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Discussion in 'Plumbing and Central Heating' started by Jezzy, 16 Feb 2010.

  1. Jezzy

    Jezzy

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    Does anyone know if there is a way on here to do a search for a particular boiler and read up on past problems etc?
    I am having problems with a Ravenheat CSI85T and want to do a search on this kind of boiler, search could be over entire history of DIYnot.
    Boiler fires up and then stops on CH & DHW after different times, not say after 30 seconds every time, just randomly? Ravenheat won't send an engineer out as winter is their 'busy time', but they will in the summer!!! Tech help say to check CH thermistor, but it's doing it on DHW too. Working through fault finding chart on my PDF manual, it could be the overheat stat. I don't really want to bankrupt the customer though, but he is ok with me changing parts from cheapest first to ignition board (£133 + vat) last.
     
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  3. onlyfitidealboilers

    onlyfitidealboilers

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    why dont you test CH thermister this overrides the DHW one also.
     
  4. Jezzy

    Jezzy

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    Have you any idea what the ohms reading for it should be? It doesn't say in the manual. Thanks for your suggestion anyway, i will try it tomorrow. Ravenheat tech guy didn't mention that it overrides the DHW one, he should have known that. When it doesn't fire up at all, i go through the fault finding and end up at the overheat stat. If it does decide to fire up, it is stopping randomly. I should have told the bloke that electrics isn't my speciality and told him to get someone else really.

    Oh and i've figured out how to search for this boiler now. Doh. I've been on here for years and i've only just figured it out, theres no hope for me!
     
  5. Jezzy

    Jezzy

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    Thanks for your suggestion OnlyfitIdealBoilers. It was the CH thermistor at fault, now working ok.
     
  6. Agile

    Agile

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    That was a nice simple fault.

    Just to be different they use a sensor with a cold resistance of about 25K.

    Tony
     
  7. Jezzy

    Jezzy

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    Tony can you answer this one for me. This CH thermistor was covered in black muck when i took it out, i cleaned it first before going to get a new one for the customer, but would the cleaned thermistor have worked if i had put it back in, or not? Put a new one in anyway, but i have been wondering since if they just get covered in gunk, and all they really need is a cleanup.
     
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  9. barryauid

    barryauid

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    There may be trouble ahead ;)
     
  10. Agile

    Agile

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    The answer would have been given by measuring the cold resistance after you took it out.

    Open circuit and its faulty.

    Too low a resistance at about 2K and it would probably have cleaned and worked as that value all the time would tell the boiler its already hot enough.

    Dirt usually only conducts enough to cause a problem on a low voltage circuit when its wet.

    Tony
     
  11. Jezzy

    Jezzy

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    Thanks for that Tony - i always read your comments cos you seem one of the more intelligent of the people who comment on here, when your not being sarky of course!!! - I just left it there, i should have checked it and brought it home with me really.
     
  12. assured heating

    assured heating

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    DEEEEEERRRR i fink i am intellygint as wel yuo know :p
     
  13. Jezzy

    Jezzy

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    You probably are, i haven't noticed you on here before though, i'll keep a look out for you 'assured heating'. And anyone else who i've inadvertently dissed by my last comment, Soz.
     
  14. Agile

    Agile

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    Now that I have read my reply again I think I weas talking at cross purposes with you !

    I was replying to a senario where the OUTSIDE of the sensor was gunked as that can lower the apparent resistance of the sensor particularly if it gets wet.

    I now think you were refering to a buildup on the INSIDE or water side.

    Although it seems rather surprising I am told that the extra thermal resistance does affect the boiler operation.

    Logic dictates that the effect will be to alter the response time constant such as when the temperature is rapidly changing either up or down but would not occur during steady state heating for example.

    The main effect is to create a poor temperature control and wider that expected variations in the output temperature.

    In your case I expect it was just failed!

    Tony
     
  15. DIYnot Local

    DIYnot Local

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    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


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