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  1. #51
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    Re: LG heat pump problem



    Yes I thought it was weird but its not on a 4C difference as we have deactivated that on one of the units as it was activated. Like i say there is 1C diff either side of setpoint so i think the control has been updated but it still runs at full whack on the setpoint.



  2. #52
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    Re: LG heat pump problem

    Does this outdoor unit have 2 compressors ?

    If it does then 1 will be inverter & 1 will be direct on line.

    Do you think the direct on line comp is switching off near set point ?

    You should see a large drop in current when it stops.

    I suspect that the unit only looks at the data once every 2 mins or thereabouts.
    If the unit can warm the room faster than 1 deg in 2 mins then the unit does not have enough time to drop out the direct on line comp & then ramp down the inverter.

    If this is a twin compressor outdoor unit , I wonder how it would work if you reduce the capacity of the outdoor unit by 50% by disconnecting the direct on line compressor ?

    The heating performance at the indoor units would be 50% & it would take much longer to get up to set point.
    But it would reduce this constant stop start problem.

    BTW
    Fair play for getting some control stratagy info. Just look at how many LG experts from all around the world have come back with some further info

  3. #53
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    Re: LG heat pump problem

    There is only one compressor inside my outdoor unit. its the new 2008 model and they did away with the constant speed compressor due to it requiring higher amps and breaker plus the high start up amps etc. This unit only has 1 compressor and when this compressor stops it takes about half a minute before the compressor has ground to a halt completly.

    A bit dissapointed at how many LG experts have come back to us on this one.

    TO be honest I dont think LG have a clue how their equipment works because the guy at LG was saying it should be winding down once it reaches set point. But the control strategy document says otherwise so this doesnt give me much confidence when the own company doesnt know how their equipment works! Kind of regret having ever got LG equipment, they have been useless at customer service, they dont like speaking to the end user and their product knowledge is poor also. Graham Hendra who emailed me on one occasion regarding the matter didnt really look into my problem properly and made me feel like I didnt know what I was talking about!

    YOu also mention about it not having enough time to reduce the compressor speed. Well for it to overshoot by 1C were looking at about 8minutes before it goes over. FOr instance I have a setpoint of 21C when it gets to 21C the compressor speed remains the same for 8minutes till it reaches 22C then the compressor shuts down.
    Last edited by back2space; 24-12-2008 at 08:46 PM.

  4. #54
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    Re: LG heat pump problem

    The equipment is sold through a distributor network to contractors who then sell & install it for endusers.

    So the installation contractor should ideally be able to resolve any problem as you would expect that he has been to training at the LG Training centre.
    If the contractor is unable to resolve a problem he should be able to call on the assistance of the distributor who's technical engineers should be fully trained in for product at the LG training centre.
    So LG UK HQ should only really be providing technical support to the distributors not fielding a multitude of calls from endusers.
    LG don't even have responsibilty for the warranty because that sell that on to the distributor as well with the equipment.

    If the contractor & distributor have been unable to provide technical assistance to resolve this issue then really that is a poor reflection on them as well as a poor reflection on the LG training.

    At the end of the day this a budget global product produced for domestic use in hot climates.
    So you can't expect it to be an 'all singing & all dancing' product.
    It may not be optamised for cooler climate heating operation, as you seem to have found.
    But as you can see from the control description it is not even optamised for low ambient cooling as the cooling outdoor fan speed control is the most crude excuse for low ambient control you are ever likely to see on any cheap split system.

    But then
    How mainy domestic endusers would look in detail at how the unit actually operates ?

    A common reply is that poor quality & performance was only a problem on last years product & that this years latest model is completely redesigned & improved & has no problems at all.
    Yeh , ok, sure, we've heard all that before last year & the year before & the year before that.

    There is always a street full of unsuspecting punters for tomorrow.

    Perhaps one of the other 25,000 members who might from time to time install & maintain LG equipment can provide some further light on this.
    Perhaps there is some really simple little thing that has been overlooked.

  5. #55
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    Re: LG heat pump problem

    Can you explain what is wrong with the fan control in Low ambient cooling?

