Designing with diversity on sockets

[GBDamo]

You are nowhere near double the rating of the fuse

I'm not sure what point you're trying to make to be honest

is it that a 100A BS1361 is not rated at 100A, and not the current at which it will blow in a given time.

or

do you believe the install in question will draw nowhere near 100A.

 

[Harry_P]

I'm not sure what point you're trying to make to be honest

is it that a 100A BS1361 is not rated at 100A, and not the current at which it will blow in a given time.

or

do you believe the install in question will draw nowhere near 100A.

You know exactly what point I have made and if you don't know then you can read my posts again. It's quite simple and you should drop the confrontational attitude and you might learn something

 

[Pete999]

There is no way that house is drawing 30+ kw of power. Common sense and arithmetic will confirm this.
Ps how much current does it take to blow a fuse that has got 100 written on it?

a hundred what?

 

[Harry_P]

I'm not sure what point you're trying to make to be honest

is it that a 100A BS1361 is not rated at 100A, and not the current at which it will blow in a given time.

or

do you believe the install in question will draw nowhere near 100A.

a hundred what?

The conversation is regarding fuses,if a fuse has got 100 written on the side of it then it's going to be a hundred.....wtf do you think???

 

[GBDamo]

You know exactly what point I have made and if you don't know then you can read my posts again. It's quite simple and you should drop the confrontational attitude and you might learn something

Bad day?

 

[Silly Sausage]

The conversation is regarding fuses,if a fuse has got 100 written on the side of it then it's going to be a hundred.....wtf do you think???

Always use the SI Units, we're professionals here!

 

[Harry_P]

Bad day?

Back to diversity.....or have you conceded that its too hard for you to grasp?

 

[Harry_P]

Bad day?

Back to diversity.....or have you conceded that its too hard for you to grasp?

Always use the SI Units, we're professionals here!

Anyone who insists on using the precise terminology during discussions with contempories is a professional prat. When on site do you ask your mate to' pass me the fully insulated to 1000 volts vde flathead 3mm tightening implement"? I would just say 'pass me the terminal driver" but each to their own

 

[GBDamo]

Back to diversity.....or have you conceded that its too hard for you to grasp?

Ok, but which diversity?

That that is described in the OSG.

Or

That which more experienced electricians use.

I've no problem with being wrong, hence my original post with the detail and the result I came to. It's there to be shot down.

I also understand pragmatism but at some point we have to comply with the BBB and I don't see where this pragmatic approach is justified in the BBB.

I'm not saying it's wrong, and it is common sense to be pragmatic.

 

[Lucien Nunes]

...
32A hob (6kw) and socket = 31A
32A kitchen sockets = 32A
32A lounge Sockets = 12.8A
32A up sockets =12.8A
32A up sockets = 12.8A
20A oven(3kw) and socket 18A
...

You've allowed 18.6kW in the kitchen. All that power turns to heat, so imagine what it would be like with nine 2kW heaters all running in the one room. It would soon be uninhabitable!

Take a large school with over 1000 pupils, in multiple buildings spread out over a site. Think of all the loads in the boilerhouse, swimming pool plant room, theatre (all tungsten lights), kitchen, computer rooms, all the lighting (mostly fluorescent) and power for classrooms, labs, offices etc. They had air conditioning installed in a building and for the first time, one of their company fuses failed. It was a 250A BS1361. The others followed. A logger showed their peak consumption was around 310A.

my previous television was 1200 watts

Either it had a 200" screen, or it was on fire. 120W sounds more like it for a decent size CRT TV.

 

[GBDamo]

I know a cooker cycles and will only draw max current for a short period, as will a hob and all the other appliances will be used infrequently therefore the max current will be much lower but the only official method of calculating load is that in the BBB AND the only official fiddle factor is diversity which is also in the BBB.

This gives me a number that I know to be overstated. There must be something official that states we can continue to mitigate the diversified figure to more accurately reflect reality but it's becoming clear I'm looking for something that doesn't exist outside the heads of more experienced electricians.

