Ravenheat RSF 820/20 Combi Boiler Problems

Discussion in 'Plumbing and Central Heating' started by Fmitch, 12 Oct 2018.

  1. Fmitch

    Fmitch

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    Hi I am new to this site but wanted to ask a question about a fault which has arisen on my Ravenheat Boiler. In the last day it has stopped delivering hot water either to the taps or the CH. The pilot remains lit, the boiler fires up and I can hear the fan working. Occasionally I get about a minutes worth of hot water then it runs cold. The Ravenheat manual suggests replacing the DHW thermostat but I am uncertain if this is the correct fix as the problem extends to the CH as well. This boiler has a High Limit thermostat - could this be the problem or should I suspect the 3 way (diverter) valve diaphram?
     
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  3. oldbutnotdead

    oldbutnotdead

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    Under what conditions does the boiler fire up? When you turn a hot tap on, when the radiators are calling for heat, both? How long does the boiler remain lit when it is firing but not delivering hot water to heating or to taps? Is system pressure normal? Is there cold water flow to the combi bit? Is the system full of air? Is the pump working? Are any zone valves working?

    Unless there is something very basic wrong (like system pressure zero or no cold water supply) then I think you'll need to pay someone qualified to sort it out- amateur tinkering with gas boilers is firmly discouraged these days :)
     
  4. Fmitch

    Fmitch

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    Under what conditions does the boiler fire up? When you turn a hot tap on, when the radiators are calling for heat, both? How long does the boiler remain lit when it is firing but not delivering hot water to heating or to taps? Is system pressure normal? Is there cold water flow to the combi bit? Is the system full of air? Is the pump working? Are any zone valves working?

    Boiler fires up both when I turn on the hot tap and when I switch on CH by putting the timer into manual.
    It remains lit all the time I leave hot tap running or CH on.
    System pressure normal (1.5 bar)
    Cold water flow to combi is normal I think. That's what is coming out of the hot taps.
    System not full of air. Worked perfect the day before.
    Not checked the pump yet as I've not removed the boiler housing, but water flow at shower & taps seems normal.
    Not sure what you mean by zone valves. It's only a small cottage so I don't think I have more than one zone.

    I don't understand why I can get about one minute of hot water out of the taps sporadically, maybe when the boiler has gone cold. Does this indicate a faulty thermostat?
    Should I go with the Ravenheat Fault diagnosis chart and replace the DHW thermostat? Should I also replace the High Limit Thermostat as well since I can't get hot water through the CH pipes? Or, does the DHW thermostat need to work to allow the heating to operate? In which case why is there a separate thermostat controlling the heating on the boiler?
    Any suggestions welcome.
    Thanks

    Read more: https://www.diynot.com/diy/threads/ravenheat-rsf-820-20-combi-boiler-problems.510617/#ixzz5ToMgdJp3
     
  5. oldbutnotdead

    oldbutnotdead

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    Use QUOTE rather than copy & paste, makes it loads easier to follow...

    When you say 'boiler fires up' is there a sight glass (visible WITHOUT removing the cover) that allows you to see a flame or are you just assuming it is firing because you can hear the fan and pump running? Is the cover getting warm when the boiler is 'firing'? Does the gas meter show that the thing is consuming gas when it is 'firing' at a consistent rate or does it use a bit then stop using any?

    I'm not sure of the exact state of the law regarding gas appliances on domestic premises- i believe that there is no actual law that prohibits a householder from messing about with the boiler in their own home.
    That being said, the questions you are asking (about DHW stat required for heating) indicate that your comprehension skills are lacking (the answers are all in that installation manual).
    I would strongly advise you to pick the phone and get a Gas Safe engineer in to sort the thing out.
     
  6. Fmitch

    Fmitch

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    There is a sight glass so I can see the boiler moving from pilot to firing up plus I hear combustion noise and the fan working.
     
  7. oldbutnotdead

    oldbutnotdead

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    And the next stage of the flow chart (boiler firing at full rate)? (Only way you'll be able to check this is by using your gas meter to measure consumption over, say, 5 minutes & comparing that to the full rate consumption figures quoted in the manual. Not very accurate but better than nowt)
     
  8. MeldrewsMate

    MeldrewsMate

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    In the words of my mate...'I don't belieeeve it'

    You are mistaken, if the boiler is alight it will be turning chemical energy from the gas into heat energy. If that is the case the water inside the boiler will rise in temperature, and get hot. If it keeps burning, as you say, that heat must be going somewhere, and if it doesn't then the boiler will shut off the gas to the burner and the flame
    will be extinguished.

    You will get a short supply of hot water if the internal heat exchanger has been heated, so that symptom is irrelevant in the context of this fault.

    Feel the CH pipe coming out of the bottom of the boiler. Does it get hot when hot water is being drawn-off at the taps? Does it get hot briefly just after the hot tap is closed? The CH flow pipe is usually the leftmost pipe, and 22mm diameter.
     
  9. DIYnot Local

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