Cat 5 with PV Power Circuits

[augie47]

I'm asking for a local inspector and may be premature as I don't have all the facts but he inquired if it was a violation to mix Cat 5 cable with Power Cable in this scenario. This particular PV install has CTs on the service conductors in the service panel. The CTs have a Cat 5 cable that terminates in the inverter. Contractor routed the Cat 5 thru the conduit carrying power between the service panel to the inverter. My opinion is that it is a violation of Art 725 but there may be an exception {perhaps 725.136(I) but that does not seem to include Cat 5} or an allowance in Art 690. Comments & Code references, please.

 

[jaggedben]

If it isn't special cat5 with and appropriate voltage rating then it's just a violation of 300.3(C). But if the cat5 has an appropriate voltage rating then I think it's somewhat hard to say. I've poured over 725 trying to figure out how CT circuits would be classifed. I've concluded that it just doesn't really say, although I'm open to having something pointed out that I may have missed. However if the CTs are not marked as class 2 or 3 then they don't seem to be described in 725.121 and therefore seem to be Class 1 circuits or not 725 circuits.

If they are Class 1 circuits then there is 725.48(B)(1) and the conductors are arguably 'functionally related'. There's also 725.49(B) which might prohibit the cat5 they used (unless it's listed for Class 1), but would allow them to pull something else through the conduit to replace the cat5.

I don't think they are Class 2 but if they are there is also 725.136(D)(2)(b) but this only applies to enclosures the way I read it.

FWIW we route CT leads in the same conduit as the inverter output all the time. But the CT leads are marked 600V. If we extend the leads with different method then we usually don't pull that with power conductors.

 

[augie47]

Interesting point. I assumed Class 2 or 3 as the terminate in an RJ45 type connector.

 

[jaggedben]

Hmm...
I'm pretty sure the connector doesn’t determine the 725 class per the NEC, although UL standards may dictate something there. But also, I've never seen CT leads terminated in an RJ45. And now I think about it, cat5 is almost certainly too small for extending CT leads. So it sounds more like RS-485 between a meter unit and the inverter. In which case it's possibly Class 2 or 3, seems likely, but I've never seen chapter and verse on how RS-485 would be classifed either. There is one manufacturer that stated that 600V rated cat-6 was okay for RS-485 in the same raceway as 600V DC, and I installed several systems that way.

 

[wwhitney]

{perhaps 725.136(I) but that does not seem to include Cat 5}

FWIW, if it's Class 2 or Class 3, then 725.136(I)(2) allows for separation "by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing". Which makes it sounds like if there's room in the conduit, something like a 1/4" corrugated tubing would be a sufficient separator, assuming the Cat5 could be pulled through that (perhaps beforehand, when both the Cat5 and tubing are straight).

Cheers, Wayne

 

[ggunn]

Hmm...
I'm pretty sure the connector doesn’t determine the 725 class per the NEC, although UL standards may dictate something there. But also, I've never seen CT leads terminated in an RJ45. And now I think about it, cat5 is almost certainly too small for extending CT leads.

EM (energy management) companies use CAT5 cable to extend CT leads all the time.

 

[ggunn]

And now I think about it, cat5 is almost certainly too small for extending CT leads.

I am not an expert on CT tech, but the way I understand it there are two types of CT. One type produces current in the leads that passes through a calibrated resistance in the receiving hardware, while the other type has the calibrated resistor on board and connects to a high impedance input on the receiving hardware. In the first case the voltage drop in the connecting cable is a consideration while in the second case there is almost no current in the leads so it virtually isn't.

 

[augie47]

I am not an expert on CT tech, but the way I understand it there are two types of CT. One type produces current in the leads that passes through a calibrated resistance in the receiving hardware, while the other type has the calibrated resistor on board and connects to a high impedance input on the receiving hardware. In the first case the voltage drop in the connecting cable is a consideration while in the second case there is almost no current in the leads so it virtually isn't.

Seemingly the 2nd type since the leads go to a RS485 and there is no provision for shorting. If so, what classification ?.

