A Technical Note

[baphenatem]

In looking at a number of solar related posts here on iRV2 I have noticed that there is a consistent National Electrical Code and best practice wiring error that is being made both by the DIY and pro PV installers. Specifically, it is the use of fine-standed conductors with wiring devices, such as PV combiner terminal bars, breakers, fuse blocks, etc. There is a Code prohibition against this practice in both 690.31(H) and 110.14. Basically, the problem is that most setscrew lugs are not listed to work with fine-stranded conductors, only Class B or Class C stranding. Class B is what we typically use for building wiring, and Class C is a bit more finely stranded, similar to what you'd see in a commercially made battery cable for a car.

The net result of using fine-strand is that the connections tend to loosen up over time, unless the appropriate crimp-on lugs, ferrules, or adapters are installed. There are some breakers and terminals that are rated for use with fine-strand, but they generally have a clamping mechanism other than just a setscrew to make the connection. If the product is listed for use with fine-strand then it should be indicated in its installation instructions.

For further reference you can go to the UL Product Spec site and check out the technical requirements for product category code ZMVV.

[ralph0808]

In reference to the above post I wonder if the fine stranded wire was first soldered and then inserted into the set screw socket? I know the soldering technique would have to be top quality but it would make a better more rigid connection. Would it qualify to for the code?

[computerguy]

Hmmm. Interesting. I suppose we should be pulling permits and getting the work inspected too?
I am thinking your words are falling on deaf ears IMO. Heck, many people will not even install a required braking device for their toad never mid how many people are completely overweight for their vehicle.

[John Hilley]

I find that marine grade cable is best for mobile installations because of it's flexibility and quality of sheath. I use lugs or ferrules on ends, lugs where I can use stud and nut combiners and bus bars and ferrules where necessary in controllers and etc.

I find that marine rated components are a better fit for RVs than regular electrical supplies.

[baphenatem]

Originally Posted by ralph0808

In reference to the above post I wonder if the fine stranded wire was first soldered and then inserted into the set screw socket? I know the soldering technique would have to be top quality but it would make a better more rigid connection. Would it qualify to for the code?

Technically, at that point it is essentially a solid conductor and should not be an issue when combined with setscrew connections. However, you would not want to solder it and then use it with the DIN style clamping connections, or with crimped connections, as they have been know to burn up under such conditions. One big issue with soldering/tinning is that most folks do not have the requisite skills, tools, and materials to do it. Ferrules are an easier alternative, but again you have to have the proper tooling and ferrules. The other obvious choice is to simply use conductors with conventional Class B stranding.

[baphenatem]

Originally Posted by computerguy

Hmmm. Interesting. I suppose we should be pulling permits and getting the work inspected too?
I am thinking your words are falling on deaf ears IMO. Heck, many people will not even install a required braking device for their toad never mid how many people are completely overweight for their vehicle.

While the Code covers both RV's and PV installations, most state laws do not require permits and inspections for work done on RV's. I know that this is esoteric stuff to most folks, and you're right, it is probably falling on deaf ears. I just thought that I would mention it to possibly save some folks the aggravation of premature wiring failures.

[Mark-]

Originally Posted by baphenatem

I just thought that I would mention it to possibly save some folks the aggravation of premature wiring failures.

Thank you. I did find it interesting.

[C.Martin]

Originally Posted by baphenatem

While the Code covers both RV's and PV installations, most state laws do not require permits and inspections for work done on RV's. I know that this is esoteric stuff to most folks, and you're right, it is probably falling on deaf ears. I just thought that I would mention it to possibly save some folks the aggravation of premature wiring failures.

Please don't be persuaded that your comments are falling on deaf ears. I, for one, would prefer to know as much as I can. I realize too...depending on pre-wiring, cost constraints, component selection, etc...some form of necessity is driving our choices. How close we come to code, in practicality, is driven by those factors.

In my quest for knowledge---before starting on the installation we are doing on our coach---I had seen many examples of bare basic wiring, by the hundreds...which are working out well for people. It becomes easy to mimic these practices, unless someone throws out constructive remarks as to what may be a better, safer practice. We can evolve the knowledge base in a positive manner.

Solar is fantastic! It can add untold flexibility to the RV lifestyle when properly integrated. That said...the last thing any of us want to do is introduce RISK. I would hate for us to be out on a nice day. And come home to find our Coach and our Pets consumed by a fire caused by faulty wiring, that I chose --- knowingly, or unknowingly --- to put there.

Lastly, the information you share regarding code is also very important in another way. If, in the future...a friend looks at my solar installation and wants to install one like it. If there are code inconsistencies in my installation...I would want them to know so that they can improve upon it, or at least make a well informed decision on their own.

