Heating, insulation, ventilation, VMC, cooling ...A solution to my problem of micro air bubbles in the heating circulator?

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newstarnord
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A solution to my problem of micro air bubbles in the heating circulator?

Unread Messageby newstarnord » 16/10/20, 09:44

Hello,

I have a heating with an oil boiler and water circuit. The boiler is a low temperature.
The problem is that at 40 ° boiler water temperature, no problem.
On the other hand, at 70 ° it is there that we hear microbubbles of air circulating, the circulator then makes an abnormal noise.

How to overcome these air bubbles; I must specify:
- That the pressure does not drop (therefore no leak): 1,2 bars
- That the automatic purgers expel micro-bubbles of air at very slow speed (I put a little vinegar in the valve of the purger and I see very small bubbles appear every 30 seconds); so it is indeed a problem linked to the presence of air
- That I replaced the expansion tank, and that in fact the phenomenon is amplified; I had to introduce more air
- That I do not want to drain, because there is neutralization product in the circuit, I do not want to lose this one
- Before replacing the expansion tank, I had noise + a pressure which rose abnormally to 70 °
- There the pressure is stable but the noise is amplified
- I bleed the radiators, but I did not evacuate much air; no radiator makes a "gurgling" noise

How do I get rid of these air bubbles knowing that I cannot currently drain and install an air separator?
Raise the circuit to 70 ° and cut the boiler then open all the thermostats then wait for the temperature to drop then purge?
I have an old vent in the upper part of the installation, should I change it (I cannot check it because its air outlet is at 90 °)?
This old trap was working the last time I drained the installation.
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Macro
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Re: A solution to my micro air bubbles problem

Unread Messageby Macro » 16/10/20, 10:02

Do you have a mix of different radiator materials .... At one time on my heating I had a salvaged aluminum radiator while those on the ground floor were in cast iron and those on the first floor in steel .... I had exactly this micro air bubble problem ... Since the aluminum radiator was removed from the loop ..... No more worries ...
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Re: A solution to my micro air bubbles problem

Unread Messageby Ahmed » 16/10/20, 10:31

Agree with Macro: it must be electrolytic corrosion and it produces gas bubbles (and not air) ... Apart from removing the material part involved, it is possible to mix a passivating product with the water in the circuit. It is a simple and effective solution.
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Re: A solution to my micro air bubbles problem

Unread Messageby newstarnord » 16/10/20, 10:45

Hello,

I have a steel radiator which I use very little: its tap is normally always closed (unless the children touch it), because it is an air conditioning system that heats this part of the house. Otherwise the other radiators are made of cast iron.

I think the steel is compatible with cast iron because my heating pipes are black steel?
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Re: A solution to my micro air bubbles problem

Unread Messageby newstarnord » 16/10/20, 11:15

On the other hand, I had a problem with the seal on my first-price circulator: I screwed the bleed screw too hard (I thought we
could well screw it on as on a Wilo circulator), the O-ring as a result of this cracked.

Having no O-ring, I replaced it with a 15x21 seal soaked in sealing paste, it worked, no leaks, the pressure remains constant; could it be that this seal allows air to pass through but not water? As I could read somewhere on the net (air porosity)?
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Re: A solution to my micro air bubbles problem

Unread Messageby Christophe » 16/10/20, 12:14

Uh, wouldn't that just be cavitation? Who will be removed by an increase in pressure in the circuit?

1.2 bars is not much for a heating circuit ...

Here's how to calculate the pressure necessary to avoid cavitation: heating-insulation / vase-and-boom-tuning-of-the-pressure-and-mounting-t9118.html
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Re: A solution to my problem of micro air bubbles in the heating circulator?

Unread Messageby Ahmed » 16/10/20, 12:27

I don't understand what you mean by "cavitation"?
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Re: A solution to my micro air bubbles problem

Unread Messageby sicetaitsimple » 16/10/20, 12:59

Christophe wrote:Uh, wouldn't that just be cavitation? Who will be removed by an increase in pressure in the circuit?

1.2 bars is not much for a heating circuit ...


It's possible...

But if so it's easy to verify. If all goes well at 40 ° C and 1,2 bar, it suffices to raise the pressure of the saturated vapor pressure difference between water at 40 ° C and water at 70 ° C. If it was pure water (we forget the additives), it would be around 0,25 bar.

So has Newstarnord to check what happens at 70 ° C and 1,4 to 1,5 bar.

Edit for Ahmed, whose post I had not seen: cavitation is a phenomenon (generally local) in a liquid flow, where there is partial vaporization of the moving fluid. Of course, the hotter the fluid and the closer to its vaporization temperature, the greater the risk of cavitation.
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Re: A solution to my problem of micro air bubbles in the heating circulator?

Unread Messageby newstarnord » 16/10/20, 14:05

Alright I'll watch this.

But there is 6m of static height so 0,6 + 0,2 rounded to 1 bar = 1 bar pressure of the expansion vessel (house with radiator at the top and boiler at the bottom; the heating circuit is only on only one floor). Or 1,2 of installation pressure.

And when I was at 1,5 bars I had this phenomenon except that the pressure increased abnormally to 2 bars with the old expansion tank (which was inflated to 1 bar I believe). This old vase was over 12 years old, I thought it came from him.

And in fact the phenomenon is not localized to a precise place it "resonates" everywhere in the pipes.
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Re: A solution to my problem of micro air bubbles in the heating circulator?

Unread Messageby Christophe » 16/10/20, 14:17

Put 2.5 bars directly !! : Cheesy:
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