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Thread: Evohome - boiler on VERY frequently

  1. #21
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    Quote Originally Posted by Rameses View Post
    Yes - and the action of opening of the valve will fire the boiler (have the same at home)
    It's not there on an s-plan set-up! It is only there if you have a boiler relay BDP91 which is a heating only configuration, or a figure 4 configuration

  2. #22
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    afraid I'm the same as Jonstatt - I don't have this option either as I don't have an actual boiler relay.


    So, I did some (rather sad) investigating overnight, and found that my Evohome system is calling for heat every 10 mins but only for about 30-40 seconds. I have used a couple of old IP cams I had laying around to video the boiler status display and, separately, the BDR91 relay box. This is a tiny sample from the video (which is hours long):



    The video shows separate shots of the BDR91 and the boiler at or around 3.05am (time stamps aren't exactly sync'd, one camera was slightly behind - but it does serve to show how long the heat demand was).

    As you can see in the first part, there is an extremely short call for heat from the relay box lasting only about 30-40 seconds. The second part of the video (blurry I know) shows the boiler's response, initiating firing and then actually firing - but by the time it has fired, Evohome has switched it off again, so the boiler is in action for maybe 10 seconds - which is as good as useless.

    This repeats every 10 mins. Why would Evohome be calling for heat every 10 mins, for less than 30 seconds each time? This can't be good for the boiler itself, especially as the pump and fan run on for 5mins after each of these pathetic 10 second runs!

    Something's not right, and I doubt it's the binding.

    ANY advice appreciated.
    Last edited by garmcqui; 14th March 2015 at 06:57 PM.

  3. #23
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    Quote Originally Posted by garmcqui View Post
    afraid I'm the same as Jonstatt - I don't have this option either as I don't have an actual boiler relay.


    So, I did some (rather sad) investigating overnight, and found that my Evohome system is calling for heat every 10 mins but only for about 30-40 seconds. I have used a couple of old IP cams I had laying around to video the boiler status display and, separately, the BDR91 relay box. This is a tiny sample from the video (which is hours long):



    The video shows separate shots of the BDR91 and the boiler at or around 3.05am (time stamps aren't exactly sync'd, one camera was slightly behind - but it does serve to show how long the heat demand was).

    As you can see in the first part, there is an extremely short call for heat from the relay box lasting only about 30-40 seconds. The second part of the video (blurry I know) shows the boiler's response, initiating firing and then actually firing - but by the time it has fired, Evohome has switched it off again, so the boiler is in action for maybe 10 seconds - which is as good as useless.

    This repeats every 10 mins. Why would Evohome be calling for heat every 10 mins, for less than 30 seconds each time? This can't be good for the boiler itself, especially as the pump and fan run on for 5mins after each of these pathetic 10 second runs!

    Something's not right, and I doubt it's the binding.

    ANY advice appreciated.
    The 3am is significant, it is the start of a new day.

    I heard of this before and if I remember correctly it was incorrect binding to do with the Heating relay being double bound as boiler relay.
    You need to do a clear binding on both heating and hot water relays (hold down grey button for 15 seconds, yes 15 seconds until the red light blinks 0.1 sec on 0.5 seconds off

    Then go into installer mode, system devices and make sure under 'heat demand' it says NONE
    Then in installer mode do guided config for the HOT WATER path, bind the hot water sensor then bind the BDR91 relays as 2 x 2 ports, heating and hot water respectively

    You don't need to redo the guided config for the zones if you don't want, existing settings will not have been erased

    Let me know if this resolves this behaviour, thanks!
    I work for Resideo, posts are personal and my own views.

  4. #24
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    Hi Top Brake,

    It wasn't just 3am though, I just happened to choose this time as an example. The same thing happened at from 10am last night (when I started recording), then 10.10, 10.20, 10.30 and every 10 minutes (approx) all the way through until 5am when the boiler came on for longer due to hot water demand.

    Regarding the double binding - since installing it, I have always had the "Boiler Demand" set to NONE - but Rameses above seemed to suggest that myself and Jonstatt should be able to see settings such as cycle rate, minimum on time etc, which we couldn't.

    Tonight I have done a factory reset on the Evohome controller, removed the batteries for 30+ mins, done a hard reset on each HR92 and cleared the binding on both BDR91 relays.

    I am now in the process of slowly rebinding them, being sure to leave plenty of time between each one so as not to confuse it.

    Thanks, and apologies if the above is confusing!

    Gareth
    Last edited by garmcqui; 14th March 2015 at 08:03 PM.

  5. #25
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    Was there a zone that was anywhere close to the setpoint? In other words: was there any reason for the boiler to be fired at all?

