max demand

[scott 123]

went to domestic job today where max demand was 236A (around 175A after diversity) main fuse is 100A so demand seems high to me...just wondered when you design what demand do you go to

 

[shanky887614]

Are you adding the mcbs together to get 236?

Your max demand sounds a little strange really.

If it is a very big place I would imagine it has a 2/3 phase supply

 

[scott 123]

Yes..... and its big house but
single phase

 

[dazza1981]

Be interesting to see how your diversity calcs gave you the 175 Amp figure !!!

 

[shanky887614]

Yes..... and its big house but
single phase

I think you should have a look im osg etc on diversity.


Go home put everything on max and then clamp tails from meter, you won't get anywhere near 100amps


i live in a 4 bed house that has two electric showers, induction hob etc

Between these 3 rated amps is over 120amps

 

[Simonslimline]

Has the fuse ever blown!!!

 

[scott 123]

Top of my head calcs

5 x6a lights 15.84
1x6a smokes 6
3 x 32 ring 25.6
20a dish washer 20
20 a outside sockets 20
20 a boiler 20
20 a cooker 20
50 a garage

 

[DPG]

Dishwasher pulling 20 amps?? Garage using 50 amps?? Daz

 

[dazza1981]

50 Amps in the garage ??????
ARRRR other Daz beat me lol

 

[Simonslimline]

Anything nice growing in the garage?

 

[dazza1981]

Anything nice growing in the garage?

:sifone::tree:

 

[Corbs]

must be one big boiler to pull 20amps

 

[Silly Sausage]

went to domestic job today where max demand was 236A (around 175A after diversity) main fuse is 100A so demand seems high to me...just wondered when you design what demand do you go to

Did you try clamping the Line tail?
Domestic Diversity, do your calculations then divide the answer by at least 10!

 

[scott 123]

Original question was how much do u go to

 

[scott 123]

Didnt clamp...just thinking about design

 

[Silly Sausage]

Original question was how much do u go to

To the size of the incoming fuse!

 

[scott 123]

Garage and boiler thats the cicuit the installer installed

 

[scott 123]

Not that helpful

 

[Andy78]

Not that helpful

Neither is your info. What's in the garage that is drawing 50A ?

 

[scott 123]

Original question was how much do u go to

To the size of the incoming fuse!

Lots of boards ive seen are over incoming fuse

 

[Andy78]

Which of these do you think is closest to the actual current draw of an installaton ?

• the ratings of all the mcbs added together
• the ratings of all the mcbs added together with diversity applied by the OSG method
• the ratings of all the mcbs added together multiplied by the rule of thumb figure of 0.4
• the rated total of all connected loads

Your clamp meter knows the answer...

 

[scott 123]

50 amp supply from main to board to board in garage with 32 a ring ...6a lights...6a outside lights .....16a hot tub.....20a outside socket ...I know it wont use any near but thats what the design is..I didnt design it I just interested in design opinions

 

[Silly Sausage]

Not that helpful

Neither is your info. What's in the garage that is drawing 50A ?

What Andy says, a list of MCB/circuit max ratings is vague to say the least!

 

[scott 123]

How do u clamp..at design stage..would b intersing to see that being done :O

 

[R G]

Anything nice growing in the garage?

Could be , just seen another thread where the storage heaters have got a real high , the op says the storage heaters are tripping !!!LOl..

 

[Silly Sausage]

Not that helpful

How do u clamp..at design stage..would b intersing to see that being done :O

You're at an existing installation, presumably with the cts you've listed, clamping it might just give you an idea of the actual demand.
Without knowing the full details of an installation, trying to do a design spec on an internet forum is nonsense.

 

[Andy78]

50 amp supply from main to board to board in garage with 32 a ring ...6a lights...6a outside lights .....16a hot tub.....20a outside socket ...I know it wont use any near but thats what the design is..I didnt design it I just interested in design opinions

So did the designer. Design includes diversity. How you choose to apply diversity depends on the way you were taught and your experience.....

