Discuss Working out Maximum Demand. in the Electrical Forum area at ElectriciansForums.net

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always been a bit of a guesstimate. either add all breaker In values and divide by 2, or use the Ib of each circuit, allowing 100% for shower and 0.4 of the rest added, or just put in the In of the service fuse.
 
For a domestic i'd just times all the breaker values by 0.4. ...And even that will be airing on the safe side of things!! What i can tell you, is using the formula as laid out in BS7671 and it's OSG's will give you a figure that is so unrealistic or out of this world, it's untrue!! lol!! You will never see any Electrical Design Engineer ever come close to using such figures.

If a typical domestic installation sees over 40 to 45A for any extended period of time, it'll be doing well!! Yet people still insist they need a 100A supply!! lol!!
 
In our house we use no more electricity than we did before I rewired and replaced the DB. Now, however, there are more than twice the number of breakers and circuits than there were before. On paper, depending on how you work it out, you could come up with any number of figures for max demand. So you need to use a method that fits for the installation in question (and the paperwork!). It really is the rating of the main service fuse.....but apparently these scam outfits don't like you using that. So just calculate it using a method that comes in under the rating of the main fuse. :)
 
40 is a magic number. Literally every cert i've come across, people just stick the number 40...maybe it's just this neck of the woods lol.

x0.4 for me.
 

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