LG Therma V set up quirks and info

[Dillsue]

I've started this topic to document some of the quirks I'm finding in getting our Therma V installed and up and running. There's lots of other topics covering some of the quirks which I've read several times to try and understand how Heat pumps work and in particular how the Therma V works. Some of what's said elsewhere will likely be repeated here!

 

Our HP is a secondhand 7kw unit built in late 2020. The part number ending in U43 says its a series 3 unit as that's what the last digit denotes. Our software version from the remote controller is 3056.

 

The first quirk is the installation manual says the transition from series 3 to series 4 was from August 2020 to Setember 2020. The date on our HP is 20 October 2020 yet it's a 3 series! Double check the manual/HP model to make sure your reading the correct info applicable to your series.

 

Next quirk is that I've seen a number of posts where one person is describing a feature and another person doesn't seem to have that feature. What I have found is that what the remote controller displays/how it acts can be dependant on DIP switch/ link settings. If you enable the use of a third party thermostat the On/Off button on the controller stops working and displays function blocked if you try to switch the heating off from the remote control panel. Similarly our HP had previously been used with glycol and there was a DIP switch AND a linked plug that had been set to use glycol. This then gave an "antifreeze" option within the installer menu. I'm not using glycol so have reset the DIP switch and link to reflect this. The "antifreeze" option has now disappeared from the installer menu. Be conscious that if there's differences in features between your system and others of seemingly the same model, it can be just that the settings are different that either add or remove features!!

 

Resetting CH14 low flow errors can be achieved by cycling the thermostat input On, Off then back On rather than power cycling. Whilst commissiong our system I've had the HP hydraulically isolated which stopped the HP circulating water and generated a CH14 error a few times. I'm intending to run with WC and use the thermostat as a temperature limiter rather than for control but switching it seems to be able to reset faults. The HP has a "forced run" feature to stop the pump seizing up which was configured to run the pump every day for a few minutes. I think it was this routine that caused the CH14 fault whilst I had the HP powered up but the water circuit isolated?? Not had the fault since so I'm making this diagnosis but keeping my fingers crossed!!

 

On the subject of low flow, I've read few posts where people talk about cleaning the strainer inside the HP but very little mention of cleaning the magnetic filter that should be on the return pipework to the HP. If youve not got a mag filter, get one as they pick up lots of bits. Ours also has a fine mesh, much finer than the strainer in the HP so pretty much renders the HP strainer redundant. LGs documentation says a mag filter is mandatory, so if you've not got one ask your installer why not!!.

 

I've seen few posts asking if it's possible to set back the HP flow temp overnight with the answer seemingly no. I'm not sure this is correct but I haven't tried it yet.  There's a feature called "Energy state" which allows you to increase or decrease flow temperature/DHW temperature based on switching a pair of digital inputs or over modbus. This feature seems to be intended to be used dependant on a battery state but no reason the digital inputs can't be triggered by a timer to increase or decrease flow temps overnight or to match up with a TOU tariff? More investigation needed but looks viable.

 

On the remote controller there's a button with a symbol of what I thought was a pointing finger with 2 hills in the background. I couldn't for the life of me work out what it was but it's a pair of lips and a finger saying "shhh"......puts the HP into quiet mode!! Couldn't see this in the user manual!!

 

If you want a quick boost to DHW temp and have the HP set up to control your cylinder immersion you can activate the immersion from the remote control panel. Scroll through though the buttons to get the DHW selected(shower symbol) then use the On/Off button to switch on the DHW. Now press and hold the back button. After a few seconds a lightning bolt/electrical hazard symbol appears on the DHW button. I believe the the immersion will now be powered. Press and hold the DHW button again to turn it off. I don't have my immersion connected to the HP but this feature works anyway on my remote controller.

 

Hope that helps anyone scratching their heads over their Therma V or at least points you in the right direction for some further research. More to follow as and when I come across them but feel free to add any quirks you've found but dont forget to reference your series number to make things meaningful.

Edited September 23 by Dillsue

[HughF]

Is there a hidden setting to stop the circ pump when the 3 port changes over? We’re getting banging noises from the primary pipework when the valve changes from dhw back to heating and I’m pretty sure it’s because the pump is still running.

[Dillsue]

9 hours ago, HughF said:

Is there a hidden setting to stop the circ pump when the 3 port changes over? We’re getting banging noises from the primary pipework when the valve changes from dhw back to heating and I’m pretty sure it’s because the pump is still running.

What series have you got? I'm guessing that the DIP switch to enable DHW functionality is set correctly or you'd likely not have any DHW options at all. Assuming the switch is set correctly, any options for DHW settings should be showing in the installer menu but I dont remember seeing anything about settings during changeover.

 

If you've got rattling pipework options I'd look at would be-

Secure the pipework

Throttle the pumps maximum output in the installer menu

Change your diverter for one that doesn't block the flow when it's changing from one port to the other

[HughF]

This is a 5kW gen4 on 3.06.9

 

I’ll try setting the pump to a fixed dT5, it’s set to maximum flow at the moment (we were chasing a ch14 error)…..

 

Valve is a standard Honeywell diverter in 28mm… same as used on my Vaillant cylinder (heated by a CoolEnergy), and a Samsung I commissioned at another property.

Edited Thursday at 07:05 by HughF

[Dillsue]

I'm guessing that if there's some knocking when the diverter changes over that there's a short period when it's closed to both DHW and CH which is causing the knocking?? Slowing the flow might be the easiest fix but if that doesn't work then a change of valve or securing the pipework could be the next step. I think you've got a display of flow rate on the series 4 so can see if you're maintaining a decent flow if you back off the pump

[HughF]

I don’t get this behaviour on my CE iVT9, with the same diverter, but I’m pretty sure that stops the pump on changeover.

[Dillsue]

4 hours ago, HughF said:

I don’t get this behaviour on my CE iVT9, with the same diverter, but I’m pretty sure that stops the pump on changeover.

If the ivt9 stops the pump then that seems to be different to the Therma V?? A bit of experimentation needed

[Dillsue]

Another potential quirk may have happened this morning. It's been too warm during the day recently for the HP to modulate down enough so it doesn't short cycle so we've used the thermostat to turn it off during the day but leave it to run in the cheap overnight period which finishes around 5 am. When I looked at the controller first thing this morning the inlet and outlet temperatures were around 19/20 degrees having cooled from 30 degrees that would have been running at up til 5.30. An hour or so later the inlet and outlet were both at 22 degrees which is room temperature so I think the circulation pump must have fired up?? It was pretty cold outside but no where near freezing, maybe 10-12 degrees, so no need for any freeze protection but maybe it's an anti condensation feature to keep the section with the PCBs dry?? Antifreeze protection seems OTT at those temperatures but anti condensation seems more plausible??

[JohnMo]

8 minutes ago, Dillsue said:

I think the circulation pump must have fired up?

There are generally 4 operating modes for a circulation pump.

 

On with the compressor, off when compressor stops.

 

Pre start and after run timers to add to the above. So pump will run for say 60 secs prior to compressor starting and 4 or 5 mins after it stops.

 

On all the time

 

Intermittent (sniffer mode) periodic starts after a defined time, runs for a defined time, repeat. If compressor starts the cycling starts again once the compressor stops.