a selected protection device, it does make some sense having it external to the machine as it can be placed where it can be accessed. I have had special instructions as to what fuse to use, be it a semi-conductor fuse or a machine rated.
However where I worked with had a competent person as he was called then in charge, where with domestic we only have an ordinary person in charge. So domestic has some special rules, like using of type tested distribution units called consumer units. So it is open for debate as to if a manufacturer of domestic appliances which are not portable should expect the installer to select the correct over current protection device?
Where the fixed appliance is supplied with a 13A plug, is it permitted to remove that protection? OK swap from plug to FCU, but if you hard wire an oven which came with a plug into a cooker connection unit with a 32A overload in the case of something going wrong what would the court say?
If we can show we have followed BS7671 then in the main the court we say we did everything expected, however the reverse is also true. In the main it is unlikely anything will go wrong, so we are unlikely to see a court case. But I am sure you can see line of questioning, what size cable was recommended for the appliance, what is the published current carrying capacity of that cable, did you fit a protective device appropriate to that cable size?
I have looked inside an oven, and the wiring is not that thick, I don't care if you can terminate a 10mm cable onto the oven terminal block, it is clear the wires inside an oven will not take 45 amp. Technically you may be able to say I followed BS7671 to the letter, there is nothing wrong with me using 10 mm cables and a 45A overload. However if it all goes wrong, do you think the court will pat you on the back and say yes you did nothing wrong, or will they say in your opinion did you really think a 45A supply was appropriate for a 16A appliance? If not then whatever BS7671 says why do it.
The simple question I am asking is with an oven over 13A but under 16A if you supply it from a 45A MCB and some one dies with the court find the manufacturer or the installer at fault, if shown that the accident would not have happened with a 16A supply?
As I said, I am talking about "thinking, knowledge and common sense", not 'rules'.
This is where, in my opinion, the knowledge and common sense comes into play. Other than in (negligible impedance) L-E or L-N 'fault' conditions (against which a properly designed installation will already have adequate protection), under what circumstances do you envisage that the wiring inside a ("16A" or "13A") oven would find itself carrying a sustained current of 45A, or anything like it?
Again, I have to ask you how you think someone could die as a result of protecting a "16A" oven with a 45A MCB? IF it were possible for there to be a sustained current in excess of 45A flowing in the internal wiring of an oven, I suppose there would be a (very) small chance of a house fire resulting, as a consequence of which someone died, but, as above, I do not believe such a situation is going to 'ever' arise.
Kind Regards, John
Look inside a cooker with a three element oven and a four element hob; you will find the same wiring, each related to the demand of the individual element, plus a 15W lamp.
So, seven elements all wired in what? 10A, 16A or 20A wire.
What can you do with this arrangement other than have an OPD that is theoretically too big for each wire?
But -
The elements will not cause an overload on their individual wiring so there is nothing to protect them from.
Even if there was a cable melting and being its own fuse would not be that important; they do not catch fire.
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I would agree that in the main the ELI should be low enough to cause the supply to automatic disconnect. However personally left the employ of a firm fitting electric cookers as they would not supply me with any test gear, and at that time I could not afford to buy my own. The shop chain mainly sold gas cookers, and they employed a gas fitter and an electrician on the delivery van and we mated for each other, the gas man had every tool you can think of to test the gas supply, and around 1/3 rd of the calls we came away without fitting the gas cooker because it did not comply in some way to regulations, however the attitude was electric cookers are not dangerous just fit it.
OK a long time ago, I hope that has changed, the ELI should be tested before the cooker is fitted and if this is done and it complies then there is no danger I agree. Today the loop impedance tester is part of most electricians tool kits. But even 2004 when my mothers wet room was fitted the electrician doing the work had no more than a multi meter when he renewed the consumer unit. And he actually connected the earth wire for the party line telephone as the main earth. It would seem the house was TT with the water pipes forming the main earth, the change to plastic in the street resulted in effect there being no earth, I had to get the DNO to provide a TN-C-S supply.
So yes if fitted by a proper electrician who has a warrantee of skill as it is called, then unlikely there would be a problem, but that electrician employed by the builder installing my mothers wet room did not have a warrantee of skill nor did the person who had replaced the electric meter when if fell due for calibration. Part P had only just come in at that point, but it was in, however the builder had not applied for any permissions and the electrician it would seem was not a scheme member, my sister selected them, I had to sort out the mess.
Are you saying we no longer have people who claim to be electricians, but are just chancers crossing their fingers they don't get caught? To my mind, the good electrician would swap the MCB for a size appropriate to use, it is the chancers who would fit an oven to a 45A supply, and it is also the chancer who will not actually measure the ELI to ensure it will auto disconnect.
You seem to have moved the goalposts.