    The fan control seems fine, it seems to regulate the speed dependant on outside temp. Which is what I guessed it did? The only time it remains off is if its in defrost mode and the temp is below zero.

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    Re: LG heat pump problem

    What I'm seeing here is a control strategy for a multiple compressor unit, which this unit is not. We can't tell if the system has a problem if we don't know what the system is supposed to do or how it is supposed to do it.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    Well for it to overshoot by 1C were looking at about 8minutes before it goes over. FOr instance I have a setpoint of 21C when it gets to 21C the compressor speed remains the same for 8minutes till it reaches 22C then the compressor shuts down.
    I'm confused. Please define each of the above "it"s.

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    Re: LG heat pump problem

    As Gary has already pointed, you are discussing control strategy of unit with two compressors, and this one in question, is not with two compressors, therefore, this latest discussion is pretty much pointless.

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    Re: LG heat pump problem

    Quote Originally Posted by Gary View Post
    I'm confused. Please define each of the above "it"s.
    Gary

    All of the Its Refer to the indoor unit It = Indoor unit.

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    Re: LG heat pump problem

    Quote Originally Posted by nike123 View Post
    As Gary has already pointed, you are discussing control strategy of unit with two compressors, and this one in question, is not with two compressors, therefore, this latest discussion is pretty much pointless.
    Nike123 LG advised me to disregard the bit referring to the 2nd compressor as this is only used in back up on previous units when the unit needs high capacity.

    The newer unit which is mine has a larger inverter compressor so they didnt require the 2nd stationary compressor.

    LG say the control strategy is the same just without the 2nd compressor kicking in.

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    Re: LG heat pump problem

    If the room temperature is the same as or higher than the set temperature and the outdoor capacity is equal to the capacity of the fan coils then the compressor will be told to run at full speed.
    This doesn't make sense. It is wrong statemant or bad translation from original.

    Why would compressor run in full speed when room temperature is same or higher than set temperature.
    It looks like it is copy/paste from cooling control description.
    I would not take this document for good explanation of control strategy.

    Could you email me that document and I will then upload it to some server and link it here? Or you could done that at this page (you need to register first).
    Last edited by nike123; 25-12-2008 at 08:17 AM.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    Gary

    All of the Its Refer to the indoor unit It = Indoor unit.
    Exactly where and how are you getting your temperature measurements?

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    Re: LG heat pump problem

    Trying to piece the puzzle together:

    According to the control strategy, the unit is designed to overshoot temp by 4C in heating mode. According to Thermatech, this function has been overridden by a dip switch on the indoor unit. The unit now overshoots by 1C.

    Is this a problem or is this normal?

    If the compressor is running 100% in heating mode with on/off as opposed to modulating control, then some minimum overshoot is needed in order to avoid short cycling.

    If the compressor runs 100%, then we cannot expect ramped down wattage... so is the wattage a problem or is this also normal?

    Does this system have a problem or does it not have a problem?
    Last edited by Gary; 25-12-2008 at 04:05 PM.

  14. #64
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    Re: LG heat pump problem

    The 1C overshoot is not a problem for me as I guess this is to avoid short cycling. They (LG) told me the unit has a 1C buffer zone either side, when the unit reaches its set point of 21C then the unit should ramp down even further to maintain that, however if the temp continues to rise for instance overshooting to 22C the compressor is then told to switch off.

    The issue I have is why is it not ramping down when it is approaching set point. The time it takes to overshoot 1C is approx 10minutes so plenty of time for it to ramp down but it still runs as if it is trying to achieve the set point.

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    Re: LG heat pump problem

    Quote Originally Posted by nike123 View Post
    This doesn't make sense. It is wrong statemant or bad translation from original.

    Why would compressor run in full speed when room temperature is same or higher than set temperature.
    It looks like it is copy/paste from cooling control description.
    I would not take this document for good explanation of control strategy.

    Could you email me that document and I will then upload it to some server and link it here? Or you could done that at this page (you need to register first).

    Nike can you message me your email address please.

    Thank you.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    Nike can you message me your email address please.

    Thank you.
    Download my Vcard! It is there.

  17. #67
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    Re: LG heat pump problem

    Ok bud

    You have mail!!

