Why is my Vaillant atmoTEC plus not starting up?
- RRichard LeeNov 2, 2025
If your Vaillant Boiler isn't starting up, resulting in no hot water and cold heating, start by checking if the gas stopcocks (both on-site and on the product) are open. Also, ensure the cold-water isolation valve is open. Verify the power supply and fuse in your building. Make sure the boiler is switched on. Check that the heating flow and domestic hot water temperatures are not set too low. If the system pressure is insufficient (indicated by fault messages F.22, F.23, or F.24), you need to fill the heating installation. If the issue persists, there may be air in the heating installation, which needs to be purged by a professional. If the boiler shows fault message F.28, press and hold the Reset button for one second to attempt another ignition. If the fault persists after three attempts...









