E08 error and thermostat reboots intermittently or freezes.

Safety first: Switch off power to the thermostat at the breaker before removing it from the wall.

• Step 1 – Hard reset: Remove the thermostat from its wall base or disconnect its power for at least 2 minutes. Restore power and observe if E08 reappears.
• Step 2 – Factory reset: From the settings menu, perform a factory reset (this will erase schedules and Wi‑Fi settings). Confirm and allow the thermostat to reboot fully.
• Step 3 – Firmware update: Connect the thermostat to Wi‑Fi or use the Atlantic app to check for a firmware update. Apply any available update, ensuring power and Wi‑Fi remain stable during the process.
• Step 4 – Check power supply: Measure the low‑voltage supply at the thermostat backplate (e.g. 24 V AC from the HVAC transformer). Voltage significantly below spec or fluctuating can cause memory errors; replace the transformer or correct wiring if needed.
• Step 5 – Replace thermostat: If E08 persists after factory reset and firmware update, the internal flash memory or microcontroller is likely defective. Replace the thermostat main module.