Or maybe we could set aside design calculations as looks to be the case for these heater circuits.

Well that photo is exactly the sort of thing I had in mind when discussing the fact that you can do stuff which is really miles off the regs and it all still works !!

- trunking where you can't get the lid on without gorilla force, let alone the text book  50 percent  fill to allow airflow, - Yep seen that before Sometimes with random choc bloc joints and things in it as well. Actually I have watched a lid being hammered while apprentice pre-loads the screw driver on the lid turnbuckles as a desperate bid to  make it go on.

not really sure what the grouping factor is in that vertical bundle, but its a common installation method - 'braiding ' or 'rats nesting' perhaps.

Then to add to the charge sheet we see. the exposed basic insulation, the missing cover on the MCBs at the left, and the positively cavalier approach to making good the ceiling, that I really hope is not supposed to double a the fire break.

But there may be saving factors - for example if we knew the incomer was perhaps 100 A then we would also know that at most haf a dozen  16 A circuits or 3 32A ccts or equivalent can be at full chat at once, and in reality probably never that. or perhaps there are things that mean that the loads are not on at the same time, or perhaps they are, but only in winter when its cold. But we don't know.

In that photo the cable colours of R and B tell us it is at least 2 decades old, and the trunking has presumably been stuffed all that time, and no signs of obvious distress, so apart from,  or maybe in spite of, all the faults listed above ,  the job's a good adequate one.

It's also work by electricians like these that mean that I don't worry too much about conscientious DIYers and the finer details of the paper trails, as enough professionals and members of trade bodies have been known to have their off days.

M.

mapj1 said:

But there may be saving factors - for example if we knew the incomer was perhaps 100 A then we would also know that at most haf a dozen  16 A circuits or 3 32A ccts or equivalent can be at full chat at once, and in reality probably never that. or perhaps there are things that mean that the loads are not on at the same time, or perhaps they are, but only in winter when its cold. But we don't know.

;

One of the very special distribution circuit fuses. For which I couldn’t get a BS number!

mapj1 said:

But there may be saving factors - for example if we knew the incomer was perhaps 100 A then we would also know that at most haf a dozen  16 A circuits or 3 32A ccts or equivalent can be at full chat at once, and in reality probably never that. or perhaps there are things that mean that the loads are not on at the same time, or perhaps they are, but only in winter when its cold. But we don't know.

;

One of the very special distribution circuit fuses. For which I couldn’t get a BS number!

A real class act  !

I'm sure that's a holder for a lugged BS-88 cartridge, but the fuse rating of that wire we can only estimate from the onderdonk equation, and it fails to replicate the graceful short circuit behaviour of the original - the insides of a cartridge fuse are complicated for a reason, presumably a reason that the installer  was unaware of.

Mike