I'm looking at a design that calls for bare copper ground conducotrs to be used for grounding the various PV modules/structures in an array. I was wondering however if there was anything in the NEC that required these conductors to be bare, or if they could be THHN conducotrs with a jacket? I do not believe there is anything preventing the use of THHN cables other than it will be easier to terminate the bare copper condutors to the modules since you dont have to strip the cable to land it on grounding lugs.

For all the ground cables from the combiner boxes to the inverter, etc.. regular THHN cable is called for the ground? Is there anything in the NEC that dictates what type of cable bare conductor or otherwise is to be used for PV installations?

I'm looking at a design that calls for bare copper ground conducotrs to be used for grounding the various PV modules/structures in an array. I was wondering however if there was anything in the NEC that required these conductors to be bare, or if they could be THHN conducotrs with a jacket? I do not believe there is anything preventing the use of THHN cables other than it will be easier to terminate the bare copper condutors to the modules since you dont have to strip the cable to land it on grounding lugs.

For all the ground cables from the combiner boxes to the inverter, etc.. regular THHN cable is called for the ground? Is there anything in the NEC that dictates what type of cable bare conductor or otherwise is to be used for PV installations?

Are the grounding lugs for the modules listed for stranded wire?

I'm looking at a design that calls for bare copper ground conducotrs to be used for grounding the various PV modules/structures in an array. I was wondering however if there was anything in the NEC that required these conductors to be bare, or if they could be THHN conducotrs with a jacket? I do not believe there is anything preventing the use of THHN cables other than it will be easier to terminate the bare copper condutors to the modules since you dont have to strip the cable to land it on grounding lugs.

For all the ground cables from the combiner boxes to the inverter, etc.. regular THHN cable is called for the ground? Is there anything in the NEC that dictates what type of cable bare conductor or otherwise is to be used for PV installations?

The NEC allows insulated or bare EGCs.

However if the design calls for bare why would you use anything else?

The NEC allows insulated or bare EGCs.

However if the design calls for bare why would you use anything else?

I am the one behind the design and have the contractor asking if he can use either.

I specified bare because I thought it would be easier to terminte on module lugs.

I want to give contractor the option of using either, but want to make sure there are no code issues with using either.

So are you esentially saying that ground conductors weather they are ECG, GEC's, etc.. can be either bare or stranded (THHN)? If they want to use stranded for grounding the modules I do not see an issue with this, I just want to make sure this is not violating any code issues?

I am the one behind the design and have the contractor asking if he can use either.

I specified bare because I thought it would be easier to terminte on module lugs.

I want to give contractor the option of using either, but want to make sure there are no code issues with using either.

So are you esentially saying that ground conductors weather they are ECG, GEC's, etc.. can be either bare or stranded (THHN)? If they want to use stranded for grounding the modules I do not see an issue with this, I just want to make sure this is not violating any code issues?

I don't think you can use THHN where the wiring is outdoors and exposed, but either way I'll wager that the installer would prefer to use solid bare copper. Having to strip insulation at every lug would be a pain.

I don't think you can use THHN where the wiring is outdoors and exposed, but either way I'll wager that the installer would prefer to use solid bare copper. Having to strip insulation at every lug would be a pain.

This is what I would have thought, that the contractor would not want to strib the stranded cable at every lug but he is the one who is asking?

So are you saying that you cant use standed cable where not protected in a raceway such as conduit? I have seen many installation where a stranded ECG was run ouside of a raceway? Any NEC requirment?

One of the construction managers is saying that he doesn't think bare copper conductors can be run in conduit? Any truth to this in the NEC? The only thing I recall in the NEC related to this is that I believe a bare grounding electrode conductor (GEC) can't be run in conduit due to a choke effect? Does anyone know of any section prohibiting the use of bare copper in conduit? I wouldn't use stranded wire THHN wire for an exposed EGC on a PV array, because I wouldn't trust it to be as mechanically durable if the insulation decays in the sun and comes off. That said, I don't know where in the NEC it is clearly prohibited to use stranded wire.

If it is okay to use a bare solid conductor for an EGC, then it stands to reason that it is okay to use an insulated solid conductor (THHN or otherwise), because the insulation is superfluous to the purpose and it does not matter if it decays. Perhaps the contractor can find insulated wire at a cheaper price because there is more supply, and is willing to strip insulation because he thinks he will still save money. I would say that is his prerogative, as long as it solid wire.

I have both heard and know from experience that it is often a stupid idea to run larger solid conductors inside conduit, bare or otherwise. I would tell you not to run a bare #8 ground inside 3/4" conduit because your wire pull will turn a good day into a bad one. But it doesn't violate the NEC AFAIK.

