I have posted a piece here which is also on the TT topic, but is more general and I think a new thread would be better. Your voice is heard. See below.
I think that your description of trying to calculate diversity with real loads is interesting, and a serious part of proper installation design. However you will probably see at once that one 32A circuit for the clothes (cloths?) machines is adequate, and one for the kitchen (with dishwasher, kettle, microwave and small appliances) is also adequate. It is very unlikely that either of these will suffer nuisance tripping unless you really try, and even then the intermittent nature of them all will require considerable coordination of actions. If you have electric heating you would need to add another circuit. The potential loads for other socket circuits in the house is fairly trivial, but several final circuits may be installed for convenience. Ignoring cookers and showers for the moment, your maximum demand at any time on socket circuits is likely to be significantly less than 64A, and for any period of more than a few minutes, less than 32A. (that is 32A general sockets, 32A kitchen, 32A washing). However using the Hager "rules", you would need a 100A RCD for these circuits I have described, because all 3 circuits are the maximum rating so must be added at 100%. A reasonable designer would see that this is incorrect and would be quite safe with a 63A RCD, sustained operation at more than this is very unlikely indeed. If you add a few lighting etc. circuits at 6A each, a shower at 50A, a cooker at 40A, you may not use a 100A rated CU at all, you need at least 2! Even under the "rules" the outcome is dubious as 50 A and 40% of the rest comes out at over 100A, the main switch rating. The 100A DNO fuse will stand 140A for the best part of half an hour, but apparently the main switch in the CU will not. The 16mm internal cables would be quite hot by now, as would the tinny "busbars" and steel neutral strips. The 25mm tails you have used would be slightly warm to the touch.
The meaning of "protection against overload" here is being abused, in that overload is not an instantaneous current of a bit more than the maximum continuous current, but a fully diversified maximum current taking time and consumption into account. If one assumes that actual maximum without the time factor, almost all installation designs fail at once. Take a factory with electric motors. These take roughly six times the FLC at startup, and may take 30-60 seconds to reach FLC, so the whole installation must be designed to deal with a simultaneous start of all the motors, poor National Grid.
The point at issue here is that one can never be sure that the current will not be maximum for a long period, but it is extremely unlikely. This is the judgement, which is entirely missing from the Hager leaflet, although it is to some extent present in the BEAMA one. However, inspection is still a major problem, the MI make this pretty much impossible for most installations. One would have to give a C2 as potentially dangerous according to the MI.
I think that your description of trying to calculate diversity with real loads is interesting, and a serious part of proper installation design. However you will probably see at once that one 32A circuit for the clothes (cloths?) machines is adequate, and one for the kitchen (with dishwasher, kettle, microwave and small appliances) is also adequate. It is very unlikely that either of these will suffer nuisance tripping unless you really try, and even then the intermittent nature of them all will require considerable coordination of actions. If you have electric heating you would need to add another circuit. The potential loads for other socket circuits in the house is fairly trivial, but several final circuits may be installed for convenience. Ignoring cookers and showers for the moment, your maximum demand at any time on socket circuits is likely to be significantly less than 64A, and for any period of more than a few minutes, less than 32A. (that is 32A general sockets, 32A kitchen, 32A washing). However using the Hager "rules", you would need a 100A RCD for these circuits I have described, because all 3 circuits are the maximum rating so must be added at 100%. A reasonable designer would see that this is incorrect and would be quite safe with a 63A RCD, sustained operation at more than this is very unlikely indeed. If you add a few lighting etc. circuits at 6A each, a shower at 50A, a cooker at 40A, you may not use a 100A rated CU at all, you need at least 2! Even under the "rules" the outcome is dubious as 50 A and 40% of the rest comes out at over 100A, the main switch rating. The 100A DNO fuse will stand 140A for the best part of half an hour, but apparently the main switch in the CU will not. The 16mm internal cables would be quite hot by now, as would the tinny "busbars" and steel neutral strips. The 25mm tails you have used would be slightly warm to the touch.
The meaning of "protection against overload" here is being abused, in that overload is not an instantaneous current of a bit more than the maximum continuous current, but a fully diversified maximum current taking time and consumption into account. If one assumes that actual maximum without the time factor, almost all installation designs fail at once. Take a factory with electric motors. These take roughly six times the FLC at startup, and may take 30-60 seconds to reach FLC, so the whole installation must be designed to deal with a simultaneous start of all the motors, poor National Grid.
The point at issue here is that one can never be sure that the current will not be maximum for a long period, but it is extremely unlikely. This is the judgement, which is entirely missing from the Hager leaflet, although it is to some extent present in the BEAMA one. However, inspection is still a major problem, the MI make this pretty much impossible for most installations. One would have to give a C2 as potentially dangerous according to the MI.
