Sorry for OTGW off-topic in this forum, but OTGW users can help me with diagnostic of this issue.
About month ago I noticed on OTGW graph modulation instability of my boiler.
The boiler is Geminox THRi 2-17 DC (Siemens LMU64 ver. 3.03). As you can see in attached graph, modulation level (and boiler water temperature) oscillate a little bit. Sometimes more, sometimes less. Question is why.
My guesses:
1) there is something wrong with boiler ventilation (it is EBM RG128/1300-3612 and is known for problems with capacitors)
2) it is normal behaviour
3) something else is wrong
After few weeks of thinking I decided to change the ventilator. It was done today, but the behaviour is the same:
To be sure that this really is the issue and not the correct behaviour I would like to kindly ask other OTGW users to look at their OTGW graph and send me their experience with modulation level (in)stability. Any idea what can be wrong is of course very welcome.
Thank you,
Roman
off-topic: modulation instability
Moderator: hvxl
Re: off-topic: modulation instability
I don't see much to worry about with the modulation level. Sure, it goes up and down a little bit, but not wildly. My boiler doesn't behave like this, but that's because it doesn't have to strain as much as yours to keep the house at the desired temperature. Mine only runs at its minimum modulation level for about 25% of the time. Yours is constantly on and needs to adjust its modulation level to produce the necessary water temperature. Due to the slow feedback in a central heating system there can a bit of oscillation. It looks like either your house is not well insulated or the heating system is quite minimal.
One thing that is unusual is that your boiler seems to regard the control setpoint as the average between boiler water temperature and return water temperature. It normally specifies the desired boiler water temperature.
One thing that is unusual is that your boiler seems to regard the control setpoint as the average between boiler water temperature and return water temperature. It normally specifies the desired boiler water temperature.
Schelte
Re: off-topic: modulation instability
I believe it is because the boiler is dual circuits system. It has the underfloor heating circuit as well as the radiator circuit. Boiler water temperature is a function of control setpoint circuit 1 and control setpoint circuit 2.hvxl wrote: One thing that is unusual is that your boiler seems to regard the control setpoint as the average between boiler water temperature and return water temperature. It normally specifies the desired boiler water temperature.
But it looks like there is another issue when OTG is in use with this system. Look at the dump of OpenTherm communication:
Code: Select all
20:42:15.517283 T1081020A Write-Data Message ID 129: 522
20:42:15.885969 BD081020A Write-Ack Message ID 129: 522
20:42:16.505755 T80000200 Read-Data Status: 00000010 00000000
20:42:16.874543 B40000200 Read-Ack Status: 00000010 00000000
20:42:17.544392 T10101580 Write-Data Room setpoint: 21.50
20:42:17.863048 BD0101580 Write-Ack Room setpoint: 21.50
20:42:18.533021 T90171580 Write-Data Room Setpoint CH2: 21.50
20:42:18.851678 B50171580 Write-Ack Room Setpoint CH2: 21.50
20:42:19.521556 T901815F4 Write-Data Room temperature: 21.95
20:42:19.840078 B501815F4 Write-Ack Room temperature: 21.95
20:42:20.509922 T80800000 Read-Data Message ID 128: 0
20:42:20.829965 BE0800000 Data-Inv Message ID 128: 0
20:42:21.032454 T01000100 Read-Data Status: 00000001 00000000
20:42:21.422388 BC110D21B Read-Ack Room setpoint: -45.89
20:42:21.634796 T02100000 Read-Data Room setpoint: 0.00
20:42:22.015963 BC210001E Read-Ack Room setpoint: 0.12
20:42:22.183218 T83100000 Read-Data Room setpoint: 0.00
20:42:22.475643 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:22.650418 T83100000 Read-Data Room setpoint: 0.00
20:42:23.003959 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:23.176466 T83100000 Read-Data Room setpoint: 0.00
20:42:23.463774 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:23.654906 T83100000 Read-Data Room setpoint: 0.00
20:42:23.992343 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:24.183368 T83100000 Read-Data Room setpoint: 0.00
20:42:24.451901 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:24.620655 T02100000 Read-Data Room setpoint: 0.00
20:42:24.980607 BC210001E Read-Ack Room setpoint: 0.12
