Module leads (USE-2) need to be in conduit

[BillK-AZ]

Definations

Definations

A series or parallel collection of photovoltaic (PV) cells, sealed in an assembly is a photovoltaic MODULE.

A set of PV modules, connected together, is a PV PANEL.

The collection of the PV panels in a PV SYSTEM is a PV ARRAY.

Breaks between or within CELLS are internal to a module.

Most of this discussion concerns connections between modules with the normal module interconnection cables.

A related conduit problem is how to deal with the micro inverters that have rather large AC connectors on the tails and/or on the factory assembled parallel connection cable. Any conduit that would pass the connector can not terminate to the thin and relatively small inverter, so a conduit solution is difficult.

 

[jaggedben]

Will PV panel reference suit you better?

It would suit me better. PV panels (aka modules) are made up of many cells, typically 60 or 72. But the voltage still depends on the particular make of panel.

 

[ggunn]

Will PV panel reference suit you better?

Actually, from context I assume you are referring to PV modules. See NEC Article 690.2 Definitions. I would not have brought it up, but if you are going to presume to educate me on PV systems design (which is how I make my living) and the ethics of debating, I believe that you should at least get your terminology correct.

My opinion on the subject is that if a fence is sufficient to keep the unwashed public from going into power substations and hurting themselves, it should be sufficient for ground mounted PV arrays. Installing conduit encasing every module lead would be prohibitively expensive and unnecessarily restrictive on construction methodologies. Nothing is 100% safe; if cars had to be totally safe they would be required to have Nerf bumpers, the speed limit would be 2 mph, and barricades would prevent pedestrians from crossing the street.

 

[weressl]

Your question was more like "what is a number plus a number?" "A number" is an acceptable answer, IMO.

The question was: "If you have several, say 4, cells connected in series and a wire is broken, can you tell me what the potential difference will be between the two ends? "

Substitue 'panel' or 'module' for cells, if you will, but from the OP and ensuing exchanges it is clear that the discussion was centered on the units that one would assemble in the field for a solar plant supply and not the individual cells that one may use for tinkering.

 

[ggunn]

The question was: "If you have several, say 4, cells connected in series and a wire is broken, can you tell me what the potential difference will be between the two ends? "

Substitue 'panel' or 'module' for cells, if you will, but from the OP and ensuing exchanges it is clear that the discussion was centered on the units that one would assemble in the field for a solar plant supply and not the individual cells that one may use for tinkering.

And the answer is, as Bill correctly answered, "it depends". PV "cells" as you call them, come in many voltages.

 

[jaggedben]

A related conduit problem is how to deal with the micro inverters that have rather large AC connectors on the tails and/or on the factory assembled parallel connection cable. Any conduit that would pass the connector can not terminate to the thin and relatively small inverter, so a conduit solution is difficult.

What code section would even require that? 690.31(A) specifically refers to PV source and output circuits.

 

[weressl]

Actually, from context I assume you are referring to PV modules. See NEC Article 690.2 Definitions. I would not have brought it up, but if you are going to presume to educate me on PV systems design (which is how I make my living) and the ethics of debating, I believe that you should at least get your terminology correct.

My opinion on the subject is that if a fence is sufficient to keep the unwashed public from going into power substations and hurting themselves, it should be sufficient for ground mounted PV arrays. Installing conduit encasing every module lead would be prohibitively expensive and unnecessarily restrictive on construction methodologies. Nothing is 100% safe; if cars had to be totally safe they would be required to have Nerf bumpers, the speed limit would be 2 mph, and barricades would prevent pedestrians from crossing the street.

I did not direct ANY comments toward you concerning the ethics of debate, however you may feel that it was applicable to you.

I agree that ground mounted PV arrays maybe justifiably enclosed in a fenced area, but for an entirely different reasoning you present. I would find the fencing necessary to protect the property.

I think that the PV leads installation method is a great departure from ANY OTHER permitted installation methods for other devices and items in the NEC. Now if we are going to go ahead and change our general, primary wiring method to cable/clamp from conduit/box, then fine. (I do not have a major heartache over the matter itself, it is the inconsistency that irks me.)

 

[ggunn]

Well, this has been fun, but I need to get back to work designing a couple of commercial PV systems with free air conductors all over the place.

 

[weressl]

Well, this has been fun, but I need to get back to work designing a couple of commercial PV systems with free air conductors all over the place.

So you consider this response an open and honest exchange?

 

[weressl]

It would suit me better. PV panels (aka modules) are made up of many cells, typically 60 or 72. But the voltage still depends on the particular make of panel.

