LG Therma V Monobloc CH14 flow error

[Tim Pearson]

Anyone got any experience on approach to resolving constant CH14 flow error on LG AWHP?

Following 4/22 service, I’ve had a further 3 instances this year (annus horribilis 😏)

6/22 cleaned out filter and resolved.

10/22 checked filter, no success, then called out installer for service but resolved itself before they arrived, (after multiple shut downs/restarts).

12/22 arrived home from Egypt after UK cold snap to discover AWHP running but not producing heat. No error messages, later reported CH14 error.

My installer yet to confirm repair visit a week after reporting - reckon they’re far too busy on new installs to deal with service/support issues..

T

 

 

[ReedRichards]

This might help:

 

[ProDave]

This seems to be the bane of these units, the way the error is handled and reported, is in my opinion poor.

 

First the context please?  Is this a new install? or an old install that has run for a long time and only just started throwing this error?  Is it UFH, radiators or a mixture?

 

I had this problem right from the start.  The two issues were nowhere in the manual did it state what the minimum water flow rate was, and there was no means to measure it.  A phone call to LG told me it was about 10 litres per minute approximately that it needs to see, but there was a bit of tolerance in the actual value the flow switch registers as okay.

 

I then installed a flow meter so I could actually see the flow rate I was achieving and it was only just enough.  So I installed a second circulating pump in the house in addition to the one inside the ASHP which improved the flow rate and solved the issues.

[Tim Pearson]

Thx to ReedRichards and ProDave for those prompt replies. Will check out the details tomorrow. Appreciated. T.

[akjos]

Every heatpump needs about 2x to 2.5x the capacity of flow rate in l/min.

so if you have a 6kw unit, about 12l/min.

 

Make sure your system can achieve that and ypur zones are not closing.

[Tim Pearson]

Ok so thx to all so far -  update and system overview. 

Update - switched off/on ASHP multiple times and on 26th it started heating again. That lasted a full 24 hours and then CH14 error reappeared.

No heating/DHW and error message on LG controller.

Actions - bled rads whilst system was working.

 

System Configuration

Heating

HM121M.U33 LG R32 Therma-V 12 Kw Monobloc (installed 5/19)

Buffer Tank - 50L Cordivari Volano Termico PDC Hanging

 

Radiators - 6 across 55 sq m

UFH - 4 zones across 65 sq m

Heatmiser UH8 - RF
Wilo Para 25/6 43/SCU  pump

Pressure steady at 2 bar

 

DHW Storage

180L horizontal unvented cylinder

Pump - Grundfoss UPS3 15-5065 130

 

Controllers

Therma V controller, wired to AWHP

Honeywell Home Hub wireless relay box, T3 controller 

Heatmiser xone controllers for UFH 

 

Comments

1. Flow Rate Error

How do you identify where the CH14 flow error is occurring, in the DHW or the heating system?

The buffer tank acts as a hyperbolic separator, so there are 2 flow rates : heat pump flow rate and terminal flow rate.

Can the LG control monitor both flow rates?

Assuming the AWHP pump must be sized correctly (for the HPFR), surely an additional pump should only be of benefit in increasing the terminal flow rate?

NB The Grundfoss pump on the Therma V (water side) is the same model (UPML 20-105 CHBL) across all the 12, 14 and 16 KW versions.   

 

 

 

[ProDave]

You are not going to solve this by keep on re booting it.

 

The flow is measured by a single flow switch inside the heat pump.  It turns on when the flow rate reaches the minimum required.  There is only one flow switch so it will be measuring the flow rate at the time which might be heating or it might be hot water.  If it does not turn on, the flow rate is too low.

 

If it had previously worked reliably, it might be the strainer filter inside the heat pump is blocked.  Have you tried checking that?

 

Otherwise you will have to do as I did and increase the flow rate some how, I fitted a second external pump to do that, but changing the internal pump (small wilo pump in mine) for something more powerful may be another option?

[JohnMo]

Think the flow switch is in a failed condition, so read a huge flow rate.  This allows the heat pump to run for a while until the controller logic says, that cannot be correct, let's shutdown.

 

First check the wires for the flow meter meter, disconnect then reconnect the wires first.  If that fails the switch may be goosed. 

 

However if under warranty call the installer, that's what the warranty is for.

Edited December 28, 2022 by JohnMo
Missed words

[ProDave]

You can check the flow switch.  It will need a partial drain down (easier if your installer fitted isolating valves in the flow and return to the ASHP)  Once partially drained you can remove the strainer filter and check for debris, and you can lift the float switch out of it's housing, on mine it is 4 little screws and the switch itself lifts out of the housing but it was not the easiest thing to reach.  Then you can check the flapper of the switch moves okay and there is no objects stuck to the flapper.  Make sure you put it back facing the same way it came out.

[Tim Pearson]

Ok thanks to all.

Will follow up on suggestions.

T

[ReedRichards]

6 hours ago, Tim Pearson said:

Comments

1. Flow Rate Error

How do you identify where the CH14 flow error is occurring, in the DHW or the heating system?

 

 

If it's one or other then it should be able to heat the hot water without error or run the heating system with out error.  If it's both then it's one of the 5 possible causes listed under "Heat and Tank Mode" (unless it's a valve problem that occurs when switching between DHW-"Tank Mode" and Central Heating-"Heat Mode"). 

 

The water pressure is good so that eliminates one of the five possibilities.  That leaves:

 

Strainers and filters blocked

Water pump fault 

Flow switch abnormality

PCB fault

 

Don't worry about the WIlo pump for your radiators; that could be completely dead and the Therma V would not know.  So it's not the problem; nor is anything on the central heating side of the buffer tank. 

