Retrieve boilerstatus by OTGW, boiler controlled by on-off

[jan341]

My boiler can be operated by:
1- opentherm thermostat
2- on/off thermostat
These have separate, different connectors on the boiler. I have to figure out whether or not I can operate the on/off thermostat and simultaneously query the opentherm interface.

Initially, I controlled the boiler by opentherm, but the boiler algorithm forced water temperature to too low levels (modern boilers try to minimize water temp). The OTGW has been an indispensable instrument to really measure what's going on.

So, now I have an on/off setup. Can I retrieve the boiler parameters by OTGW ? As I read from documentation I should leave open the thermostat connector of OTGW (I have no interest of controlling the boiler by OTGW).

As there is no thermostat connected, I presume, the OTGW will send the message listed under Gateway Operation.
Is this a message from OTGW to boiler and subsequently a message from bolier to OTGW ?
Will OTGW send this messages periodically ?
If so, what is the time interval ?

Or, alternatively, can I send the serial command PS=1 periodically ?

Any help appreciated

[hvxl]

I give that an extremely low chance of working. But you have all the necessary components, so why not just try it?

The sequence of messages mentioned on the stand-alone operation web page will repeatedly be sent by the OTGW at a rate of about 1 every second. If the boiler doesn't respond, the message is repeated.

The PS=1 command will not help you. It only changes the way the information is reported on the serial interface.

I don't completely understand the issue with using opentherm to control your boiler. Maybe you can connect the on/off thermostat to the OTGW, as described on the same web page. Or does that result in the same problem?

[MartasBrno]

Jan,

just to give you my experience:
I have an older Baxi Prime 1.240-1 Boiler (Siemens LMU34)and QAA73 room control. As i had a few weird reasons, i had let the internal boiler control to run its own outdoor reset heating function enabled by its on-off thermostat input. it may be a thermostat, switch or short wire, it makes some "zone".
QAA73 has its own regulator (zone) i am not using that time, and it works fine, i can see through OTG all the communication regardless of time schedule of QAA, or so. QAA now controls my DHW tank as it has a separate shedule for it i need.

Does this case help you?
i do not understand your issues / hypothesis about low water temperature. Do you run some kind of outdoor reset / ekvitherm mode?

Martin

[blackbile]

A related question as I don't want to open another thread:

can I power off the OTGW now in summer - an Intergas similar boiler connected by opentherm connection and a Lyric T6R thermostat - will the boiler work - as I have an DHW indirect tank besides the boiler?

Thank you.

[hvxl]

A related question as I don't want to open another thread

Why not? The forum doesn't charge anything for a new thread. I don't see how this is in any way related to the thread you posted in. Hijacking an old thread just makes your question more difficult to find in the future.

[fox]

My boiler can be operated by:
1- opentherm thermostat
2- on/off thermostat
These have separate, different connectors on the boiler. I have to figure out whether or not I can operate the on/off thermostat and simultaneously query the opentherm interface.

Initially, I controlled the boiler by opentherm, but the boiler algorithm forced water temperature to too low levels (modern boilers try to minimize water temp). The OTGW has been an indispensable instrument to really measure what's going on.

So, now I have an on/off setup. Can I retrieve the boiler parameters by OTGW ? As I read from documentation I should leave open the thermostat connector of OTGW (I have no interest of controlling the boiler by OTGW).

As there is no thermostat connected, I presume, the OTGW will send the message listed under Gateway Operation.
Is this a message from OTGW to boiler and subsequently a message from bolier to OTGW ?
Will OTGW send this messages periodically ?
If so, what is the time interval ?

Or, alternatively, can I send the serial command PS=1 periodically ?

Any help appreciated

I have a slightly similar problem with "modern boilers" that "try to minimize water temp".
For me, if I set 40°C, the boiler will become lazy and let the real CS temperature fall very low only if one radiator valve of the house is open, and only when it's almost closed (slightly open).
(I suspect the boiler also mesures the water throughput in the heating system, and if it's too low, the pump is still on, but it refuses to heat.)
Don't know if you had similar issue.


I also want to share with you my current setup with a combo of OpenTherm with OTGW for monitoring purposes (MQTT status topic), and a Zwave relay installed on the traditional on/off thermostat terminals.

On my Viessman Vitodens 100-W B1KF-25, there is what they call "external demand".
In some installer and configuration menus, I was able to
- Put the boiler in OpenTherm mode
- And additionally say I want the on/off thermostat terminals to serve as an alternative meaning of "external demand".
- Then in another boiler menu, I could say that external demand means "CH1" and I can configure the fixed setpoint for that "external demand".
I've noticed the "external demand" has priority over OpenTherm. So, once the relay closes, the heater obeys the settings of the "external demand". And you can still receive and send OpenTherm messages on the OTGW!

However on my side, the relay with "external demand" will soon become a secondary control.
It's just I haven't had time yet to implement the transmission of commands on the serial interface (CH and CS) and associated MQTT control topic.
So the relay for now serves as a temporary way to activate heating without sending any serial command to OTGW.