LG Therma V mono block Air Source Heat Pump

[Transition]

1 hour ago, ReedRichards said:

 

I have just radiators and a 12 kW  (monobloc) Therma V. 

 

I assumed that my average radiator water temperature was 2.5 C less than the LWT.  My heat pump is specified to heat the house when the outside temperature is -3.7 C the inside temperature is 21 C and the LWT is 50 C.  So that's a temperature difference, inside to outside, of 25 C (rounded to the nearest degree).  And a Delta T for the radiators of 47.5 - 21 = 26.5 C.  I assumed that the heat loss from my house varied linearly with the inside to outside temperature difference and used a lookup table for how the heat output from my radiators varied with Delta T to calculate what LWT I would need for a range of outside temperatures between -4 C and 18 C.  Then I found a straight line that gives a reasonable fit to what is actually a gentle curve.

 

By coincidence @Ronny has a heat pump specified for the same operating parameters as mine so If I have calculated my weather compensation line correctly then it should work equally well for them.  But it's only as good as the heat loss calculations for my/their house are accurate. 

Thanks for your speedy reply!

Our situation has some things in common. We have the same Heat pump (12 kW), use radiators only and use third party thermometer. British houses, especially the more traditional ones, have due to the thicker walls, better insulation. So on that part I will have to make corrections. And outside temperatures are probably a bit lower here in winter. It can get to -5 (and extremely to -10). But apart from these parameters, your settings will give me a head start. Thanks for sharing. 

[ReedRichards]

@Transition do you know what (maximum) temperature your radiators were sized to work at?  And what outside temp was assumed in the calculation?  Or if you don't know those design parameters, have you ever yet encountered an outside temperature so low that your heat pump could not keep your house warm enough?

 

Here it could get to -5 overnight in winter but only rarely would the temperature stay below -5 for 24 hours or more.  It's only for an extended period below -5 that my heat pump might not have enough output to cope, at least in theory.    

[Transition]

11 hours ago, ReedRichards said:

@Transition do you know what (maximum) temperature your radiators were sized to work at?  And what outside temp was assumed in the calculation?  Or if you don't know those design parameters, have you ever yet encountered an outside temperature so low that your heat pump could not keep your house warm enough?

 

Here it could get to -5 overnight in winter but only rarely would the temperature stay below -5 for 24 hours or more.  It's only for an extended period below -5 that my heat pump might not have enough output to cope, at least in theory.    

What I know is that the radiators are designed to heat the living room to 21 degrees. The water temperature in is 50 degrees and out is 45. This should be to at least -10 outdoor temperature. On top of that I know the wattage (is that English?) each radiator is able to supply at 50 degrees water temperature.

At the current circumstances (outdoor 10 degrees) a water temperature of 38 is sufficient to reach indoor temperature of 21 degrees (easily).

This is going to be our first winter with the heat pump installed. But we tested for two years with our previous central heating (gas) system, set to a max of 12 kW and a water temperature of 45 degrees. We never had problems heating the house and we had cold periods of at least -10 at night and during daytime also below zero.

 

At the moment I'm experimenting with a fixed water temperature. When it gets colder, I'll  increase the water temperature to a level that delivers the target room temperature. This way I expect to define the (what you call) the weather compensation line for our house.

Edited November 17, 2022 by Transition

[ReedRichards]

2 hours ago, Transition said:

 

At the current circumstances (outdoor 10 degrees) a water temperature of 38 is sufficient to reach indoor temperature of 21 degrees (easily).

...

At the moment I'm experimenting with a fixed water temperature. When it gets colder, I'll  increase the water temperature to a level that delivers the target room temperature. This way I expect to define the (what you call) the weather compensation line for our house.

 

At 10 degrees outside my target water temperature would be about 37 degrees.  If you really want to experiment, you should decrease your fixed temperature from 38 C to find out how low it can be and still keep your house at 21 C.  If the water temperature is warmer than it needs to be then the heat pump is using more electricity than it needs to and so your running costs are higher than they need to be.

 

"Weather Compensation" is UK terminology for a particular control feature commonly used by both heat pumps and gas boilers and intended to cause the heat source to operate more efficiently.  

