Offline module

Definition

A panel that does not produce cannot convert the sunlight it absorbs into electricity, and that energy turns into heat. When a single panel is offline while the rest of the string works, the string current usually flows through that panel's bypass diodes. The panel remains in the circuit electrically but does not contribute to production.

Signs in the imagery

In the thermal image the whole panel is uniformly warmer than its neighbours, with no cell or band pattern. The junction box area may also be warm. In the RGB image the panel usually looks intact.

Possible causes

• A broken ribbon or cell interconnect inside the panel
• An internal connection broken in the junction box
• The panel cable short-circuited or wrongly connected
• A diode problem affecting all substrings

Effect on production and safety

All of the panel's output is lost and the string voltage drops. Because the diodes carry the string current continuously, the junction box heats up. If several panels in the same string go offline, the inverter's operating point can be affected too.

Recommended action

Raise a work order and check the junction box, connectors and cables in the field. If the panel's internal connection is broken, replace it and attach the measurement history to the warranty claim. At the flight after the repair, confirm that the panel is back at the same temperature as its neighbours.