F23 error Vaillant EcoTec Plus

Discussion in 'Plumbing and Central Heating' started by tan8856, 22 Nov 2009.

  1. tan8856

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    Hi

    Im hoping someone can explain to me why we keep getting the F23 error message and how we can prevent it happening again.

    We have a combi boiler (downstairs) and a hot water cylinder (upstairs). As far as I understand it the combi heats the hot tap water downstairs directly, all the rads in the house, the underfloor heating we have in the upstairs bathrooms and the hot water cylinder upstairs.

    A month ago we got the F23 error. A vaillant engineer said it was because we have the rads upstairs on low which is causing a significant temp diff between the combi flow and return which causes f23. He made some adjustments to the boiler and said it shouldnt happen again.

    Yesterday we decided to test the piped underfloor heating we have in the upstairs bathrooms. Weve never used it before. The previous owner of the house said it may take 1-2 days to heat the floor tiles up which sounds like a long time to me but i know nothing about UFH. After leaving it on for 24h the tiles were still stone cold and the combi fell over with the f23 again.

    Weve turned the UFH stat right down and darent try using it again!

    So I guess its 2 questions really...

    1) Anyone know whats going on with the combi and how we can stop f23?

    2) Can someone explain my UFH? How come the tiles were still cold after 24h? When we turn the stat up the boiler fires up but it wasnt firing for that whole 24h period, it kept stopping and starting periodically. Also, surely the UFH wouldnt be running during the night when our heating is turned off? The previous owner said the UFH is on the same circuit as the towel rads but the towel rads have always worked fine and come on with the room rads when the UFH stat is turned right down. (ps the previous owner built this house).

    We are confused :confused:
     
  2. kevplumb

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    F 23 water shortage temp spread between flow and return ntc to large :idea:
     
  3. spudkey

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    has the ufh got a manifold with a pump and mixing valve
     
  4. jackthom

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    F23 happens when the flow of CH water through the boiler isn't sufficient to quickly carry away the heat being generated.

    For example if the pump isn't set to a high enough speed or more likely in this case if there's some restriction in the radiators/pipework.
     
  5. dangermouse46

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    Has the boiler been range rated? What size is the flow and return pipework? How clean is the system? What bypass arrangement is there? Is the boiler aav open? Has the system been balanced properly?
     
  6. tan8856

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    I know little about boilers but will try and answer some of your questions...

    has the ufh got a manifold with a pump and mixing valve
    sorry no idea, what do they look like and where would they be?

    F23 happens when the flow of CH water through the boiler isn't sufficient to quickly carry away the heat being generated.
    For example if the pump isn't set to a high enough speed or more likely in this case if there's some restriction in the radiators/pipework.

    Thats exactly what the vaillant guy said. What he did was turn down the heat being generated by the boiler (i think??)

    Has the boiler been range rated?
    Dont know but previous owner built this 4-bedder and said combi was up to the job.

    What size is the flow and return pipework?
    Around 22mm

    How clean is the system?
    Good question! We had lots of problems with gunk when we first moved here and have had 2 power flushes (got them back again as didnt do first flush fully!) So it should be very clean but our magnaclean is still picking up some gunk, not a lot though.

    What bypass arrangement is there?
    Sorry dont know

    Is the boiler aav open?
    Sorry dont know

    Has the system been balanced properly?
    The guy who did the flush said he balanced all the rads to work optimally.
     
  7. kevindgas

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    to find out if the boiler has been range rated

    press i and hold whilst pressing +
    d.0 should now be displayed
    press i and it should show = then a number this is the kw setting if it is 24 then boiler has not been set and is running on maximum

    press the button with a line through a flame to reset the boiler to normal operation

    how many rads do you have?
     
  8. tan8856

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    i will get back to you re the range rating.

    we have 18 rads.
     
  9. Agile

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    There are too many unknowns about yourt system.

    The boiler is quite capable of running what you have but a competent boilers would be needed to design and fit that system.

    It sounds like a bodged DIY job with a UHF part which does not work.

    The UFH should have a manifold, blending valve and a pump! Surely you could recognise a pump somewhere?

    Tony
     
  10. tan8856

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    The reading is 15.
     
  11. tan8856

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    We have a pump next to the HWC that powers the showers, a stuart turner, could that also be doing the ufh? There are also a couple of small white boxes that occasionally whirr, are they pumps?

    There is nothing obvious to me in the airing cupboard (or anywhere else come to that) that screams ufh.
     
  12. kevindgas

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    then yes its been range rated but !!

    if you have 18 rads then there should be no need to range rate it.

    the way we range rate them is to allow 5,000 btu per rad (irrespective of size as some are over, some are under) this divided by 3412 = kw's
    so 18x5,000/3412 = 26.3 Kw's

    it sounds like the fault is with the design of the system not the boiler. and as suggested it may be something to do with the UFH, its mixer and the bypass around it.
     
  13. Agile

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    Why not make life simpler for yourself and avoid the need for a calculator?

    Just say 1.5 kW per rad making 27 kW which you can work out in your head!

    Tony
     
  14. Agile

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    Of course I would leave the setting at 15 for the moment so the boiler is operating more efficiently. It can always be increased if it gets cold.

    Now after 11pm it still 9.8° C outside!

    The heating demand is currently only at 50% of the maximum which is only required when its -1°C outside.

    Tony
     
  15. kevindgas

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    cause i'm an old git set in my ways!!! :LOL: :LOL:
     

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