How can i get my demand clacs down for assesment

[Robinson]

Bit confused as to a way around this. Got house extension. im having a 80 amp up grade to incomer but i think it will need 100amp. but they wanna charge nearly £2000..
we already took another shower plus some bits of their list but still up there

AM i doing this right.? as i wanted to use this as an assesment..

Old exsisting house circuits

32 ring Up 100% then 40% of other circuits = 32
32 ring dwn 40% = 12.8
6 light
16 Immer 100% f.l = 16

New circuits (customer wanted sep Raidals for app's)

16 Fridge the 40% = 6.4
16 Freezer the 40% = 6.4
16 D/W the 40% = 6.4
16 W/M the 40% = 6.4
16 Boiler the 40% = 6.4
32 Cooker 10amp + 30% f.l = 16.6
40 shower 100% f.l = 40
32 Ring the 40% = 6.4
6 light loads spots
6 light loads spots all 3 circuits 66% max demand = 11.8


Using Diversity from Tab 1b i still 167.6 amps. which is just way over..

am i doing something wrong here. It says i must on notes for Tab 1b that if using this table the max demand for any circuit is the rated current of OP dvice of that circuit..
i cant use tab 1a within it...

pulling my hair abit here .

as i know the house wont ever pull that, BUT how will i explain this to the assesement officer maybe just getting anxious cos its next week... sorry for long one

 

[tony mc]

http://www.electriciansforums.net/e...ml?highlight=re+tony+cable+and+maximum+demand

This may help

 

[Robinson]

Yeah does help. i mean. i know as i have had fair amount of experience just working for firms though , and i know that this house is going now where near that figure but what im concerned about it how to get that across to the assessor when i am the one who should of done design calcs etc..

 

[SirKit Breaker]

That lot looks hard work. are you trying to work out the maximum demand to put in the box on the EIC? If so add up the sum of all your breakers, then multiply it by 0.4, your answer is near enough and will do. It was good enough for my Elecsa assessor, so its good enough for me.

Cheers........Howard

 

[Robinson]

That lot looks hard work. are you trying to work out the maximum demand to put in the box on the EIC? If so add up the sum of all your breakers, then multiply it by 0.4, your answer is near enough and will do. It was good enough for my Elecsa assessor, so its good enough for me.

Cheers........Howard

TELL me about it......i would always do the old 0.4 but it comes to 112.8, SO are you saying your Elecsa assessor (who im going with too) would allow you to have a figure like that in box?

 

[johnboy6083]

my 2 p's worth.
you are using the rating of the breakers to work out your diversity, when IMO, 5 of those circuits are massivley underloaded. Fridge, freezer, boiler, wahding machine and dishwasher. by using the rating of those appliances for your diversity xalculation instead of the breakers, then that alone will bring your calcs under 100 A, when combined with the 40% method.

 

[ian]

when i apply diversity i get 102 amps.
ian

 

[telectrix]

i'll go with johnboy. washer 8A full load . d/washer ditto.pstairs ring never more than 5A, etc. i would enter a figure of 80A ,

 

[ezzzekiel]

not really as if using the 40% rule you should take the full rating of the largest breaker and then 40% of the remainder.

 

[SirKit Breaker]

TELL me about it......i would always do the old 0.4 but it comes to 112.8, SO are you saying your Elecsa assessor (who im going with too) would allow you to have a figure like that in box?

Yes! This is the maximum demand, in reality you will never reach it, and if you did it would only be for a very short period of time.
Look at it another way. You have a radial circuit in 2.5mm T&E protected by a 16a 60898 mcb, it is 20 metres long and has 20 twin socket outlets, so you could in reality plug in 40 appliances at 13a....so what is the maximum demand for that then...but it will never happen.

This is one of those questions that crop up frequently, dont read too much into it or beat yourself up, you have to make an educated guess, and no more.

Cheers........Howard

 

[londonlec]

If you look at this from the other angle, all those radials you have are pushing the Demand figure up.

Imagine if they were ALL on a ring, you would have an installation that is well within 100amps.

I feel this is why the figure is so high, because you have those appliances seperated, as opposed to all together on one ring.

(I realise this has been said but I wanted to go into a bit more detail!)

 

[Robinson]

Yes! This is the maximum demand, in reality you will never reach it, and if you did it would only be for a very short period of time.
Look at it another way. You have a radial circuit in 2.5mm T&E protected by a 16a 60898 mcb, it is 20 metres long and has 20 twin socket outlets, so you could in reality plug in 40 appliances at 13a....so what is the maximum demand for that then...but it will never happen.

This is one of those questions that crop up frequently, dont read too much into it or beat yourself up, you have to make an educated guess, and no more.

Cheers........Howard

Cheers Howard. Yeah thats the thing it is a new domain for me to go through the scheme provider and just wanna get it right...I have done the 0.4 in head for long time...yet never needed to actually deal with it on paper if you get me, someone done it for me......

Lets move on.....

 

[DurhamSparky]

i remove said fuse from carrier at property!!! look at rating and write that down...!!

 

[Robinson]

If you look at this from the other angle, all those radials you have are pushing the Demand figure up.

Imagine if they were ALL on a ring, you would have an installation that is well within 100amps.

I feel this is why the figure is so high, because you have those appliances seperated, as opposed to all together on one ring.

(I realise this has been said but I wanted to go into a bit more detail!)

I do agree its not ideal is it, but what im faced with. learning curve for sure

 

[Knobhead]

I seem to recall another thead extoling the vertues of radials. Hmmm