Help with diversity

[Markymark981]

[COLOR=rgba(0, 0, 0, 0.701961)]Hi wonder if u could help me [/COLOR][COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Just rewiring a 3 storey house that's going to be student lets, communal kitchen lounge bathrooms etc[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]I have worked out the following diversity and demand [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Emergency lights 6a x 0.66 = 2.64a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Smoke alarm 6a x0.66 = 2.64a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]4 light circuits 4 x 6a x 0.66 = 10.56a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]4 ring mains 32a + (3 x 32 x40% = 38.4a) = 70.4a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]That all totals 86.24a [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Dilemma I have is adding electric cookers and electric radiators [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Customer ideally wants 2 stand alone electric cookers but I've worked out each cooker assuming 40a would equal 29.16a if he had 2 it would be 58.32a [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Then he wants 500w convector heaters either 7 or 15 of them spilt over 3 floors in total 15 would bring 7kw and need to be on a 32a fuse and if he went for 7 it would be 3.5kw and need a 16a fuse, apply diversity and that would add 21a or 13a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Questions I have are[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]1. if he had the electric rads could I put 3 radial circuits into one 32a fuse [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]2. As it stands without cookers or rads it's would be[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]86.24a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]115a with one cooker[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]144a with 2 cookers[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]157a with 2 cookers and 7 rads[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]165a with 2 cookers and 15 rads[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Which would be acceptable, my old old lecturer stated if it exceeds 100a it'll just blow main fuse so don't worry

Also found someone using the add up all themcb values and times by .40 anyone else used this or know if it's ok?

cheers

[/COLOR]

 

[Deleted member 72666]

I take it that there's no gas in the building.

 

[Markymark981]

There will be but he prefers electric

 

[Markymark981]

As the rads are 500w each could I put those on on FCU on existing ring mains as one floor would have 6 which would be 3kw another floor would have 5 which is 2.5kw and the last floor would have 4 which would be 2kw?

then I would still have 86a including electric rads

 

[Markymark981]

Customers dropped now that he needs two electric water heaters I'm assuming 16a each would add another 32a to the total

 

[Lucien Nunes]

could I put 3 radial circuits into one 32a fuse

One fault takes out all heating in the house: inadequate design.

Do a sanity check: 165*230=38kW heat dissipation. House might get rather warm rather quickly.

But what caught my eye (sorry it's not terribly relevant or helpful) is that any smoke alarm circuit using 0.66*6 = 4A will very soon set fire to the building!

 

[davesparks]

As the rads are 500w each could I put those on on FCU on existing ring mains as one floor would have 6 which would be 3kw another floor would have 5 which is 2.5kw and the last floor would have 4 which would be 2kw?

then I would still have 86a including electric rads

Take a step back and apply some common sense to this!
How did you work out the size of the heaters? The same size heater in every room does not sound like a well designed install.

 

[malcolmsanford]

It maybe old, but so am I and I still work!!!!

Domestic, add up the loads and multiply by 0.4 and you won't be far off, even today

 

[Markymark981]

I was trying to get in a heatin system for the lowest possible amps as know I close to diversity demand I know larger rooms need bigger ones but customer wants smallest and cheapest way to heat tbh I still think gas central heating is the better option for him but u know what customers are like

 

[malcolmsanford]

If he wants cheap and has the room ground pumps are getting better and better each year

 

[snowhead]

You won't have 70amp on the Rings
All they will have in is Laptop and Ipod chargers.

 

[davesparks]

You won't have 70amp on the Rings
All they will have in is Laptop and Ipod chargers.

And electric heaters to make up for the severe lack of installed heating!

 

[davesparks]

I was trying to get in a heatin system for the lowest possible amps as know I close to diversity demand I know larger rooms need bigger ones but customer wants smallest and cheapest way to heat tbh I still think gas central heating is the better option for him but u know what customers are like

Do you understand how heating works? If your heating input is less than the losses in the room then it will be constantly heating and you won't get the load cycling which gives you diversity.
Installing undersized heaters will increase the demand as the residents plug in a lot of extra heaters.

 

[Leesparkykent]

I would tell the customer to stop being a skinflint. Offer the customer your best advice which would be to install a gas boiler with a wet heating system, an electric boiler with wet heating system or have his cutout/CCU upgraded to accommodate the additional calculated load of appropriate sized electric heaters.

Tell the customer to stop trying to get you to polish a turd of an idea that they have come up with!:teeth_smile:
As ultimately it will be you it comes back on when it isn't up to scratch.

 

[davesparks]

You have surely got to realise something is wrong when the proposed heating for the building is 7KW and the proposed lighting for the building is 7.2KW! (4x6A of lighting + 6A of em lighting = 30A)
And as for 1.2KW of smoke detectors????