errors and their repair, callbacks, and the loss of performance they create—and to
do this at the lowest possible cost.
Getting Installation Right for Top System Performance
Every part of PV system installation matters to overall system performance. The
following sections explain some things you need to know to get top
performance.
AC/DC Installation
The installation of PV systems tied to public electricity grids is different from that
of those that are off-grid. Pay special attention to these differences. Common
practices with AC installations can cause faults with DC installations.
CHECKLIST NO. 1: GETTING STARTED
Note: Be sure to have personal protection equipment (hardhat, gloves, and eye protection)on
hand prior to PV system testing.
Ground the metal equipment (metal boxes, array frames, racks, etc.) properly.
Place all labels and safety signs where they need to be as specified in the design plans.
Open all disconnect switches (the main AC disconnect to the combiner fuse switches).
Tag each box with a warning sign to signify that work on the PV system is in progress.
Remove all combiner fuses and make certain that no voltage is present at the output of
the combiner box.
Inspect all plug and receptacle connectors between the arrays and panels.
Pull all the cables and cords on strain reliefs/cable clamps to confirm that they are correctly
installed.
Examine the mounting brackets for any misalignments between the bracket and panels.
Look for cracks in all arrays.
Check to see that all wiring is neat and well supported.
Look at the wires that run from PV arrays to the combiner box to ensure there is no voltage
on them.
Review the fuses to verify they have all been removed and that all switches are open.
Systematically reconnect the wires to the DC string combiner box terminals.
Make sure labeling is clearly visible.
CHAPTER 1 Introduction to Advanced Photovoltaic System Installation 11
When you’re doing a DC installation, ensure that the PV meter current is set
to DC, not AC, amps. Check all insulated conductors for nicks in the insulation;
over time these can create a short. Remember that an installation fault could
cause a permanent arc, damaging the entire PV system. Use circuit breakers and
fuses that have the proper rating and proven DC switching capacity. Don’t use AC
breakers or fuses.
Always ensure correct polarity and energy flow direction when connecting
circuit breakers and fuses or making any other connection. PV panels and arrays
are live. You need to consider them live when you handle, mount, or install them.
CHECKLIST NO. 2: SOURCE CIRCUIT STRINGS
C
omplete the following procedure for each source circuit string. (A source circuit string is
two or more modules connected in series.) Do it systematically, either east to west or north
to south. The best conditions are from March through October on cloud-free days
around noon.
Check to verify that all panels in a string have the manufacturer’s required open-circuit
voltage in the full sun.
Make sure that string connectors are permanently marked positive and negative.
Repeat this sequence for all source circuit strings.
Examine the DC disconnect switch again to make certain that it is open and its tag is still
intact.
Confirm each source circuit string’s polarity.
Refer to the manufacturer’s installation manual to make sure that open-circuit voltage is
within the appropriate range.
Number each string and note string position on site drawing.
Secure the DC string combiner box terminals. Reversing the polarity on one of the source
circuit string can start a fire that can destroy the combiner box and other equipment. The
equipment warranty may not cover damage caused by reverse polarity on an inverter.
Ensure that the main service panel is the only place where the AC neutral is grounded.
Verify that the main AC disconnect voltage is at 115–125V AC for 120 volts and 230–250V
for 240 volts.
Repeat Step 10 if there is more than one AC disconnect switch.
Check each switch starting with the main service entrance to the inverter AC disconnect
switch.
Close each switch afterward, except for the final switch before the inverter. The PV system
may have only one AC switch.
12 ADVANCED PHOTOVOLTAIC INSTALLATIONS
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