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Boiler power!

Discussion in 'Plumbing and Central Heating' started by Dannyg78, 10 Feb 2021.

  1. Dannyg78

    Dannyg78

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    Hi chaps/chapesses

    recently moved into a new house and the boiler is struggling. It’s a valiant ecotec 637r 37kw I think on a system system (we have a big water tank next to the boiler downstairs. The boiler is approx 14 years old.

    the house is over 3 floors
    23 radiators
    1x bath 2xshowers

    The hot water flow is fine but the boiler is really struggling to heat the house up. Upstais floors are fine the downstairs floors really struggle to circulate water all round the rads. I have gone through every bit on the internet on balancing the system and I’m not getting anywhere. The pressure on the system is fine. I’m beginning to wonder is the boiler strong enough Kw wise to handle the size of the house.

    Can someone one advise if I’m right or could there be something else I’m missing. Pulling my hair out

    cheers Dan
     
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  3. muggles

    muggles

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    Unless your radiators are huge and/or the house is particularly draughty I'd be very surprised if it's an issue with boiler power. If anything it's likely to be oversized. You're much more likely to be suffering with a circulation problem. You can check by looking at the boiler when the heating is on. If it is reaching temperature and shutting off, coming down then coming back on again, all is likely to be well there. If it's burning continuously and never ever hits the set flow temperature, it's likely to be undersized (or has been de-rated in the settings)
     
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  4. Dannyg78

    Dannyg78

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    Thanks for the reply muggles
    The house is very very draughty , the rads aren’t oversized at all. The boiler is continuously burning but I put this down to the thermostat not hitting the desired temp meaning the boiler would keep going...
    All 12 rads upstairs have had the lock shields closed to a quarter turn but the downstairs rads are not getting hot at all. Not even the flow pipes to the rads
     
  5. ianmcd

    ianmcd

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    How many room thermostats do you have
     
  6. jackthom

    jackthom

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    Be interested to know what the flow temperature is getting up to on the boiler and whether it sounds like it's running at lower power.
     
    Last edited: 10 Feb 2021
  7. Dannyg78

    Dannyg78

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    1 room thermostat
     
  8. Dannyg78

    Dannyg78

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    Is the flow temp what is displayed on the boiler? Or the temp of the flow pipe coming out of it?
     
  9. jackthom

    jackthom

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    It is the temp of the flow leaving the boiler and on many Vaillants it is displayed on the LCD screen.
     
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  11. fezster

    fezster

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    It's possible the pump integrated in the 637 is undersized to overcome the resistance of the hex + your evidently large system.

    Do you know what the required head for your index circuit is?
     
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  12. Dannyg78

    Dannyg78

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    Cheers for the replies...
    The flow temp is between 71/72 degrees C
     
  13. Dannyg78

    Dannyg78

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    not sure what that is where would I find that info ?
     
  14. fezster

    fezster

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    The index circuit is the one with the radiator with the highest resistance (usually the furthest, but not always). The heat exchanger in the 637 has it's own resistance, which increases with flow rate. The pump needs to be adequately sized to overcome the internal resistance of the hex + the resistance of your index circuit.

    From experience, the hex in higher output vaillant boilers are very restrictive and will use up most of the available head on domestic CH pumps.
     
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  15. Dannyg78

    Dannyg78

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    To be honest I’m not sure how I would take that reading on the index.
    If what you have explained is the case what is the best option to try? Is it a new boiler or can I install a external pump?
    House is Baltic downstairs
     
  16. ianmcd

    ianmcd

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    Check D:40 and D:41 on the boiler display that will tell you what the flow and return temperatures are and will give us an idea what is happening
     
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  17. muggles

    muggles

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    Also look at what d.0 is set to
     
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