Suddenly showing no flow Axomia heat meter after months of normal running

I’m familiar with air issues it took me quite some time to get reliable heat readings my last air issue was 3rd Dec 24.

Since then I’ve had no air issues until yesterday (1st May) when running the the DHW cycle it got no heat recorded at all the day before (30th April) was fine

I’ve checked system pressure approx 1.5bar which it is has been for months no change.
There have been no changes to the system the only difference is for the last week or so we have not run any heating its only been running DHW cycles.

With that last point in mind this morning i ran the heating a couple of times to see and again i’m showing no flow at all which is odd as with air issues before i would get flow with lower temps until the temp got hot enough for the air to come out of solution.

Can anyone help advise whats happened please?

Thanks
Ian

Hi Ian,

I always start out playing dumb…
Does the flow meter still have power?
Is it still connected to the EmonHP?

On the EmonHP front lcd display, what values do you see?
On the EmonHP inputs page, are readings coming in every few seconds?

Good luck, David.

Hi David,
Heat meter LCD display still on so assume that means it has power.
I disconnected and reconnected cables to EmonHP then power cycled the EmonHP
I can’t look at the display at the moment as I’m at work.
Yes all inputs reading every 30s ish

I’m stumped?

Hi Ian,

I’m at work now too but when home will check my Axioma display to see if there is a register on the unit that shows present flow-rate. (I’ve never inspected that display )

If there is, we can determine if the “fault” is at the axioma end or the emon end.

It’s encouraging that you are seeing flow and return temps from the axioma and I’m assuming that your heating is working OK, and that this is just a metering error?

Cheers, David.

Many thanks
Must admit I’ve never looked at the heat meter display either never been a need.

Yes heating and hot water is not a problem its just a monitoring issue of flow all other variables are still working fine.

I’m away for the long weekend shortly so can’t check anything till Monday night at the earliest.

when I’m back I might try bumping up the pressure to 2bar just to be 100% its not an air issue, but I really don’t think it is at the moment.

Thanks again for your help

I’m sure bumping up the pressure to 2bar won’t hurt, but low pressure seems unlikely to be the main cause here (the issue exhibits at low flow temps which , in my experience , isn’t when air becomes a problem)

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Hi Ian,
I checked on the display of my Axioma and yes, it does have a register that displays total cubic metres of flow. It increments when the HP is working.
Does yours?
Cheers, David.

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Hi David,
Thanks for checking yours for me.

I’ve just got back from a weekend away and increased the pressure a bit more not quite 2 bar and just manually turned on a hot water cycle and even from stone cold I’m not seeing any flow at all.

I’ve checked the m3 screen while it’s running and it’s not increasing.
Also every screen has a small exclamation triangle in the bottom right hand corner there is also a screen with Er 4001 (quick update ive also seen it show Er 0001) but a quick Google isn’t turning anything up?

Anyone know what this error means ?
Has my unit gone faulty?

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4001 apparently means temperature differential is lower than permissible limits (that’s the 4) and no signal, the flow sensor is not filled with water (that’s the 1)

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The fact that the system is running and heating the house must mean a faulty unit?

… or perhaps a damaged cable between the display unit and the flow pipe assembly?

At least now we have narrowed it down to being an issue at the Axioma end of things :slight_smile:

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Cables all look good nothing under any tension or sharp bends and they don’t flap about.

I think I’ll open a support case with the shop and see what they say.

Thanks for your help.

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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!

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It’s very unusual for this to be the case. Very little exists to actually break with these meters.

The error code for “I think I’m full of air” is the meter’s best guess as to why it isn’t getting a good enough signal travelling from one transducer to another.

It doesn’t KNOW this for absolute certain. It only thinks that this is the explanation. Plausibly ot could be other things and I’ve suggested a couple above to look out for before condemning the unit and exchanging.

For future reference manual is linked at the bottom of this page:

Page 27 is error codes.

Meters do occasionally die. It’s usually more catastrophically obvious. Here’s a dead E3 (brass body version) which is interesting because on the video I show how to navigate to the “live” values for temperature/flowrate - long press the button twice to get to the “3rd loop” of clickable display items:

Your unit happily measuring temperatures ays that the measurement logic is operating. This particular meter (the 4044th ever produced) did have a firmware bug that in ultra specific circumstances could crash the measurement subroutine. Long since fixed by 2024 though!

We do see some interesting failure modes out in the field. I think my favourite is a bad batch of seals that allowed water from a heating system to leak past the transducers, into the cable to the transducers, and from that “pipe” formed by the cable into the electronic part where it promptly partially short circuited the M-Bus network used to read all the meters in the building…

I therefore wouldn’t rule anything out! :slight_smile:

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Hi Marko,

Many thanks for all this very useful information its very helpful.,

I’m just arranging for my installer to visit to replace the unit but I will make sure I’m there when he removes the existing unit so I can see if there is debris that might be dangling in the flow causing the issue, before he fits the new unit.
The shop has asked me to return the unit so assuming there is no obvious reason for the issue once its removed I will be retuning it for your analysis.

Thanks Again
Ian

Thanks @IRMartini. Do supervise how the unit is tightened up too. No “wringing it out” like a dish cloth using big wrenches. :-o

@glyn.hudson I am very interested in what has occurred on this one. If it comes back to the shop and doesn’t test ok on the rig etc please don’t bin it / do ship it for a rebate. :slight_smile:

I’ll show him the video on where to grip to loosen and tighten the unit.

I’ll also have a look at the centre of the body of the unit for any wrench marks to see if there is any evidence the unit was twisted when first installed.

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Will do! Thanks :+1:

You’re unlikely to see any. When they get twisted it is by holding the HEX section at the end with a wrench…but the opposite end to the one that you’re tightening the union on. (picture wringing out a dishcloth by twisting it)