![]() The labels depicted below indicate that the PV installers used an existing exterior main panel. Labeling must be visible from the home’s exterior so that power company employees and firefighters can see it without having to enter the home. The labels in the photos above are for a grid-tie system whose main electrical panel is located inside the home. Grid-tie system for a home with an interior main panel Here’s how to tell the difference between grid-tie and off-grid systems. ![]() Grid-tie systems require specific disconnects and labeling that are different from those for off-grid systems. The most important difference is that grid-tie systems can energize utility power lines, potentially endangering power company employees working on them. Such systems have different inspection requirements from those that are entirely off-grid. Some systems use batteries and are also connected to the public utility power grid (called grid-tie systems). When the batteries are full, excess electricity produced by the panels may be diverted from the batteries to the home. Most homes have a backup generator that will automatically activate to charge the batteries when a sensor indicates that the charge has dropped to a specified level. This electricity charges a bank of batteries that power the home, as well as store power for use during the night and when the sun is not shining strongly enough to allow the panels to produce enough electricity to meet the home’s electrical demands. Instead, the home uses rectangular solar cells that are connected together to form PV modules, commonly called panels, that convert sunlight into electricity. Off-grid home (rear) with a pole-mounted array at leftĪn off-grid system describes a home’s electrical system that is not connected to the local power utility’s electrical grid. ![]() Some aspects of the upgrade failed to meet current safety standards for that reason, it is a good representation of some of the conditions that inspectors may encounter. The system was upgraded in 2006 using both old and new components. Most of these photos show an off-grid home built in 1984 that originally had a PV system installed. Such training should include the ability to recognize and identify obvious defects for and limitations of the unit, rather than determining whether it is in acceptable condition. Because different jurisdictions may have different installation and maintenance requirements, an inspector who wishes to incorporate PV array inspections (as part of a green inspection, etc.) should seek specific training that covers the typical models and systems that s/he may encounter in his/her service area. Safety is especially important, as an ancillary inspection of a PV system, or even encountering one in the course of a standard roof inspection, carries with it certain hazards, such as burns, electrical shock, and even electrocution, which can be fatal. Although InterNACHI’s Standards of Practice for both residential and commercial property inspections explicitly exclude PV arrays, recognizing their components and knowing how these systems work will help inspectors to be safe on the job. Home and commercial property inspectors should understand the fundamentals about off-grid photovoltaic (PV) systems as part of their ongoing professional education.
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