First post, please be nice, prob with heat mode

[back2space]

Hello Gents

My first post hope you guys can help me.

DOnt want to call out a service tech as we feel we get fobbed off all the time.

We have 2 indoor convertible units connected to a multi split system one in in the living room & the other in our extension at the back. The system works perfect in cooling, maintaining room temp to within 1 degrees C, so comfortable room conditions are always possible in this mode.

However we are having a problem with the maintaining of room temps. THe system has no problem outputting heat but far too much of it.

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. We have noticed that the unit doesnt measure the room temp once the thermostat has shut off as the fan stops completly and doesnt come on again until well below set point as I guess it is measuring the temperature inside the unit which is going to be warmer as the thermister is behind a nice warm filter! I know that the coil sensor will stop the fan operating if its below 28c but in the manual still states the fan shud operate for 10seconds every 3mins to measure ambient... it doesnt do this and lg say it should do this despite their manual saying otherwise!

We have measure the temp at the intake of the unit where the sensor is and we have noticed because these are mounted below our window sill about half a foot from the floor that the temperature down there is usually 1 or 2 degrees below what our digital thermometer says on our mantel piece. SO this is probably why it is not shutting off at about 22/23 as it hasnt reached that desired temp at the intake sensor.

We are not sure what to do as presently we feel we are not getting benefits from the unit and will revert back to our cheap portable electric heaters as these maintain the temp better.

We want to know what our options are with regards to this, the equipment is LG (some sighs i hear from doing a search on LG) LG say there isnt a fault with the units and we feel we are getting fobbed off our installer also doesnt seem to think there is a fault.

We have had to look into matters our self and had advise of heating engineers

We have noticed that if the sensor is poking out the intake grille so it is sensing the room air the unit comes back on if the temp drops below the set point by about 1.0c so we know that if its inside the unit in its correct place because the fan doesnt "cycle" every 3 minutes this is why room temp drops too much.

We also have figured out that because the temp at floor level is going to be cooler than at the mantel piece this is probably why the unit is staying on for a lot longer with the large temp increases.

With this being an inverter as well we find it still cycles on and off everytime it reaches thermostat off, it doesnt seem to wind down enough and it uses more electricity than it did on cooling mode when the outdoor temp is about 12c so its not having to work that hard either! The whole reason we spent so much on a system was to save money!!! Sometimes the actual time the system is giving out heat can be as little as 4minutes on and then 15minutes off. Is this bad for an inverter as we were told they dont shut off only wind down. Again on cooling mode works perfectly no probs whatsoever, with longer cycles on but still cycles off at set point. The units were purposely oversized so that they can heat and cool the entire ground floor of our house which they do very well! They were oversized by about 1.5kw we were told at install to allow for this? Perhaps this explains the cycling issue also in heat mode?

What can we do now to avoid these large temp increases? Is it possible to install one of those room thermostats like you control your central heating with as these are very precise i think? Our hotel room on holiday had air con where you could only control the room temp and had the same as in the pic attached. Room temp was always perfect.

Sorry for the long war and piece but judging from other peoples posts it seems that you guys prefer to have more information than not enough.

Equipment are LG 3.5kw Convertible units.

Kindest regards
Julia

[nike123]

Did you cleaned filters recently?
What is fan speed setting!
I think that, mostly, problem is in placement of indoor unit.
You could find some electrician to relocate indoor unit air temp. sensor to position of about 1,5 m height and far from windows, and heat sources.

[back2space]

Did you cleaned filters recently?

Filters are cleaned every 2 weeks, we know this is not a problem with the filters as they are always spotless.

We clean them more often than they need to be cleaned, when we take them out they have nothing in them but we like to keep everything dust free.

[paul_h]

No, those controllers are no good, this is an inverter system and a simple wall thermostat does not interface with them.

May be an install problem, are the units mounted very high, close the the ceiling?
Or mounted above book cases, in corners or recessed walls?
Are the unit's mounted very close to the outdoor unit (1m or less pipe work between them)?
Do you run the indoor fan on high, or do you run it on quiet/super low/low?

[back2space]

No, those conrtollers are no good, this is an inverter system and a simpe wall thermostat does not interface with them.

May be an install problem, are the units mounted very high, close the the ceiling?
Or mounted above book cases, in corners or recessed walls?
Are the unit's mounted very close to the outdoor unit (1m or less pipe work between them)?

Hello Paul

Thank you for such a quick reply, we have got the units mounted under our baywindow in our lounge see picture attached.

Distance to outside pipework on one unit is about 2metres.

The lounge unit is about 1foot off the floor where the other unit is about 1.5 foot off the floor, both units have the same problem but the other unit one being higher off the ground seems to maintain temp better.

Pic attached is the position of indoor unit in lounge, the main problem unit!

[back2space]

Forgot to add, we run the fan in low speed, we have 3 speeds, low, med or high, we find that because the units are oversized if we run them on high cooling and there are is a small cooling load it reaches set point far too quick, cooling is performed best in low speed so we assumed the same would be for heating. We have tried the system operating with the louvres also operating but find that it then reaches set point too quick as i assume warm air is directed to all levels of the room but then set point is reached at the unit very quick and our digital thermometer on the mantle piece is usually still below the 22c.

