Amperage normes - why?

[thunderhorse]

I'm trying to understand the why? with electrical normes.

For example, my dishwasher is stamped 2300w, which implies a current draw of about 10 amps max. The normes advocate a 20 amp disjoncteur. Is this 20 amp a maximum? Why won't a 16 amp DJ suffice i.e. 3.5kw+ ?

I also note in L'installation électrique in respect of electric radiators that the DJ is dependant on wattage, so it's user discretion in that case.

Six daisy-chained sockets in bedrooms where the max load will be from a 1300w vacuum cleaner. Again, is the advocated 20amp DJ a maximum? Why not 16 amp, or even 10 amp?

Are these ratings for DJs a maximum rating or a no-choice rating? Is there a safety aspect in an apparent higher than warranted DJ rating (that's what loses me). If the ratings are to protect the general circuits of 1.5mm2 and 2.5mm2 wiring, and not the appliances, where do 10amp DJs fit in?

Could someone explain the logic behind them for the betterment of understanding?

Many thanks, guys.

Cheers

[Nick Trollope]

These are maximums, if you want to use a smaller breaker then you are quite entitled to do so.

Heater wiring is less discretionary, I would say. For a power (or lighting) circuit, 1,50mm cable "fits" with a 16A disj. The max fuse rating for a 1,50mm heater circuit is 10A (being 2200W).

 

[thunderhorse]

Many thanks, Nick. That about sums it up for me.

Cheers. [:D]

[powerdesal]

[quote user="thunderhorse"]I'm trying to understand the why? with electrical normes.

For example, my dishwasher is stamped 2300w, which implies a current draw of about 10 amps max. The normes advocate a 20 amp disjoncteur. Is this 20 amp a maximum? Why won't a 16 amp DJ suffice i.e. 3.5kw+ ?

I also note in L'installation électrique in respect of electric radiators that the DJ is dependant on wattage, so it's user discretion in that case.

Six daisy-chained sockets in bedrooms where the max load will be from a 1300w vacuum cleaner. Again, is the advocated 20amp DJ a maximum? Why not 16 amp, or even 10 amp?

Are these ratings for DJs a maximum rating or a no-choice rating? Is there a safety aspect in an apparent higher than warranted DJ rating (that's what loses me). If the ratings are to protect the general circuits of 1.5mm2 and 2.5mm2 wiring, and not the appliances, where do 10amp DJs fit in?

Could someone explain the logic behind them for the betterment of understanding?

Many thanks, guys.

Cheers
[/quote]

Regarding the max bedroom circuit loads of 1300w, what about other items, such as table lamps, tv / radio (possibly if thats your thing), fan heater on a cold winter evening, hair styling stuff, all simultaneous loads. Even silly low low load items like phone chargers, lap tops etc. They all add up.

[thunderhorse]

[quote user="powerdesal"]Regarding the max bedroom circuit loads of 1300w, what about other items, such as table lamps, tv / radio (possibly if thats your thing), fan heater on a cold winter evening, hair styling stuff, all simultaneous loads. Even silly low low load items like phone chargers, lap tops etc. They all add up.[/quote]

Fully agree, and 1300w may stretch to 1500w or 2.5kw. But I was querying the principle and logic employed in arriving at the published ratings.

Cheers