CT wiring and conductors

[Greentagger]

What Class of wiring would the CT conductors or cables used to monitor PV system be considered? Are they Class 1 or 2? Something else? I’ve seen some in Cat 6 cable in same raceway as power wiring and some with actual 600V conductor insulation in raceway with power conductors. In what manner can they be installed in a compliant manner from source panel to inverter? Clarification and code references appreciated. Thanks.

 

[don_resqcapt19]

If the CT output is 0-5 amps of something like that I would see it as a Class 1 non-power limited circuit.
If the output is 4-20 mA or something like that I would see it as a Class 2 circuit.

 

[Todd0x1]

Theyre usually class 1. For example enphase (even though their current transformers have built in burden resistors and the output is millivolt) they say its class 1.

I have seen a bunch of installers using cat5/6 as well. Needs to be TC or a twisted pair of 600v conductors but the problem is none of the 18ga types like TFFN are listed for wet location. We've been using twisted pair of UL1015 MTW 18awg as its the same wire coming out of the CTs. Every once in a while an inspector sees it and thinks its low voltage wire but is ok after hes shown the tag or the 600v printing on the wire. So many in the industry just have no clue what they're doing. Right now I am arguing with a company who is running SO cord on peoples roofs and they are convinced its ok.

 

[jaggedben]

... Needs to be TC or a twisted pair of 600v conductors but the problem is none of the 18ga types like TFFN are listed for wet location. We've been using twisted pair of UL1015 MTW 18awg as its the same wire coming out of the CTs. ...

I don't know if any reason the 600V conductors absolutely need to be twisted pair. I'm using TFFN that's crosslisted as MTW and I think it's fine in a raceway in any location.

 

[Todd0x1]

I don't know if any reason the 600V conductors absolutely need to be twisted pair. I'm using TFFN that's crosslisted as MTW and I think it's fine in a raceway in any location.

some of the equipment manufacturers say the wire should be twisted

 

[petersonra]

some of the equipment manufacturers say the wire should be twisted

What would be the point of twisted pair?

 

[Todd0x1]

What would be the point of twisted pair?

I could be way off here, but when the wire is carrying millivolt signals is it so both wires pick up any induced voltage evenly? Same as how phone wires are twisted?