[nike123]

Forgot to add, we run the fan in low speed, we have 3 speeds, low, med or high, we find that because the units are oversized if we run them on high cooling and there are is a small cooling load it reaches set point far too quick, cooling is performed best in low speed so we assumed the same would be for heating. We have tried the system operating with the louvres also operating but find that it then reaches set point too quick as i assume warm air is directed to all levels of the room but then set point is reached at the unit very quick and our digital thermometer on the mantle piece is usually still below the 22c.

Put fan at auto and try like that few hours!
Also check my first post, it is updated!

[back2space]

Put fan at auto and try like that few hours!
Also check my first post, it is updated!

Thank you, we dont have an auto fan setting. I have checked your first post as well, not sure about the location of the unit, it is a rectangle shaped room approx 4 by 5metres.

it is mounted on the widest part of the room so blown across the width of the room.

And how do we go about getting the sensor mounted further up the wall, it seems only a small cable and not long enouogh to mount up the wall but then we would want a neat fitting we dont want a black thermister cellotaped to the wall so to speak!

[back2space]

I also found this link on google which seems to mention about the problem of units only sensing off of one thermister, the inverter doesnt adjust properly so provides too much output? Here it is but put the at the beggining

freepatentsonline.com/4891953.htm

[nike123]

Thank you, we dont have an auto fan setting. I have checked your first post as well, not sure about the location of the unit, it is a rectangle shaped room approx 4 by 5metres.

it is mounted on the widest part of the room so blown across the width of the room.

And how do we go about getting the sensor mounted further up the wall, it seems only a small cable and not long enouogh to mount up the wall but then we would want a neat fitting we dont want a black thermister cellotaped to the wall so to speak!

In order to have good distribution of hot air, floor air conditioners should have their flap in horizontal position in heating mode to blow air at low height possible. Also, fan speed should be higher than what is for cooling to force that hot air more to the floor area.
That way you achieve better heat distribution and more uniform temperature.
I am not familiar wit LG control logic, but better manufacturers have fuzzy logic to compensate that high fluctuations of temperature.

Cable could be extended and you need to choose between aesthetic and comfort.

[back2space]

Ok the flap blows at a 45 degree angle so it points at lower level automatically when you set it onto heating mode. We have found if we set the flap any lower the unit cycles too quick and the sensor thinks that it has reached set point when really it hasnt as the floor area must get warmer quicker. I assume that putting it on a higher fan speed is only going to make it reach this set point even quicker.

Were worried about possible wear on the inverter compressor due to the short cycles?

[back2space]

Thank you ever so much for the replies so far, you guys taking the time to help out I find really kind. We have had nothing like this from LG and at the end of our tether.

[nike123]

From picture you posted, I see that air conditioner is surrounded with glass and therefore high temperature fluctuations. Because air conditioner have some protection functions it does not respond quick enough to that changes.
It works perfectly OK, you need only to position sensor as I said, and do not sit in these chairs, because that is worst place to be.
You could always cover sensor with some plant.;)

[nike123]

Ok, then click to scales at our headers!

[back2space]

DOnt understand that bit about scales?

This even happens with the curtains drawn they come over the top of the window sill like the one on the left, they are thick curtains so insulate well.

Is it normal for inverters to cycle? and will 4 mins on 20mins off damage?

[nike123]

DOnt understand that bit about scales?



http://farm4.static.flickr.com/3222/2933852455_22fb420b22_o_d.jpg

[back2space]

From the point of where the picture was taken is a sofa we usually sit here, guests sit near the unit but we dont have problems of people being cold when its on cooling. Usually on the sofa is where they complain as there is a wall behind and a curtain of cold air coming down it from the air throw of the unit.

[nike123]

Is it normal for inverters to cycle? and will 4 mins on 20mins off damage?
1. Yes, if they reached temperature and it still rise.
2. No!

4mins ON and 20mins OFF indicate that AC is too big for that heat loss and air distribution.
Also it could be because fuzzy logic in AC doesn't adapt to that conditions very well.

[back2space]

Oh ok! I will do this from now on when any new replies come in. most helpful so far.

[back2space]

On our old fixed speed unit we was told that this cycling on and off for short period can damage compressor, what is the difference?

[paul_h]

With a normal split, they are designed for cooling. When they go into heat mode, the indoor unit is really undersized for the job of heating. It's better to run the fan on high when using a split on heat, otherwise they may overheat or incorrectly sense room temp and shut down the compressor speed.
Inverters don't cycle normally, if yours is cycling on and off it's may be cutting out on a fault, like overheating.
That's what i suspected at first with your issues, but most of what I said doesn't apply due to the fact you are running floor consoles rather than hi wall mount splits (ie close to the ceiling).
If your system doesn't run better with high fan, you may have a piping or unit problem, or it may be a manufacture/design fault.
sorry, I've never seen floor mount LGs, so I'm no expert on them.
But basically most systems will shut down if the discharge pipe temp in the outdoor unit gets too hot, or they will slow the compressor down if the indoor coil temp gets too hot. Either can be caused by poor installation or even a fault with the unit.
In australia, all such follow up work is done by the companies engineers or contracted people who know the system well. I really don't know what you can do in the UK when you have only the installer to deal with and no one to check the system out fully.
There's an LG rep that is a member here and can maybe help, his name is hendrag and he does UK support for LG.

