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Thread: stripping MI cable.

  1. #11
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    Quote Originally Posted by electricalperson
    if the cable is fire rated shouldnt the boxes be fire rated as well? i think terminating it in a 4" square would defeat the purpose of the cable
    Where I have used and where I have see MI used both ends where terminated in panels that where located in fire rated rooms.

    The MI connected emergency distribution panels and had to be fire resistant as it passed through the building.

    Here is a picture of some MI leaving a panel.


  2. #12
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    i noticed the Alamo in san antonio texas is wired with that, for everything -general lighting, receptacles, etc. It was either MI or some other type of cable cased in a copper tube about the diameter of a 12/3 sjo.

    This just made me think of this stuff I saw in a magazine (popular mechanics or something) sometime in the late 80s or early 90s. It was a smooth aluminum tube, looked just like the soft aluminum tubing you can buy at the hardware store, except it came with thhn conductors in it. This stuff was supposed to be the new best thing when it came to wiring. I dont remember what it was called, and i wonder what became of it.

  3. #13
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    Quote Originally Posted by peter
    how much does that cost?

    Not exactly MI cable but I hooked up one end of thefunctional equivalent. It was $10 per foot. This was maybe 5 runs of a couple of hundred feet each to fire exhaust fans in a Lowe's.
    It had a copper, corrugated cover which, according to instructions, I cut with a [plumber's] tubing cutter. That went well.
    Inside were maybe three wires covers with about 1/8" [1/4" dia.] very soft white insulation. This is supposed to puff up and form some sort of ceramic when exposed to high heat.
    That's all I know. Hope this helps.
    ~Peter
    interesting. do you remember what it was called?

  4. #14
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    Quote Originally Posted by peter
    [COLOR="Red"]Not exactly MI cable but I hooked up one end of thefunctional equivalent. It was $10 per foot. This was maybe 5 runs of a couple of hundred feet each to fire exhaust fans in a Lowe's.
    It had a copper, corrugated cover which, according to instructions, I cut with a [plumber's] tubing cutter. That went well.
    Must be Lowe's spec as I saw the same thing at some Lowe's the company I work for did.

    Inside were maybe three wires covers with about 1/8" [1/4" dia.] very soft white insulation. This is supposed to puff up and form some sort of ceramic when exposed to high heat.
    I cut off about a 12" piece of the conductor itself and while at break I hit it with a plumbers torch for a good 5 minutes.

    It did not change much but it also did not burn or fall apart. :smile:

  5. #15
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    Similar cable is used here in the UK, where it is generally known as M.I.C.C. (mineral insulated copper covered)
    Sometimes also known as "pyro" which is an abbreviation for "pyrotenax" which is the most well known brand of such cable, manufactured I believe by BICC.

    This cable is generally considered to be the safest and most durable wiring system available.
    It has a number of applications
    1) for life critical systems that must function even if the cable is innvolved in a fire, such as central battery emergency lighting, fire alarms, fire pumps, smoke extract fans etc.

    2) as an extra safe wiring method, for general purpose circuits, in places where fire would have especialy serious consequences such as museums and art galleries containing ireplaceable exhibits, or historic wooden buildings, or buildings with insufficient fire exits that cant be improved for historic reasons.

    3) Where an increased level of safety is required due to the presence of highly flamable or explosive materials, such as oil refineries, petrol filling stations, explosives works, munitions stores etc.

    4) For reasons of appearence, especialy in old buildings were wiring cant be concealed but must be clipped to the surface, Neatly clipped MICC is certainly better looking than conduit or armoured cable, or "twin and earth" (similar to romex) run on the surface.

    5) in very hot surroundings where any type of plastic or rubber cable would be damaged, near or above ovens, furnaces or boilers for example.

  6. #16
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    Quote Originally Posted by electricalperson
    how much does that cost?
    $12.57 a foot
    Brian John
    Leesburg, VA

  7. #17
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    Quote Originally Posted by wireguru
    i noticed the Alamo in san antonio texas is wired with that, for everything -general lighting, receptacles, etc. It was either MI or some other type of cable cased in a copper tube about the diameter of a 12/3 sjo.

    This just made me think of this stuff I saw in a magazine (popular mechanics or something) sometime in the late 80s or early 90s. It was a smooth aluminum tube, looked just like the soft aluminum tubing you can buy at the hardware store, except it came with thhn conductors in it. This stuff was supposed to be the new best thing when it came to wiring. I dont remember what it was called, and i wonder what became of it.
    In a structure that is made of Adobe (?) MMMMMMM, our taxes at work?
    Brian John
    Leesburg, VA

  8. #18
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    Quote Originally Posted by brian john
    In a structure that is made of Adobe (?) MMMMMMM, our taxes at work?
    might have been done for appearance since it was exposed. Probably cheaper than the labor to fish romex through adobe :wink:

  9. #19
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    Quote Originally Posted by electricalperson
    i was reading the electricians handbook and came across the section of stripping MI cable. i never worked with it before. they shown a picture of someone stripping the copper jacket off. what do they do with the material inside? does it break off or just turn to powder? i take it they also need to ring out the conductors when they strip the last end before they slide the insulation on?
    The manufacturer has detailed instructions on how to prepare termination on an MI cable. It is VERY tricky.(Some MV kits are actually simpler.) Make sure you leave a loop at each termination in case you ruin it. Practice the termination on a scrap piece of cable several times, before you feel profficient and head for the real thing. Special termination kits are also needed. The main issue is how to finish up the compressed magnesium oxide insulation, so that it does not 'leak' out and water does not migrate into the material which is highly hygroscopic. Meggering is very important to prove that there is no grounding or shorting happened.

    This is what I remember, now lets see what they say:

    http://www.tycothermal.com/assets/Am...ation_0907.pdf

  10. #20
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    Quote Originally Posted by weressl
    The manufacturer has detailed instructions on how to prepare termination on an MI cable. It is VERY tricky.(Some MV kits are actually simpler.) Make sure you leave a loop at each termination in case you ruin it. Practice the termination on a scrap piece of cable several times, before you feel profficient and head for the real thing. Special termination kits are also needed. The main issue is how to finish up the compressed magnesium oxide insulation, so that it does not 'leak' out and water does not migrate into the material which is highly hygroscopic. Meggering is very important to prove that there is no grounding or shorting happened.

    This is what I remember, now lets see what they say:

    http://www.tycothermal.com/assets/Am...ation_0907.pdf
    Interesting link, Laszlo.
    Not a lot has changed since I last did Pyro a very long time ago.
    It was a pain then too.
    I think I'd rather have live wasps stuffed up my anus than have to do that for a living.
    :grin:

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