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    Re: LG heat pump problem


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    Re: LG heat pump problem

    I recently installed a non sale LG switched unit at home (a solution to its occupying storeroom shelf space) To get it to behave in any reasonable manner -- for heating -- I had to place the ambient sensor outside the casing of the unit, since then it follows room temperature quite adequately. It is not the first time that I have done this.... in the case of heating I suspect that the sensors can get "poisoned" by radiant heat from the coils and the units do not cycle/ramp at the correct temperatures. Incidentally the programming of the unit is weird (it allows short cycles and other oddities - part of the reason I think the switched units were removed from catalog and were quite expensive because of the decoration).

  20. #70
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    Re: LG heat pump problem

    Momo, the installer tried to have the sensor pointing outside the unit as u r correct the sensor was being affected by the temperature inside the unit. However this resolved problems of the temp not being monitored.

    We are having remote sensors installed to fully resolve the problems of temp control, However putting the sensor outside the unit has not allowed the unit to ramp down either.

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    Re: LG heat pump problem



    Here on diagram should be written below picture:
    Delta T = Set temperature - return air temperature

    Also this description should have one word changed:
    It can be seen that the units all operate to 4 degrees higher than set temperature so if you set 20 degrees C on the controller the unit will continue to heat to 24 degrees C. If the room temperature is the same as or lower than the set temperature and the outdoor capacity is equal to the capacity of the fan coils then the compressor will be told to run at full speed.
    From what I see in diagram, control strategy is OK and it is executed in 4 capacity steps. Dip switch you moved should be back to its original position and sensor positioned as I firstly said long before.


    Then, your target temperature will be maintained as set temperature +- 1K and maximum speed of compressor will be when return temperature is 20°C and compresor will stop at 24°C or more. That is control band of 4K and should not be changed.

    Also, stop looking at temperature display (cover it with duct tape) and set temperature higher or lower according to your feeling of comfort. Be sure to not stand in air path.

    You should experience lowest power consumption only when space heat loss is small and compressor then need to lower his output to last step. That is when return air temperature is between 23°C and 24°C (sensed at sensor as that value).
    When return air temperature is 21°-22°C you should have power consumption one step lower than max. And when return air temperature is 20°C or lower your power step is max.
    That strategy is OK by me, only what is lacking is some fuzzy logic.

    Return your dip switch to position before intervention and then coll your flat to 16°C. Then switch on your AC and record return air temperature, time of changes, and power consumption, to establish is this AC works as it should be.
    Last edited by nike123; 26-12-2008 at 08:30 AM.

  22. #72
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    Re: LG heat pump problem

    Hi Nike

    As I have 2 units I have switched the dip switch over on one unit. My installer told me that this was the high ceiling mode, as he first had to come back out after installnig as one of the units was setup in this mode by default despite them being mounted at radiator level. This unit that was in this mode seemed to keep heating until it reached 24C no matter what if the set point was 21 it would keep on going to 25C but the unit would achieve the 25C too with no sign of slowing down... cooling in this mode works fine.

    SO are you saying I have to put the unit in high ceiling mode and perhaps set the set point at 20C to perhaps happily maintain about 22C?

    Where should the sensor be positioned, currently it is poking out the front of the grille as inside the unit it didnt sense temp properly. Remote sensors are coming in January.

    The data sheet above mentions nothing abut this control strategy only working in hi ceiling mode.

    So what is the position of the dip switch for that I am using at the moment that either switches on or off the compressor should the setpoint be + or - 1C

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    Re: LG heat pump problem

    [quote]
    Quote Originally Posted by back2space View Post
    Hi Nike

    As I have 2 units I have switched the dip switch over on one unit. My installer told me that this was the high ceiling mode, as he first had to come back out after installnig as one of the units was setup in this mode by default despite them being mounted at radiator level. This unit that was in this mode seemed to keep heating until it reached 24C no matter what if the set point was 21 it would keep on going to 25C but the unit would achieve the 25C too with no sign of slowing down... cooling in this mode works fine.