[back2space]

We have spoken to him before, apparently they tested the same setup as ours in their workshop and they say the system worked fine. The installer checked all the piping and everything that he could. They say the units should heat up to +4C of the set point, but to be honest I think this is a load of rubbish as the manual states that it will only do this if it is mounted on the ceiling and set in that mode, which has been deactivated anyway.

The problem seems to be that it doesnt monitor the temp. However if the unit 2 is blowing warm air and the unit 1 is thermo off then as long as their is warm refrigeratn circulating then the unit will do the 3 minute sample of air thing. However if both units are thermo off then no warm refrigerant circulating thus no monitor of air temp unless we place the thermister outside the unit in the room air. The only reason we can see that the units are cycling in cooling and heating more so in heating is because they are oversized and apparently it cannot adjust quick enough before the room temp goes over its setpoint??? I dont know if they are talking rubbish. The units are definatly not undersized though, this unit we have kicks out 4kw of heat and a small 2kw fan heater will heat the room just as well!

I wish it didnt cycle though as much because in cooling it maintains it so well on hot days its only the cooler days where it cycles.

[back2space]

Put fan at auto and try like that few hours!
Also check my first post, it is updated!


With a normal split, they are designed for cooling. When they go into heat mode, the indoor unit is really undersized for the job of heating. It's better to run the fan on high when using a split on heat, otherwise they may overheat or incorrectly sense room temp and shut down the compressor speed.
Inverters don't cycle normally, if yours is cycling on and off it's may be cutting out on a fault, like overheating.
That's what i suspected at first with your issues, but most of what I said doesn't apply due to the fact you are running floor consoles rather than hi wall mount splits (ie close to the ceiling).
If your system doesn't run better with high fan, you may have a piping or unit problem, or it may be a manufacture/design fault.
sorry, I've never seen floor mount LGs, so I'm no expert on them.
But basically most systems will shut down if the discharge pipe temp in the outdoor unit gets too hot, or they will slow the compressor down if the indoor coil temp gets too hot. Either can be caused by poor installation or even a fault with the unit.
In australia, all such follow up work is done by the companies engineers or contracted people who know the system well. I really don't know what you can do in the UK when you have only the installer to deal with and no one to check the system out fully.
There's an LG rep that is a member here and can maybe help, his name is hendrag and he does UK support for LG.

We are even concerned as in cooling the compressor runs very slow hardly at all but in heating it whirs away and outside ambient is usually 12/13c it doesnt seem to slow down, even on low fan speed.

They have checked the inverter and they say it will run faster in heating due to more work involved to remove heat from the air but we would expect it to wind down a lot even if its 1c off set point and try to maintain it, it just seems it dont slow down enough and this is when it goes way over set point due to the ammount of heat coming from it? But perhaps the position of the sensor is making it think setpoint is lower than it is?

[nike123]

What is indoor unit model#?
By description it also could be that indoor units cables are mismatched.

[back2space]

MV12AH NE0 is the indoor unit.

[back2space]

What do you mean by mismatched?

[nike123]

What do you mean by mismatched?

When indoor unit pipes and cables are not connected at their respective places.

Like 1. indoor unit cable is connected at A cable place at outdoor unit and pipes of same unit are connected at B place and vice versa for 2. indoor unit.

It appears that everything works but temperature control and behavior is sometimes odd.

[back2space]

Can you tell that by the model number? The thing is they have checked all cabling etc when they came out, I think cables are correct as the units are opposite ends of the house so temperatures in eac room are very different, and surely the units would signal comms error if this was the case as we rarely use both units together.

[nike123]

[quote=back2space;122493]Can you tell that by the model number?

No.


The thing is they have checked all cabling etc when they came out,

If that is the case, than forget about that I mentioned it.

[back2space]

Would be interesting to find out engineers opinions who have worked on these units in the past.

Nike123, seriously though thank you for your help so far. I would give you more reputation but it wont let me do it again! :(

[airefresco]

Probably not that then. What Nike123 means is that the communication wires between each indoor unit to the outdoor have been crossed. So the outdoor unit reads the temperatures from unit A, but supplies the hot refrigerant to unit B, and not units A as it should. Easy was to find out is switch just one of the indoor units on and see which set of pipes at the outdoor unit get hot. Be careful, because the pipes could be really hot.

[back2space]

Ok just done this the units are wired correctly as the one i switched on got hottest. The other one got warm but we were told its normal for refrigerant to circulate amongst the other unit to allow for oil return, The EEV is open 10% on the unit that is switched off in heating.

[Brian_UK]

Hi Back2space and welcome to the forum, it looks like you're getting lots of input to your problem already.

One question from me, what type of controller do you have ?

Sorry, 2 questions; is it a wall mounted controller or wireless.

[back2space]

Hi Brian

Thank you for the warm welcome, this site is really friendly wish I had asked the initial questions on here rather than being given the run around by lg etc.

I have a background knowledge of ac as I used to work in a helpdesk logging maintenance jobs for ac. we would log the faults and dispatch engineers, so I have knowledge of the "jargon" most would call it! SO being technical is not going to blag me so to speak!