[Ronny]

21 hours ago, Transition said:

We do keep notes when we change settings. It helps me enormously when changes don't work out as I expected. Makes it easier to go back to old settings. And whats more, I usually only change one setting a time.

 

A bit of topic, but we do switch off some standby devices each night. Such as TV, Internet radio, soundbar, coffeemaker (we don't drink coffee at night ;-)). Turns out we save about 300 kWh per year. At current electricity rates over here (GBP 0.88/ kWh) we yearly save about GBP 265.

As far as settings are concerned i do take note of any changes i make. The settings from @reedrichards are working very nicely and maintaining a nice temperature all day. The settings i WAS using brought the house up to +-21.5 and by 16.00hrs had not come back on. I will say it again, if you are like me, the settings are so complicated and settings interlinked that i am lost.

[Transition]

5 hours ago, ReedRichards said:

 

At 10 degrees outside my target water temperature would be about 37 degrees.  If you really want to experiment, you should decrease your fixed temperature from 38 C to find out how low it can be and still keep your house at 21 C.  If the water temperature is warmer than it needs to be then the heat pump is using more electricity than it needs to and so your running costs are higher than they need to be.

 

"Weather Compensation" is UK terminology for a particular control feature commonly used by both heat pumps and gas boilers and intended to cause the heat source to operate more efficiently.  

That's good advise. Already started a run this afternoon with a target temperature of 37. Still works fine. Than again outdoor temperature was slightly higher. Tomorrow another step.

I understand the principle of Weather Compensation💪

[Transition]

3 hours ago, Ronny said:

As far as settings are concerned i do take note of any changes i make. The settings from @reedrichards are working very nicely and maintaining a nice temperature all day. The settings i WAS using brought the house up to +-21.5 and by 16.00hrs had not come back on. I will say it again, if you are like me, the settings are so complicated and settings interlinked that i am lost.

You're right that mainly because of the interlinked settings it is not always clear what the effect of the different settings is.

I'm slowly building a better understanding. Now if I change a setting, the effect is actually what I pursue, or had hoped to achieve.

LG's manuals describe every setting, but not in a way that it's completely self explanatory. It's trail and error and learning by doing.

I've reached out to a couple of suppliers. But found no one with in depth knowledge.

 

Great that @ReedRichardssettings are working nicely with your heat pump and characteristics of your house. Hope you'll reach a moment in time that there comes an end to the tweaking. I hope that after this winter, I've achieved a stable situation.

[Transition]

17 hours ago, Transition said:

That's good advise. Already started a run this afternoon with a target temperature of 37. Still works fine. Than again outdoor temperature was slightly higher. Tomorrow another step.

I understand the principle of Weather Compensation💪

This morning test with water temperature of 36 degrees and outdoor temperature 9, turns out to be too low. So I'll stick with 37.

That's one point of the weather compensation line established. This weekend temperatures will go below zero over here. Next opportunity.

[ReedRichards]

Remember, the nearer you get to the "perfect" Leaving Water Temperature, the longer it will take your heating system to increase the room temperature.  So you may need to be patient when running tests.  Or you may want to reach a compromise between economy of operation and response times, it depends on the heating schedule you use.  

 

If you actually use Air + Water control this need for patience may not apply if the Load Compensation overrides the Weather Compensation in order to reach the set temperature more quickly (which I imagine it does).

[Transition]

I expect it to be a compromise. We like the house warm at the beginning of a (work)day. We work at home most of the time. And we tend to feel the "cold" more when sitting behind our desk. So shorter response time is welcome.

This morning it was about 0 degrees when we woke up. Started with a target temperature of 40 degrees. Took a while but house (living room) is warm now.

The COP today was reduced 3.9. Last weeks used to be somewhere between 4 and 5.

Where COP = (flow per minute x delta T x 60 x 1,16) / power consumption in kW

 

Edited November 19, 2022 by Transition

[ReedRichards]

2 hours ago, Transition said:

 

COP = (flow per minute x delta T x 60 x 1,16) / power consumption in kW

 

 

I have not come across this formula before, do you have a reference?  I don't know my flow rate, in fact I have two pumps so potentially two different flow rates, one from the heat pump to the buffer and one from the buffer around the radiators.

