LG Dual Inverter Split Aircon

[matty1]

Hi,

Im wondering if im missing something here, im no aircon expert but I have this possible issue with the current system I have just had installed. Im based in the UK so generally its always cold, 6C at the moment outside

I have a dual split system installed, one unit in the living room and the other unit in the bedroom. The living room size is not huge but due to stock levels I have ended up with a 5Kw unit there and a 2.5Kw in the bedroom. Model number for the one downstairs is DC18RH NSK. Both units are giving the same possible issue.

If I set to heat mode with my set temp of 23C the room will warm up to 26C (or so says the inlet sensor) and then the aircon will shut off outside and inside. It does this nearly all the time say 99% of the time, usually takes 20 to 30 mins to warm up. Room temp will drop to 20C or thereabouts and the unit will spring back into life, heat the room up to 26C and go off inside and outside units.

However randomly the temp will heat up the room to 23C (according to inlet sensor) and continuously run for hours to the point I usually switch it off else it seems to want to run forever. It keeps a constant 23C. The compressor doesn't seem to be running constantly but the outdoor fan is as well as of course the indoor unit.

From what I have read inverter based units stay on and adjust the compressor speed to keep the room at a set temperature but my question is why does it not do this all the time? Why is it 99% of the time hitting 26C and going off after 20 to 30 mins if I have set it to 23C for example?

LG say it should get to temp and go off also.

Installer is saying its supposed to be like that but cant say why, I cant get my head around why it runs for hours randomly and not do what it normally does by going off after approx 30 minutes 99% of the time.

thanks in advance.

[back2space]

Wall mounts have a 3c offset so will heat approx 3/4c above the set point to allow for stratification of warm air otherwise it would shut off too early. Warm air rises to ceiling level so it’s always warmer at ceiling level, so where are you reading 26c on? it will always be warmer, what is the room temp at low down?

Also the inverter will ramp down, try setting them both to 30c and you will see how hard the outdoor unit runs. Now set them to a reasonable temp and you will hear it ramp down. It will never be perfectly balanced, in heating mode, to stop the cycling the unit will only be able to ramp down so far. Run the fan speed in low, which will effectively reduce the heat output so the unit will stay running for longer.

[jhaguru]

inverter Air Conditioner units will stay on if the threshold of temperature is within 3-4 c if it goes beyond that due to factors which appliance cannot control then the compressor will shut off.
Regards

[matty1]

Thanks for the replies. The readings for the inlet temps im getting from the ThinQ app which reads it directly from the indoor unit as far as I can tell.

I know 'loads' can make a difference but the temps in the UK are not overly dramatic in changes, also I dont have lots of people coming into the living room.

I have left either the indoor fan speed to Auto or low so its not quickly heating the room up as you mentioned the fan speed being low.

I think I found that the living room indoor unit and outdoor unit will constantly run for 2 hours near to my set temp of say 23C if the outside temps are 5C approx or lower. It doesn't deviate and will sit at around 24C inlet temp. After a defrost because of the 2 hour constant run the indoor unit comes back on and tops the room temp up to 26C within 20 mins and goes back to sleep. I find that odd as I would have expected it to come out of defrost mode and continue to run for 2 hours keeping a set temp like it was doing before the defrost?

Blows my mind how it operates

[frank]

Fuzzy logic

[matty1]

Fuzzy logic

Doesn't that only apply when the aircon is set to Auto rather than to Heat mode?

I did read the tech service manual but couldn't find anything overly useful in it to explain what the 2x4 was happening.

[Miguel17]

Based on your description, your air conditioning system reaches a temperature of 26°C before shutting off instead of maintaining the desired temperature of 23°C. A few different factors could cause this.

Firstly, it's worth noting that air conditioning systems may struggle to reach their optimal operating conditions in colder climates, like the UK. This is because they're designed to work best in warmer temperatures and may struggle to heat a space effectively in freezing temperatures. However, based on your description, the system can occasionally heat the room to the desired temperature, so this may not be the main issue.

The thermostat or temperature sensor on the system is not working correctly. If the temperature sensor reads the room as being warmer than it is, it may cause the system to shut off prematurely, thinking that the desired temperature has been reached. This could also explain why the system sometimes runs for hours without shutting off, as it may compensate for an incorrect temperature reading.

Another possibility is that the system needs to be correctly sized for its heating space. If the system is too small for the room, it may struggle to maintain the desired temperature and shut off once it reaches its maximum output. This could explain why the larger unit in the living room is shutting off more frequently than the smaller unit in the bedroom.
It's also possible that there is a problem with the system's control board or inverter. These components are responsible for regulating the system's output and ensuring that it operates correctly. A problem with the control board or inverter could cause the system to shut off prematurely or fail to maintain the desired temperature.

It may be worth contacting a qualified air conditioning technician to look at your system and determine the cause of the issue. They should be able to diagnose any problems and suggest a solution to get your system operating correctly.

[matty1]

Hi, Thanks for the reply. I have a temperature gun and have monitored the top of the indoor unit where air is drawn in and the readings tie up ok so I dont think that the readings are incorrect.

I have found that if it is lower than 4 degrees C outside then the indoor and outdoor unit will continue to run until it hits defrost mode. I also have opened one of the living rooms doors to let heat out and I can see the inverter running faster (drawing more power) to create more heat so I think the sensors are all ok?

I suspect, in fact I know the unit in the living room is too big as it should have been a 3.5 instead of a 5Kw unit.

The installer won't respond to me since I asked other aircon suppliers why it was happening as the installer couldn't answer as to why and just said it's supposed to do what it is doing. None of them have been out to my house so the unit has not been opened by anyone else to invalidate the warranty.

However it seems most suppliers in my area dont supply LG units, more Dakin or Mitsubishi. Interestingly they said those units which also have inverter tech do not operate the same as this LG unit I have. They said those units get the room to temp heat wise then go to sleep until they are required to top the heat up again. They have never known a unit to maintain the heat by constantly running.