Safety first: Only qualified persons should work on live electrical circuits. Always isolate power before tightening connections.

Measure supply voltage: With a multimeter and appropriate safety precautions, measure the voltage at the Oso heater’s supply terminals. Compare to the rating plate (e.g., 230 V ±10%).
Inspect terminal block: With power off, remove the cover and check that all live, neutral, and earth connections are tight and free of discoloration or heat damage.
Check cable size: Ensure the supply cable size meets Oso’s installation requirements for the heater’s kW rating and run length. Undersized cables can cause excessive voltage drop.
Look for external issues: If the building has known voltage fluctuations, consult an electrician or utility provider. A voltage stabilizer may be required.
Internal power module: If supply is stable but E07 persists, the internal low‑voltage power supply on the control PCB may be faulty and the board should be replaced.

Persistent supply issues should be addressed by a licensed electrician.

Oso water heater intermittently shuts down with E07; may be associated with very high or low mains voltage.

Possible Causes