Everything I have written has been qualified by the assumption that the circuit concerned (be it 16A, 45A or whatever) has been properly designed and installed. Are you really suggesting that one should install (or use an existing) 16A circuit for an oven rather than, say, a 45A one because (if one doesn't measure Zs) the former is more likely to have a low enough Zs for ADS?
Not really.
A good electrician would measure the Zs, and if the Zs of a 45A circuit was low enough for ADS, I see no real reason why he/she would need to change the MCB. The more difficult question relates to someone who is not an electrician who is installing an oven. Ideally that person should also check the Zs of the circuit concerned before installing anything (even a light fitting), but it might be argued that a non-electrician fitting an oven to an existing circuit may assume that the installation is satisfactory.
Don't forget that, if one doesn't test it, even a 16A circuit may not have a low enough Zs for ADS (e.g. due to poor or broken CPC connection), so the issue you're talking about doesn't actually go away even if one installs (or changes to) a 16A MCB. If there is any doubt about the circuit's Zs, it should be measured - and anyone who doesn't could, I suppose, be described as a 'chancer'.
Kind Regards, John
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I would agree all circuits should be designed correctly. So with a B type 45A MCB looking at 0.97Ω so with a 0.35Ω incoming that should not be a problem, really it should be 0.71Ω if the volt drop is within limits assuming a 10 mm² cable with a 6 mm² earth.
When I was a boy my playing with electronics caused a short line to earth which ruptured the fuse.
When the wet room was installed the ELI was over 100Ω at the consumer unit.
So between the two events some thing has happened which has resulted in a house which did have an adequate earth to no longer have one, and this is nothing to do with house wiring, I could not find any sign of an earth rod other than the one for BT party line, and there did not seem to be an earth provided by the DNO, the DNO did after supply an earth.
OK looking at around 30 years between events, and it should be tested every 10 years. But from experience I can say even if it was OK when installed it does not mean it is still OK. And the lower the ELI required to open the circuit the more likely it is to fail.
When I was a boy my playing with electronics caused a short line to earth which ruptured the fuse.
When the wet room was installed the ELI was over 100Ω at the consumer unit.
So between the two events some thing has happened which has resulted in a house which did have an adequate earth to no longer have one, and this is nothing to do with house wiring, I could not find any sign of an earth rod other than the one for BT party line, and there did not seem to be an earth provided by the DNO, the DNO did after supply an earth.
OK looking at around 30 years between events, and it should be tested every 10 years. But from experience I can say even if it was OK when installed it does not mean it is still OK. And the lower the ELI required to open the circuit the more likely it is to fail.
Indeed - so there should not be a need to change the MCB because of 'doubts' about the Zs. As I said, if there are doubts, then it should be measured, rather than changing the MCB!
Well, that obviously depends upon the CSA and length of the cable in the final circuit.
I thought that 10mm² T+E had a 4mm² (not 6mm²) CPC. With a Zs of 0.71Ω and your assumed Ze of 0.35Ω, that would leave 0.36Ω for the R1+R2 of the final circuit which, if the CPC is 4mm² would imply that R1+RN would be about 0.21Ω. If you are working out VD for 45A, that would therefore be about 9.45V (i.e. about 4.1%). However, even if one is concerned about VD (which I wouldn't be, for cooking appliances), I'm not at all sure that, for a dedicated circuit, one has to assume that 45A would be flowing, if the current drawn by the hard-wired load would be appreciably less than that.
As above, if there is any doubt about the Zs, it should be measured - rather than just decrease the MCB rating 'in case' the Zs is too high. Let's face it, if one doesn't measure, then there is no guarantee that the Zs would even be low enough for the lower-rated MCB.
I'm not so sure about that. Whatever the MCB's In, cable CSA tends to be selected as the very minimum that will result in a satisfactory Zs. A 16A circuit may therefore be just as 'marginal' as a 45A one.
Kind Regards, John
Plus, of course, there is never a need to have a 45A MCB in usual domestic.
I did have a customer once whose High Street store had refused to fit her new cooker because the circuit did NOT have a 45A MCB, so there may be some unnecessary ones around, but it, or rather the circuit, was perfectly happy on the 32A after I connected it.
Range cooker - 2 ovens, 5 hobs, small house - so unlikely anyway to have all on at once.
Total 14,255W so 25A with diversity, no cooker switch socket.
I did have a customer once whose High Street store had refused to fit her new cooker because the circuit did NOT have a 45A MCB, so there may be some unnecessary ones around, but it, or rather the circuit, was perfectly happy on the 32A after I connected it.
Range cooker - 2 ovens, 5 hobs, small house - so unlikely anyway to have all on at once.
Total 14,255W so 25A with diversity, no cooker switch socket.
Indeed, and even a 32A one is probably unnecessarily high for 'ordinary' cookers (20A would often be adequate) - but I suppose people think about 'future proofing'. However, 45A is quite ridiculous - that's about 127A pre-diversity, aka about 29kW!
Kind Regards, John
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