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Vaillant Eco tech 624 system boiler not heating water.

Discussion in 'Plumbing and Central Heating' started by Crakkers, 31 Jul 2019.

  1. Crakkers

    Crakkers

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    Hi,

    We have an Eco tech 624 plumbed as a system boiler. It has a pressurised hot water tank in the loft for hw.

    Come back off holiday to find that the boiler appears not to be heating the hot water.

    It fires up for the programmed time but no hot water. Non of the control knobs have been changed.

    Strangely the CH when tested briefly does work. When the CH is on a flame icon is displayed on the LCD screen to presumably show the boiler is heating. When the hot water program is activated the boiler kicks in but no flame icon displayed. TBH, I can't remember if that is normal or not.

    As its a system boiler, the hot water dial appears to be redundant, is that correct?

    All help and advice gratefully received .

    C
     
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  3. lightning

    lightning

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    Check pressure on boiler
    Yes hot water dial is not used on boiler
    Sounds like faulty 2 or 3 port valve
     
  4. Crakkers

    Crakkers

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    Thanks for reply.

    Yes, plenty of water pressure.

    If faulty valve can they be fixed easily?
     
  5. If it's just the motor or head then yes. If the whole thing needs changing then it's still relatively easy but requires draining down.
     
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  6. ianmcd

    ianmcd

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    Can you post a pic of the thermostat on your HW Cylinder
     
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  8. dilalio

    dilalio

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    Wireless cylinder stat by any chance? If so, check batteries and binding.

    In the meantime, use your immersion heater (which you should have).
     
  9. ScottishGasMan

    ScottishGasMan

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    Couple of things to check. Its almost certainly not the boiler thats the issue at least. What controls do you have? (by that I mean is it a vaillant controller or a normal timeclock (if not sure post a few pics up)

    Have you went up and checked the HW cylinder is cold? (this rules out plumbing issue where by cylinder is hot but cold is being diverted to taps rather than hot from cylinder)

    You should have a couple zone valves, little metal or plastic boxs on the pipework with wires going into them, can you get a pic of the one on the pipe to the cylinder (normaly up near the cylinder but could be elsewhere at the boiler for example,)
     
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  10. Crakkers

    Crakkers

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    Update.

    Repair man came today.

    1. Said hw control valve was broken, so replaced it. But still no hot water.

    2. Said air lock in primary coil so tried to vent and bleed. No good. So then tried to "drag" water up to the cylinder via a hose attached to the vent of the primary coil.

    Still no luck.

    He says boiler is gtting hot so switches off which also confirms a blockage in the primary coil.

    He's returning Monday!

    Whilst in the house he made some observations

    1. The overflow from the cylinder is plastic, he tells me it should be copper.
    2. The vent on the coil is via a wheel valve and it should be an auto air release valve.
    3. I have a rad in kitchen plumbed with 10mm pipe. Another rad is teed off this also with 10mm - he says you can't do that and it should be 15.

    Also, just noticed, we now have hot water!

    Thoughts?

    C.
     
  11. Crakkers

    Crakkers

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    Thanks for input!! Have you seen my update?
     
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