Vaillant EcoTec 831 - Help with setup

Discussion in 'Plumbing and Central Heating' started by Ian Clarke, 18 Jan 2021.

  1. rbranco

    rbranco

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    What I am surprised is that on the 4xx series they do not expose the PWM output for external pump use, do they only use it for the combi side, what is special about the other boilers that they can use PWM and not regular ones, I find this odd. I have a older 418 before ErP so I would be pre that but I do have a UPS3 but on constant speed.
     
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  3. Ian Clarke

    Ian Clarke

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    Do you know if can add a weather compensation to the VRT350F with the boiler or would have to look at replacing the lot. Think issue is VRC700F costs £210.00 so expect would take years to make that outlay back.
     
  4. ScottishGasMan

    ScottishGasMan

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    No you can't add WC to a 350f.
     
  5. Ian Clarke

    Ian Clarke

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    Cheers thanks for the quick reply, so its either 470f if find stock cheap, 700f or vsmart then
     
  6. rbranco

    rbranco

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    Look at the new VRC720f, the latest model and even works fine with my 418/VR66 setup over ecobus.

    Forget about the VRC700f, its old and has no temp control per timeslot and other issues with override temp.
     
  7. Ian Clarke

    Ian Clarke

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    Scottishgasman

    Take into account that a 10kw heat loss on a boiler with a heat exchanger and pump designed for 30kw is rarely going to manage a 20 degree flow and return difference.

    If you strangle the radiators to get 20 degrees then your also dropping the heat output of the radiators so in effect reducing their ability to get heat out.

    The most practice solution is to simply drop the flow temperature of the boiler



    SORRY reading that reply again, are you saying should leave d0 at 24 as that’s what boiler designed for and just alter temp to either 60 or 65 depending what’s better and by altering d0 down to 10 it’s making situation worse?
     
  8. ScottishGasMan

    ScottishGasMan

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    I was refering to people aiming to have a 20 degree difference between D.40 and D.41.

    You still deffo should change D.0 to 10kw or whatevers closes to your expected heat loss, and also just adjust the flow temp seasonally to what seems good for your house, ie 65 in winter, 50 spring/autum or the likes
     
  9. Ian Clarke

    Ian Clarke

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    Well what a week, thanks to you guys Id got the gas down a third, staying in the 50 not 75kwh a day, and then yesterday afternoon noticed it staying on and the receiver for the 350f in front of boiler grren light gone out, spoke to Vaillant as only got in Dec and told it's died and needs replacing, so back to plumbers merchant today for a weather comp version..

    So one question - I know with weather comp the rad temp take to max and it controls it on the graph depending on outside temp. Do I leave D0 on 10, I did an heat loss calc and got 9kwh and rads calc came to 9.5kwh but boiler manual says d0 is fully modulating, however i am think the weather comp only modulates the flow temps or does it also modulate the gas flow depending on requirements ?

    thanks in advance and for all your help this week
     
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  11. ScottishGasMan

    ScottishGasMan

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    WC only modulates flow temp, so leave D.0 on 10. (D.0 being fully modulating left at max means boiler will run on max power till flow temp gets near set point then it will modulate to what it needs to be, so better letting boiler know the rough output (10) and not having it run away with its self)
     
  12. rbranco

    rbranco

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    Wc targets a certain flow temp, the boiler decides the gas flow.
    Setting d00 correctly prevents overshooting flow temps and boiler tripping out.
     
  13. rbranco

    rbranco

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    Get the vrc720f if they have it. I got mine from Mr Central heating, next day delivery.
     
  14. Harry Bloomfield

    Harry Bloomfield

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    I agree with the override issues - I am seeing them, but I wonder what you have heard?
     
  15. rbranco

    rbranco

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    I've got a vrc720f that I installed a few says ago, what do you want to know.

    Old 700f depending on version...
    - no temp control per timeslot
    - override hard to cancel (resolved on later version)
    - one click on override makes temp permanent

    The cost is the same, so no point getting older model.
     
  16. Harry Bloomfield

    Harry Bloomfield

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    I was just wondering if the reported issue with the 700F was one of the overridden temperature sometimes making itself the permanent one, without pressing the OK button. That is what my 700F seems to sometimes do. In the past I have blamed my partner for nudging the room temperature up and pressing OK, but she assures me she doesn't.

    I have also noticed when the HW on/off time is overridden to put it on outside normal on times (boost), it seems to stay on an excessive amount of time. I would expect on, then back off once temperature is achieved.
     
  17. rbranco

    rbranco

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    They have removed the option to set permanent on the 720f, if you want that then go into schedule and adjust. Once you are on override (and how long) the screen just shows the new temp with a line under saying press << to cancel, its clear and remains like that until time has expired.
    Ive not noticed myself on boost HW, it does ask you if you want a one time boost so I would expect it to reach temp then stop, you set the cylinder temp in the controller not the boiler (boiler is set to 60 and controller to 60, the lowest takes priority but I guess if the controller was higher than boiler you would end up with a long boost time).
     
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