Yes. Just shooting around bad ideas incase you’re at a loss.
Bernoulli. If nothing was moving, then you are right. But, when water is flowing it’s a different story. If there is some restriction, say a lock shield or TRV wound almost closed, then velocity will increase through the restriction, and pressure will go down. If that pressure reduction is near a seal, then it is quite possible to suck air into the system.
Assuming air is not being sucked in as above, then the Spirovent will eventually clear out all the air. However, it may be you have a stubborn air pocket somewhere in the system, in which case it might take months (you get rid of one lot of dissolved air, a bit more of the air pocket dissolves, and so on). Do you have conventional bleed valves at all the high points in the system, because that will be where the air pocket would sit (usually)?
Thanks for the comments. Yes I have AOVs at all high points and close them after purging. I’m also letting out a minimum amount of water to drop the pressure for purging/bleeding, typically just 4 litres to reduce pressure from 2.5 bar to 0.4 bar
I’m wondering if I’m going to be subject to this issue as well, I’ve had a spirovent R2 fitted, thought I was ok but today saw the ugly heat meter error again!
Is it simply the case that it takes everyone months and months to remove all air or is there something people are doing to bypass this issue? potentially filling with demineralised water, or getting flushes done? I don’t think my installer did a full flush, mind you most radiators are new - I have 5 old ones (one really is quite rusty, so possibly its that..?)
The only thing that worked for me was the ‘Low pressure cook off’
Step 7
But 1hr was no where near long enough! I ran it for at least 4hrs.
I also covered all my radiators with blankets and towels during to allow the temp to get higher without cooking the house !
How much water did you need to remove to get down to 0.7? My system is set on VDI 2035 so I’m cautious about having to top up with mains water as I have three old radiators and wouldn’t be surprised if there’s some level of corrosion.
Don’t you mean de-oxygenated water? (It’s used in the brewing industry - slows the rate at which the beer oxidises.)
That was my experience. But take a step back. The major effect of the errors is to ruin your lovely clean readings in HPM and show horrid red dots everywhere.
Your DHW still gets heated and your rads are just as warm as you have set them to be. Your system runs at fundamentally a very similar real CoP compared to what it will do when the errors clear. (It’s just the HPM deduced CoP that is incorrect during a bubbles episode).
True, there may be some slight pipe and pump wear happening because of the micro bubbles - but those folk who never invested in proper monitoring would never have been in a position to notice it and fix it 
The bubbles are a pain, and it’s good to purge them, but in the short-term at least I think their effect is mainly cosmetic in your monitoring numbers.
Keep on purging !
Greetings,
I have had, and continue to have a data error due to ‘air’ in the system. I have a level 3 OEM with a 7 kW Vaillant HP. I have followed all the infiormation in the docs and tips, had the installer check the system, and even had the water circulating pump replaced in the HP replaced when it failed last month. The data error still persists. Question - is there a firmware update that ‘fixes’ this error and can it be remotely pushed to my system?
TIA
Hi Martin,
Supposing your level3 flow meter is not faulty then the air error indication will be a correct interpretation that you physically have air in your pipework.
This isn’t a firmware issue, so a change in firmware ain’t gonna fix it!
Hi David, thank you for th reply. Radiators have been bled - no air. The installer flushed the system- no air apparent. I have AVV and deaerator values installed when commissioned. The system ran perfect for 4 months and then the error appeared sporatically. The error has been almost constant for some months. I am led to believe that the heat meter (Axioma) is prone to an extent to slight changes in flow rates and may throw an error as a consequence. So maybe the latest firmware can be updated to ‘ignore’ the apparent air…
I haven’t learned about that. Could you point at resources discussing such limitations of the Axioma please.
What would be the benefit of HPM applying a mask to “ignore” these errors, and what does that even mean?
During these events, Axioma is reporting zero flow. How does HPM “ignore” that? What vaulue for flow do you suggest HPM uses in place of the zeros?
HPM is telling you there is a fault in your system that is making it impossible to report at certain times. The Axioma flow meter may be faulty, but much more likely you are experiencing the effect of dissolved gasses (in your circulation water) coming out of solution at high temperatures.
Can you share a link to your HPM system so we can better advise you?
David, the installer made a comment about data errors happening with the heat monitor and Vaillant HPs. I will have a look around and try and find some information regarding the monitor. I have a level 3 system…Level 3 Heat Pump Monitoring Bundle (emonHP) - Shop | OpenEnergyMonitor
I am interested to know what is actually happening. Maybe we can get to the bottom of this once and for all. Thank you for helping.
David,
At the end of the DHW cycle the Vaillant unit slows the flow I believe. If the flow is below the minimun that the heat meter can detect, then it will register no flow and hence the data error. Perhaps when the water circulation pump was replaced there may have been a slightly higher flow until the system settled down. The flow may again gone back to less than the minimum for the heat meter. It may be possible to adjust the min flow in the heat pump via installer controller settings. I will investigate.
Sorry for the late reply, I can’t remember exactly it was a year ago but I think it was 3-4Ltrs (Half a small bucket) then as the system really started heating up I kept bleeding my highest radiators and took out at least another 1 to 1/5 ltrs.
Once I hit 60deg that what I decided was my cut off plus i was getting a bit fed up with waiting as i said it was getting on for 4hrs at this point. i let the everything cool down which left the sytem pressure at approx. 0.5 bar then topped up. Never had any air issues after that.
Thank you for the input.
I just completed a DHW cycle and sure enough data error appeared. Both the flow in the HP and heat meter (using emoncms local) dropped to zero near the end of the cycle and by 2 pm all back to normal.
There is no data error when normal heating the rads.
I think I may have to tweak the pump flow rate via the controller…
Hi Martin,
This is typical behaviour when you have an air problem. The air stays dissolved in the water until the water temp exceeds a threshold and then the air comes out of solution and forms micro bubbles.
It is these micro bubbles that defeat the operation of an ultrasonic flow meter like the Axioma.
CH flow temps are typically below the threshold, DHW cycle ends above the temp threshold.
I hazard a guess this has little to do with flow settings in your heat pump.
David,
Thank you for helping. From what Ian is saying it looks like a low pressure cook off may be what is needed…
Ian,
this is what I see on the graph too. A low pressure cook off seems in order…
Thank you