---
title: "Modbus device ID collision"
description: "Fix Modbus device ID collision in TapHome. Learn how to resolve Slave ID conflicts causing communication errors between multiple Modbus devices."
url: "https://taphome.com/en/troubleshooting/configuration/modbus-id-collision/"
language: en
lastmod: 2026-10-18
generator: hugo
---

# Modbus device ID collision

Multiple Modbus devices with the same Slave ID causing communication errors

- **Service** You need the Service permission (typically your installation partner).

## How you recognise it

One or more Modbus devices (for example, energy meters) show communication errors or don’t respond. This often happens when:

- Adding multiple devices to the same bus
- Configuring a new device with factory default settings
- Two devices accidentally have the same Slave ID

## Cause

Every Modbus device on the same bus **must have a unique Slave ID**. Most devices ship with a factory default ID (often 1), causing collisions when multiple devices are connected.

## Solution

### Step 1: Identify the Collision

Service installation partner

1. Go to **Settings → Hardware** and check which Modbus devices show errors
2. Note the Slave IDs configured in TapHome
3. Check if any two devices share the same ID

### Step 2: Isolate the Device

Service installation partner

If you can’t communicate with the device:

1. **Disconnect all other Modbus devices** from the bus temporarily
2. Leave only the device you want to reconfigure
3. This ensures you can communicate with it

### Step 3: Change the Slave ID

Service installation partner

The Slave ID can be changed in one of two ways:

**Option A: Via TapHome Service settings**

1. Open the Modbus device in TapHome
2. Go to **Service settings**
3. Look for a **Service actions** related to Slave ID
4. Set a **unique ID** (e.g., 5, 10, 15 for different devices)
5. **Save** the settings

### Step 4: Option B: Via device’s own interface

Service installation partner

Some Modbus devices have their own menu or configuration interface. Refer to the device’s documentation for instructions on how to change the Slave ID.

> The Slave ID is stored in the device’s internal memory. This is different from the communication settings in TapHome.

### Step 5: Update TapHome Configuration

Service installation partner

After changing the device’s Slave ID:

1. Go to the device’s **communication settings** in TapHome
2. Update the **Slave ID** to match the new value you just set
3. The device should now communicate without errors

### Step 6: Reconnect Other Devices

Service installation partner

1. Reconnect the other Modbus devices to the bus
2. Verify each device has a unique Slave ID
3. All devices should now communicate properly

## Best Practice for Multiple Devices

When setting up multiple Modbus devices:

- **Connect one device at a time**
- Change its Slave ID to a unique value **before** connecting the next device
- Use a numbering scheme (e.g., 10, 11, 12… or 5, 10, 15…)
- **Avoid Slave ID 1** as it’s the common factory default

## Related Documentation

- [Modbus](https://taphome.com/en/docs/integration/modbus/)
- [More energy meters on a single Modbus RTU bus](https://taphome.com/en/docs/integration/modbus/multiple-meters/)

## Related issues

- [DALI lights switch on by themselves or jump to another brightness — the DALI bus is disturbed](https://taphome.com/en/troubleshooting/wiring/dali-lights-switch-on-by-themselves/)
- [Modbus RTU device with its own power supply drops out now and then — the RS-485 line has no common ground (GND)](https://taphome.com/en/troubleshooting/wiring/modbus-rtu-missing-common-ground/)

Last updated: 2026-10-18