20:42:25.149360 T83100000 Read-Data Room setpoint: 0.00
20:42:25.440421 BC3101E08 Read-Ack Room setpoint: 30.03
20:42:25.626411 T83100000 Read-Data Room setpoint: 0.00
20:42:25.970219 BC3101E08 Read-Ack Room setpoint: 30.03
We can ignore it if it is only wrong interpretation of OEM-specific datagrams. More serious would be if the OTG can harm OEM-specific communication on OpenTherm bus. Look at this log:
Code: Select all
16:59:15.649827 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:16.638688 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:17.631027 T901607E1 Write-Data Year: 2017
16:59:18.668408 T901607E1 Write-Data Year: 2017
16:59:19.657196 T901607E1 Write-Data Year: 2017
16:59:20.640789 Error 03
16:59:21.618544 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:22.606165 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:23.643714 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:24.632427 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:25.619850 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:26.608557 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:27.579800 Error 03
16:59:28.607372 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:29.594825 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:30.582216 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:31.590837 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:32.578327 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:33.565737 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:34.564532 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:35.552149 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:36.589608 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:37.559517 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:38.546858 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:39.534474 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:40.558116 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:41.545767 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:42.533378 T9014F101 Write-Data Day of week and time of day: Sun 17:01
16:59:43.517044 T001B0000 Read-Data Outside temperature: 0.00
16:59:44.554655 T001B0000 Read-Data Outside temperature: 0.00
16:59:45.543424 T001B0000 Read-Data Outside temperature: 0.00
16:59:46.579694 T801C0000 Read-Data Return water temperature: 0.00
16:59:47.517143 T801C0000 Read-Data Return water temperature: 0.00
16:59:48.504813 T801C0000 Read-Data Return water temperature: 0.00
16:59:49.486051 Error 03
16:59:50.523406 Error 03
16:59:51.500911 T00110000 Read-Data Relative modulation level: 0.00
16:59:52.488441 T00110000 Read-Data Relative modulation level: 0.00
16:59:53.455793 Error 03
16:59:54.493168 Error 03
16:59:55.470707 T80130000 Read-Data DHW flow rate: 0.00
Again this is the situation, where OT Master is in "BMU configuration mode". Again the semantics of the datagrams is OEM-specific. But now Error03 appears there (normally I can see only one or zero E03 per day). 10ms tmeout is probably not enough for this type of communication but I have no idea what the impact could be.
All this was done with Siemes (Landis & Staefa) LMU64 Boiler controller http://www.mhgheating.co.uk/wp-content/ ... p7494e.pdf which is widely used by a different boilers producer.
Can you pls. let me know if this should be analyse or we can just ignore it?
Thank you,
Roman
Re: off-topic: modulation instability
This is not an issue with the OTGW, as you claim. Those are not valid Opentherm messages. According to the spec, the lower 4 bits of byte 1 are spare and "should always be ‘0’". In your first piece of log they are not. But even so, the OTGW seems to pass them on unaltered.
The greatly increased frequency of error 03 occurrences in your second log seems to indicate that the messages in this mode even deviate so much from the opentherm spec that the OTGW is unable to decode them at all. You can try to run test 2 and 3 of the diagnostic firmware to get an idea what the signal looks like (if at lease it uses the Opentherm signal levels).
The greatly increased frequency of error 03 occurrences in your second log seems to indicate that the messages in this mode even deviate so much from the opentherm spec that the OTGW is unable to decode them at all. You can try to run test 2 and 3 of the diagnostic firmware to get an idea what the signal looks like (if at lease it uses the Opentherm signal levels).
Schelte