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* Resolved * Air in the central heating system

Discussion in 'Plumbing and Central Heating' started by Poisonata, 15 Sep 2021.

  1. Poisonata

    Poisonata

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    Feel compelled to post this as this issue has been the bane of my life for last month. Finally this evening discovered the problem. Searching various forums it appears many people have similar issues, this is how resolved mine / something easily ruled out.

    Problem - Closed loop system pressurised to circa 1 bar with a Greenstar 24i Junior catering for both the hot water / central heating system via zone values. Hot water is open vented tank.

    Every time either the heating or hot water was activated, significant amounts of air were being drawn into the system. At first found this hard to believe air could enter an already pressurised system unless by some mechanical action.

    Ruled out the usual suspects. Added more inhibitor than I care to mention (even though discerned it wasn't Hydrogen), reduced the pump speed. Nothing helped. In the end resorted to adding Aladdin auto vent valves to many of the radiators at highest points house manage this problem until resolved.

    These are really good btw, cannot recommend these enough. Fitted one on blanking end of radiator so manual bleed value remained in order to check these actually functioned. They do, extremely well.

    Only other highest point air was pooling was in the Fernox F1 magnetic cleaner (return pipe directly under the boiler). This has a manual bleed value which periodically remove after isolation the unit as easy way add additional inhibitor. Wanted to add auto vent valve here however somewhat reluctant as unit causes a cyclonic action as water enters, unsure if this would interfere with way valve worked. Apparently not, working as intended as now fitted.

    Immediately noticed the usual glugging of air ceased in the boiler / pipework. Couldn't believe it was really that effective. The manual bleed valve I'd removed in hand, looked at it and realised what the issue had been all along.

    Cyclonic effect of the water in Fernox F1 causes a degree of suction. Now the bleed value was in good shape, didn't leak, operated correctly BUT the rubber washer underneath had become flattened to the point no longer causes a hermetic seal. Obviously good enough to prevent water escaping but that powerful cyclonic effect had been causing air drawn past this washer into the unit.

    A 5 pence washer was the answer. After all that. So if you've got a similar unit & air in the system I'd encourage you to check all the seals on the unit. It's just not obvious as seals work well enough to keep pressurised water in.

    Hope that helps someone :)

    Poisonata
     
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  3. Poisonata

    Poisonata

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    May now refit one on the manual bleed valve types to the Fernox F1 magnetic cleaner as still unsure of the suitability of auto vent value on this unit even though it appears to be working just fine. Did message Fernox some weeks ago to ask them if how I intended to proceed was a viable option but zero response. But for the time I'll leave it just as experiment. My concern was could the cyclonic action which was strong enough to pull air past a flattened rubber washer also be enough to exert a negative force on the auto vent valve pulling air in. But so far it appears the answer is no. Will update with my findings.

    It is very pleasing to resolve this issues yourself, although somewhat frustrating at times.
     
  4. muggles

    muggles

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    You'll be replacing the whole thing soon enough anyway, I'm yet to come across a TF1 more than a couple of years old that isn't leaking
     
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  5. Poisonata

    Poisonata

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    @muggles If this time comes, is there a superior magnetic filter you'd recommend. There was limited choice at time of purchase, the effort to took to fit it I'd be keen not to repeat if indeed a replacement was required. Can't complain, it's done the job fairly well. But I've no experience of other types, possibly one containing a larger overall volume of water might be useful (purely add 1 litre inhibitor in one go rather than 2 lots of 500ml). If you have time would be interesting to know your thoughts.
     
  6. muggles

    muggles

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  7. Poisonata

    Poisonata

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    Looks like a nice solid bit of kit @muggles , thx for that :) Cheaper also !
     
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