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my baxi megaflo 32kw system boiler cycle - is this normal?

Discussion in 'Plumbing and Central Heating' started by andreitone, 28 Nov 2008.

  1. andreitone

    andreitone

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    Hi,

    CH water temperature is set at 55 deg Celsius

    this is how it cycles:

    burner starts at 42 deg, heats the water at 58 deg in 10 seconds, then after 2 minutes the burner stops when the water reaches 60 deg.
    the water temperature drops at 45 deg in about 30 sec, then after about 3 minutes the burner starts at water temperature of 42 deg.

    I don't know exactly what temperature is shown on the display but I think is the return temperature.

    I do think it's cycling too fast burner on/off and when the burner starts the water (return) heats up too quickly, I think it's because of the automatic integral bypass.

    My question is:

    Is this normal functioning?
    Is there a way of adjusting the automatic integral bypass in this type of boiler?

    Thanks
     
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  3. spudkey

    spudkey

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    does it do this from cold, how many rads do you have do you have a room stat
     
  4. andreitone

    andreitone

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    thanks for the reply.

    It doesn't do this from cold, but in normal cycling. I have 7 radiators and no room stat yet, also no TRV's on the rads.

    The rads are set as to have a 20 deg celsius differential on the return (so if 55 deg on the flow there is 35 deg on the return).
     
  5. spudkey

    spudkey

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    32kw is a big boiler for 7 rads how was this boiler sized, if you are trying to get 20c temp drop across rads by balancing lockshield valves then i think the bypass will be opening. Even at lowest modulation this boiler gives 9kw this is enough for many 3 bed houses
     
  6. David937

    David937

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    Have you tried a higher flow temperature?
     
  7. Agile

    Agile

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    It seems to me that this boiler has been massively oversized!

    For a start you could set the boiler to minimum output power although even that will be far too much!

    Tony
     
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  9. andreitone

    andreitone

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    I have tryed 60deg but did not watch it's cycle


    For a start you could set the boiler to minimum output power although even that will be far too much!

    Agile how can I do this?
     
  10. andreitone

    andreitone

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    thanks for the reply spudkey, would you think that a 10 deg temp drop across rads and lowering the CH water temperature will help the boiler not cicling as much?
     
  11. David937

    David937

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    Tony can you set the boiler to minimum rate by adjusting the Min rate adjustment screw?
     
  12. Agile

    Agile

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    No, you call the installer and ask him to set it at the minimum output.

    However, as he seems to have fitted a boiler which is totally oversized I would not expect that he can be trusted to do anything. I doubt that he is even CORGI registered.

    Tony
     
  13. andreitone

    andreitone

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    In my country is very hard to find a professional installer...

    Agile is it very hard to set it at minimum output? I think I saw something on the internet about this but can't find it anymore... I'd like to give it a try
     
  14. David937

    David937

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    I not sure the way I described is actually the way to do it. It might not be allowed,AIUI the adjustment screw is only for installers to adjust.
     
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