Evohome Opentherm - tearing my hair out!

[bruce_miranda]

I don't buy the learning theory for your issue. And the 1am boiler trigger could easily be a bug with either the Evohome OT implementation or the VR33's interpretation of that change in OT message.

[billytkid]

I don't buy the learning theory for your issue. And the 1am boiler trigger could easily be a bug with either the Evohome OT implementation or the VR33's interpretation of that change in OT message.

I agree on the learning, I smell BS.

Re the 1am thing, I don't see that there should be any OpenTherm message whatsoever, it's changing from all zones to being 18 degrees, to all zones being 12 degrees....

I tried it again last night by setting on the EvoHome controller to 'Custom' for 2 hrs when we went to bed, exactly the same thing happened last night.

Any chance anyone else can test this theory out? I think that when scene custom ends and it returns to standard, something on the flow control goes weird..

[DBMandrake]

I agree on the learning, I smell BS.

Re the 1am thing, I don't see that there should be any OpenTherm message whatsoever, it's changing from all zones to being 18 degrees, to all zones being 12 degrees....

I tried it again last night by setting on the EvoHome controller to 'Custom' for 2 hrs when we went to bed, exactly the same thing happened last night.

Any chance anyone else can test this theory out? I think that when scene custom ends and it returns to standard, something on the flow control goes weird..

I don't have OpenTherm but I do use the custom action as my "go to bed early action" - it has all downstairs zones set to 5 degrees 24/7, and is set to not apply to bedrooms.

Downstairs normally goes off at 11pm but if we go to bed earlier I use the Custom action set to apply only until midnight - and I have never had any problem with unexpected boiler demand in the night.

You say that the set points are going from 18C to 12C at 1am - are you saying that your custom action sets the zones to 18C and that your normal schedule at 1am is 12C ?

Perhaps it would help if you describe the exact set point schedule for your custom action, when your script is applying this, and what the normal set point schedule is of a representative downstairs room ? What you have described so far is a little vague.

Earlier you said your custom action "turns off" the heating downstairs, but neither 18C or 12C is off.... ? I would only consider 5C to be "off" as it's as close to off as you can get in Evohome.

[rotor]

I use Domoticz to set actions based on my alarm system, and when going to bed it sets EvoHome into 'Custom' mode which turns off the heating downstairs, then at 1am it sets EvoHome into normal mode.

This is where I'd start. You need to remove Domoticz and just let Evohome be Evohome all by itself.

[bruce_miranda]

Any chance anyone else can test this theory out? I think that when scene custom ends and it returns to standard, something on the flow control goes weird..

I can't seem to replicate this, but I'm not using Custom. My Heating is set to Quick Action Off (5C) if the outside temperature is above 13C, overnight when the temperature drops, IFTTT turns off my Quick Action Off, and then I am back to my normal schedule set point of 7C over night. But because the room temperatures are much higher than within 2C of the 7C set point, there is no Heat Demand created at all. I have boiler stats being logged every min and my pump over run is 20mins, so I can easily catch any boiler activity - but I don't. So I really have no idea what is causing your Heat Demand when going from a higher set point to a lower set point.

[paulockenden]

I use SmartThings to trigger various things (save current mode when the burglar alarm is set, switch to eco, push the previous mode back when the alarm is unset, for example). Never seen it cause spurious heat demands, but I don't think I've ever used custom mode.

P.

[bruce_miranda]

I've set up a test for tonight using the Custom Quick Action. Currently using Custom, all my zones are set to 10C, hopefully the outside temperature drops below 13C tonight which will turn my quick action off and all zones will drop to the night set point of 7C. I'll check in the morning if that triggered any Boiler activity.

[bruce_miranda]

@billytkid Sorry mate, my Evohome with OT, VR33 and a Vaillant boiler, doesn't do what you are seeing. Even using the Custom Quick Action and cancelling it to go to Normal doesn't trigger the boiler at all. My Custom quick action coincidentally cancelled at about 1am last night but because my normal scheduled set point was lower than what Custom was set to, no Heat Demand was created.

I can only offer another theory for your issue. But again it's hard to see. I know that sometimes zone schedules get stuck in a user schedule set mode, even if it wasn't supposed to. I've actually seen this happen quite often when Quick Actions are used. Could it be this that is affecting you. I.e. You think Custom gets set off, but for one or two zones it doesn't. They stay at the Higher set point, so that triggers the boiler when the room temp drops over night. In the morning the next Set point change for those zones has arrived, so by the time you wake up, you can't see this manual set point because it's now back to the schedule?

If it's not this, then I am out of ideas.

[paulockenden]

Thing is, boiler demand doesn’t come from the controller. Or rather, it isn’t triggered there. Any demand will have come from an HR92 (or whatever) thinking it needs heat to get to (or maintain) a setpoint. These devices know nothing about quick actions, or custom mode.

[bruce_miranda]

I was referring to the issue where the controller doesn't send out the new set point and so the HR92 is still using the older, higher set point that was set during the Custom Quick Action. Hence when the over night temperature drops, it triggers a Heat Demand wrt to the stuck Set Point, rather than the scheduled one?