twin and earth question

[Hotspot]

Hi All. I'm new here an hope to receive some knowledge and learn a lot from all you clever folks.
My question is : may you use twin an earth to wire complete installation or a part of it but surface mount the twin and earth because reg.6.4.6.1 (b) unarmoured cabels may by used for open wiring(see 6.4.5) and no were the reg.6.4.5.1 does it state that it may be installed within arms reach except 6.4.5.2 were it states "next to beams that can be used for walking on". So one may not install twin and earth surface mount on walls to switches and plugs,why do so many electricians install it that way?

[AndyD]

Open wiring is defined as
'6.4.5 Open wiring
NOTE Open wiring consists of single-core insulated conductors that operate at not
more than 250 V to earth.'

It's pretty rare to see open wiring installation nowadays, there used to be 'knob and tube' wiring which had a wrap of bitumen soaked cloth or later vulcanised rubber was used.

I'm guessing you may be getting confused by the terminology,
Open wiring is an outdated intentional system of installation where unsheathed wiring (single wires) were used and it run through porcelain tubes whenever it crossed a building structural element and was regularly supported by bobbins along its length.....Not to be confused with exposed wiring which is where wiring or copper conductor is unintentionally accessible often due to some half-wit leaving a lid or cover off something.
Wire is a single insulated conductor forming only part of a circuit, not to be confused with cable which is multiple insulated conductors (wires) sheathed together. Twin and earth is not wire so doesn't fall under regs governing only wire.
Insulation is the protection covering a conductor and giving it only electrical protection. Sheathing is the additional layer that gives mechanical and environmental protection to the insulation and the conductor. You get some wire that is sheathed and cables are sheathed. Armour is an additional layer that gives added mechanical and environmental protection. Sometimes the armour layer is further sheathed to protect it from moisture and prevent corrosion.

6.4.3.4 If a cable is not run on racks or in pipes or ducts, it shall be firmly
fixed to prevent sagging or creeping.

This would apply to twin and earth so it can be run surface without containment or rack if it's adequately clipped (or glued, see note 1).

[Hotspot]

Hi Andy. twin and earth is regarded as unarmoured multi-core thus it is covered by the regs and the reg stipulate that if the is no ceiling it shall be at least 3m above ground level,so if it says 3m above ground level it means it may not be mounted on the surface to switches,plugs and so forth. I could be wrong but that is the way I understand it and that's why I'm trying to find out the real story.

[RegElec]

As Andy said you are referring to 'open wiring'. Check out 6.3.6 which covers the use of PVC insulated multicore cables. The regs 6.4.6.1 refers to unamoured single core cables.

[Hotspot]

Hi. Thanx for the reply and I did get confused with the regs and 6.3.6 is the answer I was looking for. Thanks for the answers I rely do appreciate your time guys.