# KNX App sends lighting commands with High priority instead of Low (blocking Schneider/Merten actuators)

**URL:** https://community.homey.app/t/knx-app-sends-lighting-commands-with-high-priority-instead-of-low-blocking-schneider-merten-actuators/158304
**Category:** Apps
**Created:** [August 14, 2026, 7:13pm UTC](https://community.homey.app/t/knx-app-sends-lighting-commands-with-high-priority-instead-of-low-blocking-schneider-merten-actuators/158304 "2026-08-14T19:13:01Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Smarthome-fixer.be](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/smarthome-fixer.be/32/171894_2.png) [@Smarthome-fixer.be](https://community.homey.app/u/Smarthome-fixer.be)
#### Post date: [August 14, 2026, 7:13pm UTC](https://community.homey.app/t/knx-app-sends-lighting-commands-with-high-priority-instead-of-low-blocking-schneider-merten-actuators/158304/1 "2026-08-14T19:13:01Z")

</div>

Hi everyone,

I wanted to share a technical issue (and solution) I ran into while setting up a KNX integration with Homey Pro and a **Schneider SpaceLogic / Merten** system. I hope this can be addressed in a future update of the official Homey KNX app!

### **The Problem**

When controlling lights via the Homey KNX app, Homey can read status/temperature values from the bus fine, but **light actuators fail to toggle**.

After diving deep into the **ETS Group Monitor** , I noticed that Homey injects all `GroupValue_Write` telegrams onto the KNX bus using **Telegram Priority: HIGH** (`High`).

When standard physical KNX push-buttons or ETS send commands, they use **Telegram Priority: LOW** (`Low`).

### **Why this causes lights not to turn on/off**

In the KNX specification:

- **Low / Normal Priority:** Used for standard, manual lighting and blind controls.

- **High Priority:** Reserved for forced control, safety overrides, or higher-level logic.

Certain strict KNX actuators (such as the _Schneider Electric SpaceLogic SA1 Switch/Blind Master_ line, e.g., `MTN6705-0008`) enforce a strict priority filter on standard switching input objects

When Homey sends a switch command with `Priority: High` to a standard light output:

1. The actuator receives the packet on the bus.

2. It triggers its status-engine (and sends a status feedback object back onto the bus).

3. **Crucially: It ignores the physical relay trigger** because the incoming telegram carries `High` priority on an input expecting `Low` priority.

### **ETS Bus Log Comparison**

Here is the direct comparison from the ETS Group Monitor on the exact same Group Address (`1/1/23`):

- **Command sent via ETS (WORKS - Relay clicks):**

- **Command sent via Homey (FAILS - No relay click):**

### **Suggested Fix for Athom / Developers**

According to KNX standard practices, routine user commands (turning a light on/off, dimming, moving blinds) should be dispatched with **`Priority.LOW`** (or `Priority.NORMAL`).

It would be fantastic if:

1. Athom updates the default outgoing priority for lighting/appliance drivers in the KNX app to **`LOW`**.

2. _Or_ provides an option under the Advanced Device Settings to select the **Telegram Priority** (`Low`, `Normal`, `High`).

Has anyone else encountered this with Schneider, Merten, or ABB actuators? Hope this detailed trace helps the Athom dev team resolve this!