LG Therma V mono block Air Source Heat Pump

[JohnMo]

16 minutes ago, Transition said:

hysteresis -2/ +2

Just use a Salus SQ series thermostat, hysteresis can be set to 0.25. it can also be set to to learn your heating response time make adjustments to how it reacts.  Good for radiators not so good for very low temp thick screed UFH.

 

Or just change over to weather compensation and don't use thermostats.

[ReedRichards]

28 minutes ago, JohnMo said:

Or just change over to weather compensation and don't use thermostats.

 Not necessarily a good thing.  This is the power drawn by my house whilst I was away and I asked the system to maintain a constant temperature with AI/Weather Compensation engaged.  The house gets cold at night so consumes a lot of power when it is coldest outside so at the minimum efficiency  (but it wasn't very cold out so the heat pump cycles).

 

 

 

 

[ProDave]

1 hour ago, Transition said:

You're right, have not found this in any documentation and I've read a few 😉

We've been experimenting with a third party thermostat (Google Nest). Downgrades the heat pump to an on/off system. Had hoped to solve a couple of issues (hysteresis -2/ +2, an easier way of setting room temperature and a more understandable response). In our situation it didn't bring what we had hoped.

In order to use the third party thermostat dip switch 8 has to be set to on and than certain settings are greyed out.

So back to the LG standard thermostat (PREMTB100).

 

@ReedRichards thank you for sharing the Product and Installation Manual!! Haven't seen this manual befor. I'm sure it will help in a better understanding.

That explains something I think.

 

I have been using the external room thermostat input right from the start, so have the traditional thermostat per room connected to the UFH manifold control box and it is the call for heat contact from the manifold controller that goes to the ASHP "room thermostat" input.

 

I did once try playing with weather compensation and got a very odd result, it switched the ASHP into cooling mode.  At the time I thought I must have miss understood the settings and just put it back to normal.  Mine is an older version than most on here so has a different controller and none of the parameters were greyed out, but perhaps with the room thermostat input enabled they just don't function or at least not as expected.

[JohnMo]

@ReedRichardsYou could have few issues - Looks like you are short cycling - heat on for a short period, forced outage for 10 mins.  Issues that cause short cycling are

 

Your buffer could be too small.

Lots of zones combined with no buffer or buffer that is not big enough to compensate for the smallest zone open.  Do you have lots of zones or just one?

 

Open zones doesn't meet or exceed the min flow rate for the heat pump.

 

Or is the flow temp to high and room temp keeps hitting a thermostat set point - switching the HP on/off. 

 

Either way somethings not right.

 

The ideal of WC is you don't have a constant set temperature, but you have a couple degrees reduction in temperature during the night. 

Edited October 31, 2022 by JohnMo
Missed tag, spelling

[ReedRichards]

4 minutes ago, JohnMo said:

@ReedRichardsYou could have few issues - Looks like you are short cycling - heat on for a short period, forced outage for 10 mins.  Issues that cause short cycling are

 

Your buffer could be too small.

Lots of zones combined with no buffer or buffer that is not big enough to compensate for the smallest zone open.  Do you have lots of zones or just one?

 

Open zones doesn't meet or exceed the min flow rate for the heat pump.

 

Or is the flow temp to high and room temp keeps hitting a thermostat set point - switching the HP on/off. 

 

Either way somethings not right.

 

The ideal of WC is you don't have a constant set temperature, but you have a couple degrees reduction in temperature during the night. 

 

The cycles are 20 minutes long, approximately, so not particularly short.  I think the main reason for the cycles is that it is a 12 kW heat pump and incapable of consistently modulating down to less than 2 kW of output.  All heat pumps will cycle if the average power required from them is below the limit of their modulation range so I don't think anything is actually wrong here, it's just autumn rather than winter. 

[SteamyTea]

1 hour ago, ReedRichards said:

The house gets cold at night so consumes a lot of power when it is coldest outside so at the minimum efficiency  (but it wasn't very cold out so the heat pump cycles).

If the outside temperature was between 0⁰C and 4⁰C, then the CoP takes a dip usually as that it a strange range for water vapour. Quite often see this dip on efficiency charts.

