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Discuss Vaillant Ecotec 630 - Flow Temp in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Graeme Stewart

    Graeme Stewart New Member

    Ok so am looking for a bit of guidance.

    Last year I had a Vaillant ECOTEC 630 Plus (System Boiler Version) installed to upgrade an old Keston something or other.

    According to the manual (and if I am reading it right) I should be able to set a target flow temp for the when the water Cylinder is calling for heat and a different flow temp when it is only the heating calling for heat.

    Currently, on the LCD control panel I can only set the temp for the heating as there is no option shown for the hot water.

    The house is underfloor heated throughout with no radiators which means ideally I would like a target flow temp of about 50 as this is what the manifold brings it down to anyway before it goes into the floor. (The boiler is set to 75 to get the cylinder to 60 when it needs it).

    My question is, could it be possible the boiler has been wired up incorrectly and doesn’t know the cylinder is there or is what am looking to do not even a thing and am misreading the manual.

  2. Brambles

    Brambles Active Member

    You are reading the instructions for the two channel version, or your boiler has been reconfigured for one channel operation

    Your hot water temp is determined by your cylinder stat setting - but you know that
    Last edited: Jun 18, 2019
  3. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Any pics of the boiler / pipework going into the boiler ?
  4. Graeme Stewart

    Graeme Stewart New Member

    Offft, you are going regret asking for these.... I still cant really follow it and have been in the house 3 years!

    20190618_172723.jpg Pipes into the Boiler
    Full Pipework
    Boiler Function Code


    So I am reading the manual as when it is heating water only it should have code S.24 but in reality it is saying S.04 which makes it make think the cylinder has been connected as part of the heating circuit as that is the code for heating.

    Also the simpleton in me thinks there are two cables going into the boiler. One for power and one for the heating? Should there be a third for the cylinder? I have had a look at the install manual and apparently there is a contact for "Cylinder Contact C1/C2" so I was thinking should there be a third cable to there?

    BTW I have an extremely limited knowledge of plumbing so I could be doing 2+2 and getting 6 so if I am being thick please say.
  5. Graeme Stewart

    Graeme Stewart New Member

    That's a fair point.

    I do not have a central control point to switch off the heating. It all runs off individual thermostats in each room which can all switch the boiler on. Maybe the cylinder is just connected into the same junction box making it single channel?

    When the boiler was install I asked them to put in a controller for the cylinder to add time control as is was only on thermostat control before which is the white panel in the pic above but they didn't touch the original wiring.
  6. chris watkins

    chris watkins Plumber

    You are correct the boiler needs a sensor installed so that it knows when the hot water cylinder needs heating & can increase the temperature of the water it is sending out the heat it up.

    If you want the boiler heating to work correctly with the U/F system you will need to find a specialist heating engineer to make some adaptions to the pipe work & controls. It needs hydraulic separation & removal of the auto-bypass.
    • Agree Agree x 2
  7. chris watkins

    chris watkins Plumber

    Looks to me like a diy job all those mixed fittings, safety valve discharging into overflow etc etc.
    What part of the country are you ?
  8. Graeme Stewart

    Graeme Stewart New Member

    Thanks Chris.

    I will need to find a UFH specialist, something which seems to be a very rare thing where I am (Glasgow).

    I have the original plans for the system from when the house was built which interestingly don't cover the attic install so wouldn't surprise me if it was a bit of a DIY situation.

    Might also explain the uneven floor boards upstairs if they have been getting cooked for 15 years but that is another problem!
  9. chris watkins

    chris watkins Plumber

    Hopefully you have received a link in a PM if not please let me know.
  10. Harvest Fields

    Harvest Fields S. Mod Trusted Plumber GSR Top Contributor!!

    Does that mean it is one of your Chris?
    • Funny Funny x 1
  11. SimonG

    SimonG Trusted Plumber

    By eck that's rough.

    Is that a hint of an unvented cylinder?
    • Agree Agree x 2
  12. EvilDrPorkChop

    EvilDrPorkChop GSR

    You won't be able to set temperature of the Cylinder as it doesn't look like you've got the matching Vaillant controls.

    Having the Vaillant VR66 wiring centre, Vaillant temp probe and a matching Vaillant control panel will allow you to have HW priority, allowing you to set the flow temperature of the cylinder, KW input for the coil and the set point of the cylinder. Without this the boiler will just use the standard Switch Live from your existing controls and therefore cannot determine between heating or HW demand.
    • Like Like x 2
  13. Graeme Stewart

    Graeme Stewart New Member

    Yes it is with another expansion tank tucked round the back. It's quite the *cough* system I gather.
  14. chris watkins

    chris watkins Plumber

    It would be a bit of a trot even for me.
    • Funny Funny x 1
  15. chris watkins

    chris watkins Plumber

    Can you still use the temp prob to control an unvented ?
    I haven't done one of these but been to a few Evo's were the muppets have ripped out stats & replaced with prob.
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