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Upgrade to a semi domestic boiler

Discussion in 'Plumbing and Central Heating' started by Marc118, 2 Dec 2019.

  1. Marc118


    12 Oct 2019
    Thanks Received:
    United Kingdom
    Hi All,

    I've been having problems with my heating system since i moved into my house 12 months ago see thread below, the boiler is a Valiant Ecotec Plus 637


    The guys that were supposed to fit the low loss header and associated controls have le me down and aren't available until the new year now and so I'm left with a baby and a toddler in a house that doesn't get warm.
    The past few days have been dreadful, the boiler is constantly showing an egg timer which I have assumed is the S53 fault but this morning when I've checked its showing an 'S07 Heating mode pump overrun', not sure what that means and why it knocks the burner off?
    We can't wait for the new year at all for this to be fixed and I don't want to just get someone in that has no idea about LL headers and they come in and make it worse.

    One of my friends who's a mechanical consultant had the same problem and he said rather then faffing about like I have, he just installed a new boiler of smilar duty but I assume had a bigger pump, and it worked a treat.
    Cost isn't an issue here (within reason), I just need to get some heat in the house sooner rather than later and I feel that I could get someone to install a new boiler quicker than I could find someone to install a LL header and associated controls.
    My friends boiler is an ideal logic plus.
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  3. D_Hailsham


    18 Oct 2007
    Thanks Received:
    United Kingdom
    S codes are status codes, they say what the boiler is doing at that time. Faults are shown as F codes.

    The boiler has not been turned off because of the S07; the boiler has gone into pump overrun for 5 minutes because the boiler has been turned off. This will happen every time it is turned off; which could be because the house is up to temperature (room thermostat), or because the boiler water has exceeded the set temperature, e.g.75C. If, as you say, the house is cold we can eliminate the first cause and concentrate on the second.

    If the boiler stat is turning the boiler off, because the water temperature is exceeding the set value, then the boiler is producing heat faster than the radiators can use it. This is normally taken care of by the boiler modulating down, i.e reducing its heat output. However there is a lower limit below which the boiler cannot modulate; in your case it is approximately 6kW. If the boiler is running at minimum output and the water temperature continues to rise, the boiler goes into on/off mode. It turns off (pump overrun automatially starts), waits a few minutes unit the water temperature has dropped then starts up again. And so the on/off cycle continues.

    You need to monitor the boiler's activity over 30 minutes or more to see what is happening. A new boiler is not necessarily the solution to your problem.
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    3 Sep 2019
    United Kingdom

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