Loudest bang of my career...

[ricicle]

I blew a 500A fuse once...........

Practising your technique, were you?

Switching back on a busbar that had water pooled on top of it from a roof leak. It was one in the morning and I foolishly couldn't be ar$ed to unplug all tap off boxes to IR test the busbar. I thought it would be ok so replaced the 315A that had gone and switched back on.
The 315A went again locally along with a 500A back at the main switchroom. The fireball was impressive where the water had found its way round to the area where a 100A tap off box was plugged.

 

[securespark]

I gotta agree with RF. Pyro is the bee's bolox.

I've seen some in a power station wired up in the 30's and it' still going strong.

 

[ban-all-sheds]

So it wasn't instead of a cucumber....

 

[Spark123]

Only problem I have had with the old stuff is finding the correct size glands and pots.

 

[Adam_151]

switchroom. The fireball was impressive where the water had found its way round to the area where a 100A tap off box was plugged.

On the plus side.... you then knew exactly where abouts the fault was

 

[JBR]

Please excuse my ignorance but I am assuming that 'pyro' is the same as this stuff:

http://en.wikipedia.org/wiki/Mineral-insulated_copper-clad_cable

Again, sorry if I sound stupid, but if a length of this stuff was bent sharply around a corner, wouldn't the internal conductors be likely to come into contact. I am assuming that the insulating material inside, being a powder, may not remain between the conductors.

 

[Spark123]

Yep, Pyro is just a shortening of Pyrotenax.
You wouldn't want to go too sharp a bend on it as if you split the copper sheath it isn't any good!
On the other hand you can nigh on flatten it with a hammer though and the insulation stands up as the powder compacts the conductors too, just as long as the copper isn't split.

 

[JBR]

Yep, Pyro is just a shortening of Pyrotenax.
You wouldn't want to go too sharp a bend on it as if you split the copper sheath it isn't any good!
On the other hand you can nigh on flatten it with a hammer though and the insulation stands up as the powder compacts the conductors too, just as long as the copper isn't split.

Thanks for the explanation, Spark.

 

[securespark]

You wouldn't want to go too sharp a bend on it as if you split the copper sheath it isn't any good!

When I trained on it, we had the old-fashioned tools:

http://www.neweysonline.co.uk/neweys/pdf/Pyrotenax_Pyro_MI_Wiring_Cables_Installation.pdf

The modern versions are on page 11, but the ones I used were leather-clad bits of wood - home-made, I reckon!

 

[OwainDIYer]

You wouldn't want to go too sharp a bend on it as if you split the copper sheath it isn't any good!

When I trained on it, we had the old-fashioned tools:

http://www.neweysonline.co.uk/neweys/pdf/Pyrotenax_Pyro_MI_Wiring_Cables_Installation.pdf

The modern versions are on page 11, but the ones I used were leather-clad bits of wood - home-made, I reckon!

The BICC guide:

http://s000.tinyupload.com/index.php?file_id=32214511594611681284

 

[stillp]

if a length of this stuff was bent sharply around a corner, wouldn't the internal conductors be likely to come into contact. I am assuming that the insulating material inside, being a powder, may not remain between the conductors.

I played with some Pyro many years ago, when the college stopped teaching electrical installation. With a Megger on the end of a termianated length, tied a knot in it - no change in IR (infinite at 500V). Heated the knotted part red-hot with a blowlamp - no change in IR. Hammered it flat while still red hot - no change in IR.
Wonderful stuff.

 

[JBR]

if a length of this stuff was bent sharply around a corner, wouldn't the internal conductors be likely to come into contact. I am assuming that the insulating material inside, being a powder, may not remain between the conductors.

I played with some Pyro many years ago, when the college stopped teaching electrical installation. With a Megger on the end of a termianated length, tied a knot in it - no change in IR (infinite at 500V). Heated the knotted part red-hot with a blowlamp - no change in IR. Hammered it flat while still red hot - no change in IR.
Wonderful stuff.

Sounds good stuff. I remember my parents had an outside lamp fitted many, many years ago using this stuff. I remember it was orange-coloured, not that that matters of course!

 

[securespark]

Yeah, that'll be the PVC-coated variety.

You can also get white and red and a few other colours besides.

 

[SimonH2]

Please excuse my ignorance but I am assuming that 'pyro' is the same as this stuff:

http://en.wikipedia.org/wiki/Mineral-insulated_copper-clad_cable[/QUOTE]
Yes, as Spark123 says it's short for Pyrotenax which is one manufacturer's name for it. MICC and Pyro go together in much the same way as vacuum cleaner and Hoover.

Again, sorry if I sound stupid, but if a length of this stuff was bent sharply around a corner, wouldn't the internal conductors be likely to come into contact. I am assuming that the insulating material inside, being a powder, may not remain between the conductors.

It's packed very, very tightly. It actually starts life as a large diameter short copper pipe into which they place thick copper bars and pack it with the white powder. It's then squashed/drawn down until it ends up as a long, small diameter cable - and in the process the powder is packed "quite tightly" (tight enough to squash the cores out as it's drawn).
Very similar to the way they make sticks of rock.

It has to be stored and terminated properly. If open ends are left exposed then it absorbs moisture and the insulation fails - and the same if the sheath gets perforated. Apart form being relatively small and robust, it's also rated for much higher temperatures than the various rubber/plastic insulated cables - which is why it's is still often used for fire alarm installations (though these days there are some high temperature plastic insulated cables which are commonly used as they are easier (= cheap ) to work with. As an apprentice, we had demonstrated a piece hooked up to a transformer to get it glowing bright red - it went very flexible (nicely annealed) but was still intact and would have outlived the bells it might have been feeding in an alarm system.

I recall doing a few ends as an apprentice, but haven't had the opportunity to use it since.

 

[JBR]

Thanks for the information Simon. Much appreciated.