    SO are you saying I have to put the unit in high ceiling mode and perhaps set the set point at 20C to perhaps happily maintain about 22C?
    We don't know for fact (without instalation sheet or service manual) that that particular switch is for correction of set temperature for ceiling or floor use of indoor unit. Therefore I advise to move it back to original position and then measure and record behavior of indoor and outdoor unit.
    For this purpose (checking control sequence), I would leave set point to 20°C.

    Where should the sensor be positioned, currently it is poking out the front of the grille as inside the unit it didnt sense temp properly. Remote sensors are coming in January.
    For now, leave it there and make your measurements of temperature of return air on exactly same place.


    The data sheet above mentions nothing abut this control strategy only working in hi ceiling mode.
    From what I know from Fujitsu, control strategy remains same only what switch make is that sensor compesate his reading by 2 or 3°C.

    So what is the position of the dip switch for that I am using at the moment that either switches on or off the compressor should the setpoint be + or - 1C
    I don't know. You could check your room temperatures in both positions after unit has worked some time (2 hours or more) to establish what position gives value that is closer to your set value.

    Please, make check of control strategy as I asked in my previous post and do not change set points or anything during that check until compressor turns of or stay turned on one power step for more than half hour.

  24. #74
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    Re: LG heat pump problem

    the switch is deffo the hi ceiling mode activation switch as I am looking in the installation manual for the indoor unit and it shows a diagram pointing to this switch that says it is the hi ceiling mode button.

    The position that keeps it closer to the setpoint temperature is the one that is not for high ceiling where the unit goes 1C over set point and compressor goes off.

    I cannot find a copy of the installation manual online to show you. But this switch is deffo the high ceiling button. And as per the book it says that in high ceiling the temperature offset is 4C in heating mode.

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    Re: LG heat pump problem

    Ok, then leave it in that position.

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    Re: LG heat pump problem

    But this control thing in the data sheet is not doing as it should?? What would you do?

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    Re: LG heat pump problem

    I would not say that it is not doing as supposed, according to what you say here:

    Quote Originally Posted by back2space View Post

    When only one unit is operating in heating mode the max it will ramp down to is 1300W when its maintaining setpoint. This is no where near the 800w mark that is quoted in the specs? So im dissapointed as yes its cheaper than electric heaters but having checked with the energy meter its using more than I was expecting it to. Cooling is very cheap and within the specs quoted, heating is always like 2280W when both units are on and maintaining set point. No where near the 1368W quoted for the min input on the sheets.

    Minimum compressor speed and min power consumption is only when result of equation "set temperature - return air temperature" is -3°C on both indoor units and not when both indoor units maintain temperature and got return air temperature 19°C (100 hz or full power) or 20°C (80 hz or one step below full power), and this is where it should be according to control logic. Nowhere in documents I saw that is said that it should be at minimum power consumption when unit maintain set point.

    Compressor should stop only when result of equation " set temperature - return air temperature" is -4°C or more for both indoor unit together(-5,-6 etc.... which indicates to much generated power, ergo over dimensioned indoor units for space heat loss).

    Minimum power consumption you should expect only when outdoor temperature is high (probably more than 10°C, or even 15°C) and then you could experience set point overshoots of 3°C because of space low heat load.

    If I remember correctly, I think that is what was happening to you earlier, when outdoor temperatures are high and you wrote about that in your first post about your problematic unit.

    If a temp of 22c is selected on the controller, the unit will sometimes continue until room temp reaches 3 or 4 degrees above this limit, meaning the temperature is very high and uncomfortable, and when the unit needs to kick back in it doesnt come back on quick enough meaning large differences in room temperature.


    From data you presented here, I would not say that this unit is technically faulty in any way. It just do what it is programed and constructed to do.

    If you cannot live with such rough control, you should sell this unit to someone who can, and buy more advanced units with fuzzy logic and more linear power control from Daikin, Fujitsu, Mitsubishi, Toshiba.

    Good luck!
    Last edited by nike123; 26-12-2008 at 05:09 PM.

  28. #78
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    Re: LG heat pump problem

    Quote Originally Posted by nike123 View Post
    If I am reading the chart correctly, it is saying that the compressor ramps down to zero when the return air (average of both indoor units) temp is 4C above the setpoint. Since each unit only runs until the return is 1C above setpoint, we would expect the compressor to only ramp down to 80% at best... and that's only if both indoor units are 1C above setpoint.

