Glowworm 30CXI Combi boiler hot water cycling hot and cold.

Discussion in 'Plumbing and Central Heating' started by hairyone, 17 Nov 2017.

  1. hairyone

    hairyone

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    Location:
    Sussex
    Country:
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    So I've just had a visit from a HomeServe Vaillant/Glowworm engineer to fix my boiler.

    The water was cycling hot and cold every 4 or 5 seconds.

    He was reluctant to attend saying the problem was most certainly blocked plate heat exchanger and said I should get a power flush first.

    In the end he agreed to attend and see if the heat exchanger could be cleaned.

    When the heat exchanger was taken out he flushed it through with water and very little of the black hematite was apparent and you could see very little in the input output holes. He also remarked that the water coming out was very clear.

    But he said it could be completely blocked in the middle, so being the curious type I blew through the exchanger and there was little or no resistance.

    So it was refitted and the problem was not solved proving his diagnosis correct.

    Now my issue is that there were no fault codes and since this issue became apparent there has been a clicking noise every 4-7 seconds from the diverter valve regardless of the demand for HW or heating. If you hold the HW outlet pipe with a hot tap full on the hot cold cycle appears to coincide with the clicking from the motor on the three way valve.

    Also when the hot tap is on full the burner fires continuously and does not switch on and off in time with the hot water.

    Is it possible that he was wrong and the three way valve is just constantly spinning and never settling in HW or heating mode?

    If the exchanger had been full of black stuff or at all difficult to blow through I would have accepted his diagnosis. But the fact there is a continual clicking sound from the three way valve makes me doubt him.

    Is there an operational mode where the valve clicks ever 4-7 seconds day and night , this is not something I have noticed before.
     
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  3. hairyone

    hairyone

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    Just checked and if I unplug the cable to the three valve motor at the right point I can either have all the hot water I want or all the heating. But plugged in it just alteranates between the two.

    I am beginning to think the initial diagnosis was wrong so given that the valve works fine in either position the problem appears to the actuator.
     
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