Error. Replied to page 1: didn't realise there were so many pages
Heating an airing cupboard
- Thread starter Lofty Bob
- Start date
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I find this obsession with arguing with Bas far more tedious and irritating than any of Bas' previous transgressions.
We now have six pages where he (Bas) is unquestionable and unarguably correct and yet there is still fatuous arguing.
Will the arguers please give an example of a manufacturer (extractor fans excepted) demanding specific overcurrent protection for their product where it is not for a supplied flex?
We now have six pages where he (Bas) is unquestionable and unarguably correct and yet there is still fatuous arguing.
Will the arguers please give an example of a manufacturer (extractor fans excepted) demanding specific overcurrent protection for their product where it is not for a supplied flex?
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No. It is there to provide, in conjunction with the upstream protective devices, overcurrent and short-circuit protection for the circuit.
One good example is a lamp with a built in dimmer, such as those touch table lamps. When the bulb blows it will take out the dimmer if a 5amp or greater fuse is used, a 3 amp will usually save the dimmer.
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Not a good example Winston, the damage is caused by the bulb blowing, not by the fuse, whatever its value.
Of course it could be argued that the dimmer should incorporate a 3 A fuse, if that's what is needed to protect it...
Of course it could be argued that the dimmer should incorporate a 3 A fuse, if that's what is needed to protect it...
They could certainly write that.
But unless, for some bizarre reason, walls other than pink ones would cause damage or danger to the equipment, then the colour would be outwith their remit, and they would have no powers to enforce pink.
I've had very little to do with this thread, so I don't know whether I count as an "arguer", but there was a recent thread ( click here ) relating to two cooking appliances, at least one of which was apparently without a "supplied flex", for which the MIs required an OPD with a maximum rating of 20A - without any suggestion that one could have a higher-rated OPD if one used larger-CSA cable...
Kind Regards, John
Why extractor fans excepted? Aren't they a good and common example of where a manufacturer specifies a maximum fuse/MCB size?
Do you agree that the 15A relates to the supply necessary for operation (presumably without diversity, although for such a small appliance it may not apply. Two elements may possibly be used at the same time) and
the 20A is for the 2.5mm² cable (although this could be 25A).
If so, do you not think these requirements are merely information for those without detailed knowledge.
If not, what damage do you think may occur to the appliance were it connected with 4mm² cable, or 6mm² - or a 25A or 32A opd?
Do you think someone with a standard cooker circuit (6mm²,32A) should replace it with 2.5mm²?
... because no ones knows why the requirement is there in the first place and not all manufacturers demand it.
It is more than likely a standard circuit arrangement diagram used.
If an FCU is shown as the (not required) isolator then they may as well state a 3A fuse - the well known CMA syndrome.
Differentiation should be made between instructions and information for DIYers.
Well, it is now as we only have to take into account these "instructions".
May I wire a 40A 'bulb' with 10mm² cable and 63A opd?
Yes. Although I can't find mention of power requirements in the instructions, the OP said that the appliance itself is labelled "3.5kW" - so (without diversity) 13A is not enough, so I guess that 15A is the 'next step up'. With diversity (and I don't see why not), 13A (i.e. a plug or FCU) would be adequate.
Maybe that was their intent, but the "maximum 20A" will be taken by most readers to mean what it appears to say - and prior to July, even many electricians would probably have felt constrained to adhere to that.
As was being discussed in that other thread, that statement (without qualification) has nuisance value if one wants to run two appliances off a single 32A supply and also 'obey the MIs'. They could, had they felt it appropriate, have said that it was OK to connect it to a 32A-protected circuit if one used 4mm² cable.
If, say, the appliance contains some 1mm² conductors, then they (and the appliance) would be more likely to come to harm (or more harm) under some fault conditions if protected by a 32A OPD than if protected by a 20A one. However, as BAS says, if that is the case then, at least in an ideal world, the appliance would include appropriate internal fusing.
Kind Regards, John
Yes, but they don't have them in Europe. What do they have?
Yes, lacking knowledge.
They can't say everything. It may run to four hundred and odd pages.
Not really, there is no difference (generally) in the wiring of small ovens and large ones (smaller ones joined together).
If the wire or its spade connector should, for some unexplained reason, burn out, it doesn't matter.
Where needed they probably would and, indeed, do. My TV and boiler have several, some standard lamps, our Flukes have one.
Well, the manufacturer has no power to enforce anything, only to indicate what he considers to be necessary for safe operation of the equipment (under normal and fault conditions). If you don't heed his advice, he has no way to enforce it, but if it all goes horribly wrong later he can say, effectively, "Told you so."
That's not how I would read that extract, since it clearly states 20A maximum for the fuse but also 2.5 sq. mm minimum for the supply cable. Since those instructions don't preclude the use of a larger cable, it doesn't make sense to say that the 20A fuse requirement is only for the supply cable. If, for example, the manufacturer felt that the internal design of the equipment made it safe to protect it with a 30A fuse, why wouldn't he say so? In that case you could then happily feed it with 4 or 6 sq. mm cable on a 30A circuit.
Aside from the obvious basic electrical principle that it's not going to hurt to use a larger cable than the minimum required to carry the current, again the manufacturer has only specified 2.5 sq. mm as a minimum. There's nothing to stop you keeping the 6 sq. mm cable and feeding it from a 20A fuse in order to comply with the manfacturer's instructions.
Ok. that's fair enough; I may have overlooked the "Min" but I still think the reasons are as I said above.
Indeed, as stated in the 'instructions', 1.5mm² (t+e) would be adequate.
I don't know; that is the problem.
It is the same with showers.
The manufacturer gives a list of 'instructions' for differently rated showers with no variation.
You could but then the manufacturer would have to state the multitude of options.
As he has only quoted the minimum size cable he has stated the opd size for that cable and efficient operation.
That's true but he would have had to state the requirements for doing that.
It is also stated that you must use PVC/PVC twin and earth. Is that true or, indeed, relevant?
Is there any difference in the internal wiring of small ovens and large ones?
You apparently disagree but I consider these 'instructions' merely as information for someone who does not know what to use through knowledge.
The problem there is - at least in this particular case - that's not how it reads. I don't see that the manufacturer needs to specify every possible permutation of permitted cable sizes and protective device if all he's doing is specifying the minimum cable size required for the equipment and the maximum permitted fuse for adequate protection of the equipment. Neither do I see that specifying a minimum cable size of 2.5 sq. mm with a maximum fuse rating of, say, 30A should be mutually exclusive, so far as the requirements of the equipment itself are concerned. Isn't it up to the installer to understand that the maximum permitted fuse rating for the equipment might be too high for the minimum specified cable size?
However.....
I agree that in many cases the supplied instructions clearly are trying to cover the very basics for somebody with little knowledge. We may well examine the instructions, the piece of equipment concerned, and come to our own conclusion about the acceptability (safety wise) of disregarding something in those instructions.
But at the same time, if the manufacturer really does have some technical reason for specifying a 20A max. fuse in the supply due to the internal construction of the equipment, surely that needs to be in the instructions?
Perhaps it would be a good idea if the manufacturers were to divide up their instructions into absolute technical requirements, in which would go instructions about permitted voltage and frequency range, maximum rating of protective device permissible and so on, plus a separate section offering guidance for the uninitiated?
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