Earth sleeve

[JohnW2]

But remember most flexible cables have all 3 conductors sleeved...

Most? Are there any which don't?

... and are of equal CS.

That is, of course, also true of 1mm² T+E and, even with 1.5mm², the 1mm² CPC is, per se, more than enough for use as a live conductor of a lighting circuit.

Kind Regards, John

 

[crystal ball]

That doesn't surprise me. I believe that has been the case in Australasia for quite some time, and that other countries are gradually following suit.

Kind Regards, John

Yes indeed, I remember working with insulated CPC T&E in Australia in the 80s, not sure if it was commonplace then as I only did a smidgeon of domestic wiring

On a different tack, I worked in Zimbabwe in the 90s where bare earth cables were the norm, in fact insulated earths were prohibited on government installations, standards were very good at the time, the use of RCDs was widespread especially in schools

 

[JohnW2]

On a different tack, I worked in Zimbabwe in the 90s where bare earth cables were the norm, in fact insulated earths were prohibited on government installations, standards were very good at the time, the use of RCDs was widespread especially in schools

Yes, as I've said, there is certainly a potential 'safety' benefit in having a bare CPC - the question is whether or not that is outweighed by potential downsides of having them.

As has been previously implied (perhaps not intentionally) I think that one potential downside of having an insulated CPC is that it would probably tempt more people to use it as a live conductor if they did not have enough cores!

Kind Regards, John

 

[Mikefromlondon]

Most? Are there any which don't?

YES. There are those that are made as two core flex with overall aluminum foil screen conductor plus a non insulated drain wire, I use that everyday in a job application and is made by a USA company called Alfa Wire Company, it costs almost £150 a drum of 500 feet, 2411 20AWG, rated to 300v at 60c though I use it for low voltage application in my job, it also comes available in 18AWG.

Here is another example from Belden ; http://www.hificollective.co.uk/wire/belden-19364-mains-cable.html

 

[JohnW2]

YES. There are those that are made as two core flex with overall aluminum foil screen conductor plus a non insulated drain wire ... Here is another example from Belden ...

Fair enough, but they are hardly 'everyday' cables!

What is this "drain wire" (in both of those examples) all about?

Kind Regards, John

 

[Mikefromlondon]

Drain wire basically enables some cable manufacturers to use cheaper aluminum foil wrapping to screen a cable,instead of using a woven tinned copper braid, a braid is more costly, so they simply wrap the inner cores with an aluminium foil wrapping and run a bare earthing wire (this being in contact with foil) to drain away any electrical voltages induced into that aluminium foil screen., they just call it drain wire, it really is another name for an earth wire.

including some mains cables are required to be screened depending on equipment requirement such as some used in some Hospital equipment, to prevent radiating or picking up interference, or acting as antenna. Also to prevent electrical safety hazardous situations where in Hospitals cables can get tangled and stretched and get exposed, so a braided wire or a foil screened wire can arrest a fault early.

yes i agree these are not everyday wires, they are for special purpose equipment, I used to build 24V 5A power supplies for a customer, his requirement for mains cable was strict and I had to buy a braided 1.5mm 3 core plus the braid (there is no drain wire when they use a braid, overall diameter was almost 10mm, as you would use the braid itself as a drain wire which ultimately connects to an earth wire.

 

[JohnW2]

Drain wire basically enables some cable manufacturers to use cheaper aluminum foil wrapping to screen a cable,instead of using a woven tinned copper braid, a braid is more costly, so they simply wrap the inner cores with an aluminium foil wrapping and run a bare earthing wire (this being in contact with foil) to drain away any electrical voltages induced into that aluminium foil screen., they just call it drain wire, it really is another name for an earth wire.

Thanks for explaining. I've never come across that - I'm pretty sure that the only screened mains cables I've encountered have had the (more costly!) braided screens.

Kind Regards, John

 

[Mikefromlondon]

Braided Screen wires, most of the time you will see them in use in A&V equipment, CCTV, TV aerial down leads, satellite cables, where they are essential to reduce mains born noise along signal wires, but for mains they are rarely used on consumer electronics, only a special requirement by some NHS equipment and perhaps a few other bodies requiring absolute noise suppression, Avionics, space, Military etc.

 

[JohnW2]

Braided Screen wires .... but for mains they are rarely used on consumer electronics, only a special requirement by some NHS equipment and perhaps a few other bodies requiring absolute noise suppression,

Indeed. My experiences of seeing them used have been in relation to medical equipment/environments.

Kind Regards, John

 

[Mikefromlondon]

I just noticed something in my tool box, a braided flexible water hose, I never paid much attention to it before, but as my mind has been engaged in this discussion, suddenly, I can make sense of it why they use braided outer covering on this water hose, so just struck me of course it is to maintain electrical conductivity, and it is not really there to help in protecting the rubber hose against physical damage, which is what i had always assumed that it was to protect rubber but as the braids are not that strong, they cannot possibly protect against physical damage but only to maintain electrical conductivity, unlike the underground buried cables which have armored steel cage to protect it against physical damage which also acts as an earth.

 

[EFLImpudence]

No, nothing to do with the electrics.

 

[crystal ball]

Braided hoses can be used for heating the product in them, such as the components of polyurethane by passing a ELV current through the braid but the end connections have to be isolated,

 

[Mikefromlondon]

No, nothing to do with the electrics.

You are making me think now, Perhaps it is not intended for electrical conductivity as much as helping rubber hose from bursting through expansion under high pressure? other than that I always thought it was there for some physical protection, it also looks nice when it is there, as opposed to getting hold of one that has no braid covering, perhaps you may know the real reason why it is there, and you can tell us the secret!

 

[Iggifer]

Is this actually a serious discussion? I can't tell. Are we just talking about a standard plumbing Flexi pipe? Or something more specific

 

[JohnW2]

... a braided flexible water hose, .... i had always assumed that it was to protect rubber but as the braids are not that strong, they cannot possibly protect against physical damage but only to maintain electrical conductivity...

I wouldn't have thought so. Although they do not protect against mechanical impact or compression, they do protect against abrasion and resist expansion/bulging of the rubber pipe within - and probably provide more protection than you might think against 'kinking'.

Kind Regards, John