Furnace displays E10 and will not operate; may be associated with circulation problems.

Safety: Turn off power and allow the system to cool before working on the hydraulic circuit.

• Check isolation valves: Ensure the flow and return valves under the furnace are fully open.
• Bleed pump: If the pump has a bleed screw, place a cloth underneath and carefully loosen the screw to release trapped air until water appears, then retighten.
• Check system pressure: Confirm that the pressure is within the recommended range. Low pressure can prevent circulation.
• Clean return filter: Some Chaffoteaux models have a mesh filter on the return pipe. Close the valves, remove the filter cap, clean the mesh under running water, and refit securely.
• Restart: Restore power and reset the furnace. If E10 persists and the pump does not run or is excessively noisy, the pump may need replacement by a professional.