Glossary
MC4
A common type of weatherproof, snap-together DC connector used on solar panel cables.
MC4 is a widely used style of connector for the DC cables that come out of solar panels. Each panel usually has a pair of leads (positive and negative) with male and female connectors that click together and lock. In a plug-in kit they typically join the panels to the microinverter.
For plug-in solar, the DC side of the kit is tightly defined. The product specification allows up to four panels, no more than two in series, and no more than 120 V DC open-circuit at the inverter. It also bans Y-connectors, the splitter leads that let you join extra panels in parallel (IPS §4.2.2, §6.2.2). Outdoor components must be rated at least IP55 (IPS §5.4).
In practice, connect the kit exactly as the manufacturer’s instructions describe. Don’t add panels or splitters to a kit. Plug-in solar entries on the ENA register cover the complete kit (ENA Connect Direct), so a modified setup is no longer the kit that was listed.