I would say a bit anecdotally that when I tried the Sharky on a test setup it took me a bit more time to purge the air sufficiently than with the Kamstrup, though I may have just got better at purging the air…
I know from my own heat pump it took quite a while for me to get rid of all the air, especially in the hot water cylinder coil. I have a sontex and even audible air noise didnt seem to affect the readings… though perhaps as the DECC report notes it likely manifested as an small error rather than no flow readings…
Thanks for looking into things.
I have now run 2 hot water heat ups on the lowest setting on our pump and these completed without an issue. Is the actual flow rates are within the capabilities of the heat meter I assume the difference will just be that there is more turbulence caused by the air the faster it is moving through the meter.
I also assume that reason the problem doesn’t happen until later in the hot water heat up as at higher temps that’s when more air bubbles are forming?
I wonder, looking at where the automatic vent is on our return, if that could be a problem. It appears to come off below the 90 degree bend before the heat meter. I would have thought this isn’t a great location as it won’t vent any air that gets trapped along the horizontal section with the heat meter and magnetic filter. However both the flow and return go up to ceiling level before making their way to the ASHP above so if air is going to go anywhere it is likely to get trapped at the unit.
Any tips for venting the system? Apart from running the pump and switching between hot water and rads?
Does the return pipe go down before going up to the unit? or is it horizontal and then straight up?, the air bleed there is a bit strange … would be better at the top… do you have any way to bleed the air out at the top of your system? have you bled the radiators?
Yes I’ve been bleeding rads, there was quite a bit at the start but not much recently. There is one rad in particular in the attic where a lot of the air ends up.
I guess my system has 2 high points as the ASHP is higher than the pipework shown in the photo and my cylinder. The horizontal flow and returns where the pump and heat meter are are horizontal till they get to a 90 degree upward bend to ceiling level. The flow and return connections on the outdoor unit would be a little higher again. These have take offs just lower than the heat pump connections and I’ve turned them and only water comes out.
Thanks @ajdunlop just re-read your original thread as well. Sounds like you managed to get an improvement before further air dislodged again and so back to square one? What are your options to get the installer to look at this / add further air vents say up at the unit itself? or to re-orient the heat meter with a good length of straight pipe before it?
Yes when I first had the heat pump going I had it cutting out readings. After a bit or radiator bleeding and bringing up the pressure things improved (was still always a bit spiky later in the cycle) but looks to have gone backwards.
I believe my installer still has to come back to commission (after a few other electrical bits are done) so I’ll see if they are happy to move it then. There aren’t many good long sections without bends but a straight length that would probably be better than where it is now.
Thank you for investigating this further and drawing some sensible conclusions. Just out of interested what numbers of heat meters are we talking about here? e.g. 50% of how many? I plan to ask Mark, our heating engineer, to bleed the system on his next visit, so will report back.
50% of kamstrup systems are not showing the issue, 22% of systems did show the issue early on but the issue has now resolved and 28% of systems still appear to show the issue to varying degrees.
Hello @JohnT 34 working fine, 15 resolved and 19 still showing the issue (dont think most of these have tried to resolve the issue actively). Hope that helps
Been a few days since I bled all radiators upstairs and downstairs. There was some air in one of the upstairs radiator. I’ve been round and done this twice now with a couple of days gap in between and DHW runs. Second time no air escaping just water. System at 1.9bar. Pump at 50% speed.
Attached a 2 runs for the DHW; 25th and 30th August respectively. Seems to be much better if I’m interpreting the data correctly. Seems rather erratic on the flow rates still.
Yes, that looks much better. There are still some erratic readings but at least this will have less impact on the energy reported rather than completely missing heat data! It will be interesting to see if over the coming weeks if you keep bleeding the radiators and keep the pressure high at around 2bar to see if the trapped air will dissipate.
Thanks Glynn. I’ve marked the Solution option in this thread. I will keep bleeding the system. Once the heating season kicks in that should make it easier to get out the remaining air.
Ultimately, you wanna see if this is sorted by being able to run 100% DHW pump speed.
I found that running 50% pump speed was just a sticking plaster that masked the problem.
Plus, you should get better DHW performance running that pump with more flow rate.
I was in the loft today waiting for the DHW program to clicked in. As it started up I could clearly hear water gurgling through the 3 port valve, so I’m assuming there’s still more air in the system.
I will change the pump speed to 100% for the next runs. I’ve tried not to change too many things at once as it’s difficult to then track down what change made the difference in a positive or negative way.
Getting all the air out of the system is useful in other ways e.g. reduced corrosion, increased pump life span, increased efficiency and reduced noise, so it’s worthwhile to try and figure out what’s causing the air to be trapped and how it can be released.
@Zarch had a particularly tough time since he was using a plate heat exchanger on his Mixergy tank, apparently getting all the air out of a plate is tricky.
The easiest way to get all the air out of a plate is to mount it horizontally (all outlets pointing up).
I don’t think that’s the best way to operate it; certainly with refrigerants undergoing phase change etc; but it shouldn’t be too bad in that orientation with water and water and at high flowrates only.
We’ve started recommending that all heat meters are on the flow side in these heat pump monitoring applications. You have greater static pressure in the flow sensing element this way; which delays the point where dissolved air decides to dissolve out.
(dissolved air being MUCH harder to kick out than basic trapped / entrained air)
[edited as I said heat out of a plate not air out of a plate - thanks Gwil for the spot]
My installer was around to commission last week and I got them to move the meter onto a clearer run of pipe away from the magnetic filter and bypass valve.
Doing this introduced lots of air into the system that I have been bleeding out and the heating was on yesterday allowing air to get into radiators where I blead it off.
However the situation doesn’t look to have improved:
Will just have to give it time and see what happens.
I can’t hear much air movement apart from a slight ‘tinkly’ sound that I could hear towards the end of a cycle. Makes me wonder if this is the dissolved air mentioned by others forming bubbles when at higher temperatures.
Surely there must be some way of getting this out, presumably it is getting redissolved when the water cools down.
Also surely there must be a reason that only a small number of us are experiencing this or is it just that lots of people haven’t noticed or cared too much because they have mainly been looking at heating cycles rather than DHW?
Could it help to raise my DHW target temperature to something like 55 degrees (currently 48) for a couple of runs to get more of the dissolved air to be released and have a chance to escape?
