Diversity on a Ring Final

[junksamiad]

Hi there,

I'm just trying to get myself into cable calc and my first hurdle is demand and diversity. I understand the majority of what is coming across in tables A1 and A2 OSG but I'm just struggling to clearly understand what I should be using for demand on a domestic 32amp ring final (assuming just 13a sockets).

Could someone just clear this up for me at all?

Would the demand on a simple common 32 amp ring final be rated current? And if so, what would be the diversity applied to that if any?

Thanks in advance for any help with this.

 

[R-fur]

Item 9 in table A2 of the OSG says 100% of the first circuit plus 40% of each other circuit.
However if you take a standard house of less than 100 square meters you can wire it in one ring so the demand would be 32A but a lot of sparks wire an upstairs ring, a down stairs ring and a kitchen/utility ring so the demand according to A2 is 32+0.4x32+0.4x32= 57.6A this obviously too much for a standard house. The standard design of a ring circuit already takes diversity into account, so if the floor area is less than 100 square meters I would say take the max demand as 32A regardless of how many rings are installed and 0.4x32 ie 12.5A for every 100 square meters there after. But you must always apply some common sense and ask what loads are actually going to be connected to the rings, then apply some professional judgement.