    I still see no indication of a problem.
    Last edited by Gary; 26-12-2008 at 07:10 PM.

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    Re: LG heat pump problem

    You seem overly concerned with the wattage used by your system. In fact this is not important at all. What matters is how much heating you are getting for the amount of power used. Or as we say on this side of the pond, how much bang for the buck. Its not about the bang and its not about the buck. Its about the bang for the buck.
    Last edited by Gary; 26-12-2008 at 07:07 PM.

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    Re: LG heat pump problem

    Ok Nike and Gary.

    Ok I think im starting to understand now you are explaining it in a way I can relate to...

    I was going by the figures on the LG databooks as and the figures I was quoting were from the page 218 of http://mylg.co.uk/data%20for%20site/...%20outdoor.pdf

    If you can look at that and look at the figures for 1 unit operation which is usually the case, I only have 1 unit switched on.

    Now look at the right side of the table the "input" colums, it shows MIN, RATED & MAX,

    For rated it shows 1200w... now look at the bottom of that page it shows a note.

    This gives the heating capacity based on an indoor temp of 20C and outdoor temp of 7C... Is this to get the figures in the rated column of 1200?

    The figures above under the RATED column for input are these the ones that are based on the outdoor temp of 7C.

    So basically if its high ambient outside of perhaps 15C you might get the figure in the min column and the colder it is below 7C the more its going to be in the max column?

    Nike you mention my first post about the problems with temp control.. this is down to the postining of the return sensor as the temperutres recorded at the sensor were diff to what they were at the other part of the room. Remote sensors have rectified this issue. So temp of comp on or off is 1C above or below set point.

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    Re: LG heat pump problem

    So if the performance data is based on 230v a/c power supply & the customer has 245v a/c power supply that would make a slight difference to the compressor speed & amps drawn but would also result in slightly better heating performance.

    But the problem is not flat out performance in this case.

    The basic problem that the customer has noticed is that the compressor does not ramp down & reduce power input at low load conditions.

    What is the point of having an inverter system which should save energy by ramping down the compressor at low load conditions if it actually only works to the same control stratagy of a fixed speed compressor ?

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    For rated it shows 1200w... now look at the bottom of that page it shows a note.

    This gives the heating capacity based on an indoor temp of 20C and outdoor temp of 7C... Is this to get the figures in the rated column of 1200?

    The figures above under the RATED column for input are these the ones that are based on the outdoor temp of 7C.
    Yes... A/C systems are rated in a laboratory under tightly controlled conditions. The primary variables are the temperature, humidity and volume of the air flowing through both the indoor and outdoor coils.

    And as they say in the automotive industry... Your mileage may vary.

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    Re: LG heat pump problem

    Quote Originally Posted by Thermatech View Post
    So if the performance data is based on 230v a/c power supply & the customer has 245v a/c power supply that would make a slight difference to the compressor speed & amps drawn but would also result in slightly better heating performance.

    But the problem is not flat out performance in this case.

    The basic problem that the customer has noticed is that the compressor does not ramp down & reduce power input at low load conditions.

    What is the point of having an inverter system which should save energy by ramping down the compressor at low load conditions if it actually only works to the same control stratagy of a fixed speed compressor ?
    Nonetheless, this seems to be the case with this system in the heating mode.

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    Re: LG heat pump problem

    yes exactly what is the point! It seems it ramps down one step when goes over the set point but when it hits 1c exactly over compressor goes off. Why does the document mention it ramps down as it goes over by 4c one step for each degree but to max of 4c then cut off. But in reality were only gettin one step. This should be ramped down as it approaches set point. Never mind after.

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    Re: LG heat pump problem

    The control logic document mentiones the EEV stays 100% open in heating active indor units and 10% open in OFF inndor units.

    Such a control logic mimics a capilary tube system and has very poor performance in part load/reduced compressor speed operation as well as in low ambients below nominal (+7C) operating conditions. If the compressor was to operate at, say 40% speed in heat the result would be liquid flodback to the compressor and very poor performance.

