Guys, I was trying to explain to John (Renosteinke) in the Chat room last night about the cable we call Pyrotenax.
To give it it's correct technical name, it's called Mineral-Insulated, Metal-Sheathed or Mineral insulated Copper Sheathed.(MIMS or MICS)

It's a type of cable that is under-utilised down in this part of the world these days.
But I'm told it's still used quite a bit in the UK.
Considering it will withstand temperatures up to 250C (482F), this alone makes it ideal for fire protection circuits and the like.
Here is a guy holding a sample of the stuff:



This PDF file(331kb) tells you all you ever wanted to know about MIMS cables, even how to strip, terminate and fix this type of cable:

http://www.aeicables.co.uk/literature/mic.pdf

Believe me this isn't an easy cable to work with, it's rather finicky about being bent too sharply (just think Refrigeration piping) and the insulation inside the sheathing is very suseptible to moisture if the end of the cable is not sealed properly.
Keeping moisture out is important because the wires are bare inside the densely packed powder insulation.
There have been cases of this cable exploding, where a kink has been put in the sheath during installation of the cable and the sheath has cracked and it has gone un-noticed, until one day the cable fails.

{Message edited to re-size picture}

[This message has been edited by Trumpy (edited 05-31-2005).]

Trumpy, while I was doing my training, that's one thing I saw WAY too much of, I can still hear my mentor now.. "Dress that d*** cable, looks like a dog's hind leg, do it neatly, *DON'T yank on the seal like that*... Kids today.."
I always thought it was an odd, yet absolutely excellent concept. Nothing organic in the bare copper version, and excellent earth continuity, I believe the sheath is something like 3x the cross sectional area of the conductors.

Thanks, Trumpy, for the info. It certainly does look like a very good wiring method from an electrical standpoint- if a bit of a bother to work with!

John,
No problems, mate.
Chipmunk,
Oh and you had them comments too?.
I'm glad I worked with Pyro during my time, it's certainly saved some suprises when turning up to Industrial and some Commercial places, only to find the wiring has been run in Pyro.
I realise that it's use is rather limited but I believe it's one skill every Electrician should have under thier belt, especially jointing it.
Even though it's not being used like it was earlier on, there is still a chance you'll come across it sooner or later.
Which brings up another thought, these days with respect to Electrical apprentice training, there seems to be a lack of knowledge from newer Electricians (ie: just registered) in the repair or replacement of older wiring systems, like Steel conduit, wood trunking and of course Pyro.
It seems that the majority of trainees only ever get to work with standard PVC cables and standard fittings and once they go out on thier own, they've never worked on any "legacy" wiring systems, which could use any number of different (and strange) fittings and wiring methods.
There, that's my rant for today!.

Absolutely Trumpy ! I've been called to MIMS cable failures in old Christchurch buildings and I don't even know where to start with terminating that stuff ! MIMS is the most permanent cable type and therefore it will be in service for decades. But very few of us know how to maintain it.

MIMS cable techniques should be included in the Trade Certificate practical curriculum. It could possibly replace other outdated items such as Soldered Lugs and Bargeboard Tie-offs

Trumpy,
i fully agree with you that alot of newly qualified sparkies do not know what to do with some of the older installations installed years ago.

me personally i love Pyro, its on of the best forms of wiring i know, its not the easiest of cables to use but after a bit of practice it can look sooooo good.

in LOndon all the fire ssytems that were fitted during the reign of the GLC (Greater London Coucil) it was a requirement that all Fire Alarm Systems were installed with Pyro.

Also a national brewer that owned a few thousand public houses had ALL circuits wired in pyro, it was because of the low fire hazard that Pyro has.

i have been to installations that are prior to metrication and they are still going strong, (some of the Recepticals and switchgear needs replacing but he cable is good).

Britspark

Gidday Britspark!,
Welcome to the Forum, great to have you along.
Yeah, that's one of the good things about Pyro, it's temperature rating is basically the melting point of copper.
And yes I must agree there aren't many things that look as nice as a whole set of Pyro cables nicely laid into and clipped to a cable ladder.
Kiwi,
The only reason we were trained in it's use here, was because back in the 1950's the Power Board here used to use this cable for Commercial Service Mains (from the intake point to the Switchboard panel) and there are quite a few buildings with this set up still in them around the place here.
Always run as 4 singles, with the sheaths bonded at each end and also at regular intervals along it's length, depending upon the length of the run.

Yes, nicely run pyro cables are a joy to behold. Installing them must be a science in itself. Trumpy, I have even seen pyro mains in old houses here running right up to the old fusebox. Makes opening the door of the fusebox a bit nerve-wracking in case moving the pyro end causes it to fail ! ! Especially if you're like me and don't know the first thing about fixing it. How much can you flex those tails before they fail ? They seem kind of fragile, and I always worry about moving them.

Pyro is also installed to supply fire sprinkler pumps in multi-storey buildings, especially in hotels. I think it's a building code requirement.

