Troubleshooting
Organised by symptom: find the symptom you are seeing, then work down the table.
This page is organised by symptom. Find the symptom you are seeing, then work down the table.
Nothing happens at all
| Symptom | Likely cause | Fix |
|---|---|---|
No 5V LED on the board | No mains, or the internal 5 V regulator has failed | Check the supply at J2. Check the mains fuse upstream of the board |
| The screen is completely dark | The screen has no 5 V | Check the screen cable at J5. The screen is powered from J5 pins 1–3 |
The screen is dark but the board's 5V LED is lit | The screen's own timeout has switched the backlight off | Touch the screen. If the timeout is too short, change Display timeout in Settings → Display Settings |
The screen shows Check device connection | The screen cannot reach the controller over its RS-485 link | Check the screen cable at J5 (pins 4 and 5 carry the RS-485 pair). Check that the controller is powered |
The controller is up but you cannot reach it
| Symptom | Likely cause | Fix |
|---|---|---|
The web interface does not open at 192.168.1.195 | The address is different, or the network does not reach it | Read the address from the screen: SYSTEM INFORMATION → NETWORK. Put your computer on the same subnet |
| The web interface does not open and the screen shows no address | The unit has no network address at all | Check the Ethernet cable at J4 and the yellow link LED. If the yellow LED is dark, the cable or the switch is the problem |
| The yellow Ethernet LED is lit but the green one is dark | The link is running at 10 Mbit/s | Change the switch port to 100 Mbit/s |
| The unit is not reachable after a DHCP change | The address moved | Read the address from the screen and reconnect. If DHCP does not answer, use a fixed address |
| Modbus/TCP does not answer | The Modbus port is not the default, or the ID does not match | Check Modbus port and Modbus ID. The default is TCP 502 and ID 1 |
| The RS-485 bus does not answer | Missing termination, wrong baud rate, or the wrong node address | Fit 120 Ω at both ends of the bus. Check RS485 baud rate and Modbus ID on every device |
| The RS-485 bus works with one device but not with several | The bus is too long, or it is not a linear topology | Keep the bus linear, use twisted pair, and connect the common wire at every device |
| BACnet does not answer | The device ID is not unique, or the wrong port is used | Check BACnet device ID. BACnet/IP uses UDP 47808 by default |
| The web interface rejects a value | The value is outside the allowed range | The message names the fields that were rejected. Correct them and press Save again |
The unit does not humidify
| Symptom | Likely cause | Fix |
|---|---|---|
The mode stays Standby | Nothing asked for AUTOMATIC | Set the mode to AUTOMATIC |
The banner says Waiting: Master | The master enable input is not active | Check the wiring at J12 (MEn). The input reads as active when 24 V is present |
The banner says Waiting: Hygrostat | The hygrostat input is not active | Check the wiring at J16 (HL_ONOFF) and the hygrostat itself |
The banner says Waiting: Airflow | The airflow input is not active | Check the wiring at J14 (Airflow) and that the fan is running |
The banner says Waiting: Alarm <name> | An alarm is blocking the run | Clear the cause, then acknowledge the alarm |
| The demand reads 0 % | The demand source is wrong, or the signal is missing | Check Demand input mode against what is wired to J11. Check the wiring at the Input Signal row of the Inputs card |
The demand reads 100 % in On/Off mode | The on/off input is active | Check the wiring at J11 |
| The demand does not follow the fieldbus register | The demand source is not External demand register | Set Demand input mode to External demand register and write the demand register |
| The pump runs but no valve opens | The demand is above zero but the valve step settings exclude it | Check the valve step values. A valve whose lower level is equal to or above its upper level never opens |
| Only valves 3 and 4 are used | Valves 1 and 2 are disabled, or their levels are wrong | Check the lower and upper level of each valve |
| The output drops to 0 % at high humidity | The limiter is working | This is intended. The banner Output reduced due to Highlimit transmitter says so. Check the humidity in the supply air and the high-limit transmitter |
| The output is reduced and there is no banner | The demand is genuinely low | Check the demand source |
Water problems
| Symptom | Likely cause | Fix |
|---|---|---|
Water Pressure Low | No water, a closed valve, a blocked filter, or a leak before the pump | Check the tank, the isolation valve and the filter between the tank and the pump |
Water Pressure High | The pump is not delivering: blocked filter, air lock, or a failing pump | Check the filter and the pump |
No Motor Drive | The pump is commanded on but the motor draws no current | Check the motor, the wiring at J33, and the motor contactor. The alarm is checked while the pump runs, so it clears when the pump stops |
Motor Temperature High | The pump is blocked or overloaded | Check the pump and the water flow. The alarm clears when the motor cools down |
Conductivity High | The water is too conductive | Check the water supply and the flushing interval |
Conductivity After Flush | The conductivity stayed high for 2 minutes, or flapped 3 times in an hour | Fix the water supply, then acknowledge the alarm |
Conductivity Sensor Fault | The probe at J37 is disconnected or unpowered | Check the probe connector and the isolated 5 V LED (D38) |
Water Temperature High | The water supply is too hot | Check the water supply |
Water Leak Detected | The leak input has been triggered | Close the water supply, find the leak, fix it, then acknowledge the alarm |
| The unit flushes far more often than the interval | The conductivity or the water temperature is out of range | A flush is also triggered by Conductivity high and Water temperature high. Fix the water quality |
| The unit flushes and the demand stays at 0 % | The flush holds the valve lock, so the demand controller waits | This is intended; the unit resumes when the flush is finished |
Alarms
| Symptom | Likely cause | Fix |
|---|---|---|
| An alarm comes back right after you reset it | The condition that caused it is still there | Fix the cause first. The trip history is cleared when you reset, so the alarm latches again only if the condition returns |
| The alarm does not clear when I reset it | The alarm is not one that can be reset, or the condition persists | Only the sticky alarms have a reset button. Check the alarm list in Status and alarms |
Maintenance Required keeps coming back | The maintenance has not been acknowledged | Write 1 to the MAINTENANCE register over the fieldbus, or press Reset on the Maintenance Required card on the screen |
Input Signal Error | The demand input is carrying more voltage than it should | Check the signal source and the wiring at J11 |
Board Temperature High | The controller is too hot inside its enclosure | Improve the ventilation |
Time and history
| Symptom | Likely cause | Fix |
|---|---|---|
| The clock is wrong | The clock has never been set, or the battery is flat | Set the time on the screen or in the web interface. The clock is kept by a battery-backed cell (BT1) |
The alarm history shows error for the date | The clock was never set when the alarm was recorded | Set the clock. Old entries keep their broken timestamps |
| The alarm history is empty | Nothing has been logged yet | Alarms are recorded as they happen |
Failed to read alarm history | The controller did not answer | Check the screen link at J5 |
The unit rebooted by itself
A reboot is usually a watchdog reset, or a power interruption. Check the Reboots counter in the System card: if it keeps growing, the unit is resetting on its own. Note the values on the screen and in the web interface before it goes down again, because the counter and the logs are the only record of what happened.
Collecting information before you call for help
- Note the serial number, the model and the firmware version. They are in the web interface footer and on the screen.
- Note the alarm list and the banner text.
- Note the address of the unit and the fieldbus settings.
Next steps
- Status and alarms — what each alarm means.
- Hardware reference — the terminals and the LEDs.
- FAQ — other common questions.