Change to 3 phase?

[GavinB]

I was asked to do some work at a medium sized house ( used to an old village school now converted), when I look at it prior to fitting a new DB. I found that the property could really!! do with rewiring. So in discus-ions with the client "ie so what do you want if we are changing it all?" he has asked for,

45 light fittings 13A

1 large all electric cooker (15KW),27A

a large expanse on electric underfloor heating (8KW)35A

immersion 9A

3 ring mains32A, 13A, 13A

future supply to garden office32A

after applying the diversity off the tables in guidance note 1 amounts in blue I come out with a load of about 174 A. My question is can all this be put on a single 100 a supply head. I have already brought the overall load down from over 300A when I persuaded him to not have electric showers.

thanks

Gavin

 

[Evans Electric]

How many people in the house ?

How is the place heated ?

 

[james KEI]

Isn't there a g factor for diversity too?

You could use electric showers but pumped versions like Aqualisa rather than '10KW power showers'

Wouldn't the garden office ring count as another ring and drop the load on that too after diversity

Maybe suggest the water version of underfloor heating as it may be cheaper to install and run

 

[GavinB]

Thanks for the quick replies

the house is a family of 4, heated by radiators feed from an oil boiler (not very good),

G factor??, I have already changed them to the processor only type of showers, changing the garden office to a ring would only drop the total by 19 down to 155a.

water underfloor is not possible due to existing construction restrictions ie they can not take up the floor and can not raise the floor level

Gavin

 

[SPECIAL LOCATION]

4 people....

Max demand 174A??? :|

I don

 

[Manator]

I agree with Special Location, the principles behind his explanation are the basics of circuit/installation design. When you design an installation you have to assess the maximum loading, this is not the same as doing diversity, you can also use the maximum times any part of the installation will be used at full loading. This information, as well as the chosen characteristics of circuit protective devises can be used to apply your design diversity. The chances are that before any consumer upgrade the house functioned very well without any overload on 4 or 5 circuits, and the use of power will not increase because we have introduced more circuits.

 

[Sidewinder]

Gavin,

You could always do it the way the DNO's do it!

Max load x 0.3, try that and see what you get.

 

[Ash]

on a replacement CU I did with 16 circuits, 4 being rings, my max demand was 81A

I think you need to redo your diversity calcs.

remember you do 40% of all the circuits apart from the one with the most current demand

 

[wozz]

They may well regret that much electric UFH! Work out the running cost for them!

 

[james KEI]

There's a g factor you can apply for diversity, it's in the design guide, once you've applied diversity you can then apply the g which is 0.6-0.8 I thin. Look it up