So are you saying that you cant use stranded cable where not protected in a raceway such as conduit?

No, I am saying that I don't think THHN can be run outside of conduit outdoors whether it is stranded or solid. You could run USE-2 as an insulated EGC, I guess, but it would be very expensive and a real pain to work with. Bare copper is the industry standard for this application for a reason; it's easy to work with and cheaper than insulated wire of the same gauge. I don't see why they would want to use anything else. Has your contractor ever done solar before?

You can get bare stranded copper, you know, but I've never seen it used as a solar module EGC; you'd have to confirm that the lugs are listed for it. Also, your AHJ may have something to say about this.

No, I am saying that I don't think THHN can be run outside of conduit outdoors whether it is stranded or solid. You could run USE-2 as an insulated EGC, I guess, but it would be very expensive and a real pain to work with. Bare copper is the industry standard for this application for a reason; it's easy to work with and cheaper than insulated wire of the same gauge. I don't see why they would want to use anything else. Has your contractor ever done solar before?

You can get bare stranded copper, you know, but I've never seen it used as a solar module EGC; you'd have to confirm that the lugs are listed for it. Also, your AHJ may have something to say about this.

Just so I am correct on the terminology.

Bare copper conductors (lets say #6) are typically a solid conductor correct? But it sounds like you are also saying you can buy a bare copper stranded conductor for the same purpose as long as equipment is UL listed? Typically though bare copper is solid.

Insulated cable is stranded. Even though it is stranded it can still be used as an ECG and does not violate the NEC, it would just be more difficult to use.

So in summary:

1) For an EGC Bare solid or stranded can be used
2) For an EGC Insullated stranded can be used (has to be rated for outdoor exposure)
3) Either bare/stranded, insulated/non-insulated can be run inside conduit?

Is this correct

Just so I am correct on the terminology.

Bare copper conductors (lets say #6) are typically a solid conductor correct? But it sounds like you are also saying you can buy a bare copper stranded conductor for the same purpose as long as equipment is UL listed? Typically though bare copper is solid.

Insulated cable is stranded. Even though it is stranded it can still be used as an ECG and does not violate the NEC, it would just be more difficult to use.

So in summary:

1) For an EGC Bare solid or stranded can be used
2) For an EGC Insullated stranded can be used (has to be rated for outdoor exposure)
3) Either bare/stranded, insulated/non-insulated can be run inside conduit?

Is this correct

Yes, you can buy stranded bare copper. Whether it is suitable for EGC, as allowed by code and your AHJ, I do not know. And yes, typically bare copper is solid.

Insulated conductors may be solid (up to AWG #8) or stranded.

1) I do not know if stranded bare copper can be used as EGC.
2) Insulated conductors can be used for EGC in general. I do not know for sure that if insulated the insulation must be outdoor rated if used for module EGC, but my guess would be that it does.
3) I'm pretty sure that bare copper can be run in conduit, but usually we transition it to stranded and insulated wire for conduit runs.

The way we usually do this is to run the PV home run wiring in USE-2 and the EGC in solid bare copper from the array to a combiner/transition/junction box, where the output wires are all THHN/THWN-2 in conduit. Also, individual AHJ's are sometimes specific about what is and is not acceptable for PV array ECG conductors. Check with them.

I wouldn't use stranded wire THHN wire for an exposed EGC on a PV array, because I wouldn't trust it to be as mechanically durable if the insulation decays in the sun and comes off. That said, I don't know where in the NEC it is clearly prohibited to use stranded wire.

If it is okay to use a bare solid conductor for an EGC, then it stands to reason that it is okay to use an insulated solid conductor (THHN or otherwise), because the insulation is superfluous to the purpose and it does not matter if it decays. Perhaps the contractor can find insulated wire at a cheaper price because there is more supply, and is willing to strip insulation because he thinks he will still save money. I would say that is his prerogative, as long as it solid wire.

I have both heard and know from experience that it is often a stupid idea to run larger solid conductors inside conduit, bare or otherwise. I would tell you not to run a bare #8 ground inside 3/4" conduit because your wire pull will turn a good day into a bad one. But it doesn't violate the NEC AFAIK.

I don't have my book handy, but NEC prohibits solid wire larger than #10 from being pulled in a racceway. A single ground in a raceway may be an exception, not sure.

