TN-C earthing system

In a TN-C earthing system the power source is earthed, and one conductor, the PEN (protective earth and neutral), does the job of both neutral and protective earth. TN-C is often found in older distribution networks, while TN-C-S keeps a combined PEN in the supply and splits it into separate N and PE at the installation. Several smaller Solis S6-EH3P hybrid models are marked as not recommended for TN-C, and Solis advises against TN-C in general for residential hybrid inverter installations. If a TN-C connection cannot be avoided, keep the inverter's unbalanced output function disabled, because heavy load imbalance can put a touch voltage on the inverter enclosure. Where possible, convert the installation to TN-C-S before connecting the inverter, and have a qualified electrician do the work in line with local rules. With hybrid inverters on TN-C, the grid-side neutral is either connected at the PE-N split point or left off. In backup mode the inverter bonds N and PE inside its backup port, so do not earth the backup neutral externally.