Thank you very much for your participation in the forum. I value it greatly.

[baphenatem]

Originally Posted by C.Martin

Please don't be persuaded that your comments are falling on deaf ears.

I had seen many examples of bare basic wiring, by the hundreds...which are working out well for people....

Solar is fantastic! It can add untold flexibility to the RV lifestyle when properly integrated. That said...the last thing any of us want to do is introduce RISK. I would hate for us to be out on a nice day. And come home to find our Coach and our Pets consumed by a fire caused by faulty wiring, that I chose --- knowingly, or unknowingly --- to put there.

Thank you very much for your participation in the forum. I value it greatly.

Thank you Charlie, it's nice to know that somebody is listening. I agree that there are a great number of systems that aren't code-compliant and aren't causing problems for folks. Fortunately, as somebody once observed, the worst case scenario in electrical installations rarely occurs. 12 Volt systems are pretty forgiving due to the low system voltages. Not that you can't burn something up, as is evidenced by those folks who use a couple of lead acid batteries to do field welding. The biggest flaw that I see in these systems is the lack of proper overcurrent protection at all segments within the system, and the lack of isolating and disconnecting means for service and safety shutdown. Unsupported, open PV source and output circuit conductors are also an issue.

I also agree that the Code requirements, which are not application specific, may a bit of overkill for certain RV installations. On that note, I do plan on submitting a couple of proposals to change the 2020 Code so that some of the things that are now required for regular buildings, (rapid shutdown, specifically) are not required for RV's. In the longer term, as RV systems evolve toward higher PV and battery DC voltages I think that some of the mandated safety requirements (AFCI's and GFP's for example) that are code-required are a good move. The last thing that any of us solar fans wants to read about or see on the news is some poor souls having perished in or losing their RV due to a malfunction in their PV system.

[jimbo2013]

I hear you, thanks 4 your input.

One other point that no one speaks about is labeling that there is secondary PV power.

perhaps you could elaborate on the proper labeling on an RV

[baphenatem]

Originally Posted by jimbo2013

I hear you, thanks 4 your input.

One other point that no one speaks about is labeling that there is secondary PV power.

perhaps you could elaborate on the proper labeling on an RV

Wouldn't you know, they've revised things a bit for the 2017 Code and I had to spend some time looking them up, but here is an approximate list. Keep in mind that the Code does not differentiate as to whether it is an RV based installation.

1. 690.13(B) requires each PV system disconnecting means be permanently marked "PV System Disconnect" and if the line and load terminals can remain simultaneously energized an additional label of: "WARNING - ELECTRIC SHOCK HAZARD - TERMINALS ON THE LINE AND LOAD SIDES MAY BE ENERGIZED IN THE OPEN POSITION"

This one is a bit of a toss-up as the threshold for electric shock is generally considered to be 50 Volts or more. Most RV PV systems do not reach that point, but some do and would require the marking.

2. 690.31(G)(3) requires exposed raceways, cable trays, and other wiring methods, covers or enclosures of junction boxes, and conduit bodies with unused openings to be marked. Wiring/raceways must be marked in each exposed segment between building partitions at least once and additionally each ten feet. The wording for the labels is: WARNING: PHOTOVOLTAIC POWER SOURCE

3.) 690.51 requires DC PV modules to be marked, but this is factory-supplied on listed modules anyway.

4) 690.53 requires a label at the PV power source disconnecting means. The label must include the maximum voltage, maximum circuit current, and maximum rated output of the charge controller.

5) If the system is interactive, i.e. can supply AC power in parallel with another AC power source, then by 690.54 it must be marked as to its operating voltage and rated output current.

6) If the PV system is connected to an energy storage system then the terminal polarities at the connection point must be indicated. 690.55

7) 690.56(A) requires facilities with a stand-alone power system to have a plaque or directory that indicates that it has a stand-alone system and must indicate the location of the disconnect for the system.

Other requirements:

690.31(B) requires all PV system circuit conductors to be identified at all accessible points. (This was originally my proposed change after having worked on a number of systems with no markings to indicate what wire went where.)

Under 690.15, if a non load break isolating device is used for the disconnection of PV equipment it must be marked "do not disconnect under load".

I'm not going to get into the rapid shutdown system marking as they haven't been implemented fully and you'd be hard pressed to ever find one on an RV...but stay tuned!

[woundedpig]

My Interstate Lithium Battery Adventures - Page 14 - Airstream Forums

77 Stranded vs Solid Wire in low voltage systems

[foretexas]

Noted and appreciated.

[harryn]

Thanks for the inputs and advice. I try to follow ABYC guidelines for RV applications, but that is not alway so easy either.