Thermostat displays E5 and heating output is disabled

Safety: Turn off power at the breaker before removing the thermostat or changing wiring. Overheating components can be hot—allow them to cool.

Steps to troubleshoot E5 (overtemperature):

• 1. Check installation location: Ensure the thermostat is not installed above a baseboard heater, near a fireplace, or in direct sunlight. Relocate the thermostat if it is exposed to external heat sources.
• 2. Inspect ventilation: Make sure the thermostat's side and bottom vents are not blocked by paint, wallpaper, or furniture. Clear any obstructions and gently clean dust from vents with a soft brush.
• 3. Verify load size: Confirm that the connected heater load (in watts or amps) does not exceed the maximum rating of the Stelpro smart thermostat. Oversized loads cause internal overheating. If the load is too high, use a Stelpro relay or contactor controlled by the thermostat instead of direct switching.
• 4. Check wiring tightness: Loose line or load connections at the thermostat terminal block can create heat. With power OFF, tighten terminal screws firmly and inspect for discoloration or melted insulation.
• 5. Power cycle: After correcting any issues, turn the breaker back ON and monitor the thermostat. If E5 clears and does not return under normal operation, the issue may be resolved.
• 6. Inspect for internal damage (advanced): If E5 returns quickly, the internal triac or relay on the main board may be damaged. Look for burn marks or a burnt smell. In this case, the thermostat should be replaced.

Warning: Do not continue using a thermostat that repeatedly reports overtemperature; this can be a fire hazard. Replace the unit or consult a licensed electrician.