Computer Energy Management Control Systems - Current Trn

[ed_cogent]

What would be the correct approach to wiring a 4-20 millivolt signal (Class 2 wire, shielded)from a Current Transducer located in a 480 volt power panel. Class 2 wire has 300 volt insulation? What about seperation requirements between Class 2 witing and power wiring?

[tom baker]

You say class 2 wire, but what type of circuit per Article 725 is it? Class 1, 2 or 3? This is determined by the type of power supply in the circuit, it may be a class 1 power limited in which case you are ok if you use 600 V rated cable such as PLTC.

[leshutter]

Per NEC 300 you will have to run 600V cable within the enclosure itself. You can make the entire run the same cable or bring it out to a j-box or whatever and splice it to any standard class 2/3 cable from then on if you want to save $$ on cable. You will still have to physically seperate the 4-20mA(Class 2or3) loop cable from the HV wiring by 2" or more -or- run the LV cable in its own raceway such as chunk of suface mount track from the cable entrance to the point were it terminates to the transducer.
There are several brands of cable out there listed as audio/instrumentation use that are 600V jacketed. Okonite and Belden are two of them.