[Transition]

2 hours ago, ReedRichards said:

 Not necessarily a good thing.  This is the power drawn by my house whilst I was away and I asked the system to maintain a constant temperature with AI/Weather Compensation engaged.  The house gets cold at night so consumes a lot of power when it is coldest outside so at the minimum efficiency  (but it wasn't very cold out so the heat pump cycles).

 

 

 

 

Between 4 and 6 o'clock, 6 times on, is about every 20 minutes.  Which is okay if there was a heat demand during the night. Looking at the short time the HP was on, it doesn't have to mean there's a buffer (or volume) issue. We had the same a couple of weeks ago. We solved it by setting the room temperature back to 15 C during the night (setting Temperature Sensor is on Water+Air).

What puzzles me, is that the HP stopped heating after about 8 o'clock. What changed there?

[ReedRichards]

12 minutes ago, Transition said:

What puzzles me, is that the HP stopped heating after about 8 o'clock. What changed there?

 

After the heat pump turns off the water in the radiators takes a while to cool back to room temperature so the house is still being heated.  Meanwhile it is warming up outside so the rate of heat loss from the house decreases.  And possibly the sun was shining in through the windows so there was solar gain.  

[Transition]

15 hours ago, ReedRichards said:

I have had a request for the Product and Installation Manual so I have split it into 3 parts to enable me to upload it.

 

LG Therma V Product and Installation Manual - the final part covering settings

 

This manual is very helpful! Especially regarding settings and how they effect the HP. Thanks for sharing!

Point of attention is that is refers to U33/ U43 and U44 types, monoblock and split. This is not always clear when reading the information.

Sometimes remarks have been added (see blow e.g.). This is not an issue, just good to realise when reading.

 

 

[Ronny]

On 30/10/2022 at 10:36, Transition said:

Looking at your LWT (30 and 47) and Outdoor temp auto mode (-5 and 27) settings; did the heat pump ever reach 45 C? As far as I understand now, this will only be the case if outdoor temperature is below -5. Don't know how cold it gets in County Durham, over here we need a higher water temperature. Do you use additional heating?

I checked the log of the heating this morning and the highest water temperature recorded was 46 deg. This was at07:45hrs. I hope this helps. By the way i do not have any 3rd party thermostat and am using air + water.

[ReedRichards]

3 hours ago, Ronny said:

I checked the log of the heating this morning and the highest water temperature recorded was 46 deg. This was at07:45hrs. I hope this helps. By the way i do not have any 3rd party thermostat and am using air + water.

 

46 C is (very likely to be) too high for heating with Weather Compensation (AI) at this time of year but might occur if your were heating your hot water tank to 40 C. 

[Ronny]

4 hours ago, ReedRichards said:

 

46 C is (very likely to be) too high for heating with Weather Compensation (AI) at this time of year but might occur if your were heating your hot water tank to 40 C. 

Hi Richard. I also thought that, but the log shows that temperature. It could not be hot water as I heat that in the cheap period before 04.30. I heat the hot water to 50 deg. The log shows that temp more or less every morning round about 08.00. The house sits about 21.5 deg, again about 08.00., set to AI +1 and air + water.

[ReedRichards]

10 hours ago, Ronny said:

Hi Richard. I also thought that, but the log shows that temperature. It could not be hot water as I heat that in the cheap period before 04.30. I heat the hot water to 50 deg. The log shows that temp more or less every morning round about 08.00. The house sits about 21.5 deg, again about 08.00., set to AI +1 and air + water.

 I have been told that Air + Water gives you Load Compensation.  If your heating is off at night or set back to a lower temperature then when the target becomes 21.5 C the Load Compensation may decide that it needs to override the Weather Compensation setting in order to bring your room up to temperature as quickly as possible.  This could be the reason your LWT is hotter than you would expect it to be early in the day.   

[Ronny]

1 hour ago, ReedRichards said:

 I have been told that Air + Water gives you Load Compensation.  If your heating is off at night or set back to a lower temperature then when the target becomes 21.5 C the Load Compensation may decide that it needs to override the Weather Compensation setting in order to bring your room up to temperature as quickly as possible.  This could be the reason your LWT is hotter than you would expect it to be early in the day.   

I would think you are correct, but as i said some time ago i find the settings to be very complicated (for me). Have you got any thoughts on what would be better settings for me to try. I am located in county durham.

