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Intermittent firing of combination gas boiler...

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  • Intermittent firing of combination gas boiler...

    first let me say what a wonderful site this is. I have a Vaillant Turbomax wall hung, sealed, fan assisted combination boiler. I have maintained this boiler myself over the years and it has been very reliable, especially so after replacing the diverter valve, 2 years ago - a major task. The problem now is - and it is getting worse - that when I put the dishwasher on, say, to rinse (hot fill), the boiler makes several attempts to fire. However When the water flow is greater (e.g. I turn on the kitchen hot tap on full), this problem very nearly disappears. This only happens on the hot water side of the boiler. The Central Heating side is fine. At first I thought it might be the air pressure switch in the flue (as the fan indicator light would flicker just before the boiler shut off). But I cleaned out the (clear) air pipes, with no effect. I don't think it is the electrodes because the central heating fires cleanly. It is obviously something to do with water flow. Here are my thoughts, perhaps you could direct me forward? Could it be caused by the differential pressure switch? How does this work? Is it solely related to the central heating side? What tells the system that there is sufficient (hot) water flow, for the boiler to ignite the gas? and is it the diaphragm which recognises that sufficient water is flowing, and the boiler ignites? Or does anyone else have any ideas? Could I ask you not to state the obvious - viz: get a professional in.... Thanks William in the UK.

  • #2
    Re: Intermittent firing of combination gas boiler...

    With all due respect to the knowledge of my fellow Forum members, I suggest you go take your query to the site below. It's a place geared specifically to your type of question.
    Last edited by Plumbus; 09-08-2009, 07:10 AM.