KNX Central Functions & Central Commands: All OFF, Away Mode & Building-Wide Control

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KNX is designed to control individual rooms and devices, but professional building automation often requires commands that operate across multiple rooms, floors or zones.

Examples include All Lights OFF, All Blinds UP, Away Mode, Night Mode, Welcome Mode and building-wide shutdown functions. These are commonly referred to as central functions or central commands.

A central function is not simply a larger Group Address. It is a carefully designed communication structure that allows a single command to affect multiple devices while still preserving local control, feedback and safety requirements.

For KNX integrators, the challenge is to create central functions that are powerful enough to control the required areas without accidentally overriding functions that should remain independent.

Table of Contents

1. What Are KNX Central Functions?

A central function is a KNX command intended to affect multiple devices or zones simultaneously.

A normal room command might control one function:

Wall Switch
     │
     ▼
Living Room Light

A central command can affect many functions:

                  CENTRAL COMMAND
                        │
                        ▼
                 Group Address
                        │
          ┌─────────────┼─────────────┐
          ▼             ▼             ▼
       Floor 1       Floor 2       Floor 3
          │             │             │
       Lighting      Lighting      Lighting
       Blinds        Blinds        Blinds

The central command may be generated by:

  • A dedicated central button
  • A touch panel
  • Visualization
  • Logic controller
  • Time schedule
  • Alarm system
  • Presence system
  • Security system
  • Building management system

Typical central functions

Central FunctionTypical purpose
All Lights OFFSwitch selected lighting circuits OFF
All Blinds UPOpen blinds throughout a building
All Blinds DOWNClose blinds
Away ModePlace building into unoccupied state
Night ModeActivate night-time settings
Welcome ModePrepare selected areas when occupants arrive
Cleaning ModeProvide predefined cleaning state
Shutdown ModeReduce or switch off selected systems

Central does not always mean “everything”

This is an important design principle.

All Lights OFF does not necessarily mean every lighting circuit in the building should turn OFF.

Emergency lighting, security lighting, plant-room lighting or other critical circuits may need to remain operational.

Therefore:

A central function should have a clearly defined scope.

2. KNX Central Group Addresses

Central functions are normally implemented using dedicated Group Addresses.

Consider a villa:

0 Lighting
   ├── Local Lighting
   └── Central Lighting

1 Blinds
   ├── Local Blinds
   └── Central Blinds

2 HVAC
   └── Central Modes

3 Scenes
   └── Scene Control

4 Central
   ├── All Lights OFF
   ├── All Blinds UP
   ├── Away Mode
   └── Night Mode

A central command might therefore be:

4/1/1
ALL_LIGHTS_OFF

A number of lighting actuators can listen to that Group Address.

                    4/1/1
               ALL_LIGHTS_OFF
                      │
       ┌──────────────┼──────────────┐
       ▼              ▼              ▼
   Living Light    Kitchen Light   Bedroom Light
       │              │              │
       ▼              ▼              ▼
      OFF            OFF            OFF

Command and status should remain separate

A central command should normally not be treated as the status of every affected device.

For example:

Central Command:
4/1/1 = ALL_LIGHTS_OFF

does not necessarily mean:

Every lighting circuit = OFF

The actual states should still be available through the appropriate status objects.

CENTRAL COMMAND
      │
      ▼
 All Lights OFF
      │
      ├──► Light A
      │      └── Status OFF
      │
      ├──► Light B
      │      └── Status OFF
      │
      └──► Light C
             └── Status OFF

This distinction becomes important for visualization and diagnostics.

Central Group Address naming

Use explicit names:

ALL_LIGHTS_OFF
ALL_BLINDS_UP
ALL_BLINDS_DOWN
AWAY_MODE
NIGHT_MODE
WELCOME_MODE

For larger projects, include the scope:

BLDG_A_ALL_LIGHTS_OFF
BLDG_A_F01_ALL_LIGHTS_OFF
BLDG_A_ALL_BLINDS_UP

The naming convention should be consistent with the project’s overall Group Address standard.

3. All Lights OFF and Central Lighting Control

All Lights OFF is one of the most common central KNX functions.

A typical residential implementation might have:

                         ALL LIGHTS OFF
                               │
                               ▼
                         Central GA
                               │
        ┌──────────────┬───────┴───────┬──────────────┐
        ▼              ▼               ▼              ▼
      Ground         First           Second         Outdoor
      Floor          Floor           Floor          Lighting
        │              │               │              │
       OFF            OFF             OFF            OFF

Local vs central control

A professional system should support both:

Local control

Room Button → Room Light

and:

Central control

Central Button → Multiple Lights

These are different control paths to the same physical outputs.

