What does “suitably treated” mean in regulation 526.9.1

[Guywatton]

Is just twisting the fine wire and doubling it over suitably treated or does it require something like bootlace ferrules? I’ve been using bootlace ferrules however I’m being told although it’s best to it is not actually necessary.

 

[Lucien Nunes]

Hi and welcome to the forum.

That reg deals with a variety of termination methods, not just ferrule / no ferrule situations. Looking at the need for ferrules, it would depend on the terminal. If it is of a design that is likely to shear off some of the strands of a fine-stranded conductor, e.g. with the tip of a screw that is neither rounded nor has a protection spring, then I would consider a ferrule more or less essential. The same where there is a high chance of the twisted bundle of strands being flattened and partially squeezed out from underneath the screw, e.g. some types of barrier strip. OTOH if the terminal is somewhat more kind to the conductor and doesn't threaten to eject it, then the ferrule might be desirable but non-essential.

Other suitable treatments include the strand-welding used on the ends some CU internal jumper cables and similar, there's no ferrule but the strands have been consolidated into a solid block. Also crimp pins, which are better suited to situations where the conductor might have to be repeatedly removed and refitted (ferrules tend to wear through or split).

IMO BS7671 is not an instruction book on how to carry out electrical craftsmanship. It merely sets out minimum standards below which work is not acceptable. I wire according to good technical craft practice and would consider that any termination I make will be sound and durable and therefore acceptable BS7671, whatever the detail wording of the reg happens to be.

 

[Guywatton]

Hi and welcome to the forum.

That reg deals with a variety of termination methods, not just ferrule / no ferrule situations. Looking at the need for ferrules, it would depend on the terminal. If it is of a design that is likely to shear off some of the strands of a fine-stranded conductor, e.g. with the tip of a screw that is neither rounded nor has a protection spring, then I would consider a ferrule more or less essential. The same where there is a high chance of the twisted bundle of strands being flattened and partially squeezed out from underneath the screw, e.g. some types of barrier strip. OTOH if the terminal is somewhat more kind to the conductor and doesn't threaten to eject it, then the ferrule might be desirable but non-essential.

Other suitable treatments include the strand-welding used on the ends some CU internal jumper cables and similar, there's no ferrule but the strands have been consolidated into a solid block. Also crimp pins, which are better suited to situations where the conductor might have to be repeatedly removed and refitted (ferrules tend to wear through or split).

IMO BS7671 is not an instruction book on how to carry out electrical craftsmanship. It merely sets out minimum standards below which work is not acceptable. I wire according to good technical craft practice and would consider that any termination I make will be sound and durable and therefore acceptable BS7671, whatever the detail wording of the reg happens to be.

Appreciate the reply, this is how I interpret the regulation, I should’ve been more specific in my question. I was mainly questioning finely stranded 0.75-1.5mm flex to be terminated in a screw type terminal, personally I think something like a ferrule should be used for a better connection and to help prevent the separation of strands.
Imo I don’t think twisting and doubling over the strands on such cables, to then be terminated into a screw type terminal really counts as being ‘suitably treated’. However, like you mentioned BS7671 isn’t really an instruction book

It is good to hear other more experienced electricians opinions.

 

[Dustydazzler]

Regs are super ambiguous by nature and how they get interpreted

 

[pc1966]

I was mainly questioning finely stranded 0.75-1.5mm flex to be terminated in a screw type terminal, personally...

Usually the regs would say to check the manufacturer's instructions as to what cables are suitable. For cheap and simple screw blocks, etc, you will probably not find any instructions!

However, for things like DIN rail terminals, Wagos, etc, they will often state the acceptable types of cable (e.g. solid, coarse stranded like conduit wire, or fine stranded like flex) and sometimes a different CSA for each of them. E.g. leaver clamp Wagos are OK for all 3, but push fit Wagos are solid cable only (1-2.5mm T&E style).

Personally I would go with ferrules when you can, not only a good connection but less risk of a strand or two poking out and shorting something. For 13A plugs where they are supposed to accept fine-stranded anyway I would use ferrules if I had them with me, but otherwise twisting together and (for small CSAs) folding back is a good minimum to keep enough conductor in the clamping area.