 

[scott 123]

At last a sensible answer

 

[Silly Sausage]

Try it at home.
You can work it out in minutes from your statements or monitoring your meter for a week or so, you'll be amazed at low it is.
Unless you get HUGE bills all the time.


I average about 3 Amps max over about 18 hours a day.

 

[Plonker 3]

Here's a example for you

If a 32 amp radial had 2 single sockets on it, and another 32 amp radial has 12 single sockets on it which one is the bigger load?

 

[DPG]

Depends what's plugged in. Daz

 

[Plonker 3]

Sssshhh, trying to see if the OP could work that out.

 

[scott 123]

Or how many extension leads are plugged in

 

[DPG]

Sorry dillb. Thought you were having a blonde moment. Lol. Daz

 

[Andy78]

Or how many extension leads are plugged in

Because multiple appliances plugged into a 4 gang extension lead fitted with a 13A fuse can draw 4 times as much as a single appliance fitted with a 13A fuse right ?

 

[atm84]

Can't be bothered reading all the previous posts but DNO's allow 2KW per average domestic dwelling. That's not even 9 amps.

 

[jimjimjim]

Can't be bothered reading all the previous posts but DNO's allow 2KW per average domestic dwelling. That's not even 9 amps.

Yeah, but it doesn't stop someone pulling ten times that.

Jim

 

[jaypp]

Here's a example for you

If a 32 amp radial had 2 single sockets on it, and another 32 amp radial has 12 single sockets on it which one is the bigger load?

12 single sockets are much heavier than 2, so I'm going to say 12!
Re. thread, it'll be fine and you've got to think the designer knows it will. E.g for starters you can pretty much ignore what the smokes pull!

 

[DPG]

Ha ha never noticed that - 6A for a couple of smoke detectors! Brill. Daz

 

[trev]

I just took a look at an Aico smoke I'm installing at the weekend. 0.8w. Now I'm putting 2 in so that's 1.6w, so 1.6/240= 0.006 (recurring) amps so let's call it 0.007.
I just saved you 5.993 amps mate

 

[Dcf]

I got an owl meter from eddies recently.
my house pulls about 300-400w when there isn't much on.
that will be the fridges and freezer then.
most ive seen it draw was 4.5kw when the oven an induction hob were on
oven rated at 3.5kw and induction hob at 7.5kw.
nowhere near it.
I spoke to a engineer from sse recently who said the amount of commercial places wanting 100kw per phase supplies was unreal.
and when such supply is put in the install runs about 15-20kw a phase.
do sse up rate their substations and network cables to accommodate all these 100kw supplies
do they buggery.
its the same network that's been in for years.
most of the outgoing fuses in your local substation will be 400a.
630a at a push.
this will deal with a whole street.As archy says do the calcs and divide by 10 to get somewhere near real running loads

 

[DPG]

Agree with dcf - my house shows around 300-500W normally. Bit less when kids Playstation and stuff isn't on etc!

 

[7029 dave]

Get some load on,turn everything on then clamp it. (an look at meter) take off. lol

 

[Engineer54]

Maybe looking over the ''Similar Threads'' at the bottom of this page (All marked up with ''Max Demand'' as the title, or part of the title) will at the very least educate you a little, as to how you would go about initially assessing the max demand of an existing installation....

 

[GLENNSPARK]

Maybe looking over the ''Similar Threads'' at the bottom of this page (All marked up with ''Max Demand'' as the title, or part of the title) will at the very least educate you a little, as to how you would go about initially assessing the max demand of an existing installation....

this must have been done ..what....a thousand times eng....you can keep on till your blue in the face about Max. demand & diversity....

common sense has to prevail here.....

 

[GLENNSPARK]

i`v often seen the one where Max demand has been put down as 100A....just caus it was a 100A BS88/BS1361 bullit...

shockin...