Max demand

[shocked]

Hi All
Ive asked this question before .
does ANYBODY know the formula for working out MAX DEMAND in a property
we all have to right some thing on the certificate

Thanks for any replies

john

 

[wot]

Hi shocked,
You need to think about diversity, take a look in your OSG Appendix 1. There are two tables - 1A and 1B, although they look the same they are used for different reasons which the notes in App 1 do explain. You may have had a rule of thumb type of estimation in mind... like adding all the breakers together and using 60% as your figure for max demand but with the ever increasing division of circuits I'm not sure how accurate the old rules of thumb are ? Perhaps someone has a good way of estimating?

Regards, Wot.

 

[m4tty]

I heard its was sum of breakers x 0.42

Cheers

 

[G_FUNK]

table in the on site guide works best. its never below you main fuse any way sods law. it changes how you apply devirsity for the type of installion it is eg shops, kitchens, domestic ect etc

 

[Graeme Harrold]

If calculating using the OSG table, take extra time to read the cooker circuit. Catches a few people out.........

Anyhoo when do you have it all switchd on...............PARTY TIME

 

[shocked]

Hi All
Thanks for the replies
I made a little program using the osg table , but found it nearly always came out more than the cutout fuse especially when there was a instantaneous water heater (shower)
Perhaps its a figure they don't look at ?????
john

 

[ezzzekiel]

I heard its was sum of breakers x 0.42

Cheers

you heard wrong.
total breakers and x0.40 gives a rough indication, but to calculate max dem correctly you should follow the corrcet procedure from regulations.

 

[shocked]

you heard wrong.
total breakers and x0.40 gives a rough indication, but to calculate max dem correctly you should follow the corrcet procedure from regulations.



Hi ezzzekiel
so can you give me some examples as i said it nearly always works out larger than the cutout fuse
thanks john

you heard wrong.
total breakers and x0.40 gives a rough indication, but to calculate max dem correctly you should follow the corrcet procedure from regulations.

Hi ezzzekiel
so can you give me some examples as i said it nearly always works out larger than the cutout fuse
thanks john

 

[welsh spark]

Hi all,
Im currently doing my 2391 20 design course.this week we did max demand and diversity you can work it out as you diversity figure being roughly 80% of the total load adding all your brakers together. Though working it out is allways better and more accurate but yes it takes time. HTH ALAN

 

[Douglas]

The max load has always been not more than 80% of the rating of a fuse or circuit breaker.
Now when it gets ito finding out the demand factor of a building it is different you have to derate the rating of example a stove or electric range including electric dryers etc
Peace Douglas