Sizing of a PV isolator switch has to do with the control of power in solar systems safely. It depends on the voltage and current levels in the system, which are usually different between residential, commercial, and industrial applications. These PV isolator switches come rated for a specific current and voltage level, usually in the range of 600 to 1,500 volts DC and 16 to 63 amps. For example, a residential solar system with low power requirements would most likely require a 16-amp switch, but for larger commercial arrays, it would call for a 40-amp or higher-rated switch to handle the resulting increased current.
The rating of the PV isolator switch is given in amperage and, at a minimum, must be rated for the maximum current output of the PV array. It’s critical that this rating be provided so the switch won’t overheat or fail when the circuit is disconnected under full load. If the maximum current of a system is 32 amps, for example, it’s common to choose a switch slightly above this rating-such as a 40-amp isolator-to consider any current spikes that may happen, especially when sunlight is at optimal conditions.
It is equally important to rate the voltage, since solar systems can generate high DC voltages. Rating an isolator switch based on the peak voltage of the system protects against possible hazards from overvoltage conditions. In photovoltaic systems, this could be produced by rapid changes in sunlight intensity. Industry standards, including IEC 60947-3, ensure isolator switches are rated to durability and safety parameters for high-voltage DC handling.
For outdoor installations, an IP65 rating or higher is recommended due to dust and moisture concerns, particularly in extreme weather conditions. The enclosures are expected to be robust enough for the switch operation to be safe for at least most of its useful life span, normally about 25 years. Top brands like Schneider Electric and Eaton can supply a wide range of isolator switches that can meet such specifications and ensure compatibility and safety across different PV systems.
The solar installer, Bill Murphy, says, “Choosing the right PV isolator switch is paramount. Too low a rating might give you overheating and even system failure.” Choosing the proper PV Isolator Switch to the specifications of the system, owners can have safe and effective operations without any risk to the system and/or safety hazards.