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Heating and cooling: Stopping thermo-syphoning from thermal store and log boiler

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    • CommentAuthorjwd
    • CommentTimeOct 4th 2012
     
    I have noticed that my log gassifying boiler stays far hotter than it should after it has gone out. This leads me to believe that there is a form of thermo-syphoning going on with a flow of warmer water from the tank cooling in the boiler (an ecoangus) and going along the return back to the bottom of the tank. Any suggestions about how to stop this? Could i put in a non return valve in the return from the tank to the laddomat to allow water to flow from the tank to the boiler but not back again? Or would that be risky?

    Cheers

    Jw
    • CommentAuthortony
    • CommentTimeOct 4th 2012
     
    Fit a check valve, non return valve?
  3.  
    Have you checked with your Installer S & S Microgeneration if i am correct as he has fitted 50 of these in your area so he knows the product well?
    Always best to check with them first as he is an MCS accredited Installer. It should take 36 hours to go from 90°C to ambient temperature after batch burning.
    • CommentAuthorbillt
    • CommentTimeOct 4th 2012
     
    The Laddomat already has a non-return valve, it's inherent to its operation. If Winterbournes' suggestion is not correct, it would seem likely that, either that valve is stuck open, or there is some error in the installation.
    • CommentAuthorowlman
    • CommentTimeOct 4th 2012
     
    Posted By: jwd:
    Could i put in a non return valve in the return from the tank to the laddomat to allow water to flow from the tank to the boiler but not back again? Or would that be risky?

    I always thought that any form of check valve on the main boiler/store, flow and return was considered bad practice, bearing in mind the relatively uncontrollable way log gas boilers funtion. As billt said the loading valve already has or should have, that capability. If the loading valve is not at fault and it appears to be a system design problem, and you do decide to put in a check valve a "swing check valve" may be the best option.
  6.  
    My understanding of the Laddomat's working is that it is designed to be open circuit when the pump is not running. This is to provide a thermosyphon in the event of a power cut whilst the stove is lit and of course if the plumbing to the TS will support a thermosyphon.
    So it is quite possible that you are getting a thermosyphon back to the boiler. If you put in a non return valve, as Owlman said put in a swing check valve (non return valve designed for gravity circuits) but be sure to install it according to the instructions if you are wanting the thermosyphon to work in the event of power cut (the angle of installation of theses valves is critical).
    • CommentAuthorfinny
    • CommentTimeOct 4th 2012
     
    It will only thermosiphon if the store is below the logboiler which would be unusual?
    It could thermosiphon around the heating system, as Peter says, swing check valve will solve that..
    Sounds more like the laddomat is running on.. flue stat setting?
    • CommentAuthorjwd
    • CommentTimeOct 28th 2012
     
    Sorry about the delay in replying to all of this - no time and no internet access .

    @ winterbourne - Guy - 36 hours to cool down. I will check and time it. I havent hassled the installer about this as I am trying to inform myself as much as anything. There is no point in getting him to drive all the way out here to check something I can do myself especially as we need 36 hours to test it. If I can find a period of relatively similar weather I might consider closing a valve on the laddomat once the boiler has gone out and compare it to the "valve open" cooling time.

    @ Owlman and Peter in Hungary - Thanks - a good suggestion. I wont consider it until I have excluded Winterbourne's suggestion but it is useful to know that there is something that could be used. Incidentally - where would you put it - on the flow or on the return.


    @Finny - We dont have a flue stat in our set up. Ours works off a stat in the boiler which can cause the boiler fan to continue running long after the stove has gone out as the fan wont switch off automatically until the water in the boiler has dropped to 65 deg ( I think). I have discussed the possibility of putting a flue stat on but I dont want to lose the anti freezing feature that starts the pump running once the water in the boiler drops below a certain level. I have no real idea how to get a control system that would allow both a boiler stat and a flue stat to interact together- any suggestions. The installer has been scratching his head on this one for a while - he may have come up with a solution by now.

    Many thanks for all your helpful comments. Ill feed back what I find.

    Cheers

    Jw
    • CommentAuthorTimber
    • CommentTimeOct 28th 2012
     
    I have a wood burner and thermal store (using a pumped system) with the boiler and the thermal store at the same level. Even with them at the same level, it does still (slowly) thermo syphon back from the store to the boiler.
    • CommentAuthorjwd
    • CommentTimeOct 28th 2012
     
    @ Timber- Mine is on the same level too. the only pump involved in ours is the one in the ladomatt.

    Jw
    • CommentAuthorTimber
    • CommentTimeNov 1st 2012
     
    To solve it I have fitted a crude non-return system

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