• Jan 16, 2026 user guide viessmann vitopend 100 pend 100 boiler if it stops working? To reset the Viessmann Vitopend 100, press the reset button located on the control panel. If the issue persists, turn off the boiler, wait for a few minutes, then turn it back on. Refer to the user guide for specific reset procedures related to BY Clement Denesik