Size of supply needed for this project. Design advice

[Fred Faulkner]

Richard i totally understand im sure were all still learning everyday,

eng54 im fitting out the resturant and giving the ground floor a supply for when they get a potential buyer the fact that the supply might need upgrading isnt at a cost to me i have specified 35mm 4 core supply cable etc as i beleive this will be suitable . The question originally was will the 100amp supply thats currently there be ok and as richard pointed out if the wAnt to go down the road of upgrade 200amp would be the next step.

I dont bud against ppl im a trusted contractor supplys are abit out my brain capacity with all of the stuff i have to deal with lol

 

[Knobhead]

How did you win this contract? You clearly aren’t capable of fulfilling it.

Have you a get out clause? I would advise you to start looking for it now, before you find yourself in financial and legal trouble.

 

[Fred Faulkner]

How did you win this contract? You clearly aren’t capable of fulfilling it.

Have you a get out clause? I would advise you to start looking for it now, before you find yourself in financial and legal trouble.

thankyou mate will take your advise on board ...

 

[trev]

i have specified 35mm 4 core supply cable etc as i beleive this will be suitable .

I wouldn't believe it was suitable, I'd know. I have to agree with several others here mate, get out of this while you can.

 

[Fred Faulkner]

I wouldn't believe it was suitable, I'd know. I have to agree with several others here mate, get out of this while you can.

I think theres alot of scare mongering going on your telling me a pub with a max demand of 55amp per phase a 35mm cable couldnt hand that from the meter/ switch fuse?

 

[wozz]

You should find all your answers for working out design in BS7671

I wouldnt be looking in 7671 when it comes to maximum demand.

 

[Simlec]

I wouldnt be looking in 7671 when it comes to maximum demand.

Please don't say On site guide.

Last time I looked BS 7671 it showed me how to design final circuits Yes.
Normally a good place to start !!

Or do you just make it up as you go along.

 

[wozz]

Haha no not on site guide.

he isnt asking about final circuits, he asking about max demand and diversity. where in 7671 have you got information on this for commercial premises?

 

[wozz]

Or do you just make it up as you go along.

are you saying there are hard and fast rules for max demand and diversity? if so where? or do you use experience and judgement.

making it up indeed.

 

[Simlec]

Haha no not on site guide.

he isnt asking about final circuits, he asking about max demand and diversity. where in 7671 have you got information on this for commercial premises?

And the only way to find max demand is to apply diversity to your known final circuits.

 

[Simlec]

I think theres alot of scare mongering going on your telling me a pub with a max demand of 55amp per phase a 35mm cable couldnt hand that from the meter/ switch fuse?

I take it you meant "handle" ! I'm not sure how you got the 35mm figure from?
A 50mm or even 70mm could "handle" more! lol

 

[wozz]

And the only way to find max demand is to apply diversity to your known final circuits.

I was thinking it was based on the connected loads rather than circuits????

so can you point me to the bit in 7671 that i can use for max demand and diversity?

 

[atm84]

Do you know the square metres of the pub, restaurant and flats?

 

[mark80]

There's plenty of guides giving ESTIMATES of power usage per m2 of floor area for different types of loads. However, these are guidelines and are only really used for planning supply size when the design is still in the paper stage. Previous experience of creating similar designs is generally used to estimate supply sizes.

If the building has been fully designed then you should be able to work out the supply size quite accurately. You should know how many luminaires are required, therefore can predict the total output and applying diversity and then the same with everything other type load! Personally, I'd be surprised if the building pulled more than 200A per phase but I can't see the job! You should have a consultant do the design, as this is all going to end in tears if you get it wrong!