[Transition]

3 hours ago, Ronny said:

I would think you are correct, but as i said some time ago i find the settings to be very complicated (for me). Have you got any thoughts on what would be better settings for me to try. I am located in county durham.

Learning more and more about LG HP.

Copying settings from other installations/ locations may not have the desired effect.

My opinion: if it works fine/ good enough, don't touch it 😉

[Ronny]

30 minutes ago, Transition said:

Learning more and more about LG HP.

Copying settings from other installations/ locations may not have the desired effect.

My opinion: if it works fine/ good enough, don't touch it 😉

I take a note of my settings so i can try anything and if it does not work it is easy to change back to what it was.

[ReedRichards]

On 31/10/2022 at 14:03, Ronny said:

 i do not have any 3rd party thermostat ....

 

16 hours ago, Ronny said:

 set to AI +1 and air + water.

 

4 hours ago, Ronny said:

Have you got any thoughts on what would be better settings for me to try.

 

If the settings you are using succeed in keeping your house at the temperature(s) you want it to be then I see no reason to change them.  You are using all the sophisticated control features that your heat pump is capable of.  Load Compensation (Air and Water rather than Water) may cause your system to use more energy when the house needs to be heated quickly but less energy to maintain a steady temperature so that's swings and roundabouts.  And you should be able to increase the temperature quickly if you need to (a capability for which heat pumps generally have a bad reputation).

 

I like to experiment so I would see if AI+1 is necessary over the full range of outdoor temperatures you encounter but there is no great need for you to do that.    

[Ronny]

20 hours ago, ReedRichards said:

 

 

 

If the settings you are using succeed in keeping your house at the temperature(s) you want it to be then I see no reason to change them.  You are using all the sophisticated control features that your heat pump is capable of.  Load Compensation (Air and Water rather than Water) may cause your system to use more energy when the house needs to be heated quickly but less energy to maintain a steady temperature so that's swings and roundabouts.  And you should be able to increase the temperature quickly if you need to (a capability for which heat pumps generally have a bad reputation).

 

I like to experiment so I would see if AI+1 is necessary over the full range of outdoor temperatures you encounter but there is no great need for you to do that.    

Thanks for your thoughts, it is appreciated. My problem is there is no place where i can see what the various settings actually do and what effect they have. If i understood that it would be so much easier. IE LWT, i understand the high setting, but the low setting i do not see the relevance. I have one high level fan assisted heater in the kitchen which does not work unless the LWT is above 35 deg. Does the settings affect this in any way. If the settings get the house up to 21.5 deg how do i keep it from dropping more than 1 deg before it tops up the heat. For example, the heating is on 24hrs a day with a set back after 19.00 hrs to -1. It is set to +1 at 07.00 and the temp in the living room is at 22 deg at 08.00 all heating stops shortly after this but the heating does not cut back in even when the temp drops to 20deg. any suggestions would be appreciated. At the moment i am using on average 10Kwh a day and +-6 of these are on the cheap rate during the night to charge the batteries and heat the DHW. I hope this all makes sense.

[ReedRichards]

On 23/10/2022 at 14:10, Ronny said:

Here are the setting i am using which seem to work reasonably well.

Air heating set temp 17  26.

Water heat set temp  34   47.

Outdoor temp auto mode   -5   27

Indoor temp auto mode   16   24

LWT   30   47

These settings are working fine at the moment though it is not that cold outside yet.

This is with the mode set at air plus water.  I will watch with interest to the reply`s from users who know what they are doing. 

 

I have a third party thermostat so I use Water control rather than Air + Water.  This just gives me Weather Compensation.  With your settings and AI=0 this would mean that the LWT is 47 (C) when the Outdoor temp is -5 or less and 30 when the outdoor temperature is 27 or greater.  If the outdoor temperature was halfway between the two limits, 11, then the LWT would be halfway between the two limits, 38.5.  At any outdoor temp between the two set values there is a linear relationship between LWT and outdoor temp.  This is shown towards the end of Part 2 of the document I posted (on page 85).

 

Because you use AI=1 I believe this means the LWT is 1 degree hotter than otherwise, equivalent to changing the LWT values to 31   48

 

I have no idea how the Indoor temp auto mode settings affect matters in your case (Air + Water) and if it is documented I have not found it.

