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Thread: Evohome controller bug during Heating Off, but great job Dan and Domoticz

  1. #1
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    Default Evohome controller bug during Heating Off, but great job Dan and Domoticz

    So today we were lucky enough to have great weather for my IFTTT rule of switching the heating off past a certain temperature, to kick in. I confirmed that the control panel showed that all zones were off and the Heating Off quick action was in operation. What I also realised was that in Heating Off mode, no overrides are allowed via the controller - unlike some other quick actions. Domoticz confirmed that there was no Heat Demand too from any zone.

    So I went to one of the radiator controllers and turned the setpoint to 0.5C over the current room temperature. The controller was none the wiser and just showed the Heating completely off, Domoticz said the same because I guess it's just saying what the controller is telling it. But to my surprise the boiler fired up! Because I have OT I wanted to check what the target flow temperature was set in this condition. It said 49C. So not 90C (theoretical max) or even 65C (boiler max set).

    Warm water started flowing through my system and the radiators that were opened up slightly. But Evohome and Domoticz still displayed, full Heating Off and all setpoints at 5C.

    It was only when I looked at the Heat Demand screen did it show the zone that I had overridden with a 50% Heat Demand.

    I then set another zone manually to 0.5C over setpoint and it too jumped to 50% Heat Demand, but Evohome kept the overall Heat Demand down and continued to keep the Target Flow at 49C. Same thing continued with 3 zones too. It proved that Evohome can deal with multiple zone Heat Demands, and if the temperatures are not far from the setpoint it won't kick the boiler into full.

    It also highlights an Evohome bug, don't think your heating around the house is OFF, just because your controller or your app says so. Local Override display obviously don't work when Heating Off is in operation. So your kids could be playing with the radiator controllers and you'll be scratching your head trying to work out why the boiler is on in the middle of summer. The App and the controller showed no signs of me changing the setpoint while the Heating Off was in operation.

    Thank you Dan for taking the time to code the Heat Demand functionality into Domoticz.

    p.s. : What I have noticed is that the boiler is run almost at 50% max flow temperature for a 0.5C difference to setpoint, 1C difference to setpoint and it runs at 75%, anything higher than 1C difference and the boiler is kicked to max. This demand could be even for a single zone, so all the zones can experience overshoots if they have any Heat Demand and a single zone is below 1C from set point.
    Last edited by bruce_miranda; 30th March 2017 at 06:04 PM.

  2. #2
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    Hi,

    Just completed similar test and here is what I got:

    #1 all zones except one recording a room temp well (EDIT: *above* EDIT) the set point (more than 3 degrees) and boiler noted not firing nor pump activated

    #2 single zone increase set point by 0.5 past room temp. I see in a controlled way the boiler getting to 44 degrees or so and trying to maintain

    #3 add another zone to the mix and increase desired set point by 0.5 degrees past room temp. The boiler increases ch flow temp to 65 degrees or so and tries to maintain

    #4 add another zone - same process as above. The boiler increases ch flow temp past 70 and then the rooms reach their temps as it is warm today, so the boiler kick back down to pump only no burner.

    I'm seeing the heat demand being aggregated in the wrong/different way to yours. It's not that often only a single rad (zone in my case) is on by itself.

    That said, in a more controlled way I'm am seeing things differently to how I previously thought I saw a single zone increase by 0.5 degrees would demand max ch flow.

    I'll test again later when it's colder. Too warm to test much right now. ;-)
    Last edited by StephenC; 30th March 2017 at 08:28 PM.

  3. #3
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    In #1 did you actually mean all zones are above setpoint?

    P.s. you complaining because it's too warm!!

  4. #4
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    Ha! Yes you got me. I meant the other way around....let me just correct that. Whoops. Good spot

    ;-)

  5. #5
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    Just tried test #1 and #2 again. (Boiler in standby then increase one zone by 0.5 degrees)

    I'm now seeing 79.5 degrees C for a single zone increase by 0.5 degrees before it backed off and went into pump only mode. Again other zones not anything to do with it.

  6. #6

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    Quote Originally Posted by bruce_miranda View Post
    So today we were lucky enough to have great weather for my IFTTT rule of switching the heating off past a certain temperature, to kick in. I confirmed that the control panel showed that all zones were off and the Heating Off quick action was in operation. What I also realised was that in Heating Off mode, no overrides are allowed via the controller - unlike some other quick actions. Domoticz confirmed that there was no Heat Demand too from any zone.

    So I went to one of the radiator controllers and turned the setpoint to 0.5C over the current room temperature. The controller was none the wiser and just showed the Heating completely off, Domoticz said the same because I guess it's just saying what the controller is telling it. But to my surprise the boiler fired up! Because I have OT I wanted to check what the target flow temperature was set in this condition. It said 49C. So not 90C (theoretical max) or even 65C (boiler max set).

    Warm water started flowing through my system and the radiators that were opened up slightly. But Evohome and Domoticz still displayed, full Heating Off and all setpoints at 5C.

    It was only when I looked at the Heat Demand screen did it show the zone that I had overridden with a 50% Heat Demand.

    I then set another zone manually to 0.5C over setpoint and it too jumped to 50% Heat Demand, but Evohome kept the overall Heat Demand down and continued to keep the Target Flow at 49C. Same thing continued with 3 zones too. It proved that Evohome can deal with multiple zone Heat Demands, and if the temperatures are not far from the setpoint it won't kick the boiler into full.

    It also highlights an Evohome bug, don't think your heating around the house is OFF, just because your controller or your app says so. Local Override display obviously don't work when Heating Off is in operation. So your kids could be playing with the radiator controllers and you'll be scratching your head trying to work out why the boiler is on in the middle of summer. The App and the controller showed no signs of me changing the setpoint while the Heating Off was in operation.

    Thank you Dan for taking the time to code the Heat Demand functionality into Domoticz.

    p.s. : What I have noticed is that the boiler is run almost at 50% max flow temperature for a 0.5C difference to setpoint, 1C difference to setpoint and it runs at 75%, anything higher than 1C difference and the boiler is kicked to max. This demand could be even for a single zone, so all the zones can experience overshoots if they have any Heat Demand and a single zone is below 1C from set point.
    Thanks. You have done tests to the limit of natural behavior (0.5 degrees) and good to know that you have demonstrated evohome can provide proportional control.
    I have passed back your observation that local override does not appear when 'heating off' is enabled. For now tell the kids to leave the rads alone ;-)
    getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

  7. #7
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    I guess a better way to be consistent would also be to allow zone overrides via the controller, during any Quick Action being in operation. There could be times when you need the entire Heating Off, but still want a single zone on. People would previously think that wasn't possible because of the controller and app limiting that. But what I found out was that local overrides are still possible, which is great and that fact just needs reflecting on the UI. I have since confirmed that this bug appears to only affect the Heating Off quick action.

  8. #8
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    Quote Originally Posted by bruce_miranda View Post
    It also highlights an Evohome bug, don't think your heating around the house is OFF, just because your controller or your app says so. Local Override display obviously don't work when Heating Off is in operation. So your kids could be playing with the radiator controllers and you'll be scratching your head trying to work out why the boiler is on in the middle of summer. The App and the controller showed no signs of me changing the setpoint while the Heating Off was in operation.
    I've known about this ever since I've had Evohome and I'm pretty sure I've discussed it in multiple threads. I'm not sure I'd call it a bug as such, but just a consequence of the way the system is designed.

    The heating off action only sets the set points of all the zones to 5 degrees, disables the schedule, and prevents further overrides via the control panel (or Phone App/API) but it doesn't stop the controller from forwarding on heat demands from HR92's to the boiler, and for very good reason.

    If the heating off mode prevented heat demands from being forwarded then frost protection could not work because the HR92's couldn't call for heat when the temperature dropped below 5 degrees. (or whatever your OFF temperature is configured to be - remember that you can customise the OFF set point, so it's not always 5 degrees)

    A consequence of this though is that if you manually turn up an HR92 (manual override is not blocked by OFF mode) then it will call for heat as normal and warm the room up even though the controller reports everything is off. (The only clue is the warmer than expected room temperature)

    If you check back in the big long wishlist thread you'll find a post from me where I suggested a few possible solutions to this situation.

    1) Only forward heat demands from zones in OFF mode if the measured temperature of the zone is below the frost protection temperature. This still allows frost protection to work, but prevents people manually turning up an HR92 from being able to fire the boiler. Another advantage is that when the OFF action is applied the boiler would stop immediately instead of after the up to 4 minute delay until HR92's close.

    or

    2) Make the controller actually display the real set point instead of OFF for a zone when a manual override of an HR92 is made. That way it is clear from looking at the control panel that one room has in fact been turned back on.

    or

    3) Send a command to lock the HR92 local override when the OFF action is used. This would result in "blocked" appearing on the HR92 if someone tried to adjust it while the controller was in OFF mode. (Might not work with a Y87RF though, as it doesn't honour the local override disable feature)

    Being able to manually turn up HR92's while the controller is in OFF mode without any indication on the controller is something that has started quite a few "why is my boiler running when the heating is off" threads on this forum alone so I think it's probably a fairly common occurrence especially in a household with kids or guests!

    Hopefully some improvement in the handling off the OFF mode will be implemented in a future software update.
    Last edited by DBMandrake; 31st March 2017 at 09:43 AM.

  9. #9
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    Did someone mention future software update

  10. #10
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    In a zone where a T87RF is being used as the temperature sensor this doesn't work. My Heating Off was in action. I changed the setpoint on the T87RF and nothing happened. The boiler didn't fire. But when I changed the setpoint on the HR80, that's when the boiler fired. So the over ride during Heating Off only works when it's done directly on the radiator controller.

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