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Imagine this Christmas day scene...
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<blockquote data-quote="TTbangbang" data-source="post: 19762" data-attributes="member: 1409"><p>The 3kW dishwasher is on as someone forgot to put it on the night before after midnight mass. The 1.5kW water heater is on for hot warming coffee. The 2.7kW hob is cooking potatoes and other veg for roasting later. There is 500W from two undercounter fridges humming away and someone has put the 3kW 6-slice toaster on for <em>breakfast</em>!</p><p></p><p>This is applying a worst case diversity according to actual habits of the occupants. The resulting current load is 46.5A which suggests using 4mmsq and 50A RCBO.</p><p></p><p>A 32A RCBO would trip under such a load in about 2.7hours. Such a long breakfast time is?! unlikely, so choosing a 32A RCBO seems more sensible.</p><p></p><p>A 2.5mmsq ring can carry 37A so it will be overloaded on Christmas day.</p><p></p><p><strong>Finally the question!</strong>, thanks for reading so far.</p><p></p><p>When designing circuits do you allow for rare short term overloading occurring (use a 50A RCBO) or do you ignore it (use a 32A RCBO)?</p></blockquote><p></p>
[QUOTE="TTbangbang, post: 19762, member: 1409"] The 3kW dishwasher is on as someone forgot to put it on the night before after midnight mass. The 1.5kW water heater is on for hot warming coffee. The 2.7kW hob is cooking potatoes and other veg for roasting later. There is 500W from two undercounter fridges humming away and someone has put the 3kW 6-slice toaster on for [I]breakfast[/I]! This is applying a worst case diversity according to actual habits of the occupants. The resulting current load is 46.5A which suggests using 4mmsq and 50A RCBO. A 32A RCBO would trip under such a load in about 2.7hours. Such a long breakfast time is?! unlikely, so choosing a 32A RCBO seems more sensible. A 2.5mmsq ring can carry 37A so it will be overloaded on Christmas day. [B]Finally the question![/B], thanks for reading so far. When designing circuits do you allow for rare short term overloading occurring (use a 50A RCBO) or do you ignore it (use a 32A RCBO)? [/QUOTE]
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