Over The Years....

[JohnW2]

Yeah, a while back I started sorting through boxes that hadn't been unsealed since moving here in 1994 and threw out practical wireless and electronics dating back to 50's, my old school books, BT course notes etc.

Similar (but probably worse!) here, except that I have yet to throw any of it out! Certainly plenty of Practical Wireless, Practical Electronics and Radio Constructor not to mention RSGB 'Bulletins' and goodness knows what out - and literally thousands of work-related journals going back 40+ years! Not only do I have my old school books, but also my late father's, and even a lot of paperwork (including business accounts etc.) of his father (my grandfather). I also have a lot of my grandfather's tools (a few of which I sometimes use), now well over 100 years old.

The trouble is that, as I grow older, the longer I put off addressing any of this the less 'heart' I have to throw anything out!

Kind Regards, John

 

[Harry Bloomfield]

That's interesting.

So, was/is it that the bare CPC merely has to be "identified" but not covered for its entire length?

It is difficult to think of a reason why it needs to be "identified" at all.

I seem to remember a number of instances where the bare earth wires were able to make contact with live terminals in tightly packed accessories. The sleeving would avoid the possibility.

 

[JohnW2]

I seem to remember a number of instances where the bare earth wires were able to make contact with live terminals in tightly packed accessories. The sleeving would avoid the possibility.

That is the obvious (and, I would say, probably essentially the only) argument for requiring bare CPCs to be sleeved.

Kind Regards, John

 

[EFLImpudence]

I seem to remember a number of instances where the bare earth wires were able to make contact with live terminals in tightly packed accessories. The sleeving would avoid the possibility.

Yes, obviously it would but in normal practice that is sort of its purpose - if the other way round.

It is like saying the metal back box should be insulated.

 

[Harry Bloomfield]

Yes, obviously it would but in normal practice that is sort of its purpose - if the other way round.

It is like saying the metal back box should be insulated.

The metal of the box would normally find it very difficult to make contact with terminals. Bare earth wires were able to twist and bend, so there was an ongoing issue with them making contact.

 

[EFLImpudence]

Yes, agreed. Perhaps covers on the terminal screws would be better.

 

[JohnW2]

Yes, agreed. Perhaps covers on the terminal screws would be better.

My memory is failing me. Can you remind me - is there actually a reg which requires bare CPCs within accessories, JBs etc. to be sleeved?

Kind Regards, John

 

[EFLImpudence]

I don't think so as there are references to bare CPC conductors - 514.4.6 where they can be identified by tape, sleeve or a disc.

That's why I was interested by Secure's post:

"Both the 13th Edition and the 14th Edition say that bare earthing conductors should be identified with the colour green."

I assumed that was the introduction of the practice of identification - rather than insulation (much the same as today but particularly specifically sized green and yellow) so what happened before?
Was it just bare bare conductors that everyone 'knew' were CPCs - like the ones twisted together outside of old round junction boxes.

 

[JohnW2]

I don't think so as there are references to bare CPC conductors - 514.4.6 where they can be identified by tape, sleeve or a disc.

Thanks. That's what I thought - so it looks as if I hadn't forgotten any reg.

514.4.6 requires identification of a bare conductor, in one of the ways you mention, "where necessary". Whilst 514.3 appears to require identification of all conductors (well, "cores of cables") there is an exception if 514.6 applies, and 514.6.1(iii) allows identification to be omitted for "bare conductors where permanent identification is not practicable" - although I'm not quite sure how to interpret 'not practicable'. I'm saying all this because I'm trying to work out whether 'identification' of bare CPCs is actually required - and, having read all those regs, I'm not at all sure - what do you think?

I assumed that was the introduction of the practice of identification - rather than insulation (much the same as today but particularly specifically sized green and yellow) so what happened before? ... Was it just bare bare conductors that everyone 'knew' were CPCs - like the ones twisted together outside of old round junction boxes.

I imagine that it probably was - and I inherited a good few round JBs wired as you describe! However, per above, I'm not yet convinced that identification of bare CPCs is necessarily 'required', even today.

Kind Regards, John

 

[securespark]

I don't think so as there are references to bare CPC conductors - 514.4.6 where they can be identified by tape, sleeve or a disc.

Well, that's almost exactly what is stated in table B4 in the 14th:

 

[SUNRAY]

Well, that's almost exactly what is stated in table B4 in the 14th:

View attachment 204528

Is that still the '66 version?
Bare CPC abounded way beyond that, In fact my school had a new building in 66 and the longer runs of tube contained a bare earth wire. The sub board in the gym was 7/0.063" white/black singles and 7/0.029 bare copper earth in tube. Likewise blue/black to library whereas stage lighting was supplied by a very thin MICC and 29A fuse [Yes 29A]. A teacher increased it and we were able to run some 15KW but it got warm, hence looking at other boards for more power.

 

[securespark]

Yes. I just snipped it from the photo I posted earlier.

 

[EFLImpudence]

514.4.6 requires identification of a bare conductor, in one of the ways you mention, "where necessary". Whilst 514.3 appears to require identification of all conductors (well, "cores of cables") there is an exception if 514.6 applies, and 514.6.1(iii) allows identification to be omitted for "bare conductors where permanent identification is not practicable" - although I'm not quite sure how to interpret 'not practicable'. I'm saying all this because I'm trying to work out whether 'identification' of bare CPCs is actually required - and, having read all those regs, I'm not at all sure - what do you think?

I missed the "where necessary" but as you know, I think wires are identified by being connected to marked terminals.
"Not practicable" - doesn't that mean "not able to achieve the desired objective"? As opposed to "not practical" meaning "not worth doing" so I don't know what it means in this respect.

I am not sure if it is actually required.

 

[JohnW2]

I missed the "where necessary" but as you know, I think wires are identified by being connected to marked terminals.

You do (and it makes sense, at least so long as the conductors are connected to terminals) - but I'm aware of nothing in BS7671 which suggests that as an acceptable "means of identification" in any situation. Maybe, however, that's where the "where necessary" comes into play?

"Not practicable" - doesn't that mean "not able to achieve the desired objective"? As opposed to "not practical" meaning "not worth doing" so I don't know what it means in this respect.

I've never been totally clear as to the meanings of the two words, but I've always thought that it is roughly as you suggest. If so, I can't really think of (m)any circumstances in which it would be "not practicable" to identify a bare conductor in one of the ways described (things like armour are already exempt from the requirement for identification, per 514.6).

I am not sure if it is actually required.

As I said, having read all of the apparently relevant regs, nor am I.

Kind Regards, John

 

[securespark]

The 4th Ed. (1903) has an interesting line:

Regulation 48 states “Fuses may be considered too large if they are not warm to the touch on full load and too small if they hiss when moistened.”

Fancy moistening any fuses??