We use remote controls to operate the units, I wanted hard wired as I know that some have remote sensors in them that you can use instead of the intake sensor which in this case is low down the wall in the unit sucking in cooler air I work out!

However our units (MV12AH) cannot be operated off hard wired so we have to use the remote controls.

There is no problem with any wiring, initially the intake sensor was out of calibration on one of the units and in cooling it was 1C out of the setpoint, so if you was set 21C on the remote the unit aimed for 19 and then came back on at 21C when really it should aim for 20 and come back on at 22C.

Thats all fixed now and cooling mode works perfect, just this damned heat mode we need to sort!

Oh and rep added for being so polite!

I have to ask wheres the biscuit tin I feel like im going to stick around and get involved on the forum!

Kind regards

[Brian_UK]

Sorry, we don't do biscuits here it's doughnuts or nothing ;)

Yes I had asked because of the sensor in the remote and doing a quick look through the LG site http://mylg.co.uk after I had posted made me think that you would only have a wireless control. (Damn-it, strike one idea)

I even see that there is a 'tech note' covering your problem exactly complete with a "tough luck" answer to it.

I tend to go with previous suggestions about relocating the sensor.

I suppose you could go exotic and buy some spare sensors. These could be mounted were you wanted and connected via a changeover switch with the unit sensor. Then you could chose which sensor you wanted depending on the mode selected.

Why have easy when complicated costs more ??

[back2space]

Brian

Ill have 2 donuts please! With Jam in!

I have seen a technical note on there (product information sheet) , see below:

It specifically states that cassettes and convertible units have the control strategy of 10seconds fan on every 3minutes to sense temperature. However LG say that that is a mistake and they dont mean convertables... i am being fobbed off totally here I think! THey either dont want to admit that the software of air con hasnt had this feature written into it when the coil sensor says that there is no hot gas circulating. As this control strategy works as long as one unit somewhere is giving out heat as refrigerant circulates through all units for oil return in heating mode.

Have you seen a different techie sheet or are we reffering to the same: See below:

<DIV dir=ltr align=left><SPAN class=140422204-04092008><DIV dir=ltr align=left>Product Technical Update Sheet 76

[back2space]

Not sure why the copy and paste aint working.

See below as I have now copied into a word document. SOrry for the above few posts being rather blank!

I have physically added the data sheet now that I have seen if there is another one Brian that you have come across can you attach it as mylg doesnt seem to be working tonight.

[Brian_UK]

Don't try to cut and paste from webpages, just copy the website address from your browser and post that as here...

http://mylg.co.uk/data%20for%20site/Prod%20sht%2076%20my%20unit%20operates%20wierdly%20in%20heating.pdf

[back2space]

I am getting some random site coming up when clicking on that.

CAn you put it into a word document, i think the mylg website is down its taking me to some travel media shopping thing.

[Brian_UK]

Just tried it again, works fine for me.

"http://mylg.co.uk/data for site/Prod sht 76 my unit operates wierdly in heating.pdf"

Also, be aware that cutting and pasting Word documents into your post may cause corrupted posts and is sometimes disallowed by the system.

[back2space]

Hmmm maybe problems with our internet (im at work) does it say anything different to the fact sheet 76 I attached.

Thank you.

[Brian_UK]

Nope, same text, same non-helpful content.

Anyway, I'm off to sleep now; hope you have a quiet night...

[back2space]

Thank you Brian, I hope its quiet now.

Could you elaborate on these extra sensors Malarky?

I was wondering if theres a better controller out there for it?

[stefs_cruiser]

When it is called a convertible, does that mean this unit can be fitted under the ceiling, as well as on the floor?

In that case, I have seen these issues before on another brand, and the indoor unit had a link or DIP switch to alter the thermostat characteristic, to allow

The unit cycling on and off, is most likely due to being oversized.
even if the unit winds down to the lowest speed, it is still heating more than required, quite common is autumn and spring.

[stefs_cruiser]

to allow for stratification, not quite sure how that bit disappeared :-)

[back2space]

When it is called a convertible, does that mean this unit can be fitted under the ceiling, as well as on the floor?

In that case, I have seen these issues before on another brand, and the indoor unit had a link or DIP switch to alter the thermostat characteristic, to allow

The unit cycling on and off, is most likely due to being oversized.
even if the unit winds down to the lowest speed, it is still heating more than required, quite common is autumn and spring.

Hi there

THanks for your reply, yes being a convertible it means it can be fitted under the ceiling or on the floor similar to how a radiator would be mounted. There is a switch inside the unit that you turn on if the unit is to be mounted on the ceiling, this then means that there is a temperature offset in heating of +4 degrees so the unit will heat to 4c above setpoint to allow for the heat that has risen at ceiling height. One of the units was set to this option by mistake but this was rectified, however these problems are still happening however its not the unit that is trying to heat to +4c as the air intake hasnt usually gone above the setpoint (we tested with a digital thermometer at the intake) and intake temp at floor level was sometimes 3C lower than at the mantel piece level.

[leestoke]

silly question,but is the pipe entry hole from outside fully sealed,if not it is possible cold air coming into the unit affecting the sensor,ie telling it more heat required

[back2space]

Yes all is sealed well with expanding foam! I dont like draughts so I checked this over after the install.

