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Vaillant ecoTEC DHW Temperature Setting

Discussion in 'Plumbing and Central Heating' started by exocet, 5 Jan 2010.

  1. exocet

    exocet

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    Location:
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    Country:
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    I've had an ecoTEC for the past 2 years with no complaints.

    It is configured with Open Vent in S Plan' configuration.
    DHW is via Megaflo pressurised cylinder.

    With rising gas prices, like many people I've been looking at efficiencies etc and as such I am looking to fit an external weather compensator.

    Whilst looking into the whole 'condensing boiler efficiency' subject I note that in reality you need to run boiler at low temps to achieve best (any?)efficiency. Setting the heating curves on the weather compensator will be interesting - during the past few days I've left the heating on 24hrs @ 56 degs flow and have a house that is lovely and warm. That would indicate a flat heating curve should surfice but I know that if I did that and reverted back to a more usual heating on / off time for say 3 Hrs in Morning and 6 hrs in evening that my house would never reach a comfortable temp. I understand the link between flow temp / outside temp / internal room temp but what allowances are made for warm up times?

    Anyway - to get back to the point, my Vaillant was installed without the VR 65 control centre (my installer didn't inform me of the need) as such I can only have one temperature (heating flow temp) - if I set this low, I'll never get DHW to 60 degs. At the moment I am manually setting this for DHW when I heat the water (how sad is that!!).

    What I don't understand is why the Vaillant boiler has a max flow temp of 75 degrees? If I want DHW at 60, the boiler will invariably spend 20 minutes in anti cycling mode to achieve the last 5 degress or so of DHW temp (return temp reaches 60 degrees, boiler goes into anti cycling mode).

    I see that the boilder can be set to 82 degrees via service mode - surely this would be better for achieving 60 deg DHW with less time wasted anti-cycling?

    If I increase max flow temp, do I sacrifice something else? I guess what I'm really trying to understand is that I want to have lower boiler flow temps on average but want DHW to heat quickly. The Vaillant manuals state that the default for Heating and DHW is 'one or the other but not both at the same time' makes sense if you are going to have different Flow temperatures for each application BUT in very cold weather, I don't want my heating going off for an hour whilst the DHW is heating up if the time can be reduced by increasing max flow temp to 82 degrees.

    Does anyone here have any experiences?
     
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  3. kevindgas

    kevindgas

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    you need to change the wiring centre to a VR65 - simple

    you will then be able to set the two sections to different temperatures
    the boiler connects with the VR65 via ebus.
     
  4. exocet

    exocet

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    Thanks Kevin

    Understand the VR 65 concept but should I also change max boiler flow temp to stop / reduce the anti-cycling when the DHW cylinder temp approaches 60 degrees? The factory default is 75 degrees but service mode allows this to be increased - my simplistic thinking is that higher flow temp = better temp differential between Flow temp and stored DHW temp = faster warmup time. As I say, at 75 degrees, DHW temp gets to within a few degrees of target temp but then spends 3 anti cycling 'cycles' to reach the magic 60 degrees....seems wasteful to me both interms of time and gas
     
  5. DIYnot Local

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