Use of type CMR cable.

[wpaul29]

Well here is the situation. A company that we are doing direct T&M work for wants to use what is known as type CMR cable for contols coming from a remote PLC that is indoors to a chemical scrubber on a roof that is outdoors. There will be 40 couple wires eventualy going from the PLC inside to a local control panel outside and several field mounted instrumentation devices. Everything will be 24vdc or less coming from the PLC. At first I felt that maybe this cable wasnt rated for cable tray use but looking into the NEC I find that article 800.52 (D) permits it but actual spec sheets from the wire manufacturer note that the cable is for indoor use only. I really feel that this is not the best cable for the job. I feel that type ITC cable should be used. Art. 727 in the NEC applies to this cable. Type CMR cable is a communication riser cable and its application really doesnt apply. The specific use will be for analog inputs, digital inputs and outputs and 24vdc supply to relays and devices. Also some cables will be doing into a power panel which has 480vac in it for motor status. Let me know what you guys think sorry that the post is so long. Thanks in advance for your input.

 

[wireguru]

if its not outdoor rated, the jacket isnt going to last long at all in sunlight. id use itc, except the itc i have seen has a 300v rating, so you would need to figure something out for your 480v cabinets.

 

[hbiss]

There is CM or CMR that is UV resistant. I agree ITC would be a better choice.

As for 480 and LV in the same enclosure, TC with its 600v insulation unless the sections are separated.

-Hal

 

[wpaul29]

Well the powers that be decided to go with type TC cable with the 600VAC insulation rating. Thanks guys for your input.

 

[hbiss]

Well, I'm glad to see that somebody agrees with me.

-Hal

 

[tom baker]

There is CM or CMR that is UV resistant. I agree ITC would be a better choice.

As for 480 and LV in the same enclosure, TC with its 600v insulation unless the sections are separated.

-Hal

See the FPN to 300.3(C)(1) Even with 600 V insulation you can't have a class 2 or 3 power limited circuit in the same enclosure raceway or cable with a power and lighting circuit. If the PLC was a Class 1 remote control and signaling circuit, and functionally assocated then its allowed. A Class 1 remote control and signaling circuit is wired using a chapter 3 wiring method.
It depends on what type of circuit the PLC is classifed as. Most are Class 2.
A class two circuit can be reclassifed as a Class 1.

 

[tom baker]

if its not outdoor rated, the jacket isnt going to last long at all in sunlight. id use itc, except the itc i have seen has a 300v rating, so you would need to figure something out for your 480v cabinets.

I belive which means I could be wrong, that ITC is rated 150 V, but mfgs make a ITC/PLTC which is rated 300V

 

[tom baker]

I use PLTC mostly, its sunlight resistant and approved for direct burial. But for an application such as yours TC may be better, I like the PLTC as its smaller and easier in cabinets