Thermostat shows E8 and the display may flicker or freeze

Safety: Turn off power at the breaker before removing the thermostat from the wall. Use a non-contact tester to confirm power is off.

Steps to troubleshoot E8 (memory error):

• 1. Power cycle: Turn the breaker OFF for 2–3 minutes, then ON. Observe whether E8 reappears after boot.
• 2. Factory reset: Using the thermostat's front panel controls, perform a factory reset (see Stelpro manual for the exact button sequence). This clears corrupted settings stored in memory.
• 3. Reconfigure settings: After reset, re-enter your schedules, setpoints, and Wi-Fi credentials. Monitor operation for several days.
• 4. Protect from surges: Install a whole-home surge protector or a dedicated surge device for the heating circuit to prevent future memory damage from line spikes.
• 5. Firmware reflash (if available): Some Stelpro models allow firmware reinstallation via the app. If offered, follow the instructions carefully and ensure power and Wi-Fi remain stable during the process.
• 6. Replace thermostat: If E8 persists after factory reset and firmware update, the EEPROM or flash memory on the main board is likely defective. Replace the thermostat.

Warning: Do not repeatedly power-cycle the unit rapidly; this can worsen memory corruption.