Under review

Response timeout with Vallox modbus

Jürgen Jürgenson 6 years ago in Devices / Modbus updated 5 years ago 4


We have 2 similar buildings, with same settings and hardware. We use Vallox ventilation and control them with USB modbus dongle. But after tomorrow we started to get response timeouts on one building(other building has no timeouts). The whole modbus line feels slower too(chaning the vent speeds works but it feels slower than before). I know the log used to be clean without any timeouts. Now im trying to debug what is causing it. So far it feels like they are responding but not for all requests. Here is a small screenshot where i get timeouts for ventilation State(4609) and Fan speed(4353)

Image 1554

Is there any other way to know witch ventilation is not responding(we have total of 19 units) The path only show the modbus dongle. I have looked at the times too and compared them to the log monitor, but it seams to me that the response timeouts are random. Sometimes they get awnsers sometimes they don't. Here are my settings for the USB dongle: 

Image 1555

Other building works just fine with the same settings, and changing vent speeds feels faster to me. 

Under review


strange to see one building working OK and other not with the same hardware/settings. Try increasing the Read interval to 1s, also if possible, try replacing the USB dongle, it could be causing the issues.

Best regards,

Increasing the read interval does not make it any better, I will try to change the dongle then. Weird for me is that it only  has problems with 3 values, state, fan speed and away temp target, all the other request get the values just fine. 

Im not sure if the interference can come from a cable that has internet, mbus and modbus all in one cable, because we had a shorted cable and no way to replace it so we had to send all signal with one cable to our server. If that is the problem then changing the dongle wont help us... I hope its not so.

Strange to see that only a couple of addresses not work. Are you 100% that these addresses are correct?

You could also try disabling this modbus, create a new modbus and add just these 3 addresses and set read function = single and see if the issue persists.

Best regards. 


Late update: I changed the dongle, that fixed the problem with no response.