    Here in Norway air to air inverter heat pumps started to be installed in great numbers some 5 years ago. All Panasonic heat pumps had capillary tube system for several years. These systems is run in heat for maybe 6.000 hours a year, a lot of the time in part load and the rest of the time in low ambients well below nominal operating conditions. This means the compressor is running constantly in a liquid floodback condition.

    It now seems like these compressors starts to wear out, loosing its pumping performance and requiring replacement in great numbers after having been in operation for 4 to 6 years.

    Luckily I didnt install any heat pumps with capillary systems.
    Last edited by SteinarN; 26-12-2008 at 11:51 PM.

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    Re: LG heat pump problem

    Perhaps that data is just for the outdoor unit.
    Each indoor unit fan motor will be about 100w to 150w.

    Are you measuring the total watts input for just the outdoor unit or the complete system including the indoor units.

    A cunning 'slight of hand ' deployed by manufacturers can be to only give power input for the outdoor unit in the performance chart.
    You then need to add the power input for the indoor units but they dont tell you that in the data book.

    However if you read the sales brochure you would expect the compressor to ramp down as it approaches set temp & run at min compressor speed at set temp.

    Two weeks ago I spent a day monitoring the performance of 3 split systems from Japan.
    They spent all day operating at min compressor speed & within 1 deg C of set point.
    From time to time they got to set point & switched off & then after a while the room temp droped 1 deg C & the compressor started again & ran again at min compressor speed.

    But then those units have much more advanced control stratagy.
    The LG units are crude by comparison.

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    Re: LG heat pump problem

    The data in the performance charts are for 7m interconnecting refrigeration pipe.

    If you have longer pipe length the power input will be slightly higher.

    But no correction factor quoted for longer interconnecting pipe lenght ?

    So there are a number of small adjustments which could be estimated for indoor unit fans, longer pipe lenght & higher than rated power supply voltage

    but

    none of that explains why the compressor does not ramp down to minimum speed.

    The possibilities are
    1/ The system has a fault which is causing incorrect operation.
    2/ The system is doing exactly what the control stratagy is requesting.
    In which case the low load heating control stratagy is very crude.

    In view of the cooling low ambient control stratagy which is about as much use as a choclate tee pot then you have to suspect that the low load heating control stratagy is also very crude.

    I still think that the system is slow to respond due to the system only making one adjustment every 2 or 3 mins.

    But LG would not want to admit to that, would they.

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    Re: LG heat pump problem

    Just a thought and I know this goes someway back to the starting point of your queries b2s but what happens if you reset the control differential from 1°C back to the high wall of 4°C ?

    I am just wondering whether the system could ramp down properly with a 4° band but with only 1° there isn't enough control logic space left (if that makes any sense). By this I mean that it could step down over 4° expecting a reasonable time for that to happen but with only 1° it has to do things four times as fast to achieve the same result; but it appears that the control cannot respond that quickly.
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    Re: LG heat pump problem

    Brian, I will try this on one unit next week but that then asks a question why there is no control strategy for the low wall applications such as mine. One of the units was left in high ceiling mode when it was installed by accident when it was first installed in June, the outdoor unit ran at full pelt at a set point of 20C until it reached 24C i didnt connect the energy meter at this time but you could tell by the loudness of the compressor how fast it was going. So the high ceiling switch just offsets the temperature to make up for lower temps at floor level and higher temps at ceiling level. All that happens is that the unit wants to achieve 24C instead of the set point of 20C so will go at 100% till it reaches this, then it should wind down like any other system.

    Thermatech, thanks for your comments, but how to tell if the system has a fault.

    One thing I can advise you is if I set the remote controller to 30C the outdoor unit current drawn is about 500watts higher than if it was maintaining the setpoint. I have just tried this now. So the compressor is not running 100% but it doesnt ramp down any more.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post

    This gives the heating capacity based on an indoor temp of 20C and outdoor temp of 7C... Is this to get the figures in the rated column of 1200?

    The figures above under the RATED column for input are these the ones that are based on the outdoor temp of 7C.
    No, all 3 columns are based at outdoor temperature 7°CDB and indoor temperature 20°CDB. What is going to be depends on what is set temperature.

