PV Installation Guide
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SECTION 3: SYSTEM INSTALLATION
3.1. General Recommendations
The following is a list of general recommendations to help the installer choose the right materials, equipment,
and installation methods that will help ensure that the system will provide many years of reliable service.
These recommendations can be used to evaluate pre-engineered system designs and compare system
features from one supplier to another.
3.1.1. Materials recommendations
• Materials used outdoors should be sunlight/UV resistant
• Urethane sealants should be used for all non-flashed roof penetrations.
• Materials should be designed to withstand the temperatures to which they are exposed.
• Dissimilar metals (such as steel and aluminum) should be isolated from one another using non-conductive
shims, washers, or other methods.
• Aluminum should not be placed in direct contact with concrete materials.
• Only high quality fasteners should be used (stainless steel is preferred).
• Structural members should be either:
o corrosion resistant aluminum, 6061 or 6063
o hot dip galvanized steel per ASTM A 123
o coated or painted steel (only in low corrosive environments such as deserts)
o stainless steel (particularly for corrosive marine environments)
3.1.2. Equipment recommendations and installation methods
• All electrical equipment should be listed for the voltage and current ratings necessary for the application.
• PV modules should be listed to UL 1703 and warranted for a minimum of 5 years (20-25 year warranties are
available).
• Inverters should be listed to UL 1741 and warranted for a minimum of 5 years (outside CA these may not be
available).
• All exposed cables or conduits should be sunlight resistant.
• All required overcurrent protection should be included in the system and should be accessible for
maintenance
• All electrical terminations should be fully tightened, secured, and strain relieved as appropriate.
• All mounting equipment should be installed according to manufacturers’ specifications
• All roof penetrations should be sealed with an acceptable sealing method that does not adversely impact
the roof warranty
• Integral roofing products should be properly rated (e.g., class A roofing materials)
• All cables, conduit, exposed conductors and electrical boxes should be secured and supported according to
code requirements.
• PV Array should be free of shade between 9:00 a.m. and 4:00 p.m. This requirement includes even small
obstructions such as vent pipes and
chimneys. A small amount of shade can have
a disproportionately high impact on system
performance
3.2. PV System Design And Installation
3.2.1. Preparation Phase
1. Contact the California Energy Commission 1-800-555-7794 (Renewable Energy Call Center) to
receive a copy of the guide for the Buydown program or download the guide from the Buydown
Website at www.energy.ca.gov/greengrid.
Figure 4 Simple PV System Diagram
PV Array
DC/AC
Inverter
Combiner
Box
Main
Service
Panel
Utility Utility
Switch
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2. Obtain past electric bills for the home if available and audit home to determine what can be done to
reduce electricity usage.
3. Determine the size of the PV system based on budget, energy cost reduction, and available
mounting area for the system. The PV system supplier typically provides the customer with sizing
and performance information. The method in section 2 of this document is intended to provide a
basis to identify those suppliers who are thorough in their sizing estimates.
4. Determine the physical size and dimensions of the PV array and its primary components. This is
critically important in determining where the PV array and ancillary equipment is to be mounted.
3.2.2. Design Phase
1. Examine location options for mounting the PV array (i.e. roof, patio cover, other structure).
2. Review available pre-engineered system packages that contain the desired options. Compare the
various product and system warranties available from each supplier.
3. Confirm that the PV equipment has the necessary listings required by building officials (e.g. UL
1703, UL 1741, and any applicable evaluation reports from National Evaluation Services (NES) or
International Conference of Building Officials (ICBO) Evaluation Services)
4. Select system options making sure the equipment meets the guidelines of local incentive programs.
For the California Buydown Program check that the PV modules and inverter are listed on the
Buydown Website at www.energy.ca.gov/greengrid
5. Contact local utility company (PG&E, SCE, or SDG&E) to obtain the required documents for
interconnection and net metering.
