ReedRichards Posted December 9, 2023 Share Posted December 9, 2023 You would think that if it is a known problem there would be a good stock of spares to enable a quick repair. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 11, 2023 Share Posted December 11, 2023 (edited) I'm experiencing a problem with my 12 kW monoblock Therma V, installed December 2020. As of yesterday it has stopped modulating. As always, it starts up at the lowest level of power, drawing approximately 2.3 kW. Normally it will gradually step up the power input as necessary but as of yesterday it is stuck at 2.3 kW and never increases (or decreases) significantly. It will heat my water up to about 30 C, which at the moment is heating my house to about 19 C. If have set it to ask for a fixed water temperature of 50 C but that makes no difference. There is no error message nor any indication that it thinks something is wrong. Has any other Therma V owner experienced the same problem and know (or can guess) what the cause/fix might be? Edited December 11, 2023 by ReedRichards Link to comment Share on other sites More sharing options...
JohnMo Posted December 11, 2023 Share Posted December 11, 2023 Switch off at mains and that should reset the logic? Link to comment Share on other sites More sharing options...
ReedRichards Posted December 11, 2023 Share Posted December 11, 2023 Already tried that, left it off for approximately 12 minutes, but it made no difference. Good suggestion, though. Link to comment Share on other sites More sharing options...
ProDave Posted December 11, 2023 Author Share Posted December 11, 2023 Check all the motorised valves are opening and closing correctly. I wonder if it is stuck trying to do heating and hot water at the same time, something it is not supposed to do. Link to comment Share on other sites More sharing options...
JohnMo Posted December 11, 2023 Share Posted December 11, 2023 1 hour ago, ReedRichards said: It will heat my water up to about 30 C, I had what looked to be similar a week or so ago. I had let the floor get very cold. Target flow temp was about 35, it wasn't moving past 30. I left it to run for hours and the temp slowly crept up. My problem the floor was just cold and the water flow heat was just being absorbed by the floor, the heat pump just looked at dT and was therefore happy. As the dT started to fall it added temperature but not until then. Check the flow and return temperature and monitor dT, see what it's actually doing. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 11, 2023 Share Posted December 11, 2023 I've had to turn off the hot water because there isn't nearly enough power to heat it up. Now I'm left trying to heat radiators with a flow of 31 and a return of 29. It's become apparent that despite the lack of heat going into the water, I am using much more power than usual. I must have suffered a significant loss of efficiency. So possibly the lack of modulation is a secondary effect because some expected threshold is not reached. I have only radiators so there is nothing slow to warm up. There isn't a motorised valve that can go wrong, as far as I can see. Link to comment Share on other sites More sharing options...
JohnMo Posted December 11, 2023 Share Posted December 11, 2023 Could be sensor or leak? Can you see the refrigerant side running parameters, check to see what the pressure is, if you are using lots of power, but getting no heat it could be refrigeration leak? Mine a different make, but should be similar. Design pressure (high/low) heat pump mode bar 42,8/1,3 If you can't see the pressure, you may be able to see the temperature at the heat exchanger or at the compressor. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 12, 2023 Share Posted December 12, 2023 I did not know what to make of the numerous parameters but I was able to create a log file and send it my installer who thinks the problem is indeed a refrigerant leak, not the best news. But he has it in hand and has always responded very positively. I am fortunate that he gave me a WiFi dongle that fits inside the heat pump and enables a tablet (actually, it's my wife's tablet) to talk to the heat pump. The tablet runs some software called LGMV to do this. I have not made much use of this hitherto, but it came in very handy today. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 13, 2023 Share Posted December 13, 2023 I have been incredibly fortunate! My installer, who I rate very highly, was able to convince LG that because of the expense of paying him to carry out a repair under warranty, which is very time consuming with a refrigerant leak, it was better to supply a new heat pump. So now I have the latest version of the Therma V with improved controls and I have to learn about all the new features. I still can't quite believe it. 3 Link to comment Share on other sites More sharing options...
Transition Posted December 14, 2023 Share Posted December 14, 2023 17 hours ago, ReedRichards said: I have been incredibly fortunate! My installer, who I rate very highly, was able to convince LG that because of the expense of paying him to carry out a repair under warranty, which is very time consuming with a refrigerant leak, it was better to supply a new heat pump. So now I have the latest version of the Therma V with improved controls and I have to learn about all the new features. I still can't quite believe it. That is incredible fortunate indeed. One of the biggest issues is the lake of information the heat-pump provides. You'll definitively will have better control over the unit and whats more the new unit is more cost effectively ;-)) Enjoy! Link to comment Share on other sites More sharing options...
ReedRichards Posted December 14, 2023 Share Posted December 14, 2023 I haven't done much with the new unit so far, except program it with my old Weather Compensation settings. The software version is 3.06.6a instead of 3.05.6 on my old version. It reports the outside temperature, which the old version didn't. And it says "anti-freezing" instead of "defrosting", which I don't like so much. Link to comment Share on other sites More sharing options...
Boy1925 Posted December 15, 2023 Share Posted December 15, 2023 Congratulations. Xmas came early for you. I am still waiting for a replacement pressure sensor from LG fitting of which I anticipate will require venting off the refrigerant and refilling etc. Did your installer figure where the leak arose in your pump? Incidentally, can you set the dhw temperature by use of the wifi dongle you recently mentioned? That is something I would very much like to be able to do. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 15, 2023 Share Posted December 15, 2023 AFAIK the dongle I mentioned is only for monitoring and does not allow you to change settings. You can set the DHW temperature on the controller by using the L/R arrows to select the shower head icon then the up and down arrows to change the set temperature. Or you can go to Menu then Schedule then Schedules and Edit and schedule different hot water temperatures at different times. If you have a schedule already set this will override any manual changes as soon as the next scheduled timeslot starts. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 16, 2023 Share Posted December 16, 2023 (edited) By the way, @Boy1925, LG should have received a broken 2020 vintage Therma V heat pump this week (my old one). If you are still waiting for spare parts, they should be able to cannibalise that to keep you going in the short term. My issue was a refrigerant leak, all the electronics should be working. Edited December 16, 2023 by ReedRichards Link to comment Share on other sites More sharing options...
