Home Automation Domotica Forum Europe, Bwired Forum

Hi all,

I've just built an opentherm interface and am looking to connect it to my boiler via the opentherm interface and use it for two functions :

1. To monitor various elements of the boiler and graph them on a PC, e.g. flow temp, return temp, flame on, etc.
2. To have a PC switch the 'hot water comfort setting' on at 8am and off at 10pm. If the comfort setting is left on then the boiler wakes me up in the night when it keeps the water warm. If I can find the commands to send, I can automate this using a scheduled task and batch script.

Can anyone advise if the boiler will send out information without an opentherm thermostat connected? I plan to continue using my on/off stat as its wifi capable and I can control it from my iphone.

At present when I connect up the interface and power on I just get the messages thermostat disconnected, followed by a few errors (1 and 3) and then thats it, nothing else.

Any help appreciated.

Thanks

Richard

As far as I know you need a master (e.g. thermostat) in order to initiate communication, the slave (the boiler) only answers requests from the master.

Richard,

Currently the gateway won't do much without an opentherm thermostat connected. However, there are some ideas floating around (see also http://home.xmsnet.nl/openthermprotocol/) to make it do something useful without a thermostat or in combination with an on/off thermostat. It will be a while before that is going to be available, though.

hvxl wrote:Richard,

Currently the gateway won't do much without an opentherm thermostat connected. However, there are some ideas floating around (see also http://home.xmsnet.nl/openthermprotocol/) to make it do something useful without a thermostat or in combination with an on/off thermostat. It will be a while before that is going to be available, though.

Thanks for the reply, I'll look forward to what comes up.

Yes, I'm interested in this too

I've got a Viessman Vitodens 100-W WB1B with an OpenTherm interface but currently control it using 240V switched from the 4 wire actuators on my zone valves. I also have their external weather compensation thermistor, and can also switch in a resistor in parallel via a relay to lower the flow temperature (an "eco" mode that tricks the boiler into thinking the outside temp is higher). Ideally though I'd like to be able to set the flow temp via my HA control, e.g. based on room temperature and how quickly we wanted rooms to heat up.

It looks like there's been great progress with the gateway though since I last investigated around 3 years ago

I saw on this page http://otgw.tclcode.com/development.html following feature:
"When the thermostat wires are short-circuited, the gateway will instruct the boiler to start heating. This allows the gateway to be used with an on/off thermostat."

It seems that this comes close to what is wanted here? Did somebody test this feature? Feedback?

I would like to use this feature because I use a PLC with temperature sensors (Pt100) in multiple rooms and I don't want to/can use a thermostat.
The PLC instructs the boiler to start heating and opens the circuits for the rooms that need heating.

Anybody any experience with custom modulation and multiple room heating?