Sharky 775 heat meter questions

Yes James.

Works fine most of the time, but has 15-20 mins where it just goes into Error mode.
Usually after the DHW run has been going a little while.

During Error, this throws MAX values into emoncms from the flow rate and power output inputs (then ultimately into your feeds)

I recorded these ‘raw’ values before any processing.

Power: 13131113
Flow Rate: 131.1

Normal values just before it flips out are:
Power: 7200
Flow Rate: 0.8

As flow rate and power (along with DT) make up the power output, this why things go belly up from an emoncms point of view.

What’s strange is that i’ve had the heating kick out just as much flow (and more) than that and not had an issue.

I’m wondering if there’s a better way these errors can be handled @TrystanLea ?

On the input process, if the error values are clear, add in a check and use the previous value for the Feed (I thought you could use the previous value)?

You could log to a ‘raw’ feed first so you know it happened.

I’d really like to work out why the thing is falling over, but need to have a bit more of a think about how to debug it. I wonder if the meter manufacturer would have some comment.

Meanwhile having some way of ‘removing’ the DHW runs in OEM / the heat pump app would be useful. You could ‘sense’ DHW run by an optical sensor on the 3-way valve lever or temp sensor on the DHW tank flow?

Or just intelligently ignore the data when the thing gives errors which I suppose is the easiest solution.

E7 is air in flow pipe detected.

Hotter water can hold less dissolved air. It will cavitate earlier.

It’s also possible that entrained air in dhw is simply not clearing the coil ever. I can’t comment on plumbing other than to say this issue is nowhere near as prevalent in the district heading space.

The manufacturer is following the mbus standard here so had already told you everything that you need to know there.

The error values displayed are being incorrectly parsed by the mbus parser. These are NOT the same register as the regular values. Get a proper mbus parser and you’ll see that they have different names and can be parsed/filtered accordingly. :slight_smile:

I’d still try to get air from your system though.

Thanks Marko.

Perhaps there is a way to get the vaillant control box to circulate water through the DHW coil for an extended period (say 24h). I have an auto air bleed valve on the coil flow so it should eventually work the air out of the coil…

Or run. Stop. (for air bubbles to consolidate and move to the top of the coil) Run. Stop. Run. Stop.

(whilst it is running the air will be entrained)

Does your auto air vent function / is it open? You’d usually open these during initial system commissioning them close the cap afterwards - to avoid any fault in the AAV pishing water everywhere whilst you’re not actively watching it.

So based on advice from @marko i’ve had the layout changed again.

We weren’t able to drop the bottom of the return right down to floor level because of the strainer and access to the fill valve.

But we did move the AAV higher and teed off the expansion.

Finally, we rotated the sharky unit 90 degrees as advised, to take the detector away from the top.

Guess what… same problem on hot water runs.

At 60% pump speed (about 700 lpm) and below, the hot water runs are fine.
Set the Arotherm anything above that (60%+) and the Sharky gives error 7, which is presented to emoncms as crazy high numbers.

But what’s daft is that I can set the flow rate way towards 1000lpm on heating and the Sharky never misses a beat!!

So i’m at a loss now.
I do have a Sontex in a box here, so i’m tempted to swap the Sharky out for the Sontex.



Good effort looking into this @Zarch cant be cheap to make all of these changes!

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Don’t remind me @TrystanLea, Damon ain’t cheap!! :rofl:

Seriously though, Sharky and Stockshed don’t seem to realise how much these changes they suggest cost me as an end user.

If I get Damon to switch in the Sontex instead, I need to talk to you about a plan of attack to save my old sharky data and have a seamless migration to the Sontex. Both locally on the HAT and pushing to both emoncms account (my account and public energystats).


I’m surprised by this @Zarch.

There ought to be no air being pulled down from the AAV / expansion sessen into that flow sensor now.

Are you fully purged of air in the DHW primary? With pump running air will be “entrained” at certain flowrates and ony “escapes” when the water stops. It can take quite a few start/stop cycles for air to purge.

Do you have a high enough static fill pressure to avoid cavitation? You want to be at least 1 bar on the heat meter flow sensor after system dP is taken into account. (a static fill pressure of 1.5 bar should do it; 2 bar probably won’t hurt)

To be clar though the meter is NOT presenting crazy high numbers to emonCMS here. EmonCMS is reading the WRONG registers from the meter (err-value rather than inst-value) when the fault occurs. There aren’t any instantaneous flowrates reported when the flow sensor is in an error state.

Thanks Marko, really appreciate the feedback.

I’ve been and released/closed the AAV each day, i’ve not noticed much in there aside from the first day or so.

Here’s a capture from last night.
And this is only at around 65% max flow rate
It always seems to get annoyed around 50C flow at the moment.

I will double check the pressure when I get home later.
I have a feeling i’m probably less than 1.5 bar.

Hello Mick, Marco,

Should we be able to recover a reading that will be sufficiently accurate even when it is in error state? sorry I meant to look into this and am happy to do this

Hi Trystan,

The telegram content on the 775 is dynamic. The content of the telgram changes depending on what is available from the meter.

Registers of type “inst-value” are real values. Temperatures/flowrates.

Registers of type “err-value” are error codes. They should not be treated/imported as temperatures/flowrates but were included for some legacy head end systems that would use extreme values for flow/temeprature to signal an error.

Other meters do this in different ways.

Kamstrup meters for example have a static telegram then “info codes” to let you know the meter state. These are also not without quirks. You need to know that “inst-vlaue” of “0” for flowrate doesnt’ actually mean zero flowrate UNLESS the info-code says all is ok. If the info-code says there’s a problem then the “inst-value” for flowrate could be total nonsense.

