Window contacts in a room can switch the HVAC system to frost protection mode through a KNX logic link.

When a window contact reports 'open', it is standard practice to drive the room controller's HVAC mode object (DPT 20.102) to Frost/Heat protection, or to force its setpoint down to the frost protection value. The link is usually implemented either directly by parametrising the room controller or through a simple logic block that translates the 1-bit window state into the matching mode telegram. This avoids heating against an open window and protects pipes during winter ventilation.

Always add a short delay (typically 1-2 minutes) before reverting to Comfort/Standby to avoid mode flapping when the window is briefly tilted.