Grid Tied System Components
PV module: Turns light into electricity. A group of solar cells in a sealed unit.
Grid-tied inverter: An inverter that reads the voltage of the grid and produces as much power and current as it can, regardless of loads. For example, a 5kW inverter can only put out 5kW. Grid-tied inverters are sold according to maximum output power. They also have dc and ac operating voltage ranges.
Microinverter: A small inverter that is mounted behind a PV module. AC module: A module with ac output listed for such use.
Loads: Any kind of device that consumes electricity.
Conductor sizes: From small (larger numbers) to larger (smaller numbers). 18AWG is a small wire, 0AWG is a large wire.
Grounded conductor: A conductor that is intentionally referenced to ground, but carries current. The colour of this is white. In AC wiring the grounded conductor is also called a neutral. Most PV systems installed in the past in the US are negatively grounded and the negative is white, while the ungrounded positive is usually black. The black wire on a negatively grounded PV system is positive and the white wire is negative. The black wire can also be red to avoid confusion. The rule is that the grounded conductor must be white or grey.
Grounding conductor (ECG): A conductor that is not meant to carry current and connects metal equipment together, so that there are no dangerous voltage differences. A grounding conductor is a green or bare wire.
Branch circuit: A circuit coming from a circuit breaker off of a load center. Inverters have dedicated branch circuits.
Transformer: A device used for changing one ac voltage to another ac voltage.
Transformerless inverter: Also called ungrounded inverter or non-isolated inverter. This inverter does not have a current-carrying conductor that is at the same voltage as ground. This is one of the most common inverters in the world.
PV source circuits (strings): PV modules connected together in series including the PV modules and the conductors. Voltage increases in series circuits and Current increases in parallel circuits.
String sizing: Determining the number of PV modules to be connected in series so that voltage is not too high when it is cold (causes overvoltage) and voltage is not too low on hot days (under voltage).
PV source circuit conductors: Connects the PV to the combiner box. If there is just one string, there is no need for a combiner (nothing to combine) and the PV source circuit conductors will connect the PV to the dc disconnect.
USE-2 wire: Common wiring method for PV source circuits where conductors are exposed to sunlight or not protected in conduit. Can be used exposed to free air.
Conduit: Pipe that is used for protecting wires.