Here in the UK, I have known the power company mains to be pyro, generally something akin to 16mm 2 core, although obviously the old imperial equivalents . This mainly seems to happen on blocks of flats (apartments) built for social housing in the 50s. The PoCo main incomer to the building will be 'normal cable', a distribution unit of some kind in the basement or service area, and pyro to the individual main fuses/meter cases. The scary thing for me was to see that they treated the pyro the same as any other cable, just had the sealing pot sat on the end, 2 sleeved conductors to the service fuse block, and a clamp for the earth. I guess it cost them less than a custom [pyro only] box for the mainfuse and neutral link.
Again, these cables seem to be in excellent condition, and were left alone during the remodel, the only part of the electrical system that wasn't totally ripped out.

quote:
---------------------------------
...the only part of the electrical system that wasn't totally ripped out.
-----------------------------------------

By the occupants.

Alan

Totally agree with you Trumpy! At school we didn't even learn about the old color codes, yet you still find them everywhere! I don't know what some of my classmates are going to think should they once open a j-box with a mess of black, grey and red wires...

Ahh, you met them.

I've often criticized the DIY manuals here for the way that some of them make no mention of older methods of wiring.

Considering that many people tackling wiring will be doing so in old homes, what's the point of a DIY manual which is written as though the existing system has been wired since the 1980s?



[This message has been edited by pauluk (edited 05-31-2005).]

QUOTE
---------------------------
Ahh. you met them.
---------------------------

No, they kept different hours to me.


Alan

Kiwi,
Being solid copper, they don't tend to like being moved about too much and I would avoid it as much as possible.
The other thing about the actual cable end/pot arrangement, is the fact that if not fitted properly in the first place, they can work loose over the years.
This can make opening a live board the same as opening a jack-in-the-box.
Safety glasses and Hot gloves are standard equipment when I work on any MIMS cabling.
No need to worry about explosiions in this case though, if it's going to occur, it will happen in the first 2-3 years of the cable being in service.
BTW, Pyro is a lot "safer" as far as cables entering a switch-board panel go, they have a proper gland on them to screw them to the panel hole.
Not like some idiots running PVC through a metal panel without even as much as a bush!.
Pyro is also quite rugged in it's construction Kiwi, I wouldn't be too concerned about moving it, unless you intend to have a full-on wrestle with it.
It's made to be moved about once it's installed.
Yes and by the way, the only cable you are allowed to run (vertically) through a lift shaft is Pyro.
NZECP 33 (now defunct I think) although brief, gives some guidance on Pyro installation and cable ratings.
Paul,
I agree totally and to a certain extent the people that write these books, although well-intentioned, have a lot to answer for, considering that the lack of information on older wiring systems, is often where the problems start for the average DIY'er, when they can't find the correct information, instead of getting a professional electrician in, these people are more likely to guess.
If we're really lucky, the powers that be will stop mucking around with the colour codes for a while and let one system get a foot-hold.
Ragnar,
Yeah you're right there, I assume this is a 3 phase circuit, not a single phase one?.


[This message has been edited by Trumpy (edited 06-01-2005).]

No confusion here in France! All the following colors must be considered hot ( live): black, red, brown, yellow, white, orange, gray, purple, pink, mauve, magenta, tan. And any other metal bits. Oh, and probably blue ( neutral), green or green/yellow (ground) and anything else vaguely conductive, like machine casings, conduit, faucets, door handles or damp wallpaper.

Alan

No. Black = hot, grey = neutral, red = ground. Old Austrian/German color coding. 3 phase would be even funnier. 4 wire 3ph systems would have been black-red-blue-grey, grey being either PEN or (usually) ground, others are phases. 5 wire is like single phase, S and T phase being blue and black (black-blue-black-grey-red).

Huh?

No problem on the basic single-phase circuit colors, but let me see if I've got this straight for 3-phase:

#1. 3-ph 4-w plus ground

Phases = Black, blue, black
Neutral = Gray
Ground = Red

If you're going to identify the phases, identify all of them I say, but at least this is consistent with 1-ph on the neutral & ground colors.


#2. 3-ph 3-wire plus ground:

Phases = Black, red, blue
Ground = Gray

So gray suddenly changes from neutral to ground (or combined N-G), but red is now a phase?

Yeah, exactly. That's about the main reason why that system was abolished.
Red could be about anything, ground, phase, switch leg (back then you often had two switches in one box, with three wires, black was the incoming phase, grey and red were the switch legs), 3-way traveler,... and besides, if they had conduit people used whatever they could get. i've seen a red switch leg and a red ground in one conduit, black wires (all but the neutral, including the ground were black), red, and two greys at a light fixture (red neutral and two grey phases, no ground),...
According to code (dating from 1956) grey could be either a neutral, a PEN or a ground wire, the latter only in a three-phase system. That was the most common setup, at least in Germany, the old 3ph sockets in most cases only had 3ph+ground. Austrians always preferred conduit over cable and used mainly un-coded phases and a red ground.

Ragnar,
Just by reading what you've posted, I would tend to agree with abolishing a system like that.
Sounds like a wiring nightmare to me.

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...