The 'ER' error code on your RV fireplace typically indicates a safety fault caused by overheating, restricted airflow, or power issues. For RV installations like yours, it is recommended to maintain at least 2–3 inches of clearance behind the unit (4 inches preferred), 3–4 inches on top, a minimum of 1 inch on the sides, and ensure the front remains unobstructed to allow proper ventilation. Even if your RV has a 50 amp supply, the fireplace runs on 120V and draws about 12–13 amps, so minor voltage drops or loose connections can trigger the error. To diagnose, try plugging the unit into a different 120V outlet and running it in flame-only mode overnight; if the error disappears, the issue likely relates to heat or airflow. Regarding the thermostat, inaccurate temperature readings may occur if it is placed away from the heater or in an unrepresentative location inside the trailer. While moving the thermostat may help, consult the manufacturer or Lippert Tech Support for guidance on relocating it safely to ensure accurate temperature control. If problems persist after confirming proper clearance, ventilation, and power supply, contacting Lippert Technical Support is recommended for further assistance.