Discuss A thought about fuses in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
Howcomes we use eg a 3a fuse from the FCU to feed a boiler that has 1.5mm wiring? Wouldn't a 13a still be ok and if not, why not?
TIA
This is something not seen much today but the UK system with 3A/5A fuses could support 0.5mm flex quite safely, where as the EU/USA/world system of unfused plugs means the flex has to cope with the I2t of something like 16A OCPD at the distribution board.MI will usually state 3amp or 5amp fused for most boilers , so a bit or 1mm flex would do the job.
Using anything larger is just a waste of money really
Also easy to forget that most of the decent DB manufacturers also make 3A MCB'sThis is something not seen much today but the UK system with 3A/5A fuses could support 0.5mm flex quite safely, where as the EU/USA/world system of unfused plugs means the flex has to cope with the I2t of something like 16A OCPD at the distribution board.
Of course now the copper saving cost is dwarfed by the desire to make products for multiple markets, so you find nothing below 1mm/0.75mm made as a result, even for small loads, as the UK market is small compared to all of those combined.
I come a lot of appliances these days come supplied with 1.25mm flex , presumably as this is the smallest ( cheapest ) sized flex for 16amp appliances around the globeThis is something not seen much today but the UK system with 3A/5A fuses could support 0.5mm flex quite safely, where as the EU/USA/world system of unfused plugs means the flex has to cope with the I2t of something like 16A OCPD at the distribution board.
Of course now the copper saving cost is dwarfed by the desire to make products for multiple markets, so you find nothing below 1mm/0.75mm made as a result, even for small loads, as the UK market is small compared to all of those combined.
True, the the fault I2t of such an MCB is usually way higher than a 3A fuse, except in the region just after the magnetic trip.Also easy to forget that most of the decent DB manufacturers also make 3A MCB's
As far as I am aware manufacturer,s only seem to get away with this in Ireland and the UK only.In other countries manufacturers are expected to take care of this issue themselves by fusing the appliance internallyWhilst the cabling is adequately protected at 13A, the vast majority of manufacturers have always specified a 3A fuse to protect the boiler.
<chough> Bathroom fans?As far as I am aware manufacturer,s only seem to get away with this in Ireland and the UK only.In other countries manufacturers are expected to take care of this issue themselves by fusing the appliance internally
you can now buy a fused fan switch<chough> Bathroom fans?
One issues is if both the permanent and switched lives both need fused. Really someone should slap down on this and say that anything falling in to those categories has to be designed as safe with a 6A MCB.you can now buy a fused fan switch
One issues is if both the permanent and switched lives both need fused. Really someone should slap down on this and say that anything falling in to those categories has to be designed as safe with a 6A MCB.
One issues is if both the permanent and switched lives both need fused. Really someone should slap down on this and say that anything falling in to those categories has to be designed as safe with a 6A MCB.
Been doing Domestics for over 20 year and I have rarely fused down a fan
If you look inside the motor's wire will blow before a 3A fuse, and that won't stop it overheating if locked either locked rotor current is going to be fraction of an amp. So really is is just looking for a weasel way out of any claims...Been doing Domestics for over 20 year and I have rarely fused down a fan
Thats a very interesting point .It would explain why these very same fans are installed all over the continent and are protected ,not by a 3 or 5 amp fuse ,but by the 16 amp circuit mcb.If you look inside the motor's wire will blow before a 3A fuse, and that won't stop it overheating if locked either locked rotor current is going to be fraction of an amp. So really is is just looking for a weasel way out of any claims...
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