Trying To Understand Diversity

[OnlQQker]

I'm trying to understand diversity a bit more.

Someone, somewhere done a calculation to determine how much use the circuits would be undergoing at any one time.
But what if somebody moved into a flat/house and didn't care how much it cost and just run everything all at once. I know this rarely probably happens but it's still a possibility isn't it?

Or am I missing something here, I'm not an electrician but just find electrics fascianting and try to understand what goes on.

Hi by the way I'm new here

Merry Christmas

 

[littlespark]

Well, they won Britain’s Got Talent back in 2009,led by Ashley Banjo who is now.......

Oh sorry.not that diversity.

Basically it had to be developed over the years as people realised not every electrical appliance would be all turned on at once. If it did, the currant demand would dictate such a huge cable size it would be uneconomical to wire a house.

 

[Baddegg]

That’s the point mate, probability and engineering judgement

 

[Wilko]

But what if somebody moved into a flat/house and didn't care how much it cost and just run everything all at once. I know this rarely probably happens but it's still a possibility isn't it?

Merry Christmas to You too OQ !
You raise an interesting point - if it was known that this was likely then a ‘load study’ would be advisable to establish exactly what loads were being used in the installation. With hot water heaters there is no allowance for diversity, as it’s always assumed to be full load because folks don’t really want their HW half hot. There is diversity allowance possible for domestic kitchen cookers reflecting the fact that no one normally fully loads all the rings and ovens with food and then starts them all heating at once. And if they did and the 6mm 32A circuit got a 40A load it would likely only happen once and for only a few minutes till something reached temperature and started to power cycle. No worries. On the other hand a chip fryer in the Hasty Tasty Restaurant will probably be fully loaded all day and should have no diversity allowance, otherwise something other than chips might start to cook .

 

[OnlQQker]

Many thanks for the replies, it does make a little more sense now.

I wonder when diversity first raised it head in electrical mathematics, I mean at some point in the past somebody had to come up with the theory and for reasons obviously stated above.
Somebody informed me not long ago that gas boilers are going to be phased out, to my understanding electric boilers are going to be replacing them, if this is the case then I guess diversity is going to be rewritten?

Anyway it's Christmas Eve and the wife is nagging me to go shopping. I've brought her a Pug for Christmas and despite the rolls of fat and bulging eyes the dog seems to like her!

 

[buzzlightyear]

I've brought her a Pug for Christma

a dog is not only for xmas bang it in with the Turkey ,lol.merry drinkus.

 

[Midwest]

Interesting point you make about electric replacing gas CH boilers, as they are phased out.

There’s some time between now and when that happens for new builds, depending on who you believe. Manufacturers will have to come up with some new ideas, as the running costs will be high, however well a house is insulated. And consideration of demand loads, especially at night in the middle of winter, charging your electric SUV etc as well.

 

[PEG]

As far as i understand things,the "electrical everything" method,was going to be powered 50/50,by hope and luck,emerging from a green revolution....

The principle,is,a sub-critical,fissile material,called corbynite,was inserted and removed,from an existing mass,or party,and the heat generated,used to drive steam turbine generation.

Failing that,i think we're all just pedalling things....which puts engineers,back at the top of the food chain ???

Happy Christmas?

 

[davesparks]

I'm trying to understand diversity a bit more.

Someone, somewhere done a calculation to determine how much use the circuits would be undergoing at any one time.
But what if somebody moved into a flat/house and didn't care how much it cost and just run everything all at once. I know this rarely probably happens but it's still a possibility isn't it?

Diversity doesn't really work on what a circuit will carry at any one time, it's more of an assessment of the predicted average.

Diversity takes in to account the nature of how electrical loads use power.
Electric heaters or cookers are a good example load for this, they are thermostatically controlled so they will be switching themselves on and off according to temperature. If you have a cooker with two ovens and four hobs and turn all elements on at once they will all start to heat up and will draw the maximum current possible. However they will very soon reach their cut-off temperature, but each one will cut off at different times,and after a period of time each one will cut back in again, but again at different times.
So after a brief period of drawing peak power it will settle down to a lower current draw.
In the real world of course not all elements will be switched on at the same time so this further lowers the average current draw.

Diversity takes all of this into account and gives us a prediction of what the load current we need to plan for is.
It's worth noting that the actual average current draw is normally less than the figure calculated using standard diversity factors from the book.

With your example of somebody running everything all at once there will still be diversity applicable, some loads will obviously draw constant current such as lighting, but other loads will still have variable current draw. In the time it takes to walk around a house and switch on every appliance possible some of them will already have started to vary their load.