YOUR GUIDE TO COMPLIANT INSTALLATION OF SOLAR PANELS
This guide will address the following topics:
- Standards and Codes
- Installation Tips
- Basic safety rules
To put a grid-connected photovoltaic system in your house you or your contractor 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 everything 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 RELEVANT CODES AND REGULATIONS
There is a number of codes and standards that govern the installation of PV panels and inverters. Of course, you don't necessarily have to know and fully understand all these standards, but you have to make sure your contractor does.
Here are some of the main documents that may apply to your system in US.
- National Electrical Code® NEC® 2020.
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 INSTALLATION RULES
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.
Here are some general requirements to the components. 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.
When solar modules are installed on rooftops, it obviously involves work in high places. This presents danger of personnel falling off of the roof. Needless to say, such installations should always be done by qualified trained professionals. 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. A typical PV module weights 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. Transformerless systems with ungrounded DC busses should additionally have proper electrical hazard warning labels per NEC® 690.35. For more details and sizing requiremenrts see our solar wiring
REFERENCES AND ADDITIONAL INFORMATION:
A guide to photovoltaic system design and installation