So how many different voltages do you see? Aren't the majority we are talking about for this particular topic are around the same 30-40V range? If there would be a great variance then how would the inverter and other auxiliary equipment manufacturers be able to cope with the designing appropriate equipment for those?

 

[iwire]

About a month ago I walked out onto the roof of a school and saw this PV installation, I asked my host if the kids had done this, he said no a solar contractor had done it.

I hear 'ground mounted array' and these are the kind of installation methods that spring to my mind.

 

[ggunn]

So you consider this response an open and honest exchange?

Of course, although I wasn't responding to anything in particular. I'd love to hang out and argue about it or anything else you'd like to throw out there, but openly and honestly, I have to get back to work.

 

[weressl]

About a month ago I walked out onto the roof of a school and saw this PV installation, I asked my host if the kids had done this, he said no a solar contractor had done it.

I hear 'ground mounted array' and these are the kind of installation methods that spring to my mind.

Thanks for making the point. One wonders how many of the PV installers are qualified electricians.

 

[jaggedben]

About a month ago I walked out onto the roof of a school and saw this PV installation, I asked my host if the kids had done this, he said no a solar contractor had done it.

I hear 'ground mounted array' and these are the kind of installation methods that spring to my mind.

You call that a method? :happyno: I think 110.12 applies no matter the situation.

 

[jaggedben]

So how many different voltages do you see? Aren't the majority we are talking about for this particular topic are around the same 30-40V range?

Yes, the majority of modules are in roughly that range, I would say 35-40V for 60 cell modules and 40-45V for 72 cells modules, and 50V or so for high efficiency modules. So for 4 modules in series open circuit voltage would be roughly between 140 and 200V, at STC. (I can't remember ever doing less than 6 modules in series on a grid-tied system, but whatever.) All of this is very obvious and was never at issue in this thread.

Again, I ask you to simply say what your point is. Everybody who has contributed to this thread agrees that exposed series strings that are hundreds of volts and readily accessible is not allowed by the code.

If there would be a great variance then how would the inverter and other auxiliary equipment manufacturers be able to cope with the designing appropriate equipment for those?

Now you are showing your ignorance of the PV industry. Every major inverter manufacturer has come up with multiple models to handle varying module or system specs, and knowing how to match inverters to modules (or module strings) is arguably the most important qualification for any PV designer. Just ask ggunn.

 

[weressl]

Again, I ask you to simply say what your point is. Everybody who has contributed to this thread agrees that exposed series strings that are hundreds of volts and readily accessible is not allowed by the code.

Quite the opposite, and that's why I kept pressing the issue, see ggunns post about the microverters.

You are showing your ignorance of the PV industry. Every major inverter manufacturer has come up with multiple models to handle varying module or system specs, and knowing how to match inverters to modules (or module strings) is arguably the most important qualification for any PV designer. Just ask ggunn.

Never claimed to be an expert. We are all learning here, at least I hope so. Your retort is a red herring though, the acceptable range of the inverter DC inputs has a limited variance, that FOLLOWS the range of marketable products.

 

[Zee]

Regarding pics of sloppy system wiring:
THAT is why I use PV wire everywhere: rooftop, groundmount. Since it is available, why not?

Some do not appreciate that NEC allowance enough. But that , that is just taking that allowance and abusing it horrendously.
Thanks for pics!

 

[ggunn]

About a month ago I walked out onto the roof of a school and saw this PV installation, I asked my host if the kids had done this, he said no a solar contractor had done it.

I hear 'ground mounted array' and these are the kind of installation methods that spring to my mind.

Being a rooftop installation, the wiring being readily accessible isn't the issue in this case. The extremely sloppy workmanship, though, is obvious. Was this installation inspected and passed by the AHJ?

I downloaded the middle picture and tried to zoom in to see if I could read the labeling on the wire, but the image just pixillates. Regardless, John Wiles says that conductors with any color insulation other than black, even if it's USE-2 or PV wire (if different colors are available) should never be installed in a location where they would be exposed to direct sunlight.

 

[Zee]

I believe, PV Wire only comes in black.

Must be USE-2.

PV wire: They CANNOT make white. They do add a white stripe to the outside of black insulation, which rubs off easily, for grounded conductors, but still black ( and white).

I don't even want to assume they used THHN/ THWN-2....... :-(

 

[Zee]

On closer inspection............I notice the plastic, flimsy caution tape.
"That'll keep 'em outta here." I imagine the installer saying.
Problem solved. hahaha