What is Diversity ?
- Thread starter Norv
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A general rule that when designing some circuits, an assumption can be made that the circuit will not carry full load current. IE an allowance can be made that only (for example) 66% of flc be assumed.
It is deemed good practice by many when designing many circuits to allow flc to be taken into consideration & an allowance for spare capacity besides.
It is deemed good practice by many when designing many circuits to allow flc to be taken into consideration & an allowance for spare capacity besides.
think of a domestic ring supplying a large number of 13A sockets which is protected by a 32A MCB...if the sockets were feeding 13A loads then more than two sockets would over-load the circuit and it would be disconnected by the MCB. The chance of this is unlikely as typically one will feed a washine machine, a lamp, television etc etc and the chance of them all being used at the same time is also remote. Diversity is the condition that only a few sockets will be in use at the same time and the loads that they feed are small.
Page 84 Appendix 1 OSG explains and allowances allowed are Table 1B
Page 84 Appendix 1 OSG explains and allowances allowed are Table 1B
Diversity for ring circuits is 100% of first and then 40% of remaining.
And for lighting it's 66% assuming 100W per lampholder.
For cookers it's 10A + 30% of remaining + 5A for socket.
So if you had 2 ring circuits and 10 lampholders, and a 10kW cooker.
It would be:
32A for first ring circuit
12.8A for second ring circuit
2.9A for lighting
25A for cooker
So max. demand after diversity would be = 72.7A
It's a better idea to ignore the figures though and clamp the tails to find the MD.
Davy
And for lighting it's 66% assuming 100W per lampholder.
For cookers it's 10A + 30% of remaining + 5A for socket.
So if you had 2 ring circuits and 10 lampholders, and a 10kW cooker.
It would be:
32A for first ring circuit
12.8A for second ring circuit
2.9A for lighting
25A for cooker
So max. demand after diversity would be = 72.7A
It's a better idea to ignore the figures though and clamp the tails to find the MD.
Davy
Work out the current:
10700w / 240v = 45A
Diversity for cookers is:
10A + 30% of what's left (45A-10A) + 5A if you have a socket on the cooker switch.
In this case it was:
10A + 10.5A + 5A = 25.5A or 20.5A without a socket.
10700w / 240v = 45A
Diversity for cookers is:
10A + 30% of what's left (45A-10A) + 5A if you have a socket on the cooker switch.
In this case it was:
10A + 10.5A + 5A = 25.5A or 20.5A without a socket.
There is also a bit of judgment to be applied:
e.g. lighting circuits: If you have a smallish house and a largish family, or any size house and one or more teenagers, it is likely that all the lights will be turned on at the same time. So I would assume 100W in every ceiling lamp when calculating load (sensible people will then fit CFLs)
Cookers: On Christmas day (I always say) you will have the turkey in oven 1, mince pies in oven 2; brussel sprouts, gravy, bread sauce and pudding on all the rings. These will all be cycling on and off on their thermostats once they have come to temperature, but some people will turn them all full on at the same time, so (I say) the cooker circuit should be sized to max appliance load, otherwise it will trip on Christmas day (but probably not the rest of the year). Worse still, after it has tripped once, all the heating elements will have cooled, so they will all be full on until they come back to temperature... so it will trip again shortly after you reset the MCB or replace the fuse
Kitchen and Utility Sockets: The circuit that provides the room where you keep your laundry appliances is likely to have the washing machine and the tumble drier running at the same time, but taking (about) 13A. If you have any other heavy loads (dishwasher, electric heaters) on the same circuit, you can expect to trip the MCB from time to time. If you have a big family and run the kettle, toaster, George Forman grill, Coffee maker and sandwich toaster all at the same time for long periods, they can also push it over the edge. However a small family will usually only run those appliances intermittently, for short periods, so not have the problem. This is why it is increasingly common to have a separate 32A ring or radial for the kitchen, in addition to one for the rest of the ground floor.
Other sockets: Unless your central heating has broken down and you are using several fan heaters or electric convectors, the socket circuit will be very lightly loaded. Most things plugged in will be TV, Video, DVD, PC, table lamps etc, which have a very light load, and you could put a plenty of such appliances on a 32A ring without overloading it.
e.g. lighting circuits: If you have a smallish house and a largish family, or any size house and one or more teenagers, it is likely that all the lights will be turned on at the same time. So I would assume 100W in every ceiling lamp when calculating load (sensible people will then fit CFLs)
Cookers: On Christmas day (I always say) you will have the turkey in oven 1, mince pies in oven 2; brussel sprouts, gravy, bread sauce and pudding on all the rings. These will all be cycling on and off on their thermostats once they have come to temperature, but some people will turn them all full on at the same time, so (I say) the cooker circuit should be sized to max appliance load, otherwise it will trip on Christmas day (but probably not the rest of the year). Worse still, after it has tripped once, all the heating elements will have cooled, so they will all be full on until they come back to temperature... so it will trip again shortly after you reset the MCB or replace the fuse
Kitchen and Utility Sockets: The circuit that provides the room where you keep your laundry appliances is likely to have the washing machine and the tumble drier running at the same time, but taking (about) 13A. If you have any other heavy loads (dishwasher, electric heaters) on the same circuit, you can expect to trip the MCB from time to time. If you have a big family and run the kettle, toaster, George Forman grill, Coffee maker and sandwich toaster all at the same time for long periods, they can also push it over the edge. However a small family will usually only run those appliances intermittently, for short periods, so not have the problem. This is why it is increasingly common to have a separate 32A ring or radial for the kitchen, in addition to one for the rest of the ground floor.
Other sockets: Unless your central heating has broken down and you are using several fan heaters or electric convectors, the socket circuit will be very lightly loaded. Most things plugged in will be TV, Video, DVD, PC, table lamps etc, which have a very light load, and you could put a plenty of such appliances on a 32A ring without overloading it.
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