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Discuss Viessmann boiler set at max just to get enough heat in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. fronty

    fronty Member

    Just had a new Viessmann Vitoden 100w heat only boiler installed, I have to turn the dial all the way to max just to get some decent heat, if I turn it all the way (so it's pointing at reset) it'll settle at around 76 degrees. Is this normal? It's modulating fine, I was maybe expecting to set the dial at the dot at 4, but that's not hot enough to heat the hot water cylinder. Pump is on medium speed setting, any slower and some of the rads don't heat up.
    IMG_20181215_110622.jpg
     
  2. gmartine

    gmartine GSR

    Heating set point is too low.
     
  3. fronty

    fronty Member

    Sorry I dunno what that means, manual seems to indicate position 6 should be giving me 80+
     
  4. gmartine

    gmartine GSR

    Do you have weather compensation, call the installer back if not sure.
     
    Last edited: Dec 15, 2018
  5. king of pipes

    king of pipes Trusted Plumber GSR

    Town will be along shortly he fits these how many radiators do you have ? and what KW output is the boiler that you have had fitted . Cheers kop
     
  6. chris watkins

    chris watkins Plumber

    As above, why have you not called the installer back to sort it ?
    How long are you leaving it on for.
     
  7. chris watkins

    chris watkins Plumber

    Just turned my one up to max & got high 60's so I would guess you have Weather comp on, If you boost the hot water does the rad disappear to be replaced with a tap?
     
  8. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    80 + , no chance its a condensing boiler , as others have said is it on WC ? Is there a bypass ?
     
  9. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I would say it's modulating down due to the temp rise
     
    • Agree Agree x 1
  10. fronty

    fronty Member

    It was only installed on Friday - will be giving them a call tomorrow.
     
  11. fronty

    fronty Member

    26kw, 13 radiators.
     
  12. fronty

    fronty Member

    I don't think I have weather comp, no mention of it by the installer. I don't have a hot water boost, it's a traditional heat only boiler. Cylinder stat is set to 65.
     
  13. Gasmk1

    Gasmk1 GSR

    does the temp go up to about 65 degrees then drops down then back up then down if so its a flow problem the return temp is out of alignment with the flow (too great a difference)
     
  14. fronty

    fronty Member

    No once it's got up to temp and modulated the flame height down, the temp stays constant, have it running at 72 at the moment and seems fine although still not sure the rads are as hot as they were on my old Baxi.

    Something else I noticed, I've had a F2 fault code (temp limit) and noticed after the boiler shut down that the latent temp kept going up and up and up, seems I don't have pump overrun any more which I had on my old boiler. Something else to call the installer about tomorrow!
     
  15. fronty

    fronty Member

    Here's the heating curves, doesn't say what they are without WC though. But position 6 should generate temps between 60-90, hence wondering why I can't get more heat when dial is on max...

    heat curves.JPG
     
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