Daikin air detected issue on HW cycle

Hardware Heatpump
1

Hi can you help,
when the pump is running a HW cycle when flow temp reaches about 48 degrees I get a air issue detected.

This happens every time, as soon as the pump goes back to space heating the message disappears.

I cannot see any leaks and the pressure is not dropping.

I have purged the system a couple of times with no effect

I do not believe I have a issue on space heating but cannot check this as I cannot get the leaving water temp to 48 degrees

Any suggestions would be very helpful

Mark

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2

Does it happen around 30 mins of the hot water starting the rating ?

3

Hi Chris
Yes around the 30 to 35 mins mark

4

Hello! Welcome to the forum :slight_smile:

Here’s the official guidance on what to do: Removing Air from Heating Systems — OpenEnergyMonitor 0.0.1 documentation

It may take many more days of running DHW and venting the system.

5

Thanks for feedback I will go over the document,

Is it common for the issue only to start near the end of the HW cycle , as I would expect it to be from the start ?

Thanks

Mark

6

Yes, it’s common to see towards the end of the DHW cycle, as the water gets hotter and the air comes out of the water.

What type of heat meter (or flow meter) do you have, and has it been installed in the correct orientation?

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7

I have the Axioma E4 DN25.
It’s installed horizontally before Any splits in the system.

The body is installed so the flat plate for the electric display is pointing 45° off the vertical line

Which is as specified in the installation guide

I assume this is correct or have I got it installed incorrectly ?

See very poor photo

Regards

Mark

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8

Hi Mark,

I feel your pain. My heatpump was fitted last August and I have been struggling to prevent getting “air in the system” errors ever since.

I’ve followed all the steps in the document

including fitting a spirovent (which didn’t make any noticable improvement).

But I’ve kept up a daily routine of venting in three places:

  1. The highest radiator in my house (which quite conveniently makes an echoey dripping sound whenever there is an air pocket in it)
  2. Releasing a teaspoon of water from the vent in the lid of the TF1 filter.
  3. Releasing a teaspoon from the vent at the bottom of my HWC coil (This vent has a manual release, not an AAV)
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I find that if I release from the filter during a DHW cycle when the flow is hot, the released water is very milky for a moment before clearing. This gives me confidence that there IS actually air in the system, and it is not a false positive error message.

After a DHW cycle, releasing from the bottom of the cylinder coil gives a short pipe “clunk” as some air escapes, which feels good :slight_smile:

So I think the culprit here is not massive gulps of trapped air from when the pipework was filled, but rather dissolved gasses in the water that take time to be released. I also have a suspicion that because we run our systems much cooler than a gas boiler system the gasses take much longer to be purged.

Another of my theories is that during a DHW cycle only a small portion of the total system volume is circulating, so only that fraction is being subjected to high temperature purging. I did try manually shifting the 3-way diverter valve to the CH position during a DHW cycle in order that all the water would be heated. I think this did some good.

There is also definitely a big influence given by water pressure. Letting the pressure fall to, say, 0.7bar (by not replenishing the water you bleed out) does certainly allow more gasses to be released. I did try raising the pressure quite high (2.8bar) anticipating that this would keep the gasses securely dissolved and so not trigger the error, but that didn’t help. As the pressure kept on falling (because of the constant bleeding and reduction of springy gas in the system) I’ve now reached a point (1.7 bar) where for the past few days I have not had an error. :tada:

I’ve left the filling loop tube connected and add water back in in small quantities (so as not to introduce too much raw gassy water in a batch) and I’m keeping everything crossed :crossed_fingers:

There are many things about this experience that I don’t understand:

  1. Do I just have gassy mains water here?
  2. Do I have some old sludge in the system that is reacting with something and releasing fresh gas into the system?
  3. Is there a pipe leak in the system somewhere that somehow allows atmospheric pressure air into a pressurised closed system?

tl:dr
But bottom line is that I think if I keep purging and purging, together with 5 AAVs, a spirovent, and all the manual bleed valves, eventually I will get to the end of it.

Good luck!
David
https://heatpumpmonitor.org/system/view?id=364

1 Like
9

Thanks for your response, in a strange way it’s good to know I am not alone, I have aav’s but only on the space heating side.
The HW return T’s in below my volumemiser so hope air will move to this which has an aav.
I was looking at the Spirovent or getting an aav added to the HW feed pipe but will leave it for a week or two to see how it gos,

Mark

10

I’m not entirely convinced that AAVs are sensitive enough for this problem. I think they are probably more suited for big gulps of air pockets rather than the micro-bubbles that are interfering here.
That’s why I’m finding value in manually releasing at the points I listed.
Another point to remember is that (in the short term at least) having these air errors is just a measurement problem. The DHW cycle is still heating perfectly satisfactirily. It’s just our statistics in heatpumpmonitor that are taking a substantial hit!
I know that the air does present long-term corrosion and wear issues, but it’s not really a massive heat pump performance problem at this early stage.

11

Very true.
Would you recommend a Spirovent then ?

12

As I say, I haven’t noticed the Spirovent doing any improvement. But that’s not to say it is not helping, but it’s not doing enough on its own.
On that basis, I wouldn’t recommend it.

I think the trick is to manoeuvre some heated water into the radiators during a DHW cycle where you will have some manual bleed points that you can use to release it.

On that highest radiator I mentioned, I did also fit an Aladdin Aav, but I don’t think this has been effective either.

13

Thanks , HW runs at 3am as cheap electric price, but I have check the rads and 2 off them have new air in them . I will give it a couple of weeks to see how it goes, then change HW schedule if needed and finally look at other methods

14

More advice in these two topics:

15

Thank you for this , it is a very good read and helps me understand the issue and some solutions

Mark

16

Shame local hire shops don’t have “vacuum degasser” units.

I expect there will be less air issues if the flow meter is in the return to the heatpump, as the air will desolve more in cooler water.

Spirovent needs to be in a flow of water that is significantly hotter then most of the system water, so may work better if dt is closer to 20c then 5c, but that’s not friendly to heatpumps.

17

This.

You need to to cook off the air in space heating mode by getting it all good and hot

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18

Thanks Marco.
When doing the “cook off” (that’s mentioned in the linked document), how does the released air find its way out of the system? Through the AAVs? It lurks at the top of radiators ready for bleeding later on? via my Spirovent?

19

All the above

20

It collects in radiators to be bled out whilst system is red hot

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