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

 

[Des 56]

This is another example of using the on site guide for a estimate of loading by circuit quantity and breaker size
It is in my opinion,one of the poorest and inaccurate ways of using diversity to calculate demand

Use lots of circuits to make a superior design and all of a sudden your figures go through the roof
Up ring, down ring, kitchen ring,cooker,shower and a couple of radials and you need Aberthaw power station as your exclusive supply

 

[KFH]

I did a diversity calc according to the OSG on my house. It came to 140A. It has been running on a 60A fuse for the last 30 years, it has never blown!

 

[1shortcircuit]

How about turning everything on and using a clamp meter to see what is actually being pulled???

 

[Robinson]

This is another example of using the on site guide for a estimate of loading by circuit quantity and breaker size
It is in my opinion,one of the poorest and inaccurate ways of using diversity to calculate demand

Use lots of circuits to make a superior design and all of a sudden your figures go through the roof
Up ring, down ring, kitchen ring,cooker,shower and a couple of radials and you need Aberthaw power station as your exclusive supply

I have to agree with you. Although I wouldnt say superior design.....LOL . I do like the idea of Separate supply's to each Appliance bUT still seemingly it good in practice bad on paper.....

 

[Robinson]

How about turning everything on and using a clamp meter to see what is actually being pulled???

Most defiantly will be !

 

[Robinson]

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

I believe its come back and taken a large bite out of ones back side ! We live we learn.

 

[Robinson]

I believe its come back and taken a large bite out of ones back side ! We live we learn.

Interesting though without going back on that old thread , how on earth do they expect to implement this suppose change over to radials if it will cause all
these type of time wasting demand through the roof problems. ! one can only wonder.!

 

[NoSparks]

......................Est Load

Fridge .......................2
Freezer .....................2
Dish Washer ..............4
Washing machine........10
Boiler........................1
Oven........................6 (Cooker is ambiguous Hobs are upto 10Kw while ovens are say 1.2Kw
Shower ...................40
32 Ring ...................13
6x50 =300W = .........1.3
6x50 =300w ............1.3

Total 81 * 40% = 32Amps

plus original
ring Up....................13
ring down.................13
6*60 = 300W...........1.3 (assuming 60w tungsten)
Immersion.................13

Total 40 * 40% = 16Amps

Grand Total 48Amps.


I believe this is realistic! My house has many more circuits than you mention (without electric shower) but the maximum load ever measured was 7Kw 30 Amps

 

[1shortcircuit]

Just spotted something there.

I thought that when calculating the max demand for a lighting circuit it is suggested that the lamps are fitted with 100 watt lamps because these can be fitted at any given time?

:thumbsup

 

[Robinson]

Just spotted something there.

I thought that when calculating the max demand for a lighting circuit it is suggested that the lamps are fitted with 100 watt lamps because these can be fitted at any given time?

:thumbsup

Yes it is but i thought when working from Tab 1B its only taken from overcurrent protective device....not from tab A... NOsparks this certainly seems the morn realistic side of things ...many thanks guys for help........

 

[SirKit Breaker]

If you want a difinitive figure, then go and plug in all the appliances you can lay your hands on, put the shower on max hot, oven on full, hob on full, etc etc etc, then shove a current clamp around the live tail.......heyho, maximum demand.........sorted.

Cheers........Howard

 

[NoSparks]

Just spotted something there.

I thought that when calculating the max demand for a lighting circuit it is suggested that the lamps are fitted with 100 watt lamps because these can be fitted at any given time?

:thumbsup

That's a thought, but can you buy 100watt lamps any more?

 

[Robinson]

That's a thought, but can you buy 100watt lamps any more?

Well you can some places but few and far.....still if you were going strict by book its says if using Tab B you work out demands by over current devices not including tab 1 OSG. so i read as they say do one or other. and then as many pointed out they say its for the competent person/designer to judge basically...