Example: residential villa

Local:
Living Button → Living Light

Local:
Kitchen Button → Kitchen Light

Central:
Exit Button → All Selected Lights OFF

The exit button may be located near the main door.

All OFF should have a defined scope

Consider:

ALL LIGHTS OFF

Which circuits are included?

  • Living room?
  • Bedrooms?
  • Kitchen?
  • Exterior?
  • Garden?
  • Security lighting?
  • Staircase?
  • Emergency lighting?

Create an explicit central-function schedule.

CircuitAll OFF?
Living RoomYes
KitchenYes
BedroomsYes
GardenYes
Security LightingNo
Emergency LightingNo
Plant RoomNo

This prevents the phrase “All OFF” from becoming ambiguous.

Commercial projects

In an office building, central lighting control may be organised by floor or zone:

FLOOR 01 ALL OFF
FLOOR 02 ALL OFF
FLOOR 03 ALL OFF

A building-wide command can then be created separately:

BUILDING ALL OFF

This hierarchy provides more control than simply putting every lighting channel onto one central Group Address.

Central OFF and automation

Central OFF can be triggered by:

  • Time schedule
  • Security system
  • Occupancy system
  • Facility management
  • Manual button
  • Building shutdown logic

However, automatic central commands should be carefully evaluated so they do not interfere with essential functions.

4. Central Blind and Shading Control

Central control is particularly useful for blinds, curtains and shading systems.

Typical functions include:

  • All blinds UP
  • All blinds DOWN
  • Floor blinds UP
  • Weather protection
  • Sun protection
  • Night position
  • Security position

Example

                    CENTRAL BLIND UP
                           │
                           ▼
                    Central Group Address
                           │
            ┌──────────────┼──────────────┐
            ▼              ▼              ▼
         Floor 1        Floor 2        Floor 3
            │              │              │
          UP             UP             UP

Weather protection

A weather station can trigger a central shading function.

For example:

Wind Speed High
       │
       ▼
Weather Logic
       │
       ▼
Blinds → Safe Position

This is different from a user pressing:

ALL BLINDS DOWN

because the weather function may have priority or special operating rules.

Avoid treating all central blind commands equally

A professional system may have:

USER COMMAND
     │
     ▼
Normal Blind Control

WEATHER COMMAND
     │
     ▼
Protection Function

SECURITY COMMAND
     │
     ▼
Security Position

The system should define what happens if two commands conflict.

Manual override

Consider this situation:

Weather System → Blinds DOWN
User → Blinds UP

Which command should win?

The answer depends on the application.

The integrator should define:

  • Priority
  • Locking
  • Manual override
  • Timeout
  • Reset behaviour
  • Status indication

rather than allowing competing commands to operate unpredictably.

5. Away, Night, Welcome and Building Modes

Central functions become more powerful when they represent building operating modes rather than individual device commands.

Away Mode

An Away Mode might trigger:

AWAY MODE
   │
   ├── Selected Lights → OFF
   ├── Blinds → Defined Position
   ├── HVAC → Energy Saving
   ├── Water Heating → Reduced
   ├── Presence Simulation → ON
   └── AV → OFF

The exact functions depend on the project.

Night Mode

A residential Night Mode might be:

NIGHT MODE
   │
   ├── Selected Lights → OFF
   ├── Exterior Lights → Security Level
   ├── Blinds → Night Position
   ├── HVAC → Night Setback
   └── Entrance → Night Lighting

Welcome Mode

Welcome Mode can be used when occupants return:

WELCOME MODE
     │
     ├── Entrance Light → ON
     ├── Hallway Light → 50%
     ├── Selected Blinds → Open
     └── HVAC → Comfort

Occupied / Unoccupied

Commercial buildings often benefit from explicit operating modes:

OCCUPIED
    │
    ├── Lighting → Normal
    ├── HVAC → Comfort
    └── Shading → Automatic

UNOCCUPIED
    │
    ├── Lighting → OFF
    ├── HVAC → Setback
    └── Shading → Defined Position

Modes vs scenes

A mode can influence how the building behaves over time.

A scene generally represents a specific predefined state.

For example:

Presentation Scene

Temporary room state

while:

Unoccupied Mode

Building operating condition

This distinction becomes useful when designing larger automation systems.

6. Central Functions vs KNX Scenes

Central functions and scenes can appear similar because both can affect multiple devices.

They should nevertheless be treated as different concepts.

Central command

A central command generally tells multiple devices to perform a common action.

Example:

ALL_LIGHTS_OFF

Every participating lighting object receives an OFF command.

