Troubleshooting ER Error on Imagine Grand Design 3500RD RV Fireplace

An “ER” display cannot be diagnosed from the Imagine 3500RD coach model or a report of good ventilation alone. Identify the fireplace manufacturer, complete model and serial number, and photograph the exact display and controls before selecting a troubleshooting procedure. Switch the fireplace off and stop using it while a repeated fault is assessed; follow its manufacturer’s instructions for safe isolation.

There is no verified universal rear, top or side clearance for the unidentified fireplace in this question. Use the installation drawing and combustible-material and ventilation requirements for its exact model and mounting arrangement. The RV’s 50-amp service rating alone does not establish the fireplace’s required supply, branch-circuit suitability or the voltage at its outlet. Have a qualified technician compare the appliance nameplate and installation with the applicable manual. Do not use an overnight flame-only test or repeated resets as proof that a fault is resolved.

The historical purchase badge names a Covenant listing with mixed LFP48-CT and W914-48FT references, also retained in the catalog reference listing. Confirm the actual label and control type rather than treating that mixed label as a model match. The Covenant W914-FT instruction manual covers the physical-button FT models, including W914-48FT; its page 4 specifies a minimum ½-inch rear spacing for the covered installation. Apply that figure only after confirming the exact appliance and manual. It is not a CT-series or universal RV-fireplace clearance, and this manual does not establish the meaning of the reported “ER.”

Keep the thermostat, sensor and safety controls in their approved positions. Do not relocate or bypass them to alter the room-temperature reading. The FT manual prohibits modifying the heater and directs malfunctioning units to qualified service. Have the exact model, displayed code, clearances and supply assessed before further operation; the available evidence does not approve a thermostat move, replacement part or repair outcome.