System Installation
Installation Notes
Each portion of PV system installation has basic rules. These rules are important
to overall PV system performance. This chapter includes things you should know
about installation.
AC/DC Installation
There are differences between the installation of PV systems tied to public elec-
tricity grids and that of those that are off-grid. The grid is the electrical utility
connection network. You need to pay special attention to those differences.
The PV array current is direct current (DC), or current flowing in only one
direction. PV installations also require careful design and work with alternating
current (AC), or current that reverses direction constantly. Keep these key points
in mind when installing a PV system:
Avoid conductor insulation faults, because they could cause an arc,
damaging the entire PV system.
Use circuit breakers that are listed for DC switching capability.
Always ensure correct polarity and energy flow direction when connecting
circuit breakers.
Remember that PV arrays, electrically connected PV modules, are live when
in the sun.
Array Mounting
If the customer’s roof slope is not ideal, the correct mounting is very important.
PV system output performance diminishes when arrays are improperly mounted
and oriented. The correct mounting can orient and tilt the array in the proper
direction. For example, reverse-pitch mounting tilts arrays to the south on a
north-facing roof. Follow these guidelines for successful installation:
Always follow manufacturer’s instructions.
Install roof penetrations in dry weather.
Goals
When you complete this chapter, you will be able to:
Install PV system components.
Install PV arrays and interconnections.
Properly ground equipment.
176 ADVANCED PHOTOVOLTAIC INSTALLATIONS
Avoid warranty issues by not drilling additional holes in mounting or
panel frames.
Handle PV arrays with great care during installation.
Do not step on arrays or place objects on them.
Pay special attention to edges and corners.
Panel Interconnection
Connecting the PV modules together requires many details. Attention to detail
provides security, safety, and reliability in an effective installation, and requires
these steps:
As with any project, measure twice and cut once.
Make sure all the panels in your arrays are of the same model.
Make sure all arrays and panels have the same slope and orientation for a
common inverter.
Join arrays together with plug connectors that are UL and NEC approved.
Remember that PV arrays produce power only during the day.
Open the circuit if panels, strings, or arrays need to be disconnected
after installation.
After opening the circuit, disconnect the plug connectors carefully.
Laying Cables
Laying the cables that connect the PV modules to the BOS is very precise task.
Here are a few pointers on cable laying:
Attach module cables to the mounting support frames, never to the
roof covering.
Protect all conductors from the sun by placing them within conduit, and
securely attach the conduit above the roof surface.
Cables need to be located in shaded areas, away from rainwater runoff, and
secured with weather-resistant fastenings.
Place cables away from children, pets, and other hazards.
Use the right amount of cabling, allowing enough for expansion
and contraction.
Pay close attention to cable bend radius, and steer clear of sharp edges or
anything that could damage the insulation.
Label cables with the type of current and polarity.
Label strings for permanent identification when connected to the
combiner box.
Create and save an accurate string map identifying which strings are in
which location.
CHAPTER 8 Connecting the Sun to the Home and the Utility 177
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