Scene

A scene represents a coordinated state.

Example:

PRESENTATION SCENE

Ceiling = 20%
Perimeter = 10%
Blinds = 80%
Curtains = Closed

Comparison

FeatureCentral CommandScene
Primary purposeCommon commandCoordinated state
ExampleAll Lights OFFPresentation
Typical valueSame actionDifferent values
Scene memoryUsually not requiredOften used
Multiple device statesPossibleCore purpose
Example commandOFFScene 3

Combining them

They can also work together.

For example:

AWAY MODE
   │
   ├── Central Lights OFF
   ├── Central Blinds DOWN
   ├── HVAC Setback
   └── Security Mode

A mode can therefore invoke several central functions and/or scenes.

Design principle

Do not create a scene simply because multiple devices need the same OFF command.

If the requirement is:

“Turn these selected lights OFF”

a central command may be clearer.

If the requirement is:

“Put this room into a coordinated presentation state”

a scene may be more appropriate.

7. Central Commands with Logic and Automation

Central functions become especially powerful when generated by automation logic.

The command source does not have to be a physical push button.

Time-based central command

Example:

22:30
  │
  ▼
Time Schedule
  │
  ▼
Night Mode
  │
  ├── Selected Lights OFF
  ├── Blinds DOWN
  └── HVAC Setback

Presence-based control

A building can change between occupied and unoccupied modes:

Presence Detection
       │
       ▼
Logic
       │
       ├── Occupied
       │
       └── Unoccupied

Alarm-triggered functions

A fire or security system can also interact with KNX.

For example:

Alarm Condition
      │
      ▼
KNX Logic
      │
      ├── Lighting → Required State
      ├── Blinds → Defined State
      └── HVAC → Defined Mode

The actual behaviour must follow the applicable life-safety design and should not be improvised as part of normal automation programming.

Energy-saving mode

A commercial building could implement:

Building Unoccupied
        │
        ▼
Energy Saving Logic
        │
 ┌──────┼────────┐
 ▼      ▼        ▼
Lights HVAC    Shading
 OFF   Setback  Defined

Logic should not create uncontrolled commands

If multiple logic functions can write to the same central Group Address, the source of each command should be documented.

For example:

GA 4/1/10
ALL_LIGHTS_OFF

Possible writers:
✓ Exit Button
✓ Schedule
✓ Away Mode
✓ Security Logic
✗ Unknown Logic

During troubleshooting, knowing who can write to a central Group Address is extremely valuable.

8. Common Central Function Problems and Troubleshooting

Central functions can affect many devices at once, so a small configuration error can have a large visible impact.

Problem 1: Central command does nothing

Check:

Central Button
      │
      ▼
Central GA
      │
      ▼
Receiving Objects

Verify:

  • Group Address
  • DPT
  • Communication flags
  • Receiving objects
  • Device parameters
  • ETS programming

Then use the Group Monitor.

Problem 2: Some devices respond, others don’t

Example:

ALL LIGHTS OFF

Living       ✓
Kitchen      ✓
Bedroom 1   ✗
Bedroom 2   ✗

Do not immediately assume the central Group Address is wrong.

Check the individual receiving objects.

Central GA
    │
    ├── Living Object ✓
    ├── Kitchen Object ✓
    ├── Bedroom 1 Object ✗
    └── Bedroom 2 Object ✗

Problem 3: Central command affects the wrong area

This is usually a Group Address architecture problem.

Check which Group Objects are linked to the central address.

For example:

ALL_LIGHTS_OFF
      │
      ├── Correct
      │
      ├── Correct
      │
      └── Accidentally linked
              │
              ▼
          Server Room

This is why central Group Addresses require careful documentation.

Problem 4: Local control stops working

A poorly designed central function can interfere with local operation.

For example:

Central OFF
     │
     ▼
Light OFF

User presses local ON
     │
     ▼
Light ON

If another automation repeatedly sends central OFF, the user may appear unable to control the light.

Use Group Monitor to identify competing telegram sources.

Problem 5: Central command and status don’t match

Remember:

Central Command ≠ Actual Status

For example:

ALL_LIGHTS_OFF = ON

means:

The central OFF command was activated.

It does not necessarily mean:

Every light is currently OFF.

Actual state should be obtained from the relevant status Group Addresses.

Problem 6: Multiple systems control the same central address

For example:

Exit Button ──────┐
Schedule ─────────┤
Logic Controller ─┼──► ALL_OFF
Security System ──┤
Visualization ────┘

This may be perfectly valid, but the project documentation should identify all possible command sources.

Practical troubleshooting workflow

1. Identify Central Function
          ↓
2. Identify Group Address
          ↓
3. Check Group Monitor
          ↓
4. Identify telegram source
          ↓
5. Identify receiving objects
          ↓
6. Check object flags
          ↓
7. Check device parameters
          ↓
8. Verify actual status

This approach is much faster than randomly reprogramming devices.

9. KNX Central Function Design and Commissioning Checklist

Central architecture

  • Central functions identified.
  • Scope of each function defined.
  • Central Group Addresses allocated.
  • Command and status separated.
  • Local control preserved.
  • Critical functions excluded where necessary.

Lighting

  • All Lights OFF defined.
  • Floor-level OFF defined where required.
  • Zone-level OFF defined where required.
  • Security/emergency circuits reviewed.
  • Status feedback tested.

Blinds

  • All UP defined.
  • All DOWN defined.
  • Weather protection defined.
  • Manual override defined.
  • Priority behaviour documented.

Modes

  • Away Mode defined.
  • Night Mode defined.
  • Welcome Mode defined.
  • Occupied/Unoccupied modes defined where required.
  • Energy-saving behaviour documented.

Logic

  • Automatic command sources identified.
  • Time schedules checked.
  • Presence logic checked.
  • Security/alarm interfaces checked.
  • Competing command sources identified.

Commissioning

  • Central telegram verified.
  • Every receiving zone tested.
  • Local operation tested afterward.
  • Status feedback verified.
  • Competing commands tested.
  • Restart behaviour checked.
  • Final Group Address list documented.

Practical Villa Example

Consider a three-floor villa.

Central Group Address structure

4 Central Functions

4/0/1   GF All Lights OFF
4/0/2   FF All Lights OFF
4/0/3   SF All Lights OFF

4/1/1   All Blinds UP
4/1/2   All Blinds DOWN

4/2/1   Away Mode
4/2/2   Night Mode
4/2/3   Welcome Mode

Exit sequence

When the owner presses the Exit button:

EXIT
 │
 └──► AWAY MODE
          │
          ├── Selected Lights OFF
          ├── Blinds → Security Position
          ├── HVAC → Setback
          └── AV → OFF

Return sequence

When the owner activates Welcome Mode:

WELCOME
   │
   ├── Entrance Light → 80%
   ├── Hall Light → 40%
   ├── Selected Blinds → Open
   └── HVAC → Comfort

The key is that Away and Welcome are building modes, while individual scenes can still be used inside rooms.

Practical Commercial Building Example

Consider an office building with five floors.

Instead of one massive central Group Address, create a hierarchy:

CENTRAL FUNCTIONS

Building
│
├── All Floors OFF
│
├── All Blinds UP
│
└── Building Unoccupied
│
├── Floor 01
│    ├── Lights OFF
│    └── Blinds UP
│
├── Floor 02
│    ├── Lights OFF
│    └── Blinds UP
│
├── Floor 03
│    ├── Lights OFF
│    └── Blinds UP
│
└── ...

This provides facility-management flexibility.

For example:

Floor 3 maintenance

Floor 3 Lights OFF

does not need to affect the rest of the building.

At the end of the day:

Building Unoccupied

can coordinate the required building-wide functions.

Central Commands vs Scenes vs Status

These three concepts should remain clearly separated:

             KNX BUILDING CONTROL
                     │
        ┌────────────┼────────────┐
        ▼            ▼            ▼
     COMMAND       SCENE        STATUS
        │            │            │
        ▼            ▼            ▼
   "Do this"    "Set this state"  "What is
                                  happening?"

For example:

ALL_LIGHTS_OFF
      │
      ▼
    COMMAND


PRESENTATION
      │
      ▼
     SCENE


LIGHT_STATUS
      │
      ▼
    STATUS

This simple distinction makes large KNX projects significantly easier to understand and troubleshoot.

Conclusion

Central functions are an important part of professional KNX system design because they allow a building to respond to common events rather than requiring individual room-by-room commands.

The most important principles are:

  1. Define the scope of every central function.
  2. Use dedicated central Group Addresses.
  3. Keep commands separate from status feedback.
  4. Preserve local control unless an intentional priority/lock function is required.
  5. Define priority between manual, automatic, weather and security commands.
  6. Use scenes for coordinated states and central commands for common actions.
  7. Document every possible source of a central command.
  8. Test central functions together with local control and feedback.

A professional KNX project should therefore have a clearly documented Central Function Schedule alongside its Group Address and Scene schedules.

The goal is not simply to create an “All OFF” button. The goal is to create a predictable building-wide control architecture where every central command has a defined scope, source, destination, priority and feedback path.

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