LG Therma V Monobloc – CH014 Flow Error (Heating Only)

[Willits]

Hi all,

I’m hoping to get a bit of insight on a CH014 flow error I’m seeing on my LG Therma V 9 kW monobloc.

I use both heating and cooling and it behaves perfectly in cooling mode. In cooling mode, there are no errors at all and the reported flow sits steadily at around 31–32 l/min.

As soon as I switch over to heating the unit starts up normally and will run for 10–15 minutes, but once the flow temperature gets to around 25 °C, the displayed flow suddenly drops (sometimes down to ~5 l/min) and it throws a CH014. It then shuts down for about a minute, restarts, runs for another 5–6 minutes, and repeats the cycle.

A few things I’ve already checked:

The circulation pump seems fine.

The system has a 4-pipe buffer tank, so I don’t think this is a downstream restriction issue.

In pump-only / no-load operation (cooling mode with no demand), the flow is stable all day.

The flow sensor itself is a Sika vortex-type sensor (no moving parts). I took it out and cleaned it — it was coated in a very fine black film.  After cleaning it did improve slightly, but the fault is still there. I’ve now added Fernox F3 and am circulating it to see if that helps.

What I’m struggling to pin down is whether:

the unit is really losing flow once heating starts, if the flow sensor is reading false once the water warms up, or maybe something different entirely.  

I was going to just replace the flow sensor to see if that solves it until I found that they are more than €300 from Sika and closer to €500 from LG.   So before swapping it out I’m considering fitting a temporary external flow meter just to confirm whether the real flow is actually collapsing or if it’s a false reading.

Has anyone seen CH014 only in heating or had experience with vortex flow sensors drifting or failing when warm on Therma V units?

I’ve searched through the forum but haven’t found anything that quite matches this behaviour.

Any thoughts very welcome — thanks in advance.

Peter

[JohnMo]

My be worth reading this, not reread it all but may be something of help

 

https://forum.buildhub.org.uk/topic/30786-lg-therma-v-monobloc-ch14-flow-error/

[Michael_S]

WE have an older series that has a paddle flow switch.  My initial thought might be that you have TRVs that were closing down the flow but with a 4 pipe buffer this should not be the issue.  I assume there isn't a mixer valve in the circuit somewhere that is for some reason set to a low value?!

[Willits]

4 hours ago, JohnMo said:

My be worth reading this, not reread it all but may be something of help

 

https://forum.buildhub.org.uk/topic/30786-lg-therma-v-monobloc-ch14-flow-error/

Thanks, I did read that thread before posting, and did some of the checks which did not make any improvements.  

[Willits]

3 hours ago, Michael_S said:

WE have an older series that has a paddle flow switch.  My initial thought might be that you have TRVs that were closing down the flow but with a 4 pipe buffer this should not be the issue.  I assume there isn't a mixer valve in the circuit somewhere that is for some reason set to a low value?!

I have a DHW loop but turned it off to be sure it was not the mixer valve.   The flow goes straight through to buffer tank without any potential restriction points.  So if there is a restriction it has to be in the heat pump.   I think the thing to do is to confirm the actual flow so I can decide if the flow sensor is suspect or not.  

[Dillsue]

With a flow sensor rather than a flow switch I guess yours is a gen 4 HP.... model number ending Ux4? In our earlier gen 3 there's a strainer inside the HP on the return pipe.  If thats fitted is it clear?

 

Have you got a magnetic filter in the return line? Ours picks up a bit of black gunk which is clearly magnetic. If youre getting a black coating inside the flow sensor and that coating has a metallic content then that could affect the sensor?? A mag filter is stated as mandatory in some LG documentation so well worth fitting and definitely worth fitting if you've got ferrous components like radiators in the system.

[JohnMo]

As mentioned above a flow sensor needs a system clean, and it needs to be air free. It seems to be the norm to install strainers, which pretty rubbish at stopping small stuff being circulated.

 

You said you put cleaner in the system the other day. I would now look to flush that out, give the flow sensor a good clean. Refill, inhibit and biocide the system (biocide if you do cooling or routinely run below 35/40 degs.

 

While you are at add a decent low flow resistance magnetic filter and delete the strainer.