Roy Allen is a technical sales engineer and trainer at ABB Solar Inverters.
Sarah Ozga is a product manager at ABB Solar Inverters.
Knowing common installation mistakes can save contractors time and money and ensure a better solar PV system. The following tips can help make your installations safe and efficient.
- Read the manual. To ensure the proper operation of solar inverters, electricians installing them must make sure the installation meets the requirements of the authority having jurisdiction and the manufacturer.
- Understand the local utility’s interconnection requirements. Hundreds of independent utilities operate in the U.S., and each has its own interconnection requirements. As the demand for PV systems increases, negative effects such as temporary over-voltage can be expected on the grid feeders. This can cause dangerous conditions and instability on the grid. Know what is expected from the utility and work to meet all the requirements set forth in the interconnection agreement prior to installation.
- Beware of “direct sunlight.” Every solar inverter manufacturer has warnings against the installation of inverters in “direct sunlight.” Most manuals do not define clearly what is meant by this term; however, it is generally interpreted to mean the inverter should only be mounted where direct sunlight on the inverter chassis/heatsink is minimized, such as on a north-facing wall or under a shade structure.
- Don’t confuse the GEC and EGC. Transformerless inverters do not require a grounding electrode conductor (GEC). A GEC is required only when a DC bonding jumper is present. Because transformerless inverters operate from floating arrays, neither side (positive or negative) of the array is bonded to ground, hence, no internal bonding jumpers exist.
Don’t confuse the GEC and equipment-grounding conductor (EGC)! An EGC is always required in a circuit with electrical contact to metal, in wet locations or operating over 150 V to ground. See sections 250.110 and 690.43 in the National Electrical Code for more information on EGCs in PV systems.
- Use care when modifying the chassis. When it is necessary to cut additional KOs or enlarge existing KOs in the inverter chassis, the installer must be very conscious of “chip control.” The inverter is full of electronics, and introducing metallic chips or shavings into the inverter circuitry can cause failure of the inverter and potentially dangerous conditions, such as shock or fire. Manufacturers may also void the warranty if the chassis is modified.
When extra KOs are needed, it is recommended a suitable conduit (KO) punch be used for any additional holes placed in the chassis. The ABB TRIO chassis is equipped with removable KO plates, which can be removed with screws, modified as required and reinstalled, eliminating the safety risk.
- Note the NEMA rating of the solar inverter. Some inverter chassis are rated NEMA 4, which are sealed to forced water sprays, like from a hose. Installers must always look at the connected raceway and ensure appropriate gaskets are used between box connectors and the inverter chassis. Further, ensure that the other end of the conduit is not oriented in such a way as to act as a water pipe during rain or wash operations, as any liquid entering the conduit will be routed to the inverter chassis. Most NEMA 4 chassis are not equipped with weep holes and water entering the chassis may build up, which can cause direct failure or other issues due to high humidity.
By Roy Allen and Sarah Ozga of ABB.
