Boiler displays E10, heating does not start, and the circulation pump may not run.

Safety first: Isolate electrical power. The pump and nearby pipes may be hot—allow to cool. Be prepared for some water spillage when opening pump vents or filters.

Step-by-step checks:

• 1. Listen and feel: With a call for heat and power on, listen for the pump. If silent, lightly touch the pump body. A humming sound without flow suggests a stuck rotor.
• 2. Vent the pump: Turn off power. On many pumps there is a central screw. Place a cloth underneath, loosen the screw slowly to release air and a small amount of water. Use a screwdriver to gently turn the pump shaft. Retighten the screw.
• 3. Clean system filter: If your Viadrus boiler has an integrated return filter or strainer, isolate the boiler, remove the filter cap, and clean the mesh of sludge and debris. Reassemble and check for leaks.
• 4. Check wiring: Ensure the pump connector is firmly attached and that there is no visible damage to the cable.
• 5. Reset and test: Restore power, reset the boiler, and check if E10 clears and radiators begin to warm.

When to stop: If the pump does not run at all or trips the fuse, it likely needs replacement. This should be done by a heating engineer.