This guide will address the following topics:

• Standards and Codes
• Installation Tips
• Basic safety rules

To install a photovoltaic system in your home you or your installer will likely need to obtain building and electrical permits from the local authorities and pass inspections when the work is done. Therefore, you have to make sure all work is done according to all applicable regulations.

In addition to this, all conductors and other components have to be properly sized. Using any product outside of its rating is a violation of NEC® Article 210.3, and could potentially open the installer to liability for misapplication of the product.

FACTS ABOUT CODE COMPLIANT INSTALLATION

There is a number of codes and standards that govern the installation of PV panels and equipment. Of course, you don't necessarily have to know and fully understand these standards, but you have to make sure your solar installer does.

Here are some of the main documents that may apply to your system in US.

• National Electrical Code® (NEC®) published by the National Fire Protection Association.
  Article 690 of the NEC covers specifically the PV system installations. A number of other articles such as 110 Chapter 2, 250 Chapter 3, 300, 310, 480, and 702 are covering general wiring methods, overcurrent protection, disconnect devices, grounding, and other issues.
• UL 1741: Standard for Safety for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources.
  Your Inverters and battery chargers (if any) should be listed to UL1741.
• UL 1703: Standard for Flat-plate Photovoltaic Modules and Panels.
  Your PV modules have to be listed to UL1703.
• UL Standard 467 Grounding and Bonding Equipment.
  This document covers grounding electrodes, bushings, clamps, etc.
• IEEE 929-2000 Recommended Practice for Utility Interface of Photovoltaic (PV) Systems.
  As the name implies, it is a not a mandatory document, but many utilities adapted its recommendations.

BASIC SOLAR INSTALLATION RULES AND FACTS

There is a number of ways to install a solar energy array at a home. Most often flat-plate panels are attached to the roof of a house by using brackets bolted into the roof joists. The modules are usually mounted parallel to the roof surface with standoffs that leave several inches of spacing for cooling and wiring. If you have a flat roof, you may want to install a separate structure to provide an optimal tilt angle. Alternatively the PV array can be mount as a shade structure, which may be a patio cover or deck shade trellis, or placed on the ground. In northern hemisphere for maximum collection of sunlight it has to face south.

All exposed materials including cables or conduits should be sunlight / UV resistant. The temperature rating of all parts should exceed the temperatures to which they may be exposed. Dissimilar metals (such as steel and aluminum) should be isolated from one another. The metals used for structural support must be corrosion resistant.

SAFETY

When solar modules are installed on rooftops, it obviously involves work in high places. This presents danger of personnel falling off of the roof. Such installations should always be done by qualified trained professionals. Needless to say, extreme precautions have to be taken to prevent accidents and injury. There should be a safety supervisor who assures strict compliance with all safety and security requirements.

If you plan to do a rooftop installation, first of all verify that your roof can handle additional weight of the modules. This is especially important for masonry roofs which may be near the limit of their weight-bearing capacity. The typical modules weight about 3-4 pounds per square foot.

An important thing to remember is the PV cells generate electricity whenever exposed to light. The voltage even from a single panel can be shock hazard or can cause a spark. Before connecting or disconnecting the panels cover them with an opaque material and wear insulating gloves.
It is important to properly size the conductors and protection devices. Particularly, transformerless systems with ungrounded DC busses should have proper electrical hazard warning labels per NEC® 690.35. For more details and sizing requiremenrts see our solar wiring guide.

REFERENCES AND ADDITIONAL INFORMATION:

A guide to photovoltaic system design and installation

The information and suggestions here are provided AS IS for reference purpose only and do not constitute a professional or a legal advice. This is not an installation manual and is not intended to substitute or replace official codes and standards (see a complete legal disclaimer linked at the bottom of this page).
NFPA 70®, National Electrical Code®, NEC® are registered trademarks of NFPA.