MI Cable

[mstrlucky74]

Below id from the Pyrotenax website. Why for single conductor but not for multi? Thanks


A brass plate is not required for multiconductor cables. Connect the brass termination gland directly to the steel enclosure using lock nuts on either side of the gland connector as shown in Figure 14. Ensure that the brass gland is properly bonded to the steel enclosure once the lock nuts have been tightened. Install multiconductor cables following all

 

[don_resqcapt19]

It is assumed that with a multi-conductor cable that all of the phase conductors and the grounded conductor( if there is one) are all in the cable and there will be no inductive heating where the cable passes through a ferrous enclosure. If you have single conductor cables, there will be inductive heating if the cables pass though a ferrous enclosure. You would remove the ferrous material, install the brass plate and pass all of the single conductor cables through the brass plate to prevent the inductive heating.

 

[GoldDigger]

Because single conductors will carry unbalanced current which can create a magnetic field with resulting heating in a ferrous metal enclosure wall while a multi conductor cable is assumed to be carrying a balanced zero net current. No magnetic heating.

Tapatalk!

 

[infinity]

The MI cable that I've installed was #2/0 solid copper. If that were in a multiconductor cable you wouldn't be able to install it.

Brass plate photo from Google:

 

[gadfly56]

The MI cable that I've installed was #2/0 solid copper. If that were in a multiconductor cable you wouldn't be able to install it.

Brass plate photo from Google:

Egads! I don't want to think what all that cable cost per foot.

 

[GoldDigger]

Try per inch!

And FWIW I have seen descriptions of two conductor MI. Never seen it in person though.

Tapatalk!

 

[Smart $]

The MI cable that I've installed was #2/0 solid copper. If that were in a multiconductor cable you wouldn't be able to install it.

...

The multiconductor MI cable that I've seen had only a single copper jacket around two conductors embedded in one mineral-based insulating fill. Had to ray-chem insulate the conductors after stripping off the mineral insulation, inside the panel enclosure.

 

[iwire]

The multiconductor MI cable that I've seen had only a single copper jacket around two conductors embedded in one mineral-based insulating fill. Had to ray-chem insulate the conductors after stripping off the mineral insulation, inside the panel enclosure.

I think his point was 2/0 multi-conductor would be too hard to bend.


I have installed 10/4 MI cable and that was a chore to do.

 

[iwire]

The MI cable that I've installed was #2/0 solid copper. If that were in a multiconductor cable you wouldn't be able to install it.

Brass plate photo from Google:

A photo I took about 10 years ago.

I will post the rest.

 

[iwire]

Not my work, I took these photos in a large hospital I was doing other work. I think this installation must have been very difficult, these cables where ran all over the large building above existing crowed suspended ceiling spaces.

 

[Dennis Alwon]

What is the benefit to MI cable rather than say emt or another wiring method?

 

[John120/240]

What is the benefit to MI cable rather than say emt or another wiring method?

What very little that I know is its durability. It is like a fire pump, for mission critical applications it is supposed to survive a fire and still deliver power to its destination.

 

[Dennis Alwon]

What very little that I know is its durability. It is like a fire pump, for mission critical applications it is supposed to survive a fire and still deliver power to its destination.

Thank you

 

[iwire]

What is the benefit to MI cable rather than say emt or another wiring method?

Its very fire resistant.

I believe it is listed for 2 hours in a flame without shorting or failing.

The inorganic construction of mineral insulated cable makes it extremely fire and heat resistant. With an operating limit equal to the melting point of copper, 1982?F, 1083?C - it can easily withstand high temperatures and heavy current overloads. It emits no smoke or toxic substances and allows no flame propagation. In contrast, a third party test proved standard conduit and wire failed at 425?F. These fireproof properties make it the best choice for connecting motor operated valves, control stations, plant shutdown systems, instruments and power devices that must remain operational under actual fire conditions.

http://www.micable.com/mic05.html

 

[augie47]

I've seen it used a couple of times. Fire pump supply to satisfy 695.6, and industrial equipment that operates at high temps.
Here is an interesting link:
http://www.micable.com/

 

[John120/240]

Augie, That is an interesting read. How flexible is the MI cable ? Comparable to 1/2" soft copper water pipe ? Do you use any special benders or is it just armstrong adjusted to fit ?

 

[GoldDigger]

What very little that I know is its durability. It is like a fire pump, for mission critical applications it is supposed to survive a fire and still deliver power to its destination.

In some of the posted pictures you can see the label stating "two hour fire resistant".
I guess that even if the copper tube softens the mineral insulation will still protect the wires to some extent.

Tapatalk!

 

[gadfly56]

Augie, That is an interesting read. How flexible is the MI cable ? Comparable to 1/2" soft copper water pipe ? Do you use any special benders or is it just armstrong adjusted to fit ?

For flexibility, I think it's more like ACR, the stuff you use for refrigerator water lines.

 

[iwire]

It is much tougher to bend than any flexible plumbing pipe. Closer to trying to bend standard water pipe.

The outer copper sheath is pretty thick, the copper conductors inside are always solid and the mineral insulation tends to 'glue' all together. Bending it, trying to run it is very tough.

 

[Fulthrotl]

It is much tougher to bend than any flexible plumbing pipe. Closer to trying to bend standard water pipe.

The outer copper sheath is pretty thick, the copper conductors inside are always solid and the mineral insulation tends to 'glue' all together. Bending it, trying to run it is very tough.

i remember your photos from the stuff you installed....
do you pull it around sheaves or something to get it
roughly in place, before strapping? if you have to
make a tight corner with it, do you use a bender, hickey
or just get yoda to look at it funny?

i may have to redo some in the engine room on a couple
tugboats, and was wondering....

edit: duh. saw your reposted photos in the middle of the thread.....
forgot the original post where you said you just were viewing them
in all their glory, and had not installed them.