[Transition]

On 19/11/2022 at 16:13, ReedRichards said:

 

I have not come across this formula before, do you have a reference?  I don't know my flow rate, in fact I have two pumps so potentially two different flow rates, one from the heat pump to the buffer and one from the buffer around the radiators.

Sorry for the late response.

I got this from a modbus steering. COP is actually the ratio of the magnitude of the heat given off to the (hot) water and the amount of energy needed to do this (power consumption). The flow/ minute (actually per hour, hence the x 60) represents the amount of water that is heated. The 1.16 has something to do with the amount of energy needed to heat a liter of water.

It represents a moment in time and the actual COP on that specific moment. It is not us full in calculating the seasonal COP, or COP over al longer period.

Edited November 22, 2022 by Transition

[Sailorman]

Hello, new to this forum and very impressed with the vast amount of information available!  I am looking to replace a 12 year old heat pump that is starting to give trouble (Ha, who am I kidding - the thing has been a PIA for the last 4 years!) and very interested in either the LG Therma V Monobloc or the Daikin Altherma 3M (both 16KW units).  For those of you who are using the LG Therma V, and aside from the issues that have been covered in this thread, would you recommend it?

 

My new installation would include a DHW tank and house heating would initially be a combination of radiators and FCU's.  Over time (as my renovation proceeds), I will be replacing all my radiators with FCU's.

[ReedRichards]

On 16/02/2023 at 08:21, Sailorman said:

For those of you who are using the LG Therma V, and aside from the issues that have been covered in this thread, would you recommend it?

 

After the first few days My LG Therma V has been trouble-free for me in over two years.  It has achieved broadly the SCOP that I was promised.  I suspect that there are subtle differences between different makes of heat pump that we don't fully appreciate.  It doesn't have a "vampire load" i.e. it uses very little power when in standby.  It can modulate down to around 20% of its nominal full output.  It starts up at low power and works its way upwards, rather than starting at full power and working down as I believe some other heat pumps do.  Some of the control options, like Load Compensation, are badly documented.  So yes, I would recommend the Therma V in general terms, but it depends a bit on exactly what heating system it will need to supply.      

[MikeJH]

On 08/02/2022 at 22:57, Chris Bottomley said:

I have a PassivLiving MMSP unit installed.  This was when the system was put in.  As far as I know it has no direct connection to the LG Therma V unit, it only uses its own sensors.

It uses the following metering:

Sontex SuperCal 531 metering unit for ASHP output, flow rate? and temperatures
Eastron SDM230-Modbus meter for ASHP power usage

Eastron SDM130-M meter for immersion power usage

Remote wireless internal air temperature sensor

Hi Chris, would you be able to explain how you connect to the PassivLiving MMSP set up? I have a Sontex Superstatic 449 Heat meter and a Eastron SDM630-Modbus V2 meter for ASHP power usage. I am trying to read up about Modbus, but my knowledge is very limited. I am used to coding in VB and Transact SQL. My initial problem is understanding how to physically connect my laptop to the PassivLiving set up. Sadly, I'm also clueless about how to access the information after that. Any pointers that you can provide would be greatly appreciated.

[Chris Bottomley]

On 29/04/2023 at 20:39, MikeJH said:

Hi Chris, would you be able to explain how you connect to the PassivLiving MMSP set up? I have a Sontex Superstatic 449 Heat meter and a Eastron SDM630-Modbus V2 meter for ASHP power usage. I am trying to read up about Modbus, but my knowledge is very limited. I am used to coding in VB and Transact SQL. My initial problem is understanding how to physically connect my laptop to the PassivLiving set up. Sadly, I'm also clueless about how to access the information after that. Any pointers that you can provide would be greatly appreciated.

 

Mike,

I have sent you a reply to your message.

[ReedRichards]

I have seen a picture of a modern Therma V controller display which shows the outside temperature as well as the other usual parameters.  That would be really helpful, when optimising the Weather Compensation settings, for example.  But as far as I am aware this is not available as a software update for older models like mine stuck on software version 3.05.6a.  Unless anyone else knows differently?  

