Overview
Two devices on the same RS485 bus are assigned the same Modbus address. The two devices respond simultaneously to every poll, corrupting each other's replies, and a neighbouring address that should have a device often shows no device at all. This is one of the more disruptive bus faults because the symptoms vary from poll to poll · sometimes a measurement gets through, sometimes it does not.
How this issue is diagnosed
The standard case is that Hybird assigns Modbus IDs to breakers before they ship, so on-site address collisions should be rare. When one is found in the field, the installer can re-address the affected breaker directly using the Hybird mobile app, or Hybird support can perform the re-addressing remotely via the controller. Hybird support reads the controller logs from Hybird Admin to identify the colliding address and confirm the diagnostic signature. If the symptoms in the next section match what you are seeing, contact Hybird support at [email protected] or +45 3020 4900 to begin the joint diagnosis.
Symptom
Intermittent or unreliable data from one Modbus ID · sometimes a measurement is returned, sometimes not.
A neighbouring Modbus ID (often one higher) shows consistent timeouts because no device is actually addressed there.
Example: two breakers both set to address 10. Address 10 returns mostly errors with occasional valid measurements. Address 11, where a breaker was expected, returns nothing.
From the support side, controller logs in Hybird Admin show two distinct signatures on adjacent addresses:
On the colliding address, a non-timeout communication error appears · typically a packet-level error rather than a timeout, because two devices are returning overlapping responses. [VERIFY: confirm the specific Modbus error wording that appears on a collision · e.g. CRC or parity-level error · as distinct from "Modbus query timed out"]
On the empty neighbour address, the standard timeout appears: [<timestamp>] [ERROR] [GET_MEASUREMENTS] Failed to read measurement from Device <modbus_id> (<device_type>): Modbus error: Modbus query timed out.
Log format may change over time as the underlying libraries are updated, so search by symptom rather than by exact string.
The pattern is unrelated to the physical position of the colliding devices in the panel or their position in the daisy chain.
Possible causes
Two breakers placed in setup mode simultaneously during commissioning. The broadcast change-address command then writes the same address to both. Setup vs work mode is selected by a small green dip switch on the breaker.
A previously addressed breaker added to a new panel without re-addressing. For example, a breaker swapped out of a different site and reused without resetting its Modbus ID.
An external meter or third-party device using an address in the Hybird breaker range. Hybird breakers use addresses 1–80; external meters should be at 120 or higher. A meter accidentally configured below 120 can collide with a breaker.
Diagnosis
Hybird support will identify the device showing intermittent data and any neighbouring Modbus ID that is unexpectedly absent. The diagnostic signature is the combination of a non-timeout communication error on one address with consistent timeouts on the adjacent address. Support will cross-reference the expected Modbus ID assignments for the site:
Hybird breaker addresses are assigned manually by Hybird at commissioning and fall in the range 1–80.
Addresses 81–119 are reserved.
Addresses 120 and above are for external meters and third-party devices.
Once the suspected colliding address is known, the installer identifies the duplicate devices on site:
Check the status LED on every breaker on the bus. A flashing purple LED indicates a breaker is currently in setup mode. If two breakers are showing flashing purple, this is the immediate cause of the collision.
If no breaker is currently in setup mode but a collision is still suspected, work with Hybird support to identify each candidate breaker physically · Hybird support cannot reliably distinguish two devices sharing an address remotely.
For a fuller checklist of what to inspect on site, see On-site visual checks · what to inspect on a Hybird panel.
Note: Modbus IDs on Hybird breakers are changed by flipping the breaker's dip switch into setup mode and then sending an address-change command. The command can be sent via the Hybird mobile app or by Hybird support via the controller · either way, the physical dip-switch step on the breaker itself is required.
RS485 is low-voltage signal wiring and can be worked on with the panel live. Do not de-energise the panel · the installation is likely powering active loads. Apply standard panel-work precautions: avoid contact with AC terminals, and follow local regulations (Stærkstrømsbekendtgørelsen in Denmark, BS 7671 in the UK, VDE 0100 in Germany) for working inside a live distribution panel.
Resolution
Identify the breaker that needs re-addressing. The panel can remain energised. Flipping a breaker into setup mode has no impact on the AC supply the breaker is protecting · the breaker continues to switch normally; only its Modbus addressing behaviour changes.
Confirm no other breaker on the bus is currently in setup mode. Look at every breaker's status LED: a flashing purple LED indicates setup mode. Only one breaker on the bus may be in setup mode at any one time during an address change · if more than one is flashing purple, an address collision will be created or repeated.
Flip the dip switch on the breaker you intend to re-address into setup mode. Confirm its LED begins flashing purple, which is your visual confirmation that you have the correct physical device and that no other breaker on the bus is also in setup mode.
Re-address the breaker to a free Modbus ID in the 1–80 range · either directly using the Hybird mobile app (which prompts you to flip the dip switch and then sends the address-change command), or by asking Hybird support to send the command via the controller.
Return the dip switch to work mode. The LED should return from flashing purple to blue (idle) or red (active), depending on whether the breaker is switched on.
Confirm the breaker is now reporting on its new address · visible in the Hybird mobile app, or confirmed by Hybird support from Hybird Admin. The previously empty address should also now show as no longer colliding.
Prevention
Hybird breakers are pre-addressed by Hybird before shipping. Modbus IDs are assigned starting from address 10, rather than from address 1 · this avoids collisions with most third-party Modbus devices, which typically default to addresses 1, 2, or 3 out of the factory.
During any on-site addressing work, only ever place one breaker in setup mode at a time. Confirm dip switches on all other breakers are in work mode before sending an address-change command.
Do not re-use a previously addressed breaker in a new panel without confirming its existing Modbus ID and either retaining or reassigning it deliberately. A swapped-in breaker that has never had its address reset is a common source of collisions.
Keep external meters at Modbus address 120 or higher. Do not place third-party devices in the 1–80 range reserved for Hybird breakers.
Scan every new breaker into the panel record at commissioning so that swapped-in units are flagged for re-addressing rather than installed silently.
When to escalate
If two devices appear to share an address but cannot be physically distinguished on site, or if address conflicts persist after re-addressing, contact Hybird support at [email protected] or +45 3020 4900. Hybird can confirm the addresses currently active on the bus and assist with reassignment.
Summary
Modbus address collisions produce a distinctive mixed signature: a non-timeout communication error on one address combined with consistent timeouts on a neighbouring address that should have a device. The cause is almost always either two breakers placed in setup mode together, or a reused breaker installed without re-addressing. The fix is to identify and re-address the duplicate via the Hybird mobile app or Hybird support, always with only one breaker in setup mode at a time.