Air can be free (a bubble at the top of a pipe/vessel), dissolved (in the water), or entrained (mixed with the water)
The amount of air that can be dissolved in water decreases with temperature and increases with pressure.
Heat the water and the dissolved air becomes entrained air. Entrained air will trip the flow sensor into an error state.
Entrained air doesn’t rise to the top of a vessel like free air. The only place entrained air becomes free air will be in radiators etc. Or in the (hot) coil of a hot water circuit when the heating cycle there stops. If there’s a coil with an appropriately placed auto-air vent this ought to (in time) purge the free air that un-dissolves as the water temperature rises, becomes entrained due to the water pumping around and around, then has an opportunity to rise up and out somewhere once the system flow stops.
Higher static fill pressures will mitigate / delay the onset of the symptoms.
If logic served I think a lower static fill pressure (and really cooking the water) will be more helpful for this purging process. (big district systems use vacuum degassers for this; these will eventually clear air pockets by dissolving them into the water then sucking that dissolved air out)
Then jacking up the static fill pressure.
Without an auto venting opportunity the only thing you can do is try to entrain the air and send it off out to the radiators (where it can become free air, and then rise to the top, and be let out before it gets cold again and becomes dissolved air) by alternating between heating and hot water mode with the system nice and red hot. Unlikely to be popular at this time of year!
Not getting carried away just yet, but this is promising.
It has been a few weeks since the Sontex went in to replace the Sharky, but i’ve not done too many hot water runs using the Arotherm cos there has been so much surplus sunshine the Eddi PV diverter has done most of the water heating.
Over last few weeks i’ve been gradually upping the DHW flow rate and reached 100% yesterday.
So over 6 weeks since I swapped the Sharky 775 out for the Sontex 789 and zero issues reported.
Granted, no heating during that time and hot water runs have been sporadic due to an amazing Solar PV month providing tons of free energy via the Eddi.
I closed the AAV a few weeks ago and occasionally open it up to release any trapped air.
Here’s another hot water run at 100% DHW pump speed.
Hi James. No, i gave up with Qalcosonic. it was odd. faultless on heating, but when it went to DHW and rose above 45C it seemed to go off. I tried a better air separator, but that didn’t help. I then fitted a Sontex and its working fine. I never found out why the Qalco was problematic
Dissolved air un-dissolving as water temperature increases and the pressure drops locally within the flow sensor.
If air does dissolve out of all detect this and err on the side of caution by not recording energy use. (which is what you want in the application these are designed for - heating bills)
Install on the flow and ensure decent static fill pressure to mitigate the effect of local pressure drop. Better still deaerate the system by getting it stinking hot and flushing the air through to radiators to be purged whilst hot.
We have these (actually the composite body E4, and in the 6m3 rated version with the same body size as the 3.5m3 rated E3) on a few heat pumps. All but one without issue. That one with issues is on the return and on a system installed with an outdoor plant room and generally impossible to bleed and full of air. It’s slowly getting better as the air is repeatedly bled from rads.
I’ve finally got things logging this weekend. Hot water run looks OK.
Note we have 2 parallel tanks heating - the ‘blip’ in the middle is where the secondary tank reaches temperature and its thermostat closes its flow valve, leaving only the larger primary tank to finish heating.
I have 3 meters of Sharky 775, and when the battery died, I changed the battery, and the mbus stopped sending readings to the gateway (ADF Mbus to Bacnet IP). Anyone who can help me with the problem?
Send a resetb0 command to the meter via M-Bus, or swap the M-Bus modules from one meter to the next. Sometimes that brings them back to life. Verify the meter primary / secondary addresses remain unchanged. Else contact the distributor for support on these.