[Transition]

18 minutes ago, ReedRichards said:

I have seen a picture of a modern Therma V controller display which shows the outside temperature as well as the other usual parameters.  That would be really helpful, when optimising the Weather Compensation settings, for example.  But as far as I am aware this is not available as a software update for older models like mine stuck on software version 3.05.6a.  Unless anyone else knows differently?  

Hi Reed,

We had our remote controller updated last year. This was done by the same company that installed our heat-pump. We did it for the same reason you described.

However, the functional result is null. That is because the heat-pump doesn't provide the triggers/ information for the remote. So no new information is displayed 😞

[ReedRichards]

Thank you, @Transition.  That's a really disappointing outcome but useful to know as I would have been tempted to try the same thing.

[TopGeared]

Hi all, new to the forum & wanted to fish for some information on the LG Therma V. We’ve just moved in to a new build with an 12kw Therma V, underfloor downstairs & radiators upstairs. We’ve been in 2 weeks now & I’ve been reading the information in this thread & set the weather compensation curve from a static 50 degrees flow temperature to using @ReedRichards target temperatures.

 

One thing I wanted to ask folks in the know, it feels like it’s using a LOT of energy. If I’m reading the summary screen right, just over 660kwh in 2 weeks. Does that sound normal for a 4 bed new build, with a B rated EPC and estimated yearly heating requirement of around 9000kwh?

[ProDave]

31 minutes ago, TopGeared said:

One thing I wanted to ask folks in the know, it feels like it’s using a LOT of energy. If I’m reading the summary screen right, just over 660kwh in 2 weeks. Does that sound normal for a 4 bed new build, with a B rated EPC and estimated yearly heating requirement of around 9000kwh?

9000kWh per year, assuming you heat the house for 6 months of the year, suggests an average of 375kWh per week in the heating season, so that would be 750kWh in 2 weeks.  So your 660kWh at almost the coldest spell you will get sounds what you would expect.

 

The fact a 4 bed new build needs a 12kW ASHP and they estimate the annual heating usage of 9000kWh shows the gapbetween developer houses and self builds.  I use 1400kWh heatimg my 3 bedroom house in a year and another 1000kWh for hot water with a 5kW ASHP.

[TopGeared]

I guess what I’m really doing is trying to gather information to question what the developer has installed & has it been installed and configured correctly, and possibly the thermal efficiency of the building. I’m trying to eek information out of them on the sizing of the system & any heat loss they did - but having met the plumber that said he installed it I have my doubts any of that was done & it was fitted like a boiler.

 

The 660kwh I mentioned, I don’t think that’s heat output I think that’s electricity used by the heat pump, as the screen seems to describe it as “usage”.

[ProDave]

So 660kWh in 2 weeks is 47kWh per day, or an average of almost 2kW continuous use all the time.

 

That sounds like the HP is running at full power about half the time, so it's probably putting an average of  6kW of heat into the house all the time. 

[Boy1925]

I would be grateful to hear if any forum users have had difficulty getting warranty repairs or parts for their LG monoblock heatpump. I have a 5kw monoblock which ran without fault for eighteen months after commissioning until on 31st October it failed and an rcd in our CU tripped. When I reset the rcd the control panel for the heatpump showed fault CH5.

Further investigation showed that a component on a  pcb in the heatpump had failed-shown by a burnt mark on the pcb.

Since then, I have been waiting for a new pcb to be sent to my local engineer for fitting. I am, as you will guess, rather fed up with the slowness of LG to supply this replacement part under warranty and wonder if I am alone in suffering such a delay?

[Boy1925]

Just to give an update, the new pcb arrived early last week but when the engineer fitted it, another fault code appeared and the unit would not run. CH35 appeared, which I believe relates to a pressure sensor fault. I am accordingly now seeking a new sensor and hoping that will resolve the problem. Apparent on removing the old pcb was evidence of a short circuit against part of the chassis due to lack of insulation. There is a suggestion that these short circuits are a known problem for LG in these machines.