Bosch Boiler: Lock or unlock the key pad
Lock or unlock the key pad on a Bosch boiler: The key pad lock blocks the high limit dial, the DHW thermostat and every button except ON/OFF, emissions test and reset. A lock symbol alternates with supply temperature when on.
Applies to: Greenstar ZBR/ZWB 21-42-3A wall-hung boilers and ZWB 28-42-3A combis
How to fix lock or unlock the key pad: step by step
- Keep pressing the key pad lock button until the lock symbol alternates with the supply temperature
- To unlock, keep pressing the same button until only the supply temperature shows
If the unit shows an error code, look it up: Bosch Boiler codes
Models
ZBR21-3AZBR28-3AZBR35-3AZBR42-3A
Source: Bosch Greenstar wall ZBR-ZWB 21-42-3A service 6721853955 (2025-11) (same content in combi service 6721853953), 8.14 Activating the key pad lock p.57. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.