[back2space]

Any one else got any input?

[Brian_UK]

Thinking sideways, as I do sometimes....

Can an adjustable resistor be fitted into the sensor circuit?

You could then use that to 'offset' the temperature being sensed and fool the controls.

Visually you would end up with a small rotary knob on the side of the unit.

[back2space]

Not sure really I wouldnt be able to do this anyway if it was possible.

I think the best thing to do is get the sensor mounted further away from the unit.

Question is how can i get this done!

[Tradewinds]

Hi Back 2 Space,
Please bare with me as I don't work on splits (much) and haven't posted here for quite a while, so you could say I'm a bit rusty. Personally speaking, I would definitely look to relocate the sensor. I would have thought that LG have a remote sensor available for this unit or failing that any electrician could extend the cable for you. It's interesting though that it doesn't vary the compressor speed on heating as well. I would have looked for a DIP switch to correct this as well. Is it the same problem on both indoor units? You could also try putting the sensor in ice to see if it runs for more than 4 minutes. This would indicate whether it is stopping on temperature or fault (if no fault indication is present).
Hope this helps,
Regards,
Stuart

[back2space]

When i touch the sensor with warm fingers the unit will switch off. We have measured the intake temp and this is always about 1c lower than the actual room temp, i assume because of the high ceilings the floor is always going to be cooler.

The sensor is therefore working correctly. The unit varys comppressor speed in cooling and i assume it is doing so in heating although maybe because it is oversized it cant slow down enough.

LG say there is no remote sensor for this model and that they would charge for an extension of the sensor! Hardly fair!!!!

[nike123]

When i touch the sensor with warm fingers the unit will switch off. We have measured the intake temp and this is always about 1c lower than the actual room temp, i assume because of the high ceilings the floor is always going to be cooler.

The sensor is therefore working correctly. The unit varys comppressor speed in cooling and i assume it is doing so in heating although maybe because it is oversized it cant slow down enough.

LG say there is no remote sensor for this model and that they would charge for an extension of the sensor! Hardly fair!!!!

Who has made decision for indoor unit position? You or them?
If you insisted that it must be there, then I don't see how is that not fair!
If they are insisted with placement of unit there and did not tell you about possible difficulties with room temperature control, then they are responsible.

[back2space]

They told me where they were putting the unit as this was really the only place to put it with the outside wall, its a victorian house and it kept pipe runs to a minimum as well. If it had been mounted anywhere else in the room on another wall i think it would have been the same problems. There a no draughts from the windows at all and the unit behaves fine in cooling but it seems that the hot air is taking longer to fill the room due to stratification so taking longer to circulate to the lower floor area. if the louvre is set to move up and down itself then the unit reaches set point very quick but the actual room temp is lower than the unit thinks then due to warm air cycling back into the unit.

[Brian_UK]

I assume being a Victorian house that you therefore have quite high ceilings.

If this is the case then there might be a valid argument for installed a ceiling fan the destratify the air.

If the fan is used to draw the air upwards then the warm air is circulated without draughts.

[airefresco]

I was just going to suggest the exact same thing as Brian.

[back2space]

I assume being a Victorian house that you therefore have quite high ceilings.

If this is the case then there might be a valid argument for installed a ceiling fan the destratify the air.

If the fan is used to draw the air upwards then the warm air is circulated without draughts.

Yes we have the high ceilings and we also have a ceiling fan in the said rooms, the bedroom unit seems to reach temperature better but this is mounted about another foot higher from the floor than the lounge one (problem one)

The bedroom one is fine even without the ceiling fan on.

If the lounge one is operated with the ceiling fan in reverse then we end up with an even worse a situation as the air is sucked upwards and thrown down the sides of the walls thus cooling it at the same time.

[Brian_UK]

I really do get the impression that that unit is well oversized.

The hot/warm air being lifted by a ceiling fan should not really create a major change of effective temperature. Unless, the air is being heated in chunks (wrong word but can't think of a better one).

This is always the drawback of blown warm air heating, as soon as the temperature of the supply air changes everybody notices.

[back2space]

The unit behaves perfectly in cooling however still cycles on and off, i dont think it can ramp down enough.

We had various quotes, most quotes said we needed 12000btu unit for cooling, however one firm said a 10000btu unit???

Obviously in cooling the indoor unit (MV12AH outputs 3.52kw of max cooling, however in heating it seems the max output increases to 3.87kw so slightly higher. See link and scroll to specs.

http://mylg.co.uk/data%20for%20site/Multi%20F%20convertible.pdf

Now when you compare this to the min/max outputs of the the outdoor unit, the max rated capacity of the outdoor in cooling is 8.5kw and the min capacity in cooling is 1.85kw whereas in heating the max is 9.38kw and the min is 2.22kw.

Now it does say that the unit should be able to ramp down to 2.22kw which is 6300btu. Surely if the one guy said 10000btu was needed for cooling then similar capacity is needed for heating.

Starting to get confused with the figures but i know the unit is oversized but we need this extra capacity as when we have friends over we have a full room then the unit doesnt tend to cycle it will ramp right down in cooling.

HMMMMM me confused you all now i bet!

