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Your not the only one, although to be fair not really the electrician but the trade organisations who tell there members this is what it means.
I went to a fair few IET lecturers when I was a member, and often the speakers were not direct from IET but one of the schemes. It was at these lecturers I finally worked out where the 106 meters came from of 2.5 mm² in a ring final.
However where we use a single 30 mA RCD or two in series, for protection there is normally some back-up lighting, narrow boats and caravans, the Hobby it seems odd one out with no 12 volt lighting. But that is German and for a long time you could not officially tow them as too wide.
But the "take into account" means in real terms a risk assessment, the major question is if a RCD trips, how easy is it to reset, and if it will not reset, can the house still function without it? And this does not really need electrical knowledge to work out. So in my mothers case, RCD trip would result in her pressing her alarm pendent and telling the call centre the electrics had tripped, as she could not reach the consumer unit under the stairs, the call centre would have likely phoned me, and I would have driven 12 miles to reset it. In both of my houses this and last one, the CU was in the garage, last house garage same level as house, so need to get dressed and go outside, but even with heavy snow, not too much of a problem, this house garage under the house, so to reset means outside and down a set of steps, which in the snow could cause problems. Also problems in the dark, as no street light illumination.
Had my mother not been in a wheel chair it would have been no problem. But 1954 when house was built no one considered wheel chair access, and there is more involved to just resetting a RCD in making a home wheel chair friendly. Access ramps, oven height, hob height etc, so it seems in some ways daft to look at socket height and thermostat height when no one in the house is disabled. And in the main people can bend down, it is the upper height limit which is the problem. So around 1200 mm is eye height so any dial or other item needing viewing from above must be below 1200 mm, and 1600 mm is about the limit one can reach in a sitting position. So CU should not really be mounted high up, or in a crawl space (under stairs) but tradition puts CU where children can't play with it. So high up, or in a cupboard under stairs which can be locked is common.
RCD's do trip, and the number of times a RCD trips is far greater than a fuse blowing, so the big question is with a rented property how much should you do to reduce problems when a RCD trips? Easy in ones own house, not so easy when house used by others. It is hard to work out where to draw the line, some children are well behaved, and not down to just parents, as seen one child in a family which is a horror, but rest of children OK, clearly all taught by same parents, and we can assess the risk with our own family far easier than with some one else's family. But there has to be a limit, just like with wheel chair users, some homes are simply not wheel chair friendly and there is really little we can do to make them wheel chair friendly.
All well and good to say dentist has to be wheel chair friendly, but not really the private home. So the rental agreement will likely have clauses allowing for when medical conditions mean the tenant needs to leave, and if pictures can be put on the walls, etc. And if the tenant can't put a screw/nail/pin in the wall, then the safe zones really don't matter for the tenant.
You can get plug in RCD's, so is there really any need for a RCD in the CU? OK Emma Shaw yes, but as @JohnW2 points out these cases are rare, so an inspector is left with three questions.
1) Is it dangerous.
2) Is it potentially dangerous.
3) Is there room for reasonable improvement.
And to answer the questions he must 'take into account' the way the property is used, a wheel chair user who seems out of control bouncing off the walls means sockets at 350 mm are very vulnerable ban on the height a wheel will hit them, I don't care what Part M says. Been there and had to do the repairs.
