class 2 and 3 voltages

[Mr.electric]

just wondering if anyone could help me out. I can't find the exact text that spells out the voltage and power limitations for class 2 and 3 circuits. I was under the assumption it was 150v for class 2 and 300 for class 3. could anyone shed some light on this for me.

 

[hbiss]

That's because it's none of your business. :lol: It's not up to use to determine whether a circuit is CL2 or CL3 or even Class 1. The class will be indicated on the power source as determined by the manufacturer using some mysterious testing method. If the information is not indicated we are to assume it's Class 1.

Those 150 and 300V voltage ratings relates to CL2 and CL3 listed cables respectively and they are only the voltage rating of the cable, nothing to do with what the actual voltages of CL2 and CL3 circuits may be. However we are not supposed to know that either. Notice it's not printed on the jacket, spool or box? You can find the voltage rating if you look up the specs for a specific cable but that is for use only if you are using it for a non NEC application.

-Hal

 

[pjholguin]

Review Article 725

 

[Mr.electric]

That's because it's none of your business. :lol: It's not up to use to determine whether a circuit is CL2 or CL3 or even Class 1. The class will be indicated on the power source as determined by the manufacturer using some mysterious testing method. If the information is not indicated we are to assume it's Class 1.

Those 150 and 300V voltage ratings relates to CL2 and CL3 listed cables respectively and they are only the voltage rating of the cable, nothing to do with what the actual voltages of CL2 and CL3 circuits may be. However we are not supposed to know that either. Notice it's not printed on the jacket, spool or box? You can find the voltage rating if you look up the specs for a specific cable but that is for use only if you are using it for a non NEC application.

-Hal

that makes sense, I suppose I'm here to build the erector set not design it. thanks for the feedback.

 

[Jraef]

Class 1 is limited to 30V if it is a "power limited" circuit (725.41.A), or if it is for "remote control and signalling", it is limited to 600V, no power restriction (725.41.B)

Class 2 and Class 3 limits are more complex based on what you are using it for, but it's all laid out for you nicely in Chapter 9, table 11A. but in no case is the Voltage to be over 150V.

 

[Mr.electric]

can anyone say why CL3 wire is listed for 300v if your power source according to chapter 9 table 11A only lists up to 150v. I was initially thinking it was for a higher voltage rating for seperation of power and lighting except your only alowed for 150v max on power conductors to have associated systems within enclosures per 725.136 (D)(2)(A).