Definition of 'electrical installation' and requirement to upgrade existing to current regs?

broadgage said:

Yes I was suggesting fitting a 20 amp  OCPD to the existing ring final. Not aware of any regulation specifically permits or prohibits  this practice, but common sense and engineering judgement says it is fine.

Agreed but see comment by the eminent Mr Paul Cook (last sentence in italics on this page);

"It is never acceptable to use a fuse or circuit-breaker as a load limiting device."

I think that one has to be careful with words like, "never", "always", etc.

Starting from scratch, it would be poor design, but here we have a potentially dangerous circuit which appears to have been extended without sufficient thought concerning the design. A 20 A MCB may be the least bad option.

Would it make any difference if this were a rented property? The circuit merits a C2 and proper remediation almost certainly requires the replacement of this circuit with two or more. It would be no good if the landlord simply claims that this is too expensive, because the Regulations are intended to ensure that installations are safe.

See Paragraph 314.

Chris Pearson said:

I think that one has to be careful with words like, "never", "always", etc.

Well, yes ... we will ever have this problem with socket-outlet circuits. They are never "load limited" and therefore require protection against accidental overload.

I think, though, there's a difference between the "kitchen sockets" vs the "upstairs sockets" when taking this into account ... clearly one usually has more propensity for accidental overload due to anticipated loads involved.

[Surely] It's that 4-bar electric fire (4kW) with a 0-4 switch (if they exist) that would be an equipment load that should 'never' be load limited by the fuse such that the user doesn't accidentally use the "4 setting" on a circuit that's not designed for it.   Or something like that.

Philip Oakley Agreed ... one could say what's the difference between the n-bar fire with n switches, and n 1-bar fires each with a plug on its own (hence the socket-outlet circuit link).

gkenyon said:

I think, though, there's a difference between the "kitchen sockets" vs the "upstairs sockets" when taking this into account ... clearly one usually has more propensity for accidental overload due to anticipated loads involved.

Which one?

I doubt that electric heaters are used as much in kitchens as bedrooms.

Moreover,

MFr said:

the other big load devices (hob, oven, washing machine) are on separate rings or radials

So in this case, the dishwasher may be the biggest load in the kitchen, but it will not be heating water for long.

I believe that one 'plans' the expected/typical value of n (number of sockets) for the n single bar fires and ensures that the circuit's cables are capable of that level of current.

So in that sense the trip is for 'fault' detection, and that normally the user would not have overloaded the circuit.

The user would have to work hard to create the problem, while in an N+1 way switch case it's easy for a user slip-up to select the overload case warned about in the extract.

A good read is Reason's "Human Error" book to see the distinction between slips, lapses and mistakes and their different protection/safety approaches.

I believe that one 'plans' the expected/typical value of n (number of sockets) for the n single bar fires and ensures that the circuit's cables are capable of that level of current.

So in that sense the trip is for 'fault' detection, and that normally the user would not have overloaded the circuit.

The user would have to work hard to create the problem, while in an N+1 way switch case it's easy for a user slip-up to select the overload case warned about in the extract.

A good read is Reason's "Human Error" book to see the distinction between slips, lapses and mistakes and their different protection/safety approaches.