    So basically if its high ambient outside of perhaps 15C you might get the figure in the min column and the colder it is below 7C the more its going to be in the max column?
    No, what is going to be, minimum or maximum or somewhere in between depends on diference between set temperature and air return (indoor) temperature of both units and result of internal equation who consider both indoor units power needs.

    Nike you mention my first post about the problems with temp control.. this is down to the postining of the return sensor as the temperutres recorded at the sensor were diff to what they were at the other part of the room. Remote sensors have rectified this issue. So temp of comp on or off is 1C above or below set point.
    I would carefully check that compressor speed and temperature readings of that sensor correlate in that matter. Turn off second indoor unit and then make measurments as I earlier asked and post here measured data and not conclusions.

    Coll your flat to 16°C. Then switch on your AC, set temperature at 20°C and record return air temperature (at place when indoor unit sensor is now placed) and power consumption in regular intervals (say, every minute) for period of 30-60 min, then we will together establish is this AC works as it should be.
    Last edited by nike123; 27-12-2008 at 09:25 AM.

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    Re: LG heat pump problem

    Quote Originally Posted by Brian_UK View Post
    Just a thought and I know this goes someway back to the starting point of your queries b2s but what happens if you reset the control differential from 1°C back to the high wall of 4°C ?

    I am just wondering whether the system could ramp down properly with a 4° band but with only 1° there isn't enough control logic space left (if that makes any sense). By this I mean that it could step down over 4° expecting a reasonable time for that to happen but with only 1° it has to do things four times as fast to achieve the same result; but it appears that the control cannot respond that quickly.
    From what I know about ceiling/floor universal units, you don't changing differential of unit with deep switches, you only offsetting probe reading for 2K, maybe 3K or even maybe 4 K, but differential stays same.

    But we cannot tell that here for sure, without service documentation.

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    Re: LG heat pump problem

    Quote Originally Posted by Thermatech View Post
    T


    but

    none of that explains why the compressor does not ramp down to minimum speed.
    Because it is not suppose to do that if heat load of conditioned space is not low. It supose to maintain set temperature within tolerance dead band of 1°C by switching between 105 hz and 80 hz (according to graph) or, if outdoor ambient is high, restricted to 60 hz when return temperature in relation to set temperature is overdrawn less than 2°C and therefore acting similar like simple on-of control of capacity.

    The possibilities are
    1/ The system has a fault which is causing incorrect operation.
    I still don't see any evidence to conclude that.

    2/ The system is doing exactly what the control stratagy is requesting.
    In which case the low load heating control stratagy is very crude.
    I bet on this option.

    I still think that the system is slow to respond due to the system only making one adjustment every 2 or 3 mins.
    I could not find any data which confirm that. In fact, we are very low on amount of data who could lead to that conclusion. If you could point me to where did you draw that information from B2S posts, I would appreciate.
    But LG would not want to admit to that, would they.
    None of manufactures do that admission. They all say that new unit has/will have better strategy, but admission is non existent.

    I know only that small inverter multi split systems doesn't have enough sensors and complex control in comparison to older brothers from VRV/VRF range (price would be probable excuse) and therefore, comfort is reduced. Small multi split systems are compromise, and as such, their performance is also compromise.
    Last edited by nike123; 27-12-2008 at 01:05 PM.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    All that happens is that the unit wants to achieve 24C instead of the set point of 20C so will go at 100% till it reaches this, then it should wind down like any other system.
    And that is exactly how it should behave according to control strategy, and if the dip switch mean that air return sensor is offset by 4K.


    Thermatech, thanks for your comments, but how to tell if the system has a fault.
    By measuring and recording compressor frequency, return air temperature, time of changes and set point setting in some time while indoor temperature changes from 16°C (or 18°C, depending on lowest possible set temperature) to set temperature + 4K on both indoor units. For that to happen, you need to simulate low and high heat load conditions by forcing some amount of indoors units discharge air to short cycle.

    One thing I can advise you is if I set the remote controller to 30C the outdoor unit current drawn is about 500watts higher than if it was maintaining the setpoint. I have just tried this now. So the compressor is not running 100% but it doesnt ramp down any more.
    Once again, it cannot ramp down if air return temperature is not higher than it is needed to switch to lower capacity step (and that must be for sum of capacities for both indoor units).

