Where does the P9 4 pin connection go to in the CCU?

Issue
Identification of the connection point and function of the P9 4‑pin plug on the CCU.

Product Line
GT250 — Discontinued
GT500MVX — Discontinued
GT500‑480 — Discontinued
GT100‑208 — Discontinued

Note: These models are legacy utility‑scale photovoltaic inverters. Hardware architecture remains unchanged for all units still in service.

Environment
3‑phase utility‑scale inverter troubleshooting

Cause
The P9 connector may appear unplugged or unclear in function during inspection or troubleshooting.

Resolution
The P9 4‑pin plug serves as the common (GND) connection for the CCU.
The conductor from the P9 connector routes directly to the GND bus bar TB2 located in the AC compartment.

This wiring is installed at the factory, typically secured with tie wraps as part of the inverter’s standard harness. If the P9 connector becomes unplugged, simply reconnecting it is sufficient—no additional adjustments or rewiring are required.