Cable Types

[mordswixed]

Can anyone give me a good source to read about Network Cables. I am looking to understand the difference between CMX and CMR and what others are available. I would like to make sure I purchase the correct cable for the job and I now understand there are different types for Residential and Commercial installs.

I have tried searching on Yahoo and Google but they seem to have become useless now that they have a Pay to Play type attitude and only people selling things seem to come up on searches now.

Thanks in advance.

 

[nforeman]

as far as cables go, you're probably going to deal with two types, CMP {Plenum rated(FT6)} or CMR {Riser rated(FT4)}. The first is required in an air return ceiling. But there are places that don't require that type of fire rating, you would have to check with your city's requirements. The second is what you would use in a riser environment, (ie. linking floors together). It can get quite intense, depending on what you're looking for, and what you're looking to do with it as well.

 

[franklin97355]

The cable manufacturers will have information on the specs, but your local building codes office will let you know what their requirements are and that is what you need to comply with.

 

[mordswixed]

Thanks I guess I will need to check with local building codes then.

I was going to look and see what they had already installed in the office I am working on but I figured that the original company might not have used the right ones.

It is a one story office so I guess CMR is not necessary but I will check anyway.

Thanks.

 

[davemiller]

When in doubt use plenum rated cable, per nforeman's note and reference to 'plenum'. If the cable burns the fumes are not supposed to kill you.

 

[Servamatic]

Most likely your local distributor only stocks CMR and some CMP, the cost difference between CM, CMX, CMG, and CMR is minor, so stocking all of them doesn't make sense.
The cost difference between CMR and CMP is another story. CMP can be 3 times the cost of CMR.

As for the properties, it is a misconception that CMP is less toxic than CMR.
The difference between them is that CMP burns slower, and gives off a whiter smoke, this is to buy time for people to be able to exit the building and be able to see better.

If you put a flame to CMR and CMP you would find the CMP should extinguish itself when you remove the flame much quicker than the CMR does. CM, CMX, and CMG will continue to burn at up to about 50 feet per minute.

Many jobs such as schools require CMP everywhere. The NEC is the authority on this subject so the Local Authority Having Jurisdiction is the final word on where it is required in your area.


Richard S. Anderson, RCDD

http://www.servamatic.net

 

[naturl]

The best book on the subject is the "The Cabling Handbook Ed. 2" by John R. Vacca.
Guys, It's my understanding that riser cable will not suport the transmission of flames rising up past firestopers through it and Plemum has less killer stuff emitted (as well as a marker) so the rest of the vent system "stays fresher longer".
Bob