Removing trapped and dissolved air from a sealed heating system is essential for maintaining efficiency, ensuring accurate heat meter readings, and prolonging the system’s lifespan by minimizing corrosion.
Ultrasonic heat meters e.g Kamstrup, Axioma, Sharky etc are unable to measure the flow rate if there’s air in the system. This will result in the flow rate being reported as zero, which then in turn results in the heat meter reported heat dropping to zero 0W. The most likely time for this to happen is towards the end of a DHW cycle when the flow temperature is highest e.g
Sontex heat meter use a different flow measurement principle, they won’t throw an error and stop reporting in the same way as ultrasonic meters, but they will quietly underreport if air is present. Sontex heat meters are also susceptible to dirt and can start quietly underreporting overtime if they get silted up with debris.
We’re interested to hear feedback on the effectiveness of these measures are at removing air, or if you have any other suggestions or methods which you have found effective?
We’re also working on a feature to flag any air issues reported by the heat meter in Emoncms to enable it to be resolved by the installer early on when the system is first installed.
Personally I specify (and use on my own system) a fill and flush valve to eliminate air from sealed systems and is the only effective way of getting rid of air on commissioning imho. If you have a buffer cylinder or hydraulic separation you would need one on the primary and one on the secondary side to be effective.
Thanks for posting this Richard - a great explanation of all the issues and specifically on page 16 why air vents where they are traditionally placed can miss a lot of what’s going through the system. The air vents fitted by our installer are both just above a bend…
We have corrugated coils in the tanks and the DHW one has always been an issue with noise which I’ve always thought was trapped air in the corrugations, so I think a fill and flush valve as you’ve referenced in the post above plus a microbubble separator is the minimum of what we need to do.
Yes, as noticed by @SianiAnni we’ve now setup error flagging which will highlight in shaded red on the MyHeatPump dashboard the period of time the heat meter is displaying an error when unable to read the flow rate due to air in the system e.g
This will be setup by default on all new systems. To add it to existing systems, you either ask us to set it up, or do it yourself by logging heatmeter_Record_error Input to a Feed with 10s interval and then selecting that Feed as the error feed in the MyHeatPump app config.
Error flagging is currently only supported with Axioma heat meters.
Looking at my heatpumpmonitor.org stats, the heatmeter error is only showing on DHW cycles. I’ve compared MyVaillant electricity and heat stats for August with heatpumpmonitor.org :
OEM Elec
MyVaillant Elec
OEM Heat
MyVaillant Heat
Heating
15.5
22.5
91.0
90.2
DHW
20.3
20.6
???
64.6
It’s clear that the electricity figures for heating aren’t comparing like for like, but the generated heat figures look very similar. And the heat meter error isn’t being reported during heating cycles.
I was going to ask whether that was because of higher flow temp for DHW, but just reread above and see that you’ve already explained that it is!