    If change in one capacity step is enough to maintain set temperature within 1K than there is no need to ramp down any more. Only if that capacity change doesn't establish 1K temperature control, outdoor unit switch to lower capacity step and etc...

    Please, read that text above carefully few times because, that is foundation for understanding of function of control logic. And, it seems, that part is most confusing to you, according to your questions.

    P.S. Sorry, if I something misunderstood, because of language.
    Last edited by nike123; 27-12-2008 at 01:25 PM.

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    Re: LG heat pump problem

    Quote:
    Originally Posted by back2space
    All that happens is that the unit wants to achieve 24C instead of the set point of 20C so will go at 100% till it reaches this, then it should wind down like any other system.

    And that is exactly how it should behave according to control strategy, and if the dip switch mean that air return sensor is offset by 4K.


    I am referring to the dip switch being activated in high ceiling mode. The system doesnt aim for 4C higher when not in high ceiling mode it only has a 1C above setpoint.

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    Quote:
    I am referring to the dip switch being activated in high ceiling mode. The system doesnt aim for 4C higher when not in high ceiling mode it only has a 1C above setpoint.
    Exactly as it should be!

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    Re: LG heat pump problem

    I mean if the control strategy sheet was right it says once it has reached setpoint of 20C it will continue to heat to 24C ramping down a step every 1C.

    In high ceiling mode the unit does not do this, once it has reached 20C it will continue at 100% tilll reached 24C. Are you sayign that if high ceiling mode is activated after it has reached 24C it will then start to ramp down and if another 4C increase is sensed it will stop?

    How complicated that sheet is!

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    Re: LG heat pump problem

    niki 123

    I was working one day last year with an engineer who had an old LG training power point presentation for the first generation R410a split systems.

    I had a quick scan though it & I seem to recall that the inverter had about 6 steps of control & the system made any required change to compressor speed & electronic expansion valve opening once every 2 mins.
    I remember commenting at the time that was very poor control in comparison to other split systems

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    Re: LG heat pump problem

    Quote Originally Posted by back2space View Post
    I mean if the control strategy sheet was right it says once it has reached setpoint of 20C it will continue to heat to 24C ramping down a step every 1C.

    In high ceiling mode the unit does not do this, once it has reached 20C it will continue at 100% tilll reached 24C. Are you sayign that if high ceiling mode is activated after it has reached 24C it will then start to ramp down and if another 4C increase is sensed it will stop?

    How complicated that sheet is!
    You are forgetting that, for control logic, if switch is in high ceiling mode, it senses that 20°C return air is in fact interpreted as 16°C. That way, control logic remains same as for floor mode and only difference is that is compensated for difference in placement of air sensor.
    Last edited by nike123; 27-12-2008 at 03:11 PM.

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    Re: LG heat pump problem

    So where does this 4C control strategy come into play then as its not doing that.

    I do feel that it is working better today though its 2C outside and the unit is only cycling off once every hour (twice max) as apposed to every 10minutes.

    The unit does seem to be stepping down perhaps only a couple of steps but its certainly not running at 100% when its maintaining the setpoint. As when I turned it on last night the room temp was 18C, set point was 22 and the unit was drawing a lot more when it was maintaining this.

    So its deffo working so perhaps the fact its drawing a little more wattage is due to the lower than rated temp outside.

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    Re: LG heat pump problem

    Quote Originally Posted by Thermatech View Post
    niki 123

    I was working one day last year with an engineer who had an old LG training power point presentation for the first generation R410a split systems.

    I had a quick scan though it & I seem to recall that the inverter had about 6 steps of control & the system made any required change to compressor speed & electronic expansion valve opening once every 2 mins.
    I remember commenting at the time that was very poor control in comparison to other split systems

    Could be also the case here, but we cannot tell that for a fact.
    Also, 2 minutes sampling rate and 1K dead band is not that bad in comparison to 6 min (10 compressor starts per hour) and 2K dead band, normally found in non-inverter systems, and peoples are still not complaining that much with old on-off systems.

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