The Diehl approach of not providing an answer if you don’t know the answer is the safe one; but “column counter” type parsers that don’t include full M-Bus decoding will get confused by them and import the wrong registers when the meters are in error state.

I am genuinely fascinated by this. (sorry, I am a saddo)

What size is the meter? If I have one in the same size (a 775) I’ll post it you for a swap out to rule out the meter.

Where is the install? If I’m passing I wouldn’t mind prodding it in person to try and understand what is happening here.

I have not come across this before but it does seem curiously repeatable!

Looks like it was running around 1.2 bar overnight (and last few months) and i’ve just raised it to 2.0.

As surprised and annoyed as I am!! :rofl:

Nothing wrong with being a saddo / geek!! :+1:

Sharky 775 Heat & Cooling Meter. 3/4" BSP qp 2.5m3/hr.
On a 5kW Vaillant Arotherm setup.

Thanks for the offer, but I’ve already got a Sontex sat here that I got from Trystan & Glyn.

My plan is to give up on the Sharky and try the Sontex.
There is no way I could get Damon back for a fifth time to tweak/mess with the Sharky and be disappointed again.


Sounds absolutely typical for me that this is a one off… only me!!! :exploding_head: :woozy_face:


The first two hot water runs after upping the mbar system pressure to 2.0 and leaving flow rate at 65% max worked okay.

I thought we had cracked it. :rofl:

NO. Upped the flow rate to 100% max and and crapped out again.
(remember, I can run the heating at 700+ flow rate no bother)

I think it’s goodbye Sharky, hello Sontex time!!!



I do have some 2.5 m3/hr Sharky meters here and would happily post you one FOC to rule out your specific meter. Not passing Sheffield any time soon to offer a free installation though I’m afraid.

I do still suspect air in system; and the error codes given by the meter would confirm it if they were logged. Completely understand the “I’ve had it” decision though.

In heating the air would be “entrained” in the pipework, shot into the radiators, and shoot up into the tops of the radiators before the water returned clean.

In hot water there may just be enough air in that loop (or plate) that it gets “entrained” at high flowrates and because it’s “entrained” it isn’t popping up to the top of that pipe stub and into the AAV whilst the water is running.

Enough cycles might clear it (pump flat out; switch repeatedly betwen heating and hot water; in order to flush the entrained air into the rads) but if you do find a Sontex relatively insensitive to air then that’ll also resolve.

You might want to try that. Avoids opening up the system at all. Is there a de-aeration cycle on your heat pump controller that you can use?

LOL Marko, that’s shame you’re not passing, it would have been good to have a saddo chat about it all. :rofl:

Thanks again for replying. Appreciate it.

So, we’ve swapped over to the Sontex 789 yesterday. We’ve placed it in the same location as the outgoing Sharky 775, so a straightforward swap out and hopefully all pipe work / bends sufficient.

I got some strange readings into emoncms over mbus from the get go, ie strange flow rate readings (high), but i’m going to put all this down to air in the system.

I don’t think I can judge the Sontex until i’ve got all the air out as you say Marko. That seems to the be goal.

Interesting side note: The Sontex just seems to give wild high flow rates (like 4.5 m3^h, rather than erroring like the Sharky did). These high flow rates then presented as high power outputs (and as such, higher cop).

heat out = flow rate x dt x SHC after all.

So if the flow rate is being reported wrong (high), the internal heat output calc will be high too. And because electric in is still low (heat output / elec in = cop), the cop looks crazy high, like 15 COP!!

Thinking back over the 7 months of having the heat pump and the Sharky, we have made lots of continual changes to the rad system in the house. Had the bathroom done and made internal rad upgrades in rooms as we’ve gone along.

So never really had a long period where the system has been truly static (and air free?).

So will spend the next few days bleeding rads and checking the system AAV.

Although with the warmer weather now, doubt the heating will be on much and the Eddi / surplus PV is doing most of our hot water! :+1: :partying_face:

Not that i’m aware of on my 5kW Vaillant Arotherm Plus. :man_shrugging:

Any other tips from anyone to de-aerate would be welcome.

I just want a working heat meter setup… I do feel there is something not right somewhere though. It seems very odd that i’m the only person having all these issues, which must point to something about my setup? :frowning_face:

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I can assure you that you are not the only person having these issues.

We see it all the damn time on bespoke / ad hoc heat meter installations for heat pumps.

Also on the upper floors of high rise buildings (cavitation due to insufficient static pressure) or on all floors of high rise buildings where some numpty has designed in “un-bleedable” design details.

With billing bureaus and ESCos happily billing punters based on what are effectively fictional reads. The ESCOs in particular are losing out on a fortune by not recovering ££s for all the heat actually supplied. Hey ho.

Vaillant boilers definitely have built in purge cycles. Arotherms do too I believe:
Installer level → Test menu → Check programmes → P.06 Purge building circuit

You need circulator running and the diverter valve winding betwene positions to purge air into radiators; with pauses for entrained air to settle out. Compressor does not need to be on.

Fascinating that the Sontex unit doesn’t trip out on air. I guess it doesn’t know the difference between collapsing air bubbles and vortices being shed.

Your setup is unusual in having a plate heat exchanger I guess. Most will have coil-in-cylinder that has fewer places for air to hide (tends to rise to the top of the coil naturally; whereas the top of the plate HX is actually between the plates and below the level of the outlet. I assume that all AAVs (including that one atop the plate HC) are open for purging and not stuck shut?