Overview
The controller is powered and online, but it cannot communicate with any device on the RS485 bus. Every Modbus ID returns timeouts in the logs. The most common cause is that the RS485 A and B wires are swapped at the controller end · meaning every device on the bus is in the wrong polarity relationship with the controller.
How this issue is diagnosed
This fault is resolved jointly between the installer on site and Hybird support. The installer reports the symptoms and performs the physical wiring fix; Hybird support reads the controller logs from Hybird Admin to confirm that the controller is online but every device is timing out. 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
No device on the RS485 bus is reporting data · every previously commissioned device shows as stale or offline.
The controller itself is powered (green power LED on) and online · the issue is local to the RS485 bus, not the upstream network.
From the support side, controller logs in Hybird Admin show Modbus timeout errors on every device address. Each affected device produces a log line in the form: [<timestamp>] [ERROR] [GET_MEASUREMENTS] Failed to read measurement from Device <modbus_id> (<device_type>): Modbus error: Modbus query timed out. There is no separate bus-wide log message · the same per-device timeout simply appears for every address. Log format may change over time as the underlying libraries are updated, so search by symptom rather than by exact string.
Possible causes
RS485 A and B reversed at the controller. The most common cause. Every device on the bus is wired consistently with itself but in the opposite polarity to the controller, so no device can respond.
Bus not physically connected to the controller. The push-in RS485 plug is not seated, or has come loose.
RS485 port on the controller damaged. If a higher-voltage bus (for example KNX) has been connected to the controller's RS485 port in the past, the port may have been destroyed. See Total bus failure after wiring to wrong terminal · troubleshooting guide.
Diagnosis
Hybird support will confirm from the controller logs that the controller itself is online and that the timeout pattern is bus-wide rather than affecting only a subset of devices:
If only some devices are timing out, the issue is not controller polarity · it is likely a daisy chain break or an address collision. See Group of breakers offline · troubleshooting guide or Modbus address collisions · troubleshooting guide.
If the controller itself is offline, this is a network connectivity issue, not a bus issue.
Once the bus-wide timeout pattern is confirmed, the installer performs the physical inspection on site:
Confirm the controller has power (green power LED on the controller body).
At the controller, inspect the RS485 A and B conductors. Compare the polarity to the convention used at the first breaker in the daisy chain. If the wire markings (one striped, one solid) are in opposite positions at the controller versus the breakers, polarity is reversed.
Confirm the RS485 plug is fully seated in the controller.
For a fuller checklist of what to inspect on site, see On-site visual checks · what to inspect on a Hybird panel.
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
Swap the A and B conductors at the controller so that polarity matches the rest of the bus. The panel can remain energised.
Re-seat the RS485 plug fully into the controller. The plug is push-in and hand-tightened; no torque value applies.
Hybird support will confirm from Hybird Admin that devices have returned to reporting. All previously commissioned Modbus IDs should return to active status.
Note: Technically the same fault can be cleared by reversing every device on the bus instead of the controller · but correcting the single controller connection is always preferable.
Prevention
Confirm the RS485 wire convention (which conductor is A, which is B) before terminating at either the controller or the first breaker.
At commissioning, power on the controller and confirm with Hybird support that all devices report before closing the panel. A bus-wide polarity error is only reliably detected by attempting to poll devices.
When to escalate
If polarity at the controller is correct and devices still do not report, the controller's RS485 port may be damaged · particularly if there is any history of the controller having been wired into a non-RS485 terminal. Contact Hybird support at [email protected] or +45 3020 4900 for further diagnostics. Hardware damage of this kind does qualify for advance replacement under warranty, but it is rare; support will work through the diagnostic path before replacement is considered.
Summary
If the controller is powered and online but no device on the bus is returning data, suspect reversed A/B polarity at the controller end of the RS485 connection. The fix is to swap the two conductors at the controller and confirm devices return to reporting.