Thoughts on earth bonding on lights please

[JohnW2]

Supplementary insulation is not just additional insulation, it is "independent insulation applied in addition to basic insulation, for fault protection"

I'm not really sure what distinction you are making here. Do you feel that "... for fault protection" makes it mean something different?

Kind Regards, John

 

[stillp]

it seems unlikely that it was ever intended that that definition applied to cables

Really? Why?

it could even be the case that the material was deliberately made 'slightly conductive' yet still be acceptable as sheathing - if that were the case, I don't think one could call it "insulation", supplementary or otherwise, could one?

Yes, if it met the requirements for a particular product. Conductive (but high resistivity) materials are sometimes used to achieve EMC.

 

[securespark]

Envelope: A covering or containing structure or layer.

Intervene: To come between time, events or people (Normally not used for objects).

 

[stillp]

I'm not really sure what distinction you are making here. Do you feel that "... for fault protection" makes it mean something different?

Kind Regards, John

Yes, it implies that there is a performance requirement.

 

[EFLImpudence]

...but - my point - are we ever required to use d.i. conductors or only i.&s.?

 

[JohnW2]

Insulation, Double (1) of a conductor. ... A conductor is said to have double insulation when insulating material intervenes not only between the conductor and its surrounding envelope (if a cable) or immediate support (if bare), but also between the envelope or support and earth.

That's obviously very different from the present-day definitions and usages we're talking about, since the latter have no interest in 'insulation from earth'. Indeed, without knowing how and where the cable is going to be installed, I'm not sure how one can really talk about 'insulation from earth' - there may be no earth around, or their might be just air (an 'insulating material'?) between the 'envelope or support' and earth - would that have qualified as 'double insulated'??!

Kind Regards, John

 

[securespark]

It seems that the definition definitely did apply to cables...

 

[JohnW2]

Conductive (but high resistivity) materials are sometimes used to achieve EMC.

True, but they're surely not then called "insulators" or "insulation", are they?

Kind Regards, John

 

[securespark]

Do they mean "earth" as in mass of or earth as in conductor?

Even if it is a cable suspended in air, there would still need to be insulting material between the envelope and "earth".

 

[JohnW2]

Yes, it implies that there is a performance requirement.

Is there not also a 'performance requirement' for "insulation", even without that qualification?

Kind Regards, John

 

[JohnW2]

Do they mean "earth" as in mass of or earth as in conductor?

I suspect either.

Even if it is a cable suspended in air, there would still need to be insulting material between the envelope and "earth".

Perhaps. Mind you, if it were high enough up, even today it could be a bare wire, without any 'envelope', couldn't it? (think pylons)

You've so far given us only the 13th ed. definition of "double insulation", as applied to a conductor. What (if anything) does it say about when such insulation is required?

Kind Regards, John

 

[securespark]

So far (I have not read the whole book), I have only seen the references in Section 4 which I have already posted, copied below:

401 Electrical apparatus operating at a voltage exceeding extra-low voltage shall be protected against dangerous earth-leakage currents by one of the means described in Clauses (i), (ii), (iii) or (iv) below:

(i) Insulation which encloses the apparatus and is durable and substantially continuous, i.e. of "all-insulated" construction.
Note.--Fixed apparatus, which although not shrouded in insulating material is nevertheless otherwise so guarded that it cannot be touched and cannot come into contact with exposed metal, may in certain circumstances be regarded as of "all-insulated" construction (see Exemption 3 to the Electricity (Factories Act) Special Regulations 1908 and 1944, and Form 928).

or (ii) Double-insulation of an appliance in conformity with a British Standard which has been recognized for the purposes of these Regulations;

or (iii) Earthing of exposed metal parts in accordance with the requirements of this Section;

or (iv) Isolation of metal in such a way that it is not liable to come into contact with live parts or with earthed metal (see Regulation 403).


Read more: //www.diynot.com/diy/threads/when-was-this-last-done.466707/page-4#ixzz4OgqLPluA

 

[stillp]

True, but they're surely not then called "insulators" or "insulation", are they?

Kind Regards, John

Yes, sometimes.

 

[stillp]

Is there not also a 'performance requirement' for "insulation", even without that qualification?

Not unless one is specified.

 

[JohnW2]

Is there not also a 'performance requirement' for "insulation", even without that qualification?

Not unless one is specified.

True, but they're surely not then called "insulators" or "insulation", are they?

Yes, sometimes.

Apologies, I suppose I forgot that we were talking about the bureaucracy of regulations and Standards, rather than common sense.

Kind Regards, John