Inspecting PV Systems

Plan Reviewers and Inspectors. What Do You Need?

Photovoltaic (PV) power systems are becoming more numerous, larger and more complex. Inspectors and plan reviewers have limited time to deal with these new systems and still carry on the routine electrical system inspections that have been done for 100 years or more. I intend for this “Perspectives on PV” articles to provide you with information on the Code requirements for these systems and also give you information on how to make the plan reviews and inspections easier and faster.

What do you need to know about concerning PV systems? Give me a call or drop me an e-mail and let me know what you would like to see in these articles. There will be a time delay since I am writing this November-December 2011 IAEI News article in August. In a hurry for an answer? Try the e-mail and I’ll try to get a fast response.

On the Front Lines

Plan reviewers and inspectors bear a heavy responsibility for the safety of the public when it comes to electrical systems, including PV systems. While most residential and small commercial electrical systems have not changed much over the past few decades or so, PV systems now have transformerless inverters for ungrounded PV arrays, microinverters, AC PV modules, dc to dc converters in the PV array and dc PV arc fault circuit protection. Couple those new “toys” with the dc current-limited outputs from the PV modules and we have a very dynamic, constantly evolving situation.

I know that many jurisdictions do not have a plan review section or person and that many inspectors only have 15–30 minutes allocated to perform a residential inspection. We all know that there are both qualified and unqualified people doing electrical installations, including PV systems. And with the significant amounts of money flowing into green electrical systems, there are many people jumping on the bandwagon that should not even be near the parade.

In this Perspectives on PV, I will share with you a PV installer checklist that covers the more import Code requirements for PV systems. The checklist will show 2005, 2008 and 2011 requirements and the differences will be noted.

Since jurisdictions vary in the availability of a plan review department and the time available for the inspection differ, I will not attempt to separate the items that would be accomplished at the plan review stage and those that need to be done at the on-site inspection. And, yes, I have tried many times to read a conductor size and type on a hot sweaty day when the conductors are cut to minimum length inside a disconnect—it sometimes is just not possible.

The following checklist is available on the author’s web site (see below) and it is double spaced for better readability.

CHECKLIST FOR PHOTOVOLTAIC POWER SYSTEM INSTALLATIONS

1. PV ARRAYS

a. Mechanical Attachment

b. Grounding

c. Conductors

Note: Suggest temperature derating factors of 65°C in installations where the backs of the module receive cooling air (4″ or more from surface) and 75°C where no cooling air can get to the backs of the modules. Ambient temperatures in excess of 40°C may require different derating factors.

(2011 690.8 substantially updates ampacity calculations to parallel calculations in other sections of the NEC.)

2. OVERCURRENT PROTECTION

3. ELECTRICAL CONNECTIONS

4. CHARGE CONTROLLERS

5. DISCONNECTS

Note: Listed PV Centers by Xantrex, Outback, and others for 12, 24, and 48-volt systems contain charge controllers, disconnects, and overcurrent protection for entire dc system with possible exception of source circuit or module protective fuses.

6. INVERTERS (Stand-Alone Systems)

7. BATTERIES

  • Note: There are no listed battery boxes. Lockable heavy-duty plastic polyethylene toolboxes are usually acceptable

8. INVERTERS (Utility-Interactive Systems)

9. GROUNDING

10. CONDUCTORS (General)

  • Standard building-wire cables and wiring methods used? [300.1(A)]
  • Wet-rated conductors used in conduits in exposed locations? [100 Definition of Location, Wet]
  • Insulations other than black in color will not be as durable as black in the outdoor UV-rich environment.
  • DC color codes correct? They are the same as ac color codes—grounded conductors are white and equipment-grounding conductors are green, green/yellow, or bare. [200.6(A)] Ungrounded PV array conductors on ungrounded PV arrays will not be white in color.

For Additional Information

The US Department of Energy funding for providing inspectors and the PV Industry with telephone and e-mail support from the author was terminated on March 1, 2011. Answers to your questions may be delayed or not answered at all depending on future funding. Consultation services are available on a contracted basis. E-mail: jwiles@nmsu.edu Phone: 575-646-6105

See the web site below for a schedule of presentations on PV and the Code.

The Southwest Technology Development Institute web site maintains a PV Systems Inspector/Installer Checklist and all copies of the previous “Perspectives on PV” articles for easy downloading. A color copy of the latest version (1.91) of the 150-page, Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested Practices, written by the author, may be downloaded from this web site: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/Codes-Stds.html

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