best practices for keeping Class 1 600V rated cables separated from Class 2 300V

[hastings4]

When
specifying cables for field installation in raceways, does anyone have any best
practices for keeping Class 1 600V rated cables separated from Class 2 300V
PLTC and communication cables. The projects I am working on use bulk 24VDC
distribution which drive the us to using standard 600V rated TC but most of the
instrument cable and ethernet cables fall into the PLTC realm. My understanding
of the NEC 725 is that I must physically separate these cables even though they
are all 24V. Do I just need 1/4" separation in cables or should I be looking
at barriers or a whole differnent tray system? Perhaps I should find a way to
use all 600V rated cables?

 

[rlundsrud]

If you wanted to mix the class 1 and 2 they would need to be for associated equipment in addition to having correct insulation rating. Is it a big problem to just separate them?

 

[kwired]

I don't see that you have any NEC problem if the cables themselves are a stand alone wiring method, or am I missing something?

 

[hastings4]

I don't see that you have any NEC problem if the cables themselves are a stand alone wiring method, or am I missing something?

Working at a client site and they are using 1 cable tray for all 24V DC cable runs

 

[kwired]

Working at a client site and they are using 1 cable tray for all 24V DC cable runs

You mentined raceways in OP.

You can't pull power conductors/class 1 control conductors in a raceway with class 2 conductors/cables. But you could pull two different cables regardless of what type of circuit designation they contain that are stand alone wiring methods into a pipe, chase, sleeve even if the pipe is otherwise the same thing that qualifies as a raceway.

 

[rlundsrud]

You mentined raceways in OP.

You can't pull power conductors/class 1 control conductors in a raceway with class 2 conductors/cables. But you could pull two different cables regardless of what type of circuit designation they contain that are stand alone wiring methods into a pipe, chase, sleeve even if the pipe is otherwise the same thing that qualifies as a raceway.

Was there a code change that disallowed the use of class 1 and class 2 conductors in the same raceway if they are for the same equipment and all insulation is rated for the highest voltage (typically 300 or 600 volt)? As an example, a HVAC RTU that has both class 1 and class 2 controls run to it all within the same conduit.

 

[GoldDigger]

Was there a code change that disallowed the use of class 1 and class 2 conductors in the same raceway if they are for the same equipment and all insulation is rated for the highest voltage (typically 300 or 600 volt)? As an example, a HVAC RTU that has both class 1 and class 2 controls run to it all within the same conduit.

If it stays Class 2 it cannot be combined even if related to the power wiring. The Class 2 must be recategorized as Class 1 and run using Chapter 3 methods, with all the additional restrictions that might require elsewhere in the circuit.

 

[kwired]

Was there a code change that disallowed the use of class 1 and class 2 conductors in the same raceway if they are for the same equipment and all insulation is rated for the highest voltage (typically 300 or 600 volt)? As an example, a HVAC RTU that has both class 1 and class 2 controls run to it all within the same conduit.

That never was allowed that I am aware of. Seen it done a few times but was not NEC allowed.

You can re classify a class 2 circuit to class 1 in some cases - but that means reclassifying the entire class 2 circuit not just the parts that share class 1 or power wiring spaces. That means on the HVAC example you can not run to a typical class 2 rated thermostat.

Now if you have over 300 volt power or control circuits in a raceway and want to run another under 300v class 1 circuit in there I believe you must still use 600 volt conductor for it.

You could however pull a UF cable for power and a CL2 cable for control through the same raceway to that HVAC unit, separation at each end of the run could be complicated some depending on how things are arranged.