Boy1925 Posted December 16, 2023 Share Posted December 16, 2023 Thanks ReedRichards, I hope to find a remote way of controlling the dhw. I am told that the replacement part I need should arrive soon so it appears that the part is available. Link to comment Share on other sites More sharing options...
JohnMo Posted December 16, 2023 Share Posted December 16, 2023 On 15/12/2023 at 15:03, Boy1925 said: anticipate will require venting off the refrigerant I hope not - as that exactly legal, they should extract and reuse or send for recycling. Then fill with new. Link to comment Share on other sites More sharing options...
ReedRichards Posted December 17, 2023 Share Posted December 17, 2023 16 hours ago, Boy1925 said: I hope to find a remote way of controlling the dhw. I think the fundamental problem is that third party controllers switch mains voltage (AC) to control DHW. The LG heat pump uses both mains voltage (AC) and logic ( 5 V DC) to control hot water so it does not interface with a third party controller. A DIY solution to this issue is suggested by @ProDave on page 5 of this thread. I don't know if that's still working. Link to comment Share on other sites More sharing options...
ProDave Posted December 17, 2023 Author Share Posted December 17, 2023 24 minutes ago, ReedRichards said: I think the fundamental problem is that third party controllers switch mains voltage (AC) to control DHW. The LG heat pump uses both mains voltage (AC) and logic ( 5 V DC) to control hot water so it does not interface with a third party controller. A DIY solution to this issue is suggested by @ProDave on page 5 of this thread. I don't know if that's still working. Yes that is still in use. I use the "room thermostat" input to call for space heating when required. As pointed out, there is no official way to "call for hot water" from an external source, so my solution was to use a relay to switch between the cylinder temperature probe (which is a thermistor) and a fixed resistor, chosen to mimic a hot water reading which fools the control system to thinking the tank is above the set point so it does not do any heating water. The way I have it, is with the relay not energised the fixed resistor is connected so no hot water heating happens. When I want it to heat the DHW I energise the relay, that connects the temperature probe and the heat pump heats the water if it is lower than the set water temperature. Link to comment Share on other sites More sharing options...
JohnMo Posted December 17, 2023 Share Posted December 17, 2023 1 hour ago, ProDave said: so my solution was to use a relay to switch between the cylinder temperature probe (which is a thermistor) and a fixed resistor, chosen to mimic a hot water reading which fools the control system to thinking the tank is above the set point so it does not do any heating water. The way I have it, is with the relay not energised the fixed resistor is connected so no hot water heating happens. When I want it to heat the DHW I energise the relay, that connects the temperature probe and the heat pump heats the water if it is lower than the set water temperature. That info is great it solves an issue I have with my heat pump, at moment my call for DHW is an on off contact, but really want to use that contacts for some else. And use the correct temperature probe connection to call for heat. So I can use a variation of the above. Link to comment Share on other sites More sharing options...
Boy1925 Posted December 17, 2023 Share Posted December 17, 2023 (edited) That sounds like a good solution to the difficulty of controlling the dhw. i wonder if the following would also work:-could a Heatmiser room stat be wired in rather than a plain resistor and thus allow the dhw temperature to be controlled remotely? I am no electrician so not able to assess any problems with this approach nor how to wire it but if it sounds ok to those more electrically competent, I’d like to try it. Clearly some recalibration would be required and that might be a complexity too far! Edited December 17, 2023 by Boy1925 Addition. Link to comment Share on other sites More sharing options...
JohnMo Posted December 17, 2023 Share Posted December 17, 2023 34 minutes ago, Boy1925 said: Heatmiser room stat be wired in rather than a plain resistor and thus allow the dhw temperature to be controlled remotely No - the heat pump reads resistance of a probe directly and then generates a temperature from that generally. So the resistance is the important bit Link to comment Share on other sites More sharing options...
ReedRichards Posted December 30, 2023 Share Posted December 30, 2023 For the information of anyone following this thread, I found a website with a recent installation manual here: https://www.lg.com/uk/support/product-support/cs-HM121MR.U34/ . This includes installer settings for both Series 3 and Series 4 versions of the Therma V. Link to comment Share on other sites More sharing options...
Boy1925 Posted January 3 Share Posted January 3 The replacement pressure sensor arrived on 16th December and my local engineer attended and fitted it the following morning for which he had to evacuate the refrigerant and solder in the new sensor then refill. Although I was by then away for Christmas, using the heatmiser app I was able to see that the heatpump was working and was able to control the heating of the whole house so arrived back to a comfortable house before New Year. The whole problem arose due to an inadequately insulated wire shorting on the metal chassis. I hope this will not happen again! Happy New Year to one and all. Link to comment Share on other sites More sharing options...
ReedRichards Posted January 4 Share Posted January 4 13 hours ago, Boy1925 said: The whole problem arose due to an inadequately insulated wire shorting on the metal chassis. I hope this will not happen again! Presumably you can check the new wire and add extra insulation if necessary? Link to comment Share on other sites More sharing options...
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