Solid vs. Stranded Ethernet Cable

Written by Don Schultz, trueCABLE Senior Technical Advisor, Fluke Networks Copper/Fiber CCTT, BICSI INST1, INSTC, INSTF Certified

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So, here you are with your brand-new shiny tools and Ethernet cable and want to start installing it. You made sure to purchase thousands of feet of ultra-high-quality stranded copper cable and have every intention of running it to 800 feet. What could go wrong? If you hear the train getting into a wreck outside your window, that is exactly what you will hear when you go through the pains of installing the wrong cable type and expecting it to work properly. 

Stranded copper Ethernet cable is used primarily for short patching applications.  Patching applications means from a wall mounted keystone jack to your end device (like a TV or computer) or from a patch panel to an Ethernet switch.  Stranded copper Ethernet is typically already terminated at both ends with 8P8C (aka RJ45) plugs and sold in pre-cut and pre-packaged lengths. 

If your intention is to permanently install your cable inside your structure, take back the bulk stranded copper stuff. You need solid copper conductors for structured cable.

What is the difference between solid vs. stranded ethernet cable? Doesn’t copper = copper? Yes and no. Yes, copper is good. CCA or Copper Clad Aluminum is bad, which this article explains: Check Your Specs, CCA is Different from Solid Copper.

Another significant difference between solid and stranded copper is how they are terminated in the field. Solid copper is best terminated with IDC style terminations such as keystone jacks, patch panels, and field termination plugs. 8P8C (aka RJ45) connectors are typically only used on factory pre-made stranded copper patch cords, but there are some exceptions. See Choosing the Right Termination - Keystone Jack vs RJ45 Connector vs Field Termination Plug.

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Using the correct type of copper conductor is key when installing Ethernet cable. It does not matter what Category type of cable for purposes of this discussion. Copper comes in solid or stranded, and both have pros and cons and specific uses.

How does each solid vs. stranded ethernet cable conductor type look inside an Ethernet cable?

Solid copper pros:

• Allows Ethernet data signals to travel further along a cable with less signal loss. Signal loss is called attenuation. Solid copper has much more surface area than stranded copper and gets a boost from the “skinning effect”.
• Provides a much better platform for use of Power over Ethernet (PoE) via the “skinning effect”, so heat dissipation capability will be far greater.
• Again, with credit given to the “skinning effect” solid copper can go the distance. Whether 24 AWG or 22 AWG, the permitted lengths are the same simply because the copper is solid.
• Solid copper conductors are ideal for outdoor installations. Outdoor installations will be limited in length according to ambient temperatures, and solid copper will provide the longest possible length due to better heat dissipation.
• Solid copper conductor Ethernet cable is usually available in a much greater variety to fit various needs such as in-wall or plenum (HVAC) space installations, and for outdoor scenarios. The outer jacket type matters a great deal, which is addressed here: Facts About Ethernet Cable Jacket Ratings.

Solid copper cons:

• The solid copper conductors are less flexible. This means solid copper Ethernet cable is designed for installation in spots where the cable is not going to be stressed by handling.
• Cable sold in bulk (spool or box) will require the installer to terminate both ends, whether to a keystone jack, patch panel, or RJ45 plug.

Stranded copper Ethernet cables have their place too. In a pinch they are great for connecting two pieces of equipment together temporarily. Stranded copper Ethernet cables, when sold as patch cables, will have RJ45 connector plugs on both ends.

Stranded copper pros:

• Flexibility. Stranded copper patch cables are the preferred and accepted way to connect a device inside a room to a keystone jack, for example. The cable might get handled frequently and the copper strands are able to withstand frequent bending.

Stranded copper cons:

• The stranded copper conductors have small air gaps between the individual copper strands, which causes signal degradation over distance. Those small air gaps don’t transmit signals very well or at all. Although there are on-going debates about this, I personally don’t recommend the use of stranded copper Ethernet cables longer than 75 feet. The official maximum per the standard depends on the gauge of the stranded copper. In the case of 28 AWG, the maximum length is 50 feet.
• Stranded copper conductors, again due to having individual copper strands, causes additional DC resistance for PoE applications especially over distance. Air is an insulator when it comes to electricity. In this scenario, it is especially important to not exceed my 75 foot recommendation for length.
• Often stranded copper Ethernet cable does not come in the cable jacket variety needed to address certain applications, such as outdoor runs or into the plenum space.

Here is an installation graphic that will help distill solid vs. stranded ethernet cables:

So, there you have it. Selecting the correct type of Ethernet cable has more to do with Category and jacket type. There is more to the decision, and when installing your Ethernet cable you want to weigh the pros and cons and use the right type! With that, I will say…

HAPPY NETWORKING!

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