    I've personally never seen Evohome firing my boiler when there was no zone to request heat (all set to OFF for example). If you would see it, I would suspect misconfiguration and that the reset/rebind would fix that.

    Let's wait and see

    If there WAS a zone rightfuly requesting heat, then the question would be how to raise the minimum ON time. 30-40 seconds is useless indeed and I thought the minimum always was 1 minute?
    Last edited by erik; 14th March 2015 at 10:28 PM.

  6. #26

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    Gareth (garmcui) let us know how it goes.

    Agree with topbrake - this behaviour is consistent to double binding. Interesting fact - the BDR91 has 4 'address slots' internally for binding (Top brake will correct me here I am sure).

    The minimum on time setting (under system parameters) is "This setting is used to prevent damage to the boiler by allowing it to keep running until it has stabilised before shutting down" / Check the boiler manufacturer handbook for the required minimum on time for your boiler"
    <copied this from the ? hint in the device menu >

    When you do get around to setting this - the default is 1min - but check your boiler specs (some larger older ones might be longer etc)
    Last edited by Rameses; 14th March 2015 at 11:18 PM.
    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. #27
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    thank you both for your replies.

    There was a room which was being kept at 18C all night (due to new baby), all other zones were set at 5C overnight so were all well above the setpoint.

    However, with regards to amending the minimum on time and cycle rate, like Jonstatt, I can't amend this as I don't have a boiler relay.

    The boiler has a manufacturing date of 2014 (house is a new build) , so not old.

  8. #28
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    Quote Originally Posted by Rameses View Post
    Gareth (garmcui) let us know how it goes.

    Agree with topbrake - this behaviour is consistent to double binding. Interesting fact - the BDR91 has 4 'address slots' internally for binding (Top brake will correct me here I am sure).

    The minimum on time setting (under system parameters) is "This setting is used to prevent damage to the boiler by allowing it to keep running until it has stabilised before shutting down" / Check the boiler manufacturer handbook for the required minimum on time for your boiler"
    <copied this from the ? hint in the device menu >

    When you do get around to setting this - the default is 1min - but check your boiler specs (some larger older ones might be longer etc)
    Indeed 4 binding slots in a BDR91, very rare that you would need to use them all. Most I have seen being 3 x evo bound into one BDR91 boiler relay (mansion with 3 floors...)

    As previously advised you need to match the evohome to your application and if your boiler would benefit from specific cycle rate and minimum run time you need to install the system with a boiler relay.
    This is possible in both combination and heat only boilers.
    The only reason evohome is supported for S Plan and Y Plan is to make retrofit easy. If you have a new stored hot water installation go for Figure 4 (single hot water valve and boiler relay).

    A fully optimised installation will also include a system bypass valve, and on modern high efficiency condensing boilers you may need to set up flow and return temperatures and anti cycling parameters.
    In this case your heating engineer should be consulted.
    I work for Resideo, posts are personal and my own views.

  9. #29
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    Hi top brake.

    A system bypass and valve is already in place.

    The figure 4 setup would require replacing the existing 2 port valves for a three port valve - yes?

    I see what you say about consulting a heating engineer, but regarding flow and return temperatures, or the boiler's cycling parameters, I can see how these would be important if it were the boiler itself which was determining the time to come on and turn off, but in my case the Evohome system is turning the boiler on for a useless amount of time, as evidemced by the relay in the video.

    I will monitor the boiler and relay overnight again to see if the full reset has done any good.

    I hope so. Will report back tomorrow.

    Thanks

  10. #30
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    Quote Originally Posted by garmcqui View Post
    Hi top brake.

    A system bypass and valve is already in place.

    The figure 4 setup would require replacing the existing 2 port valves for a three port valve - yes?

    I see what you say about consulting a heating engineer, but regarding flow and return temperatures, or the boiler's cycling parameters, I can see how these would be important if it were the boiler itself which was determining the time to come on and turn off, but in my case the Evohome system is turning the boiler on for a useless amount of time, as evidemced by the relay in the video.

    I will monitor the boiler and relay overnight again to see if the full reset has done any good.

    I hope so. Will report back tomorrow.

    Thanks
    No need to replace any valve, you can simply latch open the existing 2 port heating valve or remove it. Then re-use the existing heating relay as a boiler relay. When installing like this you need HR92 on the radiators. There is a small typo in the evohome manual at figure 4, should say V4043.

    I am not saying you need to make adjustments to the boiler, your boiler installer may need to change the settings for you now an evohome system is installed if previously no TRV were fitted. A modern high efficiency condensing boiler is a very sophisticated appliance with a modulating gas valve and clever control electronics (incidentally often made by Honeywell). The Honeywell product design and development team understands these capabilities and evohome was developed to work in harmony.
    I work for Resideo, posts are personal and my own views.

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