Why does solar stop when one grid phase goes missing?

What you will see

• Some circuits lose power while others remain on.
• The inverter reports a phase, grid-voltage or grid-availability warning.
• Solar generation stops despite sunshine.
• The problem appears during a supply disturbance or after electrical work.

Why it happens

Three-phase inverters monitor the incoming grid. Solis describes shutdowns associated with abnormal phase conditions, including grid imbalance. The cause may be the incoming supply, but local connections and cabling can also produce a phase-related fault.

Loss of power in one section of a building is therefore a symptom to investigate, not proof of a utility-side phase failure. An installer must establish whether the problem is upstream of the property, within its distribution system or at the inverter connection.

For a hybrid installation, also distinguish grid-connected generation from backup operation. Backup availability depends on the system’s capability, configuration and available energy. A phase warning should not be taken as a guarantee that every affected circuit will transfer to backup.

Record what remained operational. For example, tell us whether the inverter’s designated backup circuits continued working while other circuits failed, or whether all solar-supported circuits stopped together.

Diagram

One phase down, inverter stops

Healthy supply

L1On

L2On

L3On

Three-phase inverterRunning

One phase missing

L1On

L2Missing

L3On

Three-phase inverterStops grid operation

1. 1Utility supply upstream of the property.
2. 2Building distribution within the property.
3. 3Inverter connection cabling and terminals.

What you can check yourself

• Note the time and the areas or labelled circuits that lost power.
• Photograph the inverter warning and any phase readings shown on its normal screen.
• Check an existing utility outage notice, if available.
• Record whether the event affected nearby properties, without treating that as a confirmed diagnosis.
• Describe recent electrical work and whether power returned without intervention.
• Switch off equipment that is attempting to run abnormally using its normal controls, if safe. Do not keep trying to start a machine while its supply remains uncertain.

What not to do

• Do not bridge a missing phase from another phase, alter the neutral, bypass a changeover arrangement or probe live terminals.
• Do not disable grid protection so the inverter continues operating through a supply fault.

When to call us

• Report persistent or recurring phase warnings promptly. The installer can help establish whether the next action belongs with the utility, the building electrician or inverter service. If there is arcing, smoke or scorching, stay clear and seek urgent assistance.

Phase problems in Faisalabad and Lahore

Phase faults can start on the FESCO or LESCO side, in the building or at the inverter. Our Faisalabad and Lahore teams help work out which, so the right party fixes it.

Send us

The inverter model, complete warning, displayed phase readings, affected-circuit list, event timing, and your city and area.