the system needs. Quality materials minimize the chance of module or
Performance problems result from incorrect sizing of conductors and mis-
matching voltages among the strings. These issues are rampant in the industry.
Use of simulation programs and design tools aid in this area. They must be used
properly with the correct data input. Lightning protection may also help if an
electrical storm damages the system.
The key to maximizing PV performance is attention to detail. Careful plan-
ning, design, and installation results in higher performance of a system with min-
imal performance and maintenance issues over time.
Monitored Performance Parameters
A PV system should operate within specific safety parameters according to code
and regulations. This usually means that few factors are monitored and designed
to stay within these set parameters. Performance is not covered by the code and
requires skill and training along with the commitment to working beyond code
and to accurate monitoring. The following aspects of a system need to be
AC and DC voltages
Currents and power levels
Solar energy collected
Electrical energy produced and/or consumed
All of the above must stay within normal performance parameters so the
system runs safely and efficiently. To monitor the voltage, current, and power
levels follow the National Electrical Code practices below:
Always use open-circuit voltage as the rated voltage in a PV source circuit.
Make sure voltage is less than 600 volts.
Ensure that conductors and overcurrent devices carry at least at least 125
percent of the short-circuit current of the source circuit.
Have overcurrent protection for source circuits, inverters, and
Label operating voltage and current, open-circuit voltage, and short-circuit
current with a sign that is placed close to the system disconnect point.
Always provide all safety labeling. Use labels that will not degrade over the
life of the system. They will be very important as the system ages and
All systems should be grounded with a single ground point.
204 REVIEW GUIDE FOR THE NABCEP ENTRY-LEVEL EXAM