 

[Baddegg]

OP, once you’ve been to a few 3 bed houses with loft conversions,massive kitchens and a summer house and you see the main fuse is 60A you’ll also understand it better, as a rule I always take of the largest mcb/rcbo add the rest up and x by 0.4 then add the lot together as per osg but as others have said even after that you can apply some common sense and experience......engineering judgment my tutor used to call it

 

[Harry_P]

You've allowed 18.6kW in the kitchen. All that power turns to heat, so imagine what it would be like with nine 2kW heaters all running in the one room. It would soon be uninhabitable!

Take a large school with over 1000 pupils, in multiple buildings spread out over a site. Think of all the loads in the boilerhouse, swimming pool plant room, theatre (all tungsten lights), kitchen, computer rooms, all the lighting (mostly fluorescent) and power for classrooms, labs, offices etc. They had air conditioning installed in a building and for the first time, one of their company fuses failed. It was a 250A BS1361. The others followed. A logger showed their peak consumption was around 310A.


Either it had a 200" screen, or it was on fire. 120W sounds more like it for a decent size CRT TV.

If I had said that my OLD tv was indeed a crt model then your reply would have made sense,however it wasn't a crt and WAS in the region of 1200 watts. Thanks anyway

 

[DPG]

1200 Watts sounds very high for a flat panel TV. Mind you, some of the early plasma ones were a bit power hungry.

 

[Jjc]

That OSG max demand/diversity calculator is a little out of date, all well and good when granny had a couple of three bar heaters chugging away and a few 60 watt incandescent lamps heating the planet up.

Think about what actually runs domestically from a socket circuit.

In bedrooms there's the odd alarm clock, bedside lamp, TV, phone charger, toothbrush charger, shaver socket, occasionally the odd hair dryer and curling tongs etc. So realistically no more than say five amps.

In living areas you have the usual TV, DVD player, possibly computer, internet router, standard lamps, phone chargers etc. Again not a massive amount say around another five amps.

The odd time you may get the vacuum cleaner running around.

Kitchen is where you have your bigger appliances with larger current draw. So kettle, washing machine, dishwasher and tumble dryer. I've left an oven and cooker out of this for now as they would normally be on their own circuits. The appliances rarely run at the same time so potentially your could base your calculation on your highest rated device and add 50% for good measure. Say around 15 amps.

So there you have a basic domestic property drawing around 25 amps at a guess, TBH they're normally a lot lower than that.

This doesn't take into account electric showers, heating, instantaneous water heaters etc.

Maximum demand is really a 30 minute snap shot at one moment in time. You will get the odd spike when the tumble dryer and kettle are running at the same time then Doris decides to do the ironing whilst Desmond is hoovering upstairs, but how often does that happen?

By looking at maximum demand you can then start to work out your diversity and how to balance your circuits for maximum effect.

And then use a bit of SWAG, scientific wild arsed guess...

TBH general use sockets in a two bed domestic property you could get away with a couple of 20 amp radials with a 32 amp RFC for the kitchen/utility room.

Dosnt using Dorris and Desmond imply ageism .Naught,naughty.

 

[brianmoooore]

I own a couple of two bedroom houses, each of which ran for over 30 years on a 45A switchfuse each. They were poorly insulated and had no fixed heating of any kind. Each had a 3kW immersion heater for hot water. The properties and their supplies were uprated five years ago, and the gear removed showed no signs of overheating whatsoever.
Also supplied from the 100A DNO fuse that the two houses were on sub mains from, was a five bedroom farmhouse and a three bedroom barn conversion, plus a few farm buildings. DNO fuse never got as much as warm.

 

[SparkyChick]

There has been a report about this thread and I concur with the comment on the report, it's getting a little bit heated, so I would encourage those who are clearly being confrontational to wind your necks in a little and try and keep it nice and friendly.

Remember, not everyone may be up at your level in terms of knowledge and they are probably trying to learn and understand more (which is a good thing, I think we can all agree), so instead of trying to berate and belittle them, try and share your knowledge with explanation.

Thanks