[back2space]

the above details are for the multisplit system that I have. The indoor units are the same as the type I would have if it was just a standard back to back split.

Now what I have also looked into is the min/max ratings of standad back to back 3.5kw inverter split condenser unit. (1 indoor 1 outdoor)

I notice straight away that the standard 1 on 1 split can ramp its capacity down lower than my multi split condenser.

Cooling min = 1.40kw
Heating min = 1.62kw

So if on my multisplit condenser it has ramped right down to 2.22kw in heating and this is still too much for the room its going to cycle off isnt it. In cooling its cycle on is longer than a cycle in heating.

Another worry is how do inverters handle short cycling issues? i know standard fixed speed ones wear out.

In heating the unit cycles on for 6 minutes and then its off for about 20minutes.

In cooling it will be perhaps 10 mins on and then 10 mins off.

[murran]

Hi, I am new to the forum.
I do not have a lot of experience with multi splits as ive worked mostly with larger industrial airconds.
Ive read through all the info and what I can add is the fact that the aircond is at ground level will influance the heating capacity in particular due to the fact that heat rises.
The temp at celing will be easily 3C higher than floor level. This means that by the time setpoint is reached at floor level where the sensor is situated the room temp will be a few degrees higher.
To compensate for this you could set your thermostat at least 2 degrees lower than what you want instead of moving the sensor.
The fact that it is running at full capacity for a short period suggests undersized unit.?
The other factor in heating cycle is the outside temp.
If it is very cold,the unit will ice up(this is normal) and goes into defrost cycle shutting down the heating for short periods.
The best solution in my opinon is to relocate the aircond to ceiling level & to make sure you have sufficent capacity condensor.

Hope this helps.

[back2space]

Hi Murran

Welcome to the forum, thanks for your input, everything so far is leading to the unit being oversized as it does not struggle whatsoever with heating the room at all in fact it is overheating the room, cooling likewise however precision temp control on cooling mode probably due to the way cool air circulates back to the unit.

THe unit has never gone into defrost mode yet hasnt been cold enough does a oil recovery thing every 6 hrs though kind of like defrost operation but theres no icing up.

We think the unit is operating at high speed when it kicks back in at thermostat on but the room is heating up quicker than the inverter can adjust to conditions so ends up cycling off.

We tried compensating with lower set point (20) and found that whilst the temp at cycling off was more suitable (22). The unit would then not kick back in till the room temp had actually dropped to 19C so there was a big diff in temp, not ideal for a lounge.

[SteinarN]

They told me where they were putting the unit as this was really the only place to put it with the outside wall, its a victorian house and it kept pipe runs to a minimum as well. If it had been mounted anywhere else in the room on another wall i think it would have been the same problems. There a no draughts from the windows at all and the unit behaves fine in cooling but it seems that the hot air is taking longer to fill the room due to stratification so taking longer to circulate to the lower floor area. if the louvre is set to move up and down itself then the unit reaches set point very quick but the actual room temp is lower than the unit thinks then due to warm air cycling back into the unit.

What you want is the unit to cycle off quicker. Iow a shorter heating cycle. You mention the solution yourselv in the quote. If the overall room temperature then gets to low you have to increase the set point until you acheive the correct room temperature.

Generally speaking it is impossible to acheive an even heat distribution in the room without the direction of the air flow be either horisontal or downvard say 45 degrees. Downvard 45 degrees for ceiling or high wall inndor units and as close to horisontal as possible for low wall units. It is however important that no furnitures is in front near the inndor unit as this will cause excessive short cycling.

[back2space]

By short cycling what sort of lengths of time do we consider a short cycle?

My units cycle on for about 5-7minutes and then off for 20 or longer on the heat operation

In cooling its 7mins on and then off for ten minutes or a little less.

Do inverters wear out this way, is it bad for them?

[SteinarN]

With short cycling I ment the warm air returning back to the indoor innlet. I didn't have in mind the lenght of each heat cycle.

I dont think inverters wear out as as a result of frequent start-stop operations. There is no electric relays to wear out. Inverters starts very gently.

Try to adjust the louver to as close to horisontal as possible and remove the furniture away from the warm airflow.

[back2space]

We shall have to look into this as the airflap is already horizonatal at a 50 degree angle.

We shall see over the coming days or so.

[nike123]

We shall have to look into this as the airflap is already horizonatal at a 50 degree angle.

We shall see over the coming days or so.

What you mean by 50° angle?
From picture of that unit, its flaps can easily be parallel with floor. That is 90° angle with wall or 0° angle with floor.
What is your case? Could you post picture with flap position you usually use?

[back2space]

OK the unit is in heatnig at present and the flap is set as it automatically sets in heating mode. From the point of switching it on.

If the flap points any closer to the floor it short cycles even more as the floor area warms up too quick so this seeems the best angle.

U can see from "Untitled 3" the flap position in heating, automatically set, this seems to be the best position we have tried them all.

"Untitled" is a view of the room lengthways.

"Untitled 1" is a room widthways, the a/c blows widthways.

"Untitled 2" another view of the a/c.

[nike123]

From what you just said it is more likely that your AC is grossly over sized! Now it is important to find out your real heat loss in that (and other) spaces.

