Hi,

 

I've had an r32 5kw fitted for coming up to 2 years now. We love it, but I keep thinking it's not tuned optimally as trends to defrost every 50 mins or so in cold weather and also can easily chew through 70kwh of electricity per day on colder days which given today's prices hurts the wallet!

 

I'm currently trying out the ai/auto modes and trying to optimise that. I've been going through the settings through the installation manual and also a semi handy youtube video (

) 

 

There is one setting which I still don't write understand at the moment which is 'th on/off variable' as per https://www.manualslib.com/manual/1580071/Lg-Therma-V-Ahuw096a3.html?page=113

 

Can anyone explain the effect this will have at all?

 

Thanks.

 

I puzzled over this.  I thought maybe they were the hysteresis values for the air temperature when using Air + Water mode.  So with the Type 0 setting the unit would turn itself on if the room temperature dropped 0.5 C below the set temperature and off if the room temperature exceeded the set temperature by 1.5 C.  If so these would be end stops if it could not modulate to remain closer to the set temperature or if the water temperature did not get "out of bounds" first.

 

The thing that you can do that will most influence the power consumption is to get the weather compensation settings to match the needs of your house.  But if you are experiencing the cold weather that I am, then weather compensation probably would not make much difference at the moment.

 

There's a long thread on your/our type of heat pump here: 

   

Edited December 14, 20223 yr by ReedRichards

Can I ask what size your house? I’m having issues with my heat pump smaller than yours I was thinking it was undersized 

Whereas I have a much larger 12 kW LG heat pump yet is has never (yet) used as much as 70 kWh in a day.

2 minutes ago, ReedRichards said:

Whereas I have a much larger 12 kW LG heat pump yet is has never (yet) used as much as 70 kWh in a day.

I think a lot of these heat pumps are undersized and they have to run full speed in this weather. Resulting in high electricity usage 

Hi, thanks for the replies.

 

@ReedRichards I have previously read through that post, it's very informative. I keep hearing about weather compensation, but what settings would you say specifically relate to this? I have version 3.0.5.6 of the firmware... 

 

@Alwayslearning22... I agree. We originally were going to have a larger unit but the installer changed their mind at the last minute which admittedly did save a fair bit of money, so we can now use for increased energy costs of the less efficient pump! It's not too bad, it's only when the weather really drops the poor old girl has to really work to keep the house warm.

1 hour ago, hopefully_toasty said:

Hi, thanks for the replies.

 

@ReedRichards I have previously read through that post, it's very informative. I keep hearing about weather compensation, but what settings would you say specifically relate to this?

 The settings are "LWT temp auto mode" and "Outdoor temp auto mode".  Each setting has a pair of temperatures which you can change to suit your house.  Auto (Ai) mode engages weather compensation. 

 

My settings are:

LWT temp auto mode        29 50

Outdoor temp auto mode  -4 18

 

This means if the outdoor temperature is -4 or less my target Leaving Water Temperature will be 50 C (which is my system max.)

If the outside temperature is 18 C or more then the target LWT will be 29.

 

At intermediate temperature the target LWT varies linearly with the outside temperature.  So, for example, if the outside temperature was 7 then the target LWT would be 39.5.  

 

 

That's been very useful, thanks. I also caught up with the latter pays of that post as it seems I was a couple of months out of date!

 

I'm currently experimenting and will let you know progress!

Unless you are somewhere warmer than most of the UK, the outside temperatures are likely to be too cold for weather compensation to make much of a difference.  In my case if the temperature outside is -5 or less then I'm outside the range of weather compensation and at anything below zero it makes very little difference.

As I understand it, the target flow temp should be adjusted, based on the outside temp? 

 

So if that's the case, wouldn't it have as linear effect, regardless of how cold it was? E.g. I have tried to set it so that it updates the target flow temp by ~1 degree for every degree the outside temp drops;

 

LWT temp auto mode        25 45

Outdoor temp auto mode  -4 16

 

So the difference of target flow temp between -4 and 1 should be 5 degrees lower? It's that correct or am I completely misunderstanding?

Edited December 16, 20223 yr by hopefully_toasty

Your understanding is correct, at 1 degree outside your target flow temperature would be 40C with those settings.  By implication your system was specified to operate at a maximum 45 C flow temperature and your heat pump and radiators were sized so that the heat output would meet the demand (i.e. the building rate of heat loss) when the outdoor temperature is -4 (with whatever spare capacity was deemed advisable).

1 hour ago, hopefully_toasty said:

As I understand it, the target flow temp should be adjusted, based on the outside temp? 

 

So if that's the case, wouldn't it have as linear effect, regardless of how cold it was? E.g. I have tried to set it so that it updates the target flow temp by ~1 degree for every degree the outside temp drops;

 

There's no need for a one-to-one correspondence between the falling outside temp and the flow temperature compensation. My flow temperature only increases by about 0.3 degrees per degree of (falling) outside temp change. You need to figure out what the appropriate gradient is for your house, which may need some experimentation.

 

1 hour ago, hopefully_toasty said:

LWT temp auto mode        25 45

Outdoor temp auto mode  -4 16

 

Maybe it's just how you've written this down, but this table isn't right. When it's -4 outside, you want 45 degree flow temp, and when it's 16 outside, you want 25 degree flow temp (ignoring, for the moment, my comment above about there not being a need for a one-to-one correspondence between the falling outside temps and the rising flow temps).

1 hour ago, jack said:

 

Maybe it's just how you've written this down, but this table isn't right. 

 The table isn't right as such but the way you enter the parameters is correct.  It's just an idiosyncrasy of the LG Therma V controller.

On 16/12/2022 at 14:11, jack said:

 

There's no need for a one-to-one correspondence between the falling outside temp and the flow temperature compensation. My flow temperature only increases by about 0.3 degrees per degree of (falling) outside temp change. You need to figure out what the appropriate gradient is for your house, which may need some experimentation.

 

 

Maybe it's just how you've written this down, but this table isn't right. When it's -4 outside, you want 45 degree flow temp, and when it's 16 outside, you want 25 degree flow temp (ignoring, for the moment, my comment above about there not being a need for a one-to-one correspondence between the falling outside temps and the rising flow temps).

Thanks, yes, I get that; the 1 degree correlation just tended to work out that way in terms of where I want the temperature and heading ranges to start and stop (and it also made explaining the example easier 😂) 

So far so good by the way, the settings seem to have seen us through the worst of the weather. I've actually had to set the AI settings to -3 in the day and it's still done a sterling job.