* Resolved * Air in the central heating system

[Poisonata]

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

 

[Poisonata]

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.

 

[muggles]

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

 

[Poisonata]

@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.

 

[muggles]

Magnaclean Pro2 is my filter of choice

 

[Poisonata]

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

 

[au8830]

I'm glad you posted this, because it prompted me to have another look at my TF1 Total. Earlier in the year I had all new radiators and pipes but kept the old boiler and the TF1.

I started to get air in the system (I expected some initially after refill) - with it seeming to get worse each day. I wasn't losing any pressure, no signs of leaks anywhere in the new pipework or radiators/valves, pressure relief valve, and went up into the attic to check the new air vents (mix of manual vents and auto), and closed down the auto vents. I had suspicions that the TF1 was the culprit because of its location relative to the pump, but it was bone-dry and no sign of water marks.

After reading this I found the leak by slightly over-pressurising the system to just over 2 bar cold (without running the system). At around 2.2 bar, water began to seep out onto the lid. I suspect that's why no leaks were visible - when hot, the system would reach a similar pressure to that which it "leaks", but at that point the pump would be sucking in air (as well as effect from the shape of the filter itself), so no water leaking out. The boiler pump overrun would be keeping the pump sucking in air, even as the pressure dropped back down again, so still no water leak and no pressure drop.

On mine, the o-ring around the bleed valve was squashed totally flat, so I replaced that. Also the main top o-ring, although it looked okay, i replaced it anyway. It's really important to clean the top plastic piece thoroughly. I thought i had it clean enough, but it still leaked, and after taking it off again I saw there was a tiny amount of crud in one of the grooves, which looking at the design could cause it to sit wonky when the clamp screws it down.