Ok, more questions!;)

Do you use only one of these two indoor units when you experience these problems, or you use both units simultaneously?
What is your typical outdoor temperature/humidity these days, and what is set indoor temperature?
What kind of windows 8describe construction of windows) in that lodge you have, and what is actual height of your room? What material is that curtain and how thick it is?
Do you have knowledge of walls construction details and do you have any drawing of conditioned spaces?
Does other three walls of room looking to conditioned (heated) places?
Do you have any additional (significant) heat source in that rooms?

[back2space]

The problems are experienced whether I use one or both units. We find though that 1 unit is sufficient enough to heat the entire flat up!

We tend to use both units when on cooling mode and no problems when on heating we can have problems when they are both running, the units are separated by another 2 rooms and are not fighting against each other in anysort of way.

The construction of windows are double glazed pvc windows (no draughts)

The height of the room is standard height for victorian house, not sure of exact height dont have measure but if i jump up i can reach it just! Im 6ft 2.

The curtains are thick blackout curtains to retain the heat, these problems happen whether the curtains are drawn or not.

The only outside walls are the side of the fireplace and either side of the window.

The other unit is installed in a similar room but is a little bigger (bedroom).


No significant heat sources in the rooms unless we have a party and have disco lights going and people dancing most of the time there are 2 or 3 people in there.

Thank you.

[SteinarN]

From what you just said it is more likely that your AC is grossly over sized!

This is probably the main problem asuming the outdoor unit is actually running at lowest possibly capasity in heat mode.

[back2space]

Yeh this seems to be the case!!! Thing is we leave all the internal doors open to the hallway and the unit heats the whole hallway and the other rooms perfectly and stil cycles on and off!

SUppose thats good really aint it!!! Id rather have it overperforming than underperforming.

[nike123]

The problems are experienced whether I use one or both units. We find though that 1 unit is sufficient enough to heat the entire flat up!

We tend to use both units when on cooling mode and no problems when on heating we can have problems when they are both running, the units are separated by another 2 rooms and are not fighting against each other in anysort of way.

The construction of windows are double glazed pvc windows (no draughts)

The height of the room is standard height for victorian house, not sure of exact height dont have measure but if i jump up i can reach it just! Im 6ft 2.

The curtains are thick blackout curtains to retain the heat, these problems happen whether the curtains are drawn or not.

The only outside walls are the side of the fireplace and either side of the window.

The other unit is installed in a similar room but is a little bigger (bedroom).


No significant heat sources in the rooms unless we have a party and have disco lights going and people dancing most of the time there are 2 or 3 people in there.

Thank you.

In my practice, I was been in situations like your now, but on opposite side. I am pretty sure that calculation of required capacity is not done scientifically , it is probably done by rule of thumb. Therefore such high discrepancy in really needed and installed capacity.
There is very, very slim chance that installer will consider that as his error.
My advice is, to do as I already suggested, and install sensor on appropriate place (described earlier).

[back2space]

Does the inverter run faster when it is in heating mode as apposed to cooling mode.

It seems considerably louder when in heating mode (sounds to run faster) even when it is only maintaining a setpoint of 22C and outdoor ambient of 13C.

Wheares in cooling it can hardly be heard, we thought this was fan noise as the fan runs faster in heating but its not it is the compressor is noisier and faster. When the engineer set it up he put multimeter on and it was drawing more current in heating than cooling?

[back2space]

Reason i ask is when I check the panel at work (Mitsi Elec) you can check the Hertz of the compressor. ANd when its in heating or cooling and maintainting setpoint happily the comp hertz are about 59-60hertz. Is

[Thermatech]

LG twin split system

Ebay item 230349810459

Looks familiar :D

[sinewave]

If in doubt, flog it to some other Sucker! :D


It's doing well at £32! :p

[back2space]

If in doubt, flog it to some other Sucker! :D


It's doing well at £32! :p

Its not like that at all.

The system works fine according to LG Technical, however the installer and myself does not believe that the control strategy is working as it should, yes it heats and cools aplenty but not as efficient and per the specifications that they sell the system on.

Would be fine for conservatories, shops or retail premises, however if its for houses/ I think you will have probs with temp control, either too warm, too cold and the system not ramping down as designed to leadiing to the system cycling off due to lowering the room temp too far below the 1C above or below set point.

Cheap tat I think the fact its at that ammount says what sort of influence they have on the market. No one wants them.

One chance and they messed up.

[Yuri B.]

Hello.

P 60.
Now when you compare this to the min/max outputs of the the outdoor unit, the max rated capacity of the outdoor in cooling is 8.5kw and the min capacity in cooling is 1.85kw whereas in heating the max is 9.38kw and the min is 2.22kw.


Capacities stated of systems are in the long run the product of ambients. Thus, the heating one of 9.38kW is reached by the system at the maximal outside temp (let's say +18C), 2.22kW at the minimal (allowable) outside temp (let's say - 20C). For cooling otherwise direction.


P 71.
We find though that 1 unit is sufficient enough to heat the entire flat up!....... have problems when they are both running,


As you have mild winters in Britain, heatpumps should work with maximal productivities.
Considered "oversized" at +13C outside (value mentioned by you, I think, not once), I bet you (would) have another point of view about the AC at -13C outside.

