ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades The Pyro thread

It sounds like an accident waiting to happen to me.

I'd like to know what lunatic came up with such a crazy system in the first place!

Me too... it's pretty old. Was abolished around the late 1960ies.

Just getting back to the subject of Pyro cables, I had the chance yesterday to work on some in an old country pub, that were used as Service lines.
The boy that I had working with me (An Apprentice Line Mechanic) said he had no idea they made cables like this.
Then started a little bit of a tutorial in the Why's and What-fors of Pyro systems.
The newer ones (Pyro cables) over here are PVC served (sheathed) and I've seen the odd rodent teeth-marks on them out in the field.
There was also an Electrician who lost his registration about 6-7 years ago for making the outer sheath the B-Phase (R-Y-B) in a 3 Phase system.
He seriously injured another Electrician that was working on the system later down the track and stripped back the PVC serving.
Like I said above, every Electrician should have a good grounding in all the cables and wiring systems that they are likely to encounter in thier normal course of work.
This would mean knowing how to test them, how to identify when the wiring is deteriorating and standard Insulation Resistances for the cables.
Sure, us guys as Electrical workers are generally "in the know" about these things, but how would Joe blogs with his DIY project have a clue, DIY books never go that far into Electrical systems.

OUCH How someone can do something like that and then go home and sleep at night is beyond me. You KNOW it's going to hurt or kill someone eventually.
Actually Trumpy, I saw one book that did explain pyro, and the uses of it for the home handyman. They extolled the long life, toughness, and small size, but had the sense to tell you to call an electrician to make the connections after you'd routed the cable etc.

Chipmunk, did that book detail bend radius and sheath earthing ? Pyro should probably be installed by an electician familiar with the whole process.

Yes I believe it did, if I remember correctly, it said not to bend to less than 10 times the diameter, do NOT repeatedly bend, etc. And as for the sheath earthing, they covered that by 'leave the termination to an electrician' (hopefully not the one in Trumpy's post )

Chipmunk,
Stove elements are like Pyrotenax, not sure if the outer sheath is actually copper, but I do know that kettle (jug) elements sure are.
I would also agree with kiwi's comments, Pyro, will not tolerate being bent more than twice, unless of course, it is a very gentle bend.
Stress the outer sheath too much and it will crack.
One other little system that we imported from England, that I'm told wasn't good enough for use there, so it was sent over here, was the Dreaded MIAS(Mineral Insulated Alloy Sheathed).
Bend once or start again, it came in huge coils and you had to warm it with a propane torch set on low, to even to get it to un-roll.
That was all torn out by the late 90's, for those that actually were cheap enough to install it in the first place.
Apparently this "cable" would never even blow an HRC fuse, it would blow the cable sheath apart instead.

We never had stuff like that here, but we did have other wild stuff, like NyrUzi (please don't ask me about the upper/lower case, these should be harmonised codes), called "covered pipe wire". Basically two wires isolated with rubber and cloth, a filler that looks like several thin strands of sisal rope, everything wrapped in kraft paper and an outer sheathing made of brass. Outer thickness similar to modern NYM cable. Used for surface-mount work in finished areas. Horrible stuff, since neither the rubber nor the cloth hold up too well. Unlike the classic rag wire that was used for conduit work the cloth wasn't woven around the rubber but simply fabric wrapped around and the rubber was definitely of far inferior quality too. Then there was the heavy-duty version of this. Same interior design, but more filler, more paper. And around the brass an additional layer of very solidly woven cloth that had been drenched with bitumen. About as thick as my thumb, but actually easier to bend as the thin stuff (for the thin stuff you need a Bergmann conduit bender, the big stuff has huge minimum bendiing radii but can be bent without tools). And last not least I've recently seen some lead sheathed cable. Im'not sure though whether it's power or telecommunications, the apartment house I've seen it in also holds a telephone patch panel for at least four or five blocks... it's located in the hallway that leads to the basement and the trash cans in the yard and not locked any more... everything old as hell and every connection nicely labeled with street and number... so if you don't like somebody you know where to go...

Old underground feeders are even bigger. Bare wires cast in bitumen with an outer covering off bituminated rope. Still used in some places, you can see it running on the basement walls from the service to the main panel. 1-1 1/2" thick... for a maybe 10mm2 (or maybe even 6mm2) feeder...