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Thread: Evohome Hot Water and boiler flow temp?

  1. #11
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by bruce_miranda View Post
    But because the DHW schedule is triggered by the Evohome, the OT bridge seems to set the boiler target flow to 90C (i.e. max boiler flow temperature set). And it stays that way for the entire DHW ON scheduled period.
    Don't use OT here, but that doesn't sound right. Surely it should only do that when there's actually DWH demand?

  2. #12
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    OK ignore my last comment, I am talking nonsense! OT DOESN'T maintain the High Temperatures when DHW demand has been satisfied. I clearly need to change my medication.

  3. #13
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    Quote Originally Posted by bruce_miranda View Post
    I have maybe another issue with the way Opentherm has been implemented on the Evohome wrt to DHW demand. My DHW tank is set to 60C on the Evohome, but most days the boiler doesn't even need to heat the tank because the Solar panels have already done that and taken the temperature up to 62C (deliberately set that way). But because the DHW schedule is triggered by the Evohome, the OT bridge seems to set the boiler target flow to 90C (i.e. max boiler flow temperature set). And it stays that way for the entire DHW ON scheduled period. Evohome / OT doesn't seem to care that it doesn't need to heat the DHW. This just means that the boiler is working unnecessarily and heating up higher than needed but is only satisfying and CH demand. Ofcourse the boiler does a pretty good job of modulating, but again it's modulating between a higher than required flow temperature. Anyone else seen or noticed that?
    no, that sounds very odd. when my solar has pushed the tank temp over the temp set on the evo, then the evo HW kit doesn't fire. which is what you'd expect (thermostat says no, to rob a phrase from little britain).
    is your evo HW kit calling for heat mistakenly?

  4. #14
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    like I said @sandyman I was being stupid. Yesterday was the first day that the solar didn't heat the tank at all. And coincidentally the DHW tank took exactly as long as the scheduled ON period to get to target temperature. So when I saw the boiler target temperature held for the entire duration I thought something was wrong. I didn't even bother to look at previous days trends.

  5. #15
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    Quote Originally Posted by bruce_miranda View Post
    like I said @sandyman I was being stupid. Yesterday was the first day that the solar didn't heat the tank at all. And coincidentally the DHW tank took exactly as long as the scheduled ON period to get to target temperature. So when I saw the boiler target temperature held for the entire duration I thought something was wrong. I didn't even bother to look at previous days trends.
    yeah missed the second post. somewhat OT but curious - what solar thermal system you got that's still giving useful output on 13 dec? I have a 12 year old drainback, its gain is zero this time of year. PM if you want.

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