P 61.
Another worry is how do inverters handle short cycling issues? I know standard fixed speed ones wear out.
In heating the unit cycles on for 6 minutes and then its off for about 20minutes.


I think you are unduly worried about this issue. First, if it is invertor, no problem at all, secondly, agree, we do not change compressors very often at freezers working this way.

P 55.
the unit reaches set point very quick but the actual room temp is lower than the unit thinks then due to warm air cycling back into the unit

As the coil's residual warmth keeps warming up the sensor, many here advised You to bring it some meters away. Having it "black-scotched" to an opposite wall - for an experiment - for a week would not give you more inconvenience than struggling with temp-s across the whole place. (then You would have redone it properly, of course).

What is left to do if the control may turn out to be far imperfect, if the position of the units seems to have been a bit better? Probably, experimencing with the sensor(s) and air flows (maybe even blocking air flows - depending on temp-s outside).

Best regards.

[Yuri B.]

Every quote is actually followed by my comment, however smth went wrong when posted.

[back2space]

Hello.

P 60. Now when you compare this to the min/max outputs of the the outdoor unit, the max rated capacity of the outdoor in cooling is 8.5kw and the min capacity in cooling is 1.85kw whereas in heating the max is 9.38kw and the min is 2.22kw.

Capacities stated of systems are in the long run the product of ambients. Thus, the heating one of 9.38kW is reached by the system at the maximal outside temp (let's say +18C), 2.22kW at the minimal (allowable) outside temp (let's say - 20C). For cooling otherwise direction.


P 71. We find though that 1 unit is sufficient enough to heat the entire flat up!....... have problems when they are both running,

As you have mild winters in Britain, heatpumps should work with maximal productivities.
Considered "oversized" at +13C outside (value mentioned by you, I think, not once), I bet you (would) have another point of view about the AC at -13C outside.

P 61. Another worry is how do inverters handle short cycling issues? I know standard fixed speed ones wear out.
In heating the unit cycles on for 6 minutes and then its off for about 20minutes.

I think you are unduly worried about this issue. First, if it is invertor, no problem at all, secondly, agree, we do not change compressors very often at freezers working this way.

P 55. the unit reaches set point very quick but the actual room temp is lower than the unit thinks then due to warm air cycling back into the unit
As the coil's residual warmth keeps warming up the sensor, many here advised You to bring it some meters away. Having it "black-scotched" to an opposite wall - for an experiment - for a week would not give you more inconvenience than struggling with temp-s across the whole place. (then You would have redone it properly, of course).

What is left to do if the control may turn out to be far imperfect, if the position of the units seems to have been a bit better? Probably, experimencing with the sensor(s) and air flows (maybe even blocking air flows - depending on temp-s outside).

Best regards.

THanks for the replys and advice, believe me when I say we have tried everything. The outdoor PCB was replaced, remote sensors were brought in and placed in several places in the room to get better temperature measurement. This improved the temperature at which the unit was cutting out and meant the whole room was equal temperature, however a 1C increase in temperature takes approx 10minutes to register on the digital thermometres and approx the same on the units remote sensors, however this 10minutes the compressor will still run at the same capacity as it did 10minutes ago, it doesnt seem to ramp down.

[Yuri B.]

Outdoor PCB was most probably "unguilty". Its job is to only comply to the orders from the inside init's PCB, so my common sense says.

Did you mean set point achieved, compressor continues to run - always? How you know it runs with the "same capacity"? And what you call "capacity" here?

[Yuri B.]

I am not an expert, does anybody know whether the controls of such systems (with varying refrigerant flow) have the set point offset at the outside ambient temp? My comm sense says they should have.

[back2space]

The compressor was running at the same hertz whether it was 1C off set point or equal to set point. It only seemed to run faster when it was 3C off set point but then only seemed to step the compressor down 1 step despite having plenty of time per 1C increase to adjust the hertz = output.

When set point achieved compressor continued to run which is normal until theres a diff of 1C over the set point at which point it would cycle off. That diff between set point and 1C over the set point the compressor would not change its hertz.

Several engineers checked this over, the last one said it was the O/D PCB that was at fault.

Other engineers checked the compressor by connecting to see what voltage etc it was drawing.

I did not diagnose the PCB fault, but I do know and agree with the engineers that the control strategy is not right at all.

[back2space]

I am not an expert, does anybody know whether the controls of such systems (with varying refrigerant flow) have the set point offset at the outside ambient temp? My comm sense says they should have.

Not sure what you mean? The systems do not compare the outdoor temp to indoor temp to decide the set point indoors.

WHatever the set point on the controller is what the system will aim for inside.

Is this what you mean?

[AbsoluteWDJ]

Well, well, well....Richard....You'll make a good salesman....I'm interested in buying them....You say they've run well through the winter....Is this correct!!!:o

[back2space]

They have yes, despite the control strategy above as long as you dont need fine control of temps then you would be fine, would suit conservatories or larger heat gain rooms where there is less chance of them needing to cycle off.

Plenty of cool/heat output.

THe only reason selling is because want better temp control from Mitsis which im prepared to pay for.

[Yuri B.]

WHatever the set point on the controller is what the system will aim for inside.

(