When you complete this chapter, you will be able to:
Describe various performance challenges related to PV system design,
installation, and maintenance.
Describe performance parameters monitored in PV systems.
Compare expected PV system output with actual output and discuss why
they may differ.
Describe typical PV component maintenance requirements.
Understand safety requirements for operating and maintaining PV systems.
Identify common types of PV system failures and causes.
Understand basic troubleshooting principles associated with the
installation and operation of PV systems.
Typical System Design Errors
The International Energy Agency conducted a study on the reliability of grid-
connected systems in 2002. The study looked at a number of grid-connected sys-
tems from Canada to Japan. The research focused on residential systems. The
agency’s findings pinpoint some typical problems related to PV system design.
Here is what they found:
Inverters tend to be the weakest component of the system. Improvements in
technology continue to make inverters more reliable.
Module output is often overrated. The real power of the module is below
the power indicated on the nameplate.
Shading of the array results in lower output. Soiling of the array also results
in performance issues.
Faulty connections on the DC side of the system cause electrical failures
Systems are often not analyzed thoroughly before installation. The Modern
Class II components allow a system designer to avoid string diodes and
string fuses. This results in simpler and more reliable systems.
Interestingly, many reports in the intervening years tend to indicate much of
196 REVIEW GUIDE FOR THE NABCEP ENTRY-LEVEL EXAM
Overall, PV system failures usually fall into the following categories:
Ignorance on the part of the installation personnel—This leads to a
lack of a long-term, systems-based approach to PV, as well as system myths
and assumptions getting in the way of proper PV maintenance.
Poor or mediocre system design—The designer is insufficiently trained or
does not have the skill or knowledge about the technology and its
application; wrong components are assembled into a system; product choice
is based on only on price, rather than appropriateness for the design and is
therefore poor; designers fail to pay attention to detail.
Installation—The installing team is not well trained or not skilled or
knowledgeable about the technology and its application; a good quality
assurance (QA) system is lacking, as is detail-oriented leadership; testing is
incomplete, and there’s a lack of attention to standards, procedures,
monitoring, and details.
Many installers feel that if the system powers up and provides some level of
power, it is a working system, when often the system is only partially working.
Equipment failure—Although the inverter is often faulted as the primary
cause of technical failure, if the right product is selected and properly
applied and monitored, especially during the first year, the inverter failure
rates drop dramatically. Additional causes of equipment failure include the
wrong choices of equipment, overloading or underloading inverters,
undersizing conductors, improper conductor and mechanical equipment
attachment method, poor torque and thoroughness, and purposeful or
accidental damage from vandalism or unathorized access to the equipment
Many failures are related to technology that continues to develop and
mature. Staying on top of those changes may be the difference between a suc-
cessful application and a system failure.
Shading is a design challenge that creates problems because the salesperson,
business owner, or designer wants to satisfy the client regardless of the client’s
The best way to work around shading issues and technology failure when
designing PV systems is to do your research and be honest and straightforward
with the customer. There is always pressure to close the sale, yet the impact of a
bad design that results in poor performance will damage your reputation.
Complete a careful and specific site inspection, as well as a component
inspection. Select and buy the right materials and components from a reputable
company and double check all electrical conductor connections. If your PV
CHAPTER 10 Performance Analysis, Maintenance, and Troubleshooting 197