6. Review documents to ensure system meets local interconnection requirements
7. Purchase the equipment.
8. Send completed Buydown Reservation package to the California Energy Commission.
9. Lay out PV array on roof plan or other structure. If roof mounted, determine required location of PV
modules on roof and any potential roof penetrations due to plumbing or combustion appliance vents
that could affect array placement or shade the array. Some obstructions can be relocated to another
portion of the roof should the penetration dramatically impact the location of the array. Attempt to
provide for an aesthetically pleasing layout by attempting to follow the dimensional shape of the roof
section (example: if the roof is rectangular, try to maintain the same shape rectangle in the array
layout). If modules are to be grouped in panels of several modules for ease of wiring and mounting,
try to arrange the panels in symmetrical arrangements.
10. Calculate the impact of shading on the PV array layout with the assistance of a Solar Pathfinder
(http://www.solarpathfinder.com/). Consider other locations to mount the PV array if the
proposed location receives too much shade. Review the mounting options discussed in section two
of this guide for alternatives.
11. Measure the distance between the estimated locations of all system components and develop site
drawing and one-line diagram of PV system installation for the permit package. (See example
drawing).
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12. Assemble the permit package for the local authority having jurisdiction (AHJ). This package should
include the following:
a. Site drawing showing the location of the main system components--PV Array, conduit runs,
electrical boxes, inverter enclosure, critical load subpanel, utility disconnect, main service
panel, and utility service entrance. (see drawing EX-1 in Appendix)
b. One-line diagram showing all significant electrical system components. (see drawings EX-2
and EX-3 in Appendix)
c. Cut sheets for all significant electrical system components (PV modules, inverter, combiner,
dc-rated switches and fuses, etc…).
d. Copy of filled out utility contract.
e. Structural drawing if the system is incorporated into a separate structure.
f. Structural calculations as necessary
3.2.3. Installation Phase
1. Submit required permit materials to the AHJ and pay for permit to begin construction.
2. Receive equipment and prepare for installation. Examine all equipment to be sure that all equipment
was shipped and that none was damaged in shipping.
3. Review installation instructions for each component to become familiar with the installation process.
4. Estimate length of wire runs from PV modules to combiner and inverter.
5. Check ampacity of PV array circuits to determine the minimum wire size for current flow. Size wire
for the run based on maximum short circuit current for each circuit and the length of the wire run.
Example using drawing EX-1 in the appendix:
Check ampacity of PV array circuits:
a. Minimum wire ampacity for the wire run from modules to combiner is based on module
maximum series fuse rating printed on the listing label (i.e. 15-amps on 100-Watt module).
From Table A-1 in the appendix, use the column for 90C in an open rack, use at least #14
AWG USE-2 wire. This is the minimum wire size and may need to be enlarged to reduce
voltage drop.
b. Minimum wire ampacity for the wire run from combiner to inverter is based on the number of
module series strings times the maximum series fuse rating (5 series strings = 5 x 15 amps
= 75 amps). From Table A-1 in the appendix, use the column titled “Ampacity of 75C wet
rated conductors (45C)”, for a minimum of #3 AWG THWN wire in conduit. This is the
minimum wire size and may need to be enlarged due to voltage drop.
6. Size PV array wiring such that the maximum voltage drop at full power from the PV modules to the
inverter is 3% or less (6-amps for a 100-Watt module). If array combiner box is located remote from
the inverter, spread the voltage drop accordingly between the PV array-to-combiner wiring and the
combiner-to-inverter wiring (example from EX-1 in the appendix: with a 100-foot wire run from PV
modules to inverter (3% total) comprised of a 25-foot wire run from PV modules to combiner box and
a 75-foot wire run from combiner box to inverter—use a maximum of 1% for the 25-foot run and 2%
loss for the 75-foot section for a total of 3%)
a. wire run from modules to combiner is 25 feet. From the 48-Volt Table A-3 in the appendix,
1% voltage drop for 25 feet and 6 amps (to use table for 1% voltage drop, find D-Factor for
3% voltage drop for 6-amps at 25 feet (1.1), then multiply this value by 3 (3.3) to obtain
proper size of wire on Table A-1in the appendix), use #10 AWG wire.
b. wire run from combiner to inverter is 75 feet. From the 48-Volt Table A-3 in the appendix,
2% voltage drop for 75 feet and 30 amps (to use table for 2% voltage drop, find D-Factor for
3% voltage drop for 30 amps at 120 feet (16) then multiply this value by 1.5 (24) to obtain
proper size of wire on Table A-1in the appendix), use #2 AWG wire.
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