 

[ggunn]

Seemingly the 2nd type since the leads go to a RS485 and there is no provision for shorting. If so, what classification ?.

I have no idea, but CAT5 would likely be OK to use.

 

[don_resqcapt19]

Seemingly the 2nd type since the leads go to a RS485 and there is no provision for shorting. If so, what classification ?.

No way of knowing without the manufacturer telling you, or at least telling you the output voltage and current.

These types of questions will go away under the 2023 code as a change in 725.136 will permit the Class 2 or 3 circuits to be installed with the power circuits as long as the insulation of the Class 2 or 3 cables or conductors have a rating at least equal to the voltage on the power circuit.

 

[wwhitney]

These types of questions will go away under the 2023 code as a change in 725.136 will permit the Class 2 or 3 circuits to be installed with the power circuits as long as the insulation of the Class 2 or 3 cables or conductors have a rating at least equal to the voltage on the power circuit.

I don't see anything like that in the 2023 Second Draft Report, is this a change a subsequent change?

Cheers, Wayne

 

[don_resqcapt19]

I don't see anything like that in the 2023 Second Draft Report, is this a change a subsequent change?

Cheers, Wayne

725.136(H)

 

[wwhitney]

725.136(H)

OK, that says:

(2023) 725.136(H) Where Protected.
Class 2 and Class 3 circuits shall be permitted to be installed together with the conductors of electric light, power, Class 1, non-power-limited fire alarm, and medium-power network-powered broadband communications circuits where they are installed using Class 1 wiring methods in accordance with 724.46 and where they are protected by an approved raceway.

So that means that within a raceway, you can run your Class 2 or Class 3 circuit along with the power conductors if you use a Class 1 wiring method for the Class 2 or Class 3 circuit. If the above remains in the Final Draft and once the 2023 NEC has been adopted.

Cheers, Wayne

PS I was confused at first as to whether the language 'where . . . and where . . ." was imposing both conditions, or saying either condition suffices. But the previous section (G) uses "where . . . or where . . .". So that's the terminology for saying either condition suffices, and (H) means that both conditions are required.

 

[don_resqcapt19]

OK, that says:



So that means that within a raceway, you can run your Class 2 or Class 3 circuit along with the power conductors if you use a Class 1 wiring method for the Class 2 or Class 3 circuit. If the above remains in the Final Draft and once the 2023 NEC has been adopted.

Cheers, Wayne

PS I was confused at first as to whether the language 'where . . . and where . . ." was imposing both conditions, or saying either condition suffices. But the previous section (G) uses "where . . . or where . . .". So that's the terminology for saying either condition suffices, and (H) means that both conditions are required.

There were no certified amending motions on this section, se very very unlikely that there will be any change when the 2023 is published.
Not sure why they specified Class 1 wiring methods because new Article 724 says Class 1 systems use Chapter 3 wiring methods.

 

[wwhitney]

There were no certified amending motions on this section, se very very unlikely that there will be any change when the 2023 is published.
Not sure why they specified Class 1 wiring methods because new Article 724 says Class 1 systems use Chapter 3 wiring methods.

Right, the Chapter 3 wiring methods requirements means that (2023) 725.136(H) doesn't apply to Cat 5 wiring, the topic of the OP.

But I guess it means you can run your Class 2 or Class 3 circuit in conduit with power conductors just by using THWN-2 for the Class 2/3 circuit in the conduit, rather than having to use a cable method like NM in the conduit to get that additional barrier the overall sheathing provides.

Cheers, Wayne

 

[don_resqcapt19]

Right, the Chapter 3 wiring methods requirements means that (2023) 725.136(H) doesn't apply to Cat 5 wiring, the topic of the OP.

But I guess it means you can run your Class 2 or Class 3 circuit in conduit with power conductors just by using THWN-2 for the Class 2/3 circuit in the conduit, rather than having to use a cable method like NM in the conduit to get that additional barrier the overall sheathing provides.

Cheers, Wayne

I thought there was CAT rated tray cable, but it is Type PLTC and not TC.