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

[Deadfrog]

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?

 

[Dennis Alwon]

Article 330 specifically permits MC cable in any raceway. MI (article 332) has no permission to be run in raceway so I would say no can do.

 

[iwire]

You can sleeve MI in conduit, you would be hard pressed to actually install MI in a complete raceway.

As far as the copper touching the steel pipe, how is that any different then a code compliant bare EGC in conduit or the fact the MI will likle be touching building steel in places?

For those that do not know MI here are some pictures

 

[Dennis Alwon]

You can sleeve MI in conduit, you would be hard pressed to actually install MI in a complete raceway.

So why does 330 allow mc but there is nothing in 332 that allows MI? How would you bond it?

 

[Little Bill]

Thanks for the pics. Iwire. That looks like copper tubing. Do they still make it in a stainless steel covering?
As to whether it can be run in conduit, I don't see anything (other than what you said) that would prevent it. 332.10 says in certain conditions that it should be protected from physical damage. IMO, conduit would be a protector.

 

[iwire]

So why does 330 allow mc but there is nothing in 332 that allows MI? How would you bond it?

No need to bond it that I know of.

I do not think that the NEC allows installing MI in a complete raceway, but I also do not think the NEC prohibits running MI through things like holes. And sleeves regardless of being made from conduit or black iron pipe are nothing but long holes.

I would make sure all the MI conductors run through the same sleeve to prevent inductive heating.

 

[don_resqcapt19]

I see no prohibition in Article 332, so the xxx.22 section of the raceway articles permits its use in raceways.

344.22 Number of Conductors. The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

 

[masterinbama]

http://i249.photobucket.com/albums/gg235/iwire_bucket/MICableLahey019.jpg
Nothing to do with MI cable but why the waste of fittings?

 

[Cleveland Apprentice]

I've never worked with M.I. cable, but what are the advantages in using it as opposed to conduit, mc or ac cable? What is the intended for?

 

[iwire]

I've never worked with M.I. cable, but what are the advantages in using it as opposed to conduit, mc or ac cable? What is the intended for?

It is fire resistant, I believe it has a two hour fire rating without it shorting out. The photos were taken in the mechanical spaces of a large hospital and these where emergency or life safety feeders I really do not know which.

I had nothing to do with the MI work in the photos, I just happened to be there doing something else.

 

[iwire]

http://i249.photobucket.com/albums/gg235/iwire_bucket/MICableLahey019.jpg
Nothing to do with MI cable but why the waste of fittings?

Good question, that was existing work so I can't answer that.

 

[BJ Conner]

MI is not really pulled.

MI is not really pulled.

MI cable would be hard to "pull" into any length of conduit. IT's not really pulled but more like "Placed".
It's not good to have your people learn about MI cable on your job. It's tough but delicate at the same time. When you done and it fails a meggar test, it's do over, new cable, do it again.

 

[infinity]

I've worked with MI cable. Horrible stuff. Center core was #2/0, SOLID copper. Good luck trying to pull that in a raceway. Engineer had a great idea of trying to install it in a cable tray with about 5000 bends. Boss lost his shirt.

 

[Dennis Alwon]

I see no prohibition in Article 332, so the xxx.22 section of the raceway articles permits its use in raceways.

So solid wire larger than 10 cannot be put in a raceway but MI cable can....? That is odd. I cannot imagine it being installed in other than a straight sleeve.

Bob you say the raceway does not need to be connected to the panel? How is the jacket grounded if it is sleeved into a main panel.

 

[iwire]

I've worked with MI cable. Horrible stuff. Center core was #2/0, SOLID copper. Good luck trying to pull that in a raceway. Engineer had a great idea of trying to install it in a cable tray with about 5000 bends. Boss lost his shirt.

I have only personally worked with it in 10/4 MI and that was bad enough.

Those pictures above don't show the 1000's of feet if these MI cables that where installed above the suspended ceilings of operating hospital. They also go up and down floors. I can't imagine how many guys they had on hand to make that happen. Glad it was not one of our projects.

 

[iwire]

Bob you say the raceway does not need to be connected to the panel? How is the jacket grounded if it is sleeved into a main panel.

The copper sheath you see is the EGC, it must be connected to the enclosure of the supply panel with the fancy connectors.

 

[iwire]

So solid wire larger than 10 cannot be put in a raceway but MI cable can....?

Well maybe that is the answer, you can't put MI in conduit is sizes larger than 10 AWG.

 

[AdrianWint]

Can't comment on the NEC but....

Here in the UK M.I. cable (or MICC (mineral insulated copper covered) as we call it) is used extensively for fire alarm systems & installations in historic places such as Churches etc. It is used for its ability to keep working during a fire & also its resistance to rodent attack.

The sheath is used as the the circuit protective conductor (ground) since its cross sectional area is always more than the conductor inside it and can also be obtained with a red, orange or white PVC oversheath.

I dont think I've ever seen MICC run in conduit (other than maybe a few inches through a wall). It would be difficuilt to pull through any length & almost impossible to get round a tight 90 degree bend.

 

[Dennis Alwon]

The copper sheath you see is the EGC, it must be connected to the enclosure of the supply panel with the fancy connectors.

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.

 

[iwire]

That's my point. How can it be installed in a raceway.

You would have to wait for Don to answer that.

In a sleeve I can see ,

Which is what I think the OP intends, just like the photos show it running through sleeves for fires stopping.

But I could be wrong.