M.I. Cable, can it be run in steel conduit?

Status
Not open for further replies.

Deadfrog

Member
Location
Ontario Canada
From our friends at wikipedia

"Mineral-insulated copper-clad cable is a variety of electrical cable made from copper conductors inside a copper sheath, insulated by inorganic magnesium oxide powder. The name is often abbreviated to MICC or MI cable, and colloquially known as pyro (because the original manufacturer and vendor for this product in the UK is a company called Pyrotenax). A similar product sheathed with metals other than copper is called mineral insulated metal sheathed (MIMS) cable.

MI cable is made by placing copper rods inside a circular copper tube and filling the intervening spaces with dry magnesium oxide powder. The overall assembly is then pressed between rollers to reduce its diameter (and increase its length). Up to seven conductors are often found in an MI cable, with up to 19 available from some manufacturers.

Since MI cables use no organic material as insulation (except at the ends), they are more resistant to fires than plastic-insulated cables. MI cables are used in critical fire protection applications such as alarm circuits, fire pumps, and smoke control systems. In process industries handling flammable fluids MI cable is used where small fires would otherwise cause damage to control or power cables. MI cable is also highly resistant to ionising radiation and so finds applications in instrumentation for nuclear reactors and nuclear physics apparatus."


My use for it is for power and control wiring for a fire pump to an emergency generator about 14 floors higher.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
That's my point. How can it be installed in a raceway. In a sleeve I can see , but not in a raceway and not into a panel unless there is a special connector to transition at the end of the raceway.

I assume it is possible in some scenarios but not very likely.
You could connect the MI fitting to a plate inside the enclosure. I would not see why you would want to put MI in conduit, but I don't know of a code rule that says you can't.
 

BJ Conner

Senior Member
Location
97006
Cheap Book (free)

Cheap Book (free)

Installation manual for MI cable http://www.tycothermal.com/assets/A...intenance Manuals/4330/H57987_IW_IOM_1206.pdf

Copper covered MI cable is copper, the inside of conduit may have exposed zinc coating (it's supposed to be enameled .) Copper and Zinc make a good battery. That is the potentiial for eltrogalanic corrosion exist, especially in a wet/damp location.
If it has to be run in a damp location consideration has to given to corrosion. Copper roofs that turn green are cool, cables are not. :cool:
 

iwire

Moderator
Staff member
Location
Massachusetts
Copper covered MI cable is copper, the inside of conduit may have exposed zinc coating (it's supposed to be enameled .) Copper and Zinc make a good battery. That is the potentiial for eltrogalanic corrosion exist, especially in a wet/damp location.


If that is really a problem why does the code allow bare neutral service conductors, any EGC and GECs in conduit?
 
Hi guys,

I have a client who wants to run mineral insulated cable in steel pipe so they can easily fire stop. I have a concern with the copper and steel being in contact and corrosion issues. I cannot find anything in the code regarding the subject. Can anyone shed some extra light on the subject?

The MI Cable itself - without conduit - is suitable for installation where fire hazard exist and it is still desired to have the circuit working. It has a fire rating.

It is not designed to be installed in conduit. There is a host of reasons why you would NOT want to do it.

The dissimilar metals issue can be overcome by specifying the MI cable with a PVC or other polymer jacket. The MI cable can be suitably supported with Click non-metallic clamps or simply tie-wraps. If metallic straps used you can pad them with a nn-metallic sleve. MI is also available with SS sheeting that have a higher fire rating than copper, but the dissimilar metal problle versus cast iron clamps or stamped sheetmetal still exist.

MI cable itself provides a limited resistance to mechanical damage, I would rate it somewhere between rigid and tubing.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
When I first saw the title of this thread, I flashed back to a project many years ago where a large engineering company spec'ed out that all air lines had to be run inside rigid conduit, and then spec'ed copper tubing for the air lines.

They eventually relented and deleted the requrement to run the air lines inside rigid conduit (at least for our equipment), but it took nearly an act of God to get them to.
 
Last edited:
When I first saw the title of this thread, I flashed back to a project many years ago where a large engineering company spec'ed out that all air lines had to be run inside rigid conduit, and then spec'ed copper tubing for the air lines.

They eventually relented and deleted the requrement to run the air lines inside rigid conduit (at least for our equipment), but it took nearly an act of God to get them to.

Obviously they are not familair with the saying: "Crow best eaten while still warm...";)
 

iwire

Moderator
Staff member
Location
Massachusetts
Would that be the only thing the Code ever got wrong?;)

It will take more than your personal opinion to convince me this is a problem and that this is a case where the NEC is wrong.

Engineers (and electricians) often think the NEC is wrong when actually the only problem is the NEC does not match what the engineer wants to do.
 
It will take more than your personal opinion to convince me this is a problem and that this is a case where the NEC is wrong.

Couple of problem with this reply. You presume that I care if you're convinced or not.;) I did not say it is wrong, I offered no opinion. I said that this WOULD not be the only thing that the NEC got wrong, ever. It continoues to undergo revisions where previous errors are corrected. Errors do not have to be malicious, but it is undeniable that many of the Code provisions represents special interests that is reflective of the Code panels composition and whom they represent.

Engineers (and electricians) often think the NEC is wrong when actually the only problem is the NEC does not match what the engineer wants to do.

I am willingly conforming to the Code EVEN when I can technically substantiate the alternative to be an equally safe and often better installation.(See above.) I also would appreciate if you stop bashing engineers, but I guess you only have yourself to be the basis of accusations.
 

iwire

Moderator
Staff member
Location
Massachusetts
Couple of problem with this reply. You presume that I care if you're convinced or not.;) I did not say it is wrong, I offered no opinion. I said that this WOULD not be the only thing that the NEC got wrong, ever. It continoues to undergo revisions where previous errors are corrected. Errors do not have to be malicious, but it is undeniable that many of the Code provisions represents special interests that is reflective of the Code panels composition and whom they represent.



I am willingly conforming to the Code EVEN when I can technically substantiate the alternative to be an equally safe and often better installation.(See above.) I also would appreciate if you stop bashing engineers, but I guess you only have yourself to be the basis of accusations.

You sure do make me laugh. :grin:
 

iwire

Moderator
Staff member
Location
Massachusetts
Nah, that's my secret nickname for you chump.

Listen up, stop with the insults, I have never called you any names. I do disagree with your views in many cases but I have never made them personal attacks.

Yet so far in just this thread you have called me a chump and spineless, knock it off. Had you called other members those things I would have issued you an infraction for doing so.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Obviously they are not familair with the saying: "Crow best eaten while still warm...";)

I had almost forgotten some of the battles we used to have with the bechtels and S&Ls of the world.

If it was in the spec, it just did not matter whether it was something workable or not. It was in the spec and that was what mattered. Most of the time it was fairly easy to get the engineering people to agree with the idea that something was not workable, but getting the commercial people to change it was just tough.

There were times when we would have 20 or 30 pages of exceptions we had taken to the spec in our proposal. most of the time they would become part of the P.O., but occassionally we would get a P.O. that did not reference them so we would have to sit on the project until the P.O. was changed.
 
Status
Not open for further replies.
Top