Openthem and pump long run times

[^woody^]

I've had a new combi boiler controlled by Opentherm (Drayton Wiser) for a year now, and something really niggling me is the apparent long time that the boiler pump is running. It can literally be running for hours non stop some days.

Apparently the theory is that the boiler is made to run for longer at a lower temperature, and avoid constant cycling. Also apparently, there is more wear in on/off cycling than in having the pump run continuous for long periods.

Can anyone put my mind at rest that long pump run times are normal for Openthem?

Also what is a pump's lifetime expectancy, under almost continuous running compared to cycling. Am I worrying unnecessarily about early pump failure from this continuous running, or would the manufacturer have allowed for it?

 

[muggles]

What boiler do you have?

 

[^woody^]

Baxi 830

 

[muggles]

Ah, that may be your problem. The Baxi range is well known for being rather temperamental on OpenTherm. I believe it plays reasonably well with Nest, but not so well with some other controls. Baxi might be able to offer a firmware upgrade if you call them, but I don't know whether the issue has actually been resolved yet.

 

[muggles]

Here you go, found a relevant bit of info from someone who knows. Essentially Baxi have used some bits of the OpenTherm communication protocol to provide control, but they aren't members of the OpenTherm Association and haven't fully implemented OpenTherm in the way it was designed. Baxi boilers aren't OpenTherm certificated. Ergo, they only work with Usense and Nest.

 

[Notch7]

Here you go, found a relevant bit of info from someone who knows. Essentially Baxi have used some bits of the OpenTherm communication protocol to provide control, but they aren't members of the OpenTherm Association and haven't fully implemented OpenTherm in the way it was designed. Baxi boilers aren't OpenTherm certificated. Ergo, they only work with Usense and Nest.

View attachment 216993

I believe the new baxi boilers introduced Jun 2023 have a new pcb and are open therm certified, I don't know enough to know if that means they will now work with all open therm controllers.

I feel sorry for heating engineers trying to match all this technology together and make it work.

 

[oldbutnotdead]

Wiser only support Opentherm on the single channel controller - it does work on the dual channel but can be unpredictable. My system does run for long periods at low burn rates (not actually monitored the gas consumption but the noise levels from the boiler change noticeably) rather than the old-school flat out til the thermostat clicks then off.

 

[ukguy]

Interesting discussion…

we have the baxi 830 combi using opentherm with tado and Drayton TRV4's.

If radiators are balanced they all heat up properly and radiators are quiet until the boiler modulates down as it starts to approach the target temperature.

As soon as the boiler modulates down the lounge rad for eg starts making a motor running noise. The only way of stopping it is to fully open the lock shields (which then will mess up the balancing)

This seems to relate to the pump modulation. I have emailed baxi but have no response yet.