 

 

Edited November 2, 2022 by ReedRichards

[ReedRichards]

1 hour ago, Ronny said:

For example, the heating is on 24hrs a day with a set back after 19.00 hrs to -1. It is set to +1 at 07.00 and the temp in the living room is at 22 deg at 08.00 all heating stops shortly after this but the heating does not cut back in even when the temp drops to 20deg. any suggestions would be appreciated. 

 

I had no idea it was possible to set AI to be different at different times of the day.  There is a super-geeky way to control your heating where you set your Weather Compensation to exactly match the needs of your house and abandon the use of room and radiator thermostats.  If you have managed to achieve this state of perfection and balance then you control everything based on the LWT and you would reduce this by a few degrees overnight to make the house a bit cooler.  But unless you know exactly what you are doing I would steer well clear of this type of control and just set the room temperature to be what you want it to be at the different times of day and night.

 

I also have no idea why your room temperature shows so much hysteresis; my third party controller would not allow this.  Remind me if you have radiators or Underfloor Heating (or both).

[JohnMo]

Just to jump in,

 

If you are overshooting the thermostat, this could indicate the flow temperature is hotter than it could be.

 

If you want the room/house at 21.5, set the thermostat slightly higher than that.  If you exceed 21.5 deg tweek the flow temp down, using the information about the WC curve provided by @ReedRichards. Just do 1 to 2 degrees at a time.

 

getting the heat curve correct takes a bit of trial and error.

 

WRite down the changes you make, then you can back track easily.

[Ronny]

22 hours ago, ReedRichards said:

 

I had no idea it was possible to set AI to be different at different times of the day.  There is a super-geeky way to control your heating where you set your Weather Compensation to exactly match the needs of your house and abandon the use of room and radiator thermostats.  If you have managed to achieve this state of perfection and balance then you control everything based on the LWT and you would reduce this by a few degrees overnight to make the house a bit cooler.  But unless you know exactly what you are doing I would steer well clear of this type of control and just set the room temperature to be what you want it to be at the different times of day and night.

 

I also have no idea why your room temperature shows so much hysteresis; my third party controller would not allow this.  Remind me if you have radiators or Underfloor Heating (or both).

I only have radiators plus one high level fan assisted one in the kitchen which is also low water content which has made a big difference to the kitchen temperature. Setting the AI to be different is done by using the heating on / off settings.  IE on at 07:00 at +2 then on at 10:00 at +1. etc. I will comment more when the cold weather makes an appearance as it has been abnormally warm for the present time. Thanks to all for their help. 

[Transition]

On 02/11/2022 at 14:21, ReedRichards said:

 

I also have no idea why your room temperature shows so much hysteresis; my third party controller would not allow this.  Remind me if you have radiators or Underfloor Heating (or both).

This may answer why hysteresis is high when using the LG Remote (PREMTB100)

There are four settings to adjust hysteresis:

TH on/off Variable, heating air

TH on/off Variable, heating Water

And then there is also a setting for "TH on/off Variable, cooling Air" and "TH on/off Variable, cooling Water".

As @Ronny doesn't use cooling, I didn't add the data.
 

 

Using Type0 for Air and Type3 for Water (if not already) may reduce hysteresis.

 

Alternatively use, like @ReedRichards does, a third party thermostat and set "Select Temperature Sensor" to "Water" (in stead of "Water + Air").

Third party thermostats have hysteresis as low as 0.2.

 

Edited November 3, 2022 by Transition

[ReedRichards]

That's useful information for @Ronnybut it strikes me as very poor that the best air temperature hysteresis setting you can select has a 2 C temperature variation.  It's not rocket science or anything new to make a thermostatic control that is much more precise.  I'm sure mine (Drayton Wiser) is but at the same time it does not allow more than 3/4 switch-ons per hour in order to avoid short cycling if the thermostat is in a draughty location where the temperature fluctuates.  

[ReedRichards]

On 02/11/2022 at 12:01, Ronny said:

I have one high level fan assisted heater in the kitchen which does not work unless the LWT is above 35 deg.

 

This feature is a deliberate part of the design of many fan-assisted heaters (that I looked at).  It makes them ill-suited for use with a heat pump.  I wonder if there is an override option?  You would think the manufacturers would clue-in and provide one.