@cathoderay I did find an English manual, I think I made a pretty good translation:

@carlo - not much better, is it. It looks more like a user guide than a technical manual, see if you can find the latter. It just might have more detail (if it exists and you can find it).

@carlo I have a 16kw LG Therma V. Installed 2020 so even less data available!

Can you join the Facebook LG Therma user group? They have some good technical people & installers.

Are you using weather compensation (AI) ? My usage dropped from circa 8000kwh a year to 5800kwh. Facebook user group has an excellent document that helps setup correctly. PM me if you want it by email

@tim441 Sadly (?) I don't use Facebook but I would still like the link to the user group, I might peruse through my wife.

I still haven't set weather compensation, I will send you a PM with my email for the Grail, thank you.

Whoops, no PM, I still don't qualify due to forum rules. Can you send one to me? Maybe I can reply

@tim441 Thanks, PM received and appreciated, I can't even answer it though, I still need to post some more.

Posted by: @carlo

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I still haven't set weather compensation, I will send you a PM with my email for the Grail, thank you

Setting up WC correctly is pretty much the most important thing to do with any heat pump.

In summary:

Turn up all thermostats and TRVs to full so they are permanently on.  Make sure the heat pump has any room influence function disabled, ie it's operating purely on wc.

Operate your heat pump 24*7

Set the high OAT end of the WC curve to say 25C flow temp at 20C outside temp (or 23 C ft if you have ufh)

Set the low OAT end of the WC curve to the design flow temp at the design outdoor temp.  If you don't know these set it to ft 55 (radiators) or ft 40 (ufh) at -10 OAT

The house will overheat!

Turn down the ft at low oat end until it just keeps to the right temperature. Do this slowly, changing the flow temp by no more than 1C per day as you approach the correct value.

Leave and enjoy cheaper, more comfortable, heating!

You may need to balance the radiators to get if rooms settle at different temperatures.  Separate instructions needed for this which can be provided.

If you wish you can set trvs in any rooms that suffer from occasional ocerheating a couple of degrees above target.  Basically however you want to leave both trvs and thermostats out of the loop, ie have them permanently on.

This is best done in the coldest months because you get a more accurate setting then, but you can do it roughly in the shoulder season and tweak when it gets colder

This is the polar opposite to how we operate boilers in the UK, so is a bit counterintuitive at first.

It's worth reading this guide to heat pumps to understand better some of the differences between them and boilers.

Can post more detailed instructions if you don't connect to the lg specific ones on Facebook for any reason, the process is model independent, make and model only affects some detail of which burtons exactly you have to push to set the curve 

Time of Use tariffs are important in the mix - if available as an option. e.g.

1. With Intelligent Go overnight tariff just 7p it makes sense for us to INCREASE temps overnight (opposite of setback). In our case by 1 deg

2. Similarly we heat hot water at night on a schedule to 50deg (with top up daytime heating just 40deg if necessary). In any case hot water can have a lower target for most people - try 47deg at first and then tweak lower if possible. Will be more than sufficient for most households - unless several teenagers!

Posted by: @tim441

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Time of Use tariffs are important in the mix - if available as an option. e.g.

1. With Intelligent Go overnight tariff just 7p it makes sense for us to INCREASE temps overnight (opposite of setback). In our case by 1 deg

 

2. Similarly we heat hot water at night on a schedule to 50deg (with top up daytime heating just 40deg if necessary). In any case hot water can have a lower target for most people - try 47deg at first and then tweak lower if possible. Will be more than sufficient for most households - unless several teenagers!

Agreed with the one qualification that increasing the nighttime temperature should ideally be done by increasing the flow temperature at night not by reducing/controlling the daytime temp using a thermostat. 

Some heat pumps allow you to do this, some don't.  For ones that don't it may be better just to operate at the same temperature 24*7, or get either homely or havewise to do it for you.

@jamespa I knew of the importance of weather compensation but I wanted to identify and solve the problems with the system that I think are there before adding other variables to it.

Correct me if I'm wrong, but if I'm running the heat pump at fixed 37° flow temperature, with the outside temperature varying between 4° and 17°, I think that, at the very least, I should get the COP corresponding to 37° flow with 4° outside. But, according to my measurements, I'm getting way less than that.

I know there is a lot to set and tweak, but I would like to start from a known good system/installation. For example I can set the flow temperature to rise a bit when there is overproduction of photovoltaics (I have a 10kw array). Very rare in winter but during autumn should happen more.

Right now I'm a bit at a loss, that's way I want to gather more data.

Posted by: @carlo

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Correct me if I'm wrong, but if I'm running the heat pump at fixed 37° flow temperature, with the outside temperature varying between 4° and 17°, I think that, at the very least, I should get the COP corresponding to 37° flow with 4° outside. But, according to my measurements, I'm getting way less than that.

Yes you should, or thereabouts, but only if you are operating without thermostats or TRVs.  If you have a thermostat constantly cycling it on and off, or TRVs/zone valves shutting down much of the system, then you will almost certainly achieve a COP which is poorer, possibly quite a lot poorer, depending on how it is working.  Worst of all is a 'smart' thermostat with 'proportional' control, they can really knacker heat pump performance.

Posted by: @carlo

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I knew of the importance of weather compensation but I wanted to identify and solve the problems with the system that I think are there before adding other variables to it.

My initial reaction was fair enough.  On second thoughts (and referring to the above) its almost impossible (exception - a very low temp UFH system) for a heat pump to be working properly without WC and the house to be simultaneously comfortable, simply because of the need to match emitter output to demand.

There isnt that much that can go wrong with a heat pump system, unless the heat pump itself is at fault, which is pretty rare.  The principal issues are

• substantially oversized (and thus cycles a lot and/or operates permanently at an inefficient part of the compressor curve)
• presence of buffer, low loss header, or plate heat exchanger between heat pump and emitters, or mixers if you have UFH
• pipework restrictions/inadequate primary flow/blocked filters
• undersized emitters
• overuse of external controls, most particularly smart stats like Hive and TRVs
• incorrectly adjusted weather compensation
• poor insulation of primary pipework

Combinations of these are not unknown and that can really mess things up!

@jamespa I run 24x7 with weather compensation. So flow temps will normally increase at night. 

As my ashp was a retrofit I use simple digital thermostats to manage the target temp increase overnight. 

Afaik havenwise is a bit limited on compatibility and while Homely supports many more they don't support my 2020 installed LG. I guess both are worth considering if compatible.

I think I've got my setup reasonably good now after a few years:

1. Move to weather compensation

2. Reduced daytime DHW target temps with higher temps scheduled overnight

3. Use higher temp targets overnight for room temp to maximise cheap overnight tariff

4. Best time of use tariff (in my case Octopus Intelligent Go) ... linked to zappi charger and ev

5. Maximise IOG to fill batteries at night. I use WonderWatt to help with that (again only suited to certain compatibilities)

6. Export solar prod + force discharge batteries outside of heating season.

So inevitably it very much depends on setup,  usage, tech saviness, etc etc. This forum has helped a lot with understanding options & questions to ask!

@carlo picking up on potential inefficiency from cycling if Oversized heat pump..

One option in LG is to run in Silent/Quiet mode. I don't use it but know others have .. quite successfully reducing cycling.

Personally I'd go for weather compensation as priority .. its a chicken & egg thing! With WC set changes should become clearer.