I contacted the County of San Luis Obispo Building Department to inquire if this installation was approved. Indeed this installation had been inspected and approved. I asked how the County could justify the accessibility of these conductors. I was told that the area under any ground mount rack under 6 feet in height is considered not readily accessible. This is odd since children are most at risk for contact with energized conductors and they are quite often under 6 feet in height. Below is my communications with the County (Cell A), their official reply (Cell B) and my rebuttal (Cell C).

A. Communications from William Miller to County of San Luis Obispo Building Department:

Greetings. It has come to my attention that some County Inspectors are no longer requiring wire shielding on ground mount arrays.  One of my employees is taking a class with one of the County inspectors and overheard the inspector saying that wire shielding is no longer required.  I reviewed a project recently inspected in the Morro Bay area and observed no wire shielding.  A photograph from the back of that array is attached.

The requirement for wire shielding is still in the 2011 code under section 690.31(A).  A partial citation is below:

Where photovoltaic source and output circuits operating at maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be installed in a raceway.

The requirement is upgraded in the 2014 code.  Partial citation below:

Where PV source and output circuits operating at maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in a raceway.

Note the addition of the term “guarded” in the 2014 code.

I helped Jim Casper write a set of guidelines for PV permit packages.  That document is still on the County web site and it still requires applicants to conform to the shielding requirements.

The term raceway deserves some attention.  Solar panel manufacturers used to include J-boxes with standard conduit knock-outs that allowed the use of flexible conduit between modules.  Since about 2008 J-boxes with knockouts were discontinued.  It is no longer possible to use standard conduit raceway to guard conductors behind readily accessible PV arrays.  Instead we have been fabricating our own guards.  The 2014 code addresses and allows this.

My criteria for a suitable wire shield is below.  I am curious on your thoughts on these criteria:

1. The shield shall prevent small fingers from grasping the PV Conductors.
2. The shield must be electrically bonded to the racking.
3. The shield must be sturdy and last as long as the solar array.  20 years is a typical warranty period for PV.

We are currently using aluminum flat expanded sheeting to construct wire shields.  We bond the shields to a copper bonding conductor using dual rated split bolts or to the bonded rails using stainless star washers.  A photograph of our typical wire shield is attached to this e-mail.  I do not believe partial coverage or flimsy screen wire shielding is adequate.

______, as you know we strive to do excellent work.  One reason is we want all of our clients, their children and grandchildren and neighbor children to be safe.  A ground mount PV is essentially a jungle gym.  Kids swinging on PV wires carrying 600 volts can damage the insulation and expose fatal voltages.  If some installing contractors are allowed to not comply with code, this presents unfair competition to those doing good quality work.  And, more importantly, it exposes the public to danger.  It also seems to me that lax enforcement exposes the County to liability.

Could you please let me know what the County policy is in regards to wire shielding?   Are you comfortable that all inspectors are enforcing wire shielding in particular, and good practices in general?

Thank you for your attention to this.  If you have any questions please call or write

B. Communication from the County of San Luis Obispo with their official position on wire shielding of ground mount arrays:

As stated in my last e-mail, the County's stance is that if the wiring is properly managed additional guarding with fences, or screens are not required.  Our inspectors will get additional training in the following code language to insure safe code compliant installations. (Where PV source and output circuits operating at maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in a raceway.)

If the wiring is properly managed under a ground mounted array that is less than 6 feet tall no further protection is required.  Under the racking where someone would have to crawl is not readily accessible as we define it.  Proper attachment in and on the racking would be considered guarded.

All of the above is intended to "remove the likelihood of approach or contact."  Having to crawl and reach into a channel to have contact would meet the requirements.  The small sections that are visible under the array are fine.  If there are small children or animals on the property fencing or other means is expected.

C. Response to the County of San Luis Obispo Building Department: 

Dear ____:

I am troubled by your position on the subject.  I respectfully submit your logic may be incorrect here.  If I may:

1. Children are generally shorter than 6' and can and do access areas with overhead clearance of less than 6 feet.  The NEC definition of readily accessible from the 2011 code is below:

Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.

Ground mount arrays that one can walk up to and under without resorting to a ladder or removing obstacles are therefore by definition readily accessible.  The fact that an adult may have to crouch down does not make the wiring non-accessible.  As previously pointed out, children will not even be crouching.

2. Conductors "properly managed" are not nearly the same thing as conductors in a raceway.  As an example, one could not run even short lengths of unguarded conductors to an external AC unit or spa outside of a conduit even if they were “properly managed.”

3. Fencing:  It is my belief that the public is not protected if the choice to guard unguarded conductors with fencing is left as an option.  The codes says the conductors need to be guarded and one must assume this means entirely guarded, not partially guarded or guarded if the homeowner gets around to installing a fence.  Many homeowners may assume children will never visit but this can never be known for certain.  A party, gathering or social visit never foreseen could bring children onto the property.  As an analogy, if the code requires a swimming pool be fenced, it cannot be left to the homeowner to fence it eventually.  It must be fenced and fenced in a childproof manner before the permit is signed off.

4. Fatal Scenario:  PV wire is rugged, but PV racking has sharp edges.  Children climb and swing on trees, jungle gyms and anything else they can get their hands on.  A 60 pound child could grasp a PV wire easily by accident and bend it over a sharp edge.  The insulation on PV wire will likely be pierced if that happens.  If the damage occurs after dark, no GFCI or fusing will detect this fault.  The children come out the next day to play some more and they could be exposed to fatal voltages at fatal amperages.  This is why the code section 690.31(A) was included in the NEC.

5. Probabilities:  I know the chances of the above scenario happening are remote, but given the proliferation of solar the chances increase daily.  This is the exact reason the code is written as it is.  I define safety practices as the process of preventing some event that is unlikely to happen anyway.  Just because something is unlikely does not make it impossible. 

6. Professional ethics:  As I understand it, your responsibility is to enforce adopted codes to protect the public.  I am not sure that is happening with this particular interpretation.  It is my belief that it is my responsibility as well, and if I believe a given practice is dangerous, I can’t participate just to save or make a buck, even if you let me.

______, I am guessing this policy may not be decided by exchange of e-mail.  It might be worthwhile meeting to discuss this in person with a few key policy makers.  Would you be amenable to meeting either at your offices or on a job site appropriate to discuss this further?

Thank you again for your professionalism and accessibility.  I really enjoy my interactions with you and all of the others in your department and the healthy exchange of views on relevant subjects.

Sincerely,

William Miller

As of August 7, 2015 I have no indication that the County of San Luis Obispo has changed their position on the subject of wire shielding.

William Miller