Hi,
Second line support here - we distribute the Axoima units in the UK (B2B bulk orders only, please don’t ask to buy direct) including to the OEM shop.
Thoughts:
Low temperature difference (the 4) is not an issue.
It is only warning you that the meter is operating outside the MID certified temperature range. It will occur when nothing is happening and temperatures equalise. It can also occur with heat pumps operating with extremely high flow rates for the power being delivered (very low dT) and means your energy measurement is no longer in the certified accurate range but for practical purposes will be fine.
Air in flow sensor (the 1) is an issue.
This could be real (air in it).
This could plausibly be a false flag (meter failure and it believes that it has air in it; piece of dirt in the meter and it believes that it has air in it etc)
Assuming real:
In principle air could have become stuck in this DHW loop that would previously have been flushed out to radiators…
… which you have clearly thought of here.
I’m in agreement that it would be highly unusual to go from perfection to zero flow measurement. You’d expect deterioration and issues at higher temperatures etc.
Assuming something else:
These meters are ultrasonic. A transducer makes a noise. It goes through the water; bounces off some mirrors in the process; and is picked up by another transducer.
Air means the signal doesn’t get through or there’s too much noisy reflection from bubbles etc and it’ll flag a fault for not receiving a reflection that is in most cases due to air.
In principle it could be dirt. A piece of PTFE wiggling around in the meter that’s hanging from a union nearby for example.
In principle a mirror could have fallen off internally perhaps. A transducer could have become unstuck from outside the flow sensor body. (they’re external to the flow and “look through” the composite in these meters) This is more likely if the meter body was twisted during installation by somebody not reading the manual. Visually - grip the end that you’re tightening when installing it:
Else you’ll twist that body and even if the plastic springs back elastically there’s enough movement between this and the stainless steel mirrors inside or piezo transducers outside to potentially break bonds.
I don’t believe cable damage would do this. That should be another fault code as it would be detectable electrically. Will check tomorrow.
If this were fitted in my own system, I’d be isolating (we always fit between valves for maintenance purposes…) and removing the flow sensing element to rule out dirt or anything having fallen off…before asking for next steps.
As the distributor for these we would, if we know the meter to be squeaky clean, ask for it back from the OEM shop for bench testing or factory analysis if required and credit them for a replacement unit.
This isn’t a default offer - please don’t contact us for the usual “my system is full of air what is wrong with this meter” faults - but in this case it’s an interesting one and if it isn’t dirt that looks like air we would like to know what’s up here.
Hopefully it’s a piece of PTFE etc. Annoying but a quick fix. Please keep us posted!
