Hello,
Just wondering why do most places sell 3mm earth sleeving when it is so much bigger than the conductor? I'm thinking that the brown sleeving that you use to mark the switched live at a light switch is
3mm and that slides over the insulation as well as the conductor.Thanks, Stephen.
Probably so that sparkies only have to carry one set of sleeving that will fit all cable sizes instead of several. Also makes it easy to slide on.
Same reason you can mark a switched live using sleeving (so that the electrician doesn't have to stock two different kinds of twin'n'earth, one with two browns and one with a brown and a blue.
Philip
Or it means the seller only has to stock one size of sleeve. Chicken egg, egg chicken?
Over multiple conductors turning them into one "wire". One for ARW what do the regs say about that (if anythng). What is custom and practice? Thinking inside boxes rather than CU's.
En el artículo , Dave Liquorice escribió:
Interesting question. At ceiling roses, for example, I run all the CPCs through one piece of sleeving. I don't twist them together as that might cause one or more to fracture.
I've seen installs from years ago (1970s and 1980s) where at JBs for lighting and ring circuits, the bare earth wires were just routed outside the JB and twisted together underneath (so access to the lid was still possible). That was it - no other method of securing the connection.
Similar to this, but neater:
Saw enough of it to think it was fairly common practice at one time.
Odd. That's the way BT joined telephone cables for ages. Twisted and sleeved. You'd have to try quite hard to break copper wire by twisting - although I know it's frowned upon these days.
Seen a fair bit of that too. Think it was commonplace enough that my Dad used to run earths outside the JB into a single choc block (rather than just twisting together) even if there was a spare terminal inside. I remember him telling me that earths weren't supposed to go inside!
Who else remembers wire wrap for prototyping digital circuit boards? That was extremely reliable.
Personally, I don't think that sort of "pliers twisting" would be all that reliable in corrosive environments, and the amount of "crackle" which you used to get on BT circuits in the good old "all copper" days tends to bear me out.
In message , Dave Liquorice writes
If they are twisted together - bloody annoying when you have to come and work on them some years later. It seems to have been common practice tears back.
I always keep the wires separate and sleeve them separately
Its not 'twisting two wires together', though. That was tensioned solid core coppper wound round a hard steel post, and as long as it is not in the damp, it was very very good.
En el artículo , The Natural Philosopher escribió:
The steel post was square in section, so as the copper wire was wrapped around the pin, the corners of the post bit into the soft wire, making for a very good connection.
+1
I think you will find that most of the 'crackle' that you refer to was caused by the carbon granule microphone's that were fitted then, long since superceded.
Peter
The wire actually cold welded to the post. System X still has some wire wrap in it.
Wasn't a good wack on the nearest hard surface supposedly a fix that sometimes worked.
G.Harman
I did a lot of that stuff in my final year undergraduate project. We had a 16 bit minicomputer and I modded it to enhance the instruction set. New wires were easy, but it was tricky when I found a post had one wire already on it, right at the tip - had to unwind that and move it down. Usually just fitted a new one, but if the other end of the existing wire wasn't 'on top' of its post....
You can buy slimmer - and its much better for individual 1 or 1.5mm CSA wires. The 3 mm may be more "versatile" but its a liability IME.
The main problem I have with twisting is it makes it harder to isolate individual wires when testing.
A hard *square* steel post with sharp edges, so it bit into the copper wire.
That was often caused by damp ingress rather than an inherent design fault. Yes the carbon microphone inserts (transmitters) did generate high noise levels but only by comparison to alternative microphone designs. As far as telephony went, they were more than quiet enough for their intended use.
As you correctly asserted, they were *long* superceded, not just to the extent of disappearing from more modern telephones that started replacing the 700 series but even to the point that replacement transmitter inserts for the 700 series were updated to the use of a T4 receiver insert acting as a moving iron armature microphone with integrated current modulator amplifier built into a drop in replacement transmitter casing. AFAICR, this was well over quarter of a century ago now.
I've replaced many a handset transmitter in my time with the new "Transistorised" models but it does have to be said, I also found myself having to replace "Transitorised" units within just a year or two of service, often they'd fail 'dead'. They didn't offer the durability and graceful failure mode of the old, tried and tested, carbon microphone technology that had a history in telephony already extending back a century by 1990.
Indeed it did but only as a short term remedy. However, the later electronic models of telephone had the unfortunate knack of the receiver or transmitter going completely dead due in part to a lack of 'DC Whetting' current combined with the use of push-on connectors which could loosen and go open circuit. In this case, a good whack against a solid object was also a simple and effective short term remedy.
In message , The Natural Philosopher writes
Wire wrap doesn't respond well to pigeon crap either.
I had a 19" rack cab' in a church tower, the location was well ventilated and dry so no corrosion worries until a pigeon decided that the back of the cab' made a great toilet. By the time the board failed the wiring was no longer visible under a great pile of poo........
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