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H

hodaire

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how do i work out the design current for an installation, i have allowed for the diversity on sockets, lights and cooker

2 ring mains - 32 + 13 a
1 10kw cooker 20 a
1 10kw shower 45a
1 3kw immersion 13 a
1 light circit (10 lights 100w) 3 a


is my design current really going to be 126amps?
 
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E

electro

  • Thread Starter Thread Starter
  • #3
Hi

House or Flat?


I've worked it out about 75amps indicative using the rule of thumb method, how are you going to layout your circuits, you should have two lighting circuits for 17th compliance and split the 10 lights up into 2 * 5 lights to reduce the risk of tripping RCD/RCBO.


regards
 
G

Guest123

  • Thread Starter Thread Starter
  • #4
Hey all.

How are we arriving at our figures?? I get 77A just with the shower and first ring circuit i.e no diversity and 100% of first ring circuit respectively.??
 
A

andekoch

  • Thread Starter Thread Starter
  • #5
I have just applied the diversity allowed in the on site guide (OSG) appendix 1 and the result comes out as 119 amps (assuming 250V as the voltage), will obviously be higher if you assume 230V.

realistically I would put this on a 100A main breaker.
for now lets ignor the splitting of the lights into 2 circuits or any other installation matters.

agreed that his does seem like a big demand.

what doe the others think?
 
E

electro

  • Thread Starter Thread Starter
  • #6
Hi


I used the 40% of the overcurrent method, as this method in my experience comes closer than the osg diversity factors in flats and small houses. Lets say the house was three bedrooms plus I would revert to the osg rules as I think these would be closer to figure. More often than not connected single loads on maximum run on 50 to 70% of there rated loads.


Andekoch just brought up the circuit division as more domestic properties have failed on this, ten fold than they have on maximum demand one year on for the 17th edition meeting in London.


I know this method I have used might not sit well with everyone what do you guys think.


regards
 
S

sparkygary88

  • Thread Starter Thread Starter
  • #7
hi,random question here,i have wired 14 50w down lights,is it ok to put them on 6amp mcb or should i uppgrade to 10amp?what is the maximum on a 6amp/10amp braker...14 to many??
 
E

electro

  • Thread Starter Thread Starter
  • #8
Hi Sparkygary

sounds fine to me thats just over 3amps

Regards
 
M

maddfridge

  • Thread Starter Thread Starter
  • #9
Hi everyone

Come on everyone think about all this Diversity what is it ????????????

It is an allowance that is used to give BASIC information and if things are high it make you look at the overall design of the installtion.

Do you have to have a 45 amp shower? could it be reduced to a power shower ?

If the loading is such a big problem should you be looking at a three phase supply?

Diversity is the fact that everything may not be used at the same time

hodaire if you stick to that then it will be that but after all it is only guidance

try to think beyond the box look at the overall installation look at and make an informed decision

will all lighting be 100 watts like to see you get a 100 watt bc lamp now low energy everywhere ok there are halogens etc

This was one of the fundamental thoughts behind the recent design project i did for the 2391-20 course in december reduce the load by using energy saving appilancres etc takes down design currents etc.

hope this little rant helps


cheers
 
E

electro

  • Thread Starter Thread Starter
  • #10
Hi mad

That's the job of a EPC assessor not a sparkie, he wants to work out the maximum load not stop the ice caps from melting...



Regards
 
A

andekoch

  • Thread Starter Thread Starter
  • #11
Hi


I used the 40% of the overcurrent method, as this method in my experience comes closer than the osg diversity factors in flats and small houses. Lets say the house was three bedrooms plus I would revert to the osg rules as I think these would be closer to figure. More often than not connected single loads on maximum run on 50 to 70% of there rated loads.


Andekoch just brought up the circuit division as more domestic properties have failed on this, ten fold than they have on maximum demand one year on for the 17th edition meeting in London.


I know this method I have used might not sit well with everyone what do you guys think.


I agree with Electro (and the other comments) the calculation should be done as per a standard method eg the OSG and the result interpereted (this is where experience come into the picture). The type of proprety will also make a difference (same reason that the OSG has different diversity tables for houses, shops etc).
You should clearly note how you arrived at your decision and not simply write max demand = 119A on the installation form and then install a 100A main switch.
 
S

Scott F

  • Thread Starter Thread Starter
  • #12
Hi everyone

Come on everyone think about all this Diversity what is it ????????????

It is an allowance that is used to give BASIC information and if things are high it make you look at the overall design of the installtion.

Do you have to have a 45 amp shower? could it be reduced to a power shower ?

If the loading is such a big problem should you be looking at a three phase supply?

Diversity is the fact that everything may not be used at the same time

hodaire if you stick to that then it will be that but after all it is only guidance

try to think beyond the box look at the overall installation look at and make an informed decision

will all lighting be 100 watts like to see you get a 100 watt bc lamp now low energy everywhere ok there are halogens etc

This was one of the fundamental thoughts behind the recent design project i did for the 2391-20 course in december reduce the load by using energy saving appilancres etc takes down design currents etc.

hope this little rant helps


cheers
Have to say I agree with Maddfridge on this one.

I am as guilty as the next man following the regs to the letter .With out actually thinking about why

Probably more to do with working for firms where the thinking is done for you as opposed to working for

your self and doing just that EVERYTHING for your self.
 
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