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Thread: Boiler firing with little or no demand

  1. #1
    Automated Home Sr Member
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    Default Boiler firing with little or no demand

    I've read a lot about issues here to do with the boiler firing when there is apparently no demand and missing RF messages etc., but evohome really does appear to do some odd things sometimes. I'm currently showing 5% demand in my office, it's the only zone showing any kind of demand and yet my boiler just fired for what seemed like less than a minute and the TRV only shows 37% valve position, so not sure if it's even actually open. This happened the other day and the boiler seemed to spend hours short cycling with no heat coming from the rad although it did eventually open the TRV a bit more and I started to feel the rad warm up a little.

    I also had similar the other night, there was a small demand from the conservatory and it felt like evohome was doing it's TPI thing, but with the TRVs effectively shut the boiler was just cycling on and off for over an hour until I heard an HR92 open a little more and finally some heat started entering the radiator.

    It does seem like there's a bit of a disconnect between when water can actually pass through a TRV and what TPI is doing. I assume it "learns" the characteristics of each zone over time so will know to open a TRV a little more in future if the room doesn't get up to it's set temp within a particular time frame (and/or does it adjust the TPI schedule?) - there seems to be a lot of variables here I guess when multiple zones are calling for heat with different demand levels.

    I guess the best thing to do is just not think about it and trust it to do it's thing, but it does annoy me when I heard the boiler fire for no apparent reason!

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  2. #2
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    Is it possible you have a room just on or close to the set temperature? I had this a few weeks ago and could not understand why the boiler fired but I found I had one room that for some reason was just below it’s setting although it felt OK. Adjusting the setting in the schedule cured it.

  3. #3
    Automated Home Legend paulockenden's Avatar
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    I spent ages trying to debug something similar, only to eventually realise it was my combi keeping the DHW feed up to temperature for instant hot water.

    D'oh!

  4. #4
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    Quote Originally Posted by paulockenden View Post
    I spent ages trying to debug something similar, only to eventually realise it was my combi keeping the DHW feed up to temperature for instant hot water.

    D'oh!
    Same for me in the early days of my combi. It defaults to ECO mode. I switched ECO off and suffer no disadvantages but it would annoy me firing up in the night for no reason other than to keep a small amount of water warm.

  5. #5
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    Had this again this afternoon, all zones showing 0% demand, yet the boiler was firing every 10 mins and then cutting out because I only had my bypass bathroom radiator to dissipate the heat, it was driving me mad, in the end I turned up a rad in my office thinking that when it reached the new set point it would send the "off" signal and shut down the boiler for good. I dunno if it missed the previous "off" command or something, but sure enough when the office reached the set point I had no more false firing. I don't normally have any wifi issues in this house as all the HR92s are well within range of the evotouch panel so it's a bit of a mystery what's going on here.

  6. #6
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    I logged a ticket with Resideo and they came back with quite a comprehensive reply, interesting comment about the antenna orientation on the HR92...

    Good afternoon,

    Thank you for contacting Resideo Consumer Support team. Your case reference is 09280420.

    What is happening here is that the evohome controller still believes there to be a small residual demand from one or more of the wireless radiator controllers.

    This can be checked by pressing the override button on the wireless relay, turning it off. It will switch back on within 4 minutes as it will still be receiving the demand message passed from the evohome controller.

    The reason the evohome controller does this is because it has not yet received a 0% signal from every wireless radiator controller. The 0% signal is only sent by the wireless radiator controller when it has fully closed the radiator valve. The calibration for this point is made when the wireless radiator controller is first fitted to the radiator valve. ('cycl' in the display) It is re-calibrated at regular intervals.

    There can be several reasons why a 0% message has not been received:
    Signal weak from one or more radiator heads. If the signal is weak then it may need to be resent several times before being received correctly. Test the signal strength to each zone using the RF signal check menu on the evohome controller. Follow the instruction in the manual. Any units returning a 'poor' signal strength could cause a delay in messages. Consider re-siting the evohome controller to improve reception.
    Interference causing messages to be corrupted. Messages will be resent until received correctly, but this will cause a delay. Check the location for other causes of wireless interference, example. cordless telephones, WiFi routers and re-site devices as required. At least 1 meter should be considered the minimum for efficient operation.

    Weak or incorrect batteries. This will cause a weak transmission or not allow the controller to fully close the valve. Check the batteries are good quality alkaline.

    Radiator valve stiff to operate. This will prevent the wireless radiator controller from properly operating and closing the valve. Parameter 10 in the installer menu will allow the display to show the valve position and verify if the valve is fully closed. In addition option 6 may be selected to operate the wireless radiator controller in full stroke mode which may improve the operation on valves with longer or stiff operation. This will also result in higher battery consumption. The valve position can be recalibrated by unlocking the head from the valve adaptor and removing the wireless radiator controller head, then refitting. The display will show 'cycl' after a short period.

    Make sure all the wireless radiator controllers are properly fitted to the adaptor, and the adaptor is hand tightened to the valve. The wireless radiator controller should be secured with the locking button beneath the display.

    If some zones have multiple radiator controllers, then following a manual override they will all receive and then try to send a close message at the same time. The resulting wireless message collisions will delay some devices messages from being received. This will not affect normal operation when each valve will decide independently when to send the message, only a manual override has this effect.
    The antenna is on the left hand side of the HR92, try positioning this side away from the radiator or wall to aid clean communication with minimal interference, otherwise look for another location, orientation or height for the evohome controller.

  7. #7
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    Thats nonsense. my evohome was doing the same. I spoke to resideo as well and wasted time rebniding/resposition controller. The issue happens when the outside temp is high and the demand is very low.

    I have been able to mitigate this issue by setting boiler ignore anything below 45 or 50 cannot remeber now for sure.

    Also latetst FW helped the issue a bit but the issue is defo cause by FW on eveohome

    This is a known issue with evohome/opentherm. Have a look at my older posts.
    Last edited by m112; 11th September 2021 at 10:36 PM.

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