Flow: limits and best practices
What to know before commissioning flows on a plant: how to work safely, organize flows, avoid loops and repeated commands, node measurement units, and current limitations.
Working safely
Download before you modify. At the start of every session, press Download: Upload replaces all flows on the server with those in the editor.
Keep a copy. Before major changes, save everything with Save As. The file lets you go back at any time.
Test with Dummy nodes. Build and test the logic with Dummy nodes; replace them with the real components only when it works.
Be careful with real commands. Components and KNX nodes control the real plant: a wrong flow can switch on loads, open windows or disable alarms. Test critical logic when you are on site.
Organizing flows
One flow per function (garden lighting, irrigation, temperature control…): small flows are easier to understand and correct.
Descriptive names for flows and nodes: Stair light delay, not Stairs light 2.
Use the flow description and the node Notes field to explain choices and values (120 s requested by the customer).
Arrange nodes from left to right: sources on the left, logic in the center, commands on the right.
Avoid common issues
Repeated commands. Node outputs are sent at every calculation, even if the value does not change, and Date/Hour, Oscillator and Clock keep sending values continuously. Before a component or a KNX node, place a Trigger or a Filter, so the command is sent only when needed.
Loops. Do not connect a node's output, directly or through other nodes, to its own input: the value would circulate forever. The server stops propagation after a very high number of passes, but the flow does not work as expected. To "remember" a value, use a flip-flop or a variable.
Two wires on the same input. The last value received applies: the result depends on the order of events. Combine signals first with an OR or a Selector.
Component and flow that contradict each other. If a scenario or a Manager logic controls the same component as a flow, the last command wins. Decide who controls what.
Node measurement units
Node | Property | Unit |
|---|---|---|
Sequencer | DELAY | seconds (1–43,200) |
Scenario | Interval | seconds (1–60) |
Timer | Delay Up, Delay Down | whole seconds |
Stairs Light | Delay | seconds |
Repeat Command | Delay | seconds |
Oscillator | Timer | milliseconds (minimum 100) |
Clock | Delay | milliseconds (100–100,000) |
Astronomy Clock | Coordinates | decimal degrees |
Current limitations
KNX nodes work with a single Knx3-type KNX gateway in the project (KNX nodes).
The Astronomy Clock coordinates are read when the flow starts; an empty or invalid value does not generate an error but uses 0, 0.
In color lights, commands pass through On / Off, Hue, Saturation and Brightness (Components and Dummy).
The Javascript node has a 250 ms execution limit (Functions).
The Timer delays are in whole seconds: decimal values are truncated.