[Tim Pearson]

Ok so looking at all those comments and using @ReedRichards checklist.

 

1. Strainers and filters blocked.

Will check and clean filter (on next dry day ..).

 

2. Water pump, possible fault.

- per @AKJOS, pump capacity should be 30 LPM (2.5 * 12j. Rated flow per attached technical document is only 34.5, so little tolerance. Recommends pump set to max (need to work out how to check this setting).

 

- technical document I found refers to use of additional pump, also suggested by @ProDave, or replacement with larger pump (yes, there are isolating valves, enabling filter removal and cleaning).

I have attached this  technical document. See in particular

- piping schematic (pp 15).

- reference to CH14 errors arising from pump setting (pp28), including the following info.

“The water pump is variable type which is capable to change flow rate, so it may be required to change default water pump capacity in case of noise by water flow. In most case, however, it is strongly recommended to set capacity as Maximum.
Note
• To secure enough water flow rate, do not set water pump capacity as Minimum. It can lead unexpected flow rate error CH14.
• When installing the product, install additional pump in consideration of the pressure loss and pump performance.”.

 

3. Flow switch abnormality (leave for now).

 

4. PCB fault (leave for now).

 

PS document too big to attach, see

 

https://cms.intermetal.bg/storage/uploads/2019/12/02/5de4e66b09ef03.---LG-MONOBLOC.pdf

 

Thx for support,

Tim

 

[ReedRichards]

You might find more information in the document I posted here (Page 11, October 30, split into 3 parts).

 

[Tim Pearson]

Thx.

Just checked installer settings on the LG controller - pump capacity set to 100%.

Still need to check if the the Grundfoss pump in the outdoor ASHP unit is set to max. 

Tim

[HughF]

9 hours ago, Tim Pearson said:

Thx.

Just checked installer settings on the LG controller - pump capacity set to 100%.

Still need to check if the the Grundfoss pump in the outdoor ASHP unit is set to max. 

Tim

I would assume that LG, like all good heatpump manufacturers, use a PWM controlled primary pump so they have control over the delta-T. So there should be no need to check what speed it is running at.

[ReedRichards]

For what it's worth, my installer settings are the same; the pump capacity is set to 100%.

[dpmiller]

100% might be the max limit. On our CoolEnergy, there are settings for min and max, and for a higher startup setting (probably to ensure the flowmeter trips before settling back into deltaT control) as well as the actual deltaT across the ASHP.

[JohnMo]

Once the heat pump has got water circulation around the buffer it's not interested in any other part of the system, except when the 3 port valve opens the flow path to the hot water tank is open.

 

So things that affect flow,

Flow restrictions - filter blockage - really the most likely.

Flow restrictions - pipe size and length.  Assume your piping size is ok, how long are your pipe runs, after about 20m on 28mm pipe the 7 or 8m pump could be running out of capacity.

[Kelvin]

I was plagued with this on a Samsung unit after a pump change with it working for several days then randomly failing with flow rate errors. Fortunately we had a flow meter installed so could see the flow rate. I chased my tail for a bit thinking it must be the new pump as it was a different model from the failed pump. However it turned out to be a two way valve that was very slow to operate. 

[ProDave]

14 minutes ago, Kelvin said:

However it turned out to be a two way valve that was very slow to operate. 

From my investigations, the LG heat pumps expect the required flow to be achieved within 10 seconds of the pump starting. If your valve takes longer than that to open you will have a problem.

[dpmiller]

can this time not be adjusted in the menus?

[ProDave]

2 minutes ago, dpmiller said:

can this time not be adjusted in the menus?

No.

 

But most motorised valves take less than 10 seconds to open, and there should be some form of automatic bypass valve to give some flow even when all motorised valves are shut.

 

If you suspect this is your issue, you can manually open most motorised valves, so do that to one of your valves and see if the CH14 error stops.

[ReedRichards]

I presumed the valve being referred to is the one that controls whether the water flow is to the buffer tank or the DHW cylinder?  So it's two-way valve and wouldn't there be flow even if it was stuck half way?  

[Tim Pearson]

Ok so partially drained, filter removed (little or no debris), cleaned and reinserted.

 

Flow switch is a Sika V3. Unclear which model at this stage, but label indicates 15l/min set point.

Not yet removed to check paddle operation. Also, it may have an adjusting screw, tbc.
 

Powered by cable back to control board - blue connector.

Attached info.

Any more suggestions before I remove FS, check paddle, any flow adjustment option?

On electrical connection, what is there to check and how?

thx again

T

 

Data sheet VK3 flow switch.pdf Ea3000_FlowSwitch operating instructions .pdf

[Kelvin]

3 hours ago, ReedRichards said:

I presumed the valve being referred to is the one that controls whether the water flow is to the buffer tank or the DHW cylinder?  So it's two-way valve and wouldn't there be flow even if it was stuck half way?  

In my case it was slow to start to change and then slow to actually change. It interrupted the flow enough to cause the error but only occasionally. I suspect it was failing for a long time but the original pump’s flow rate was higher than the replacement pump so was hiding the problem. 
 

The two way valves seem to be a common failure point on every system as I’ve had at least one fail in every house I’ve lived in and replaced a few for neighbours. Consequently I kept one on the shelf just in case. That was how I stumbled across the fix as after exhausting everything else I replaced the valve and it cured the problem. 

Edited December 29, 2022 by Kelvin