calculating total load on a consumer unit

[submariner111]

this probably is a daft question and the answer maybe staring me in the face, but im going to have to ask.
ive got a 32A ring for kitchen, 32A ring for rest of flat, 45A mcb for shower, 16A for boiler, 6 A for lights, 16A for cooker = 147A
i have a bs1361 100A main incoming fuse.

Would i have to calculate the amount of sockets and lights to work out the prospected load of these circuits before subtracting diversity.
basically the question is, how do you get this to equate to under 100A. This is only a 2bed flat, and im sure that the average house must have more mcb's than this equating to a higher Amperage.

Maybe a silly question, but its got me.

nb. im still training and am not a qualified electrician.

 

[Darkwood]

You need to apply a thing called diversity which allows for the the fact that not all circuits are loaded up to the limit all the time, then you calculations will be well within the limits, you will find this relevent info in the regs or on-site guide.

 

[zupos40]

this probably is a daft question and the answer maybe staring me in the face, but im going to have to ask.
ive got a 32A ring for kitchen, 32A ring for rest of flat, 45A mcb for shower, 16A for boiler, 6 A for lights, 16A for cooker = 147A
i have a bs1361 100A main incoming fuse.

Would i have to calculate the amount of sockets and lights to work out the prospected load of these circuits before subtracting diversity.
basically the question is, how do you get this to equate to under 100A. This is only a 2bed flat, and im sure that the average house must have more mcb's than this equating to a higher Amperage.

Maybe a silly question, but its got me.

nb. im still training and am not a qualified electrician.

If you read appendix 1 Onsite guide page 95 you will see that diversity is applied to most circuits.

Basically the kitchen ring is the main one that you need to think about when designing and installation etc as it possible the only ring that could be fully loaded if you connected washing machince, tumble dryer dish washer etc.

As your still training it may be worth you finding out the loads likely to be connected to the rings, if the porperty centrally heated, also the loads connected to the lights how many energy saving lamps etc as a learning exercise. as you cooker is 16A it possibly only 3 kilo watt, is the boiler really using 16A, bet 16A it because the circuit is a 2.5mm radial power circuit.

Personnelly if you contacted edf and informed them you had Gas or oil central heating the would possilbly say you only needed a 60A supply

The diversity table in OSG are very crude and in some cases 30 years out of date, commerically I use watt per metre at present it about 11W per m for power and 13W for lighting, 45W for kitchens.

Please do not worry I been in larger properties where if you added up all the circuit breakers the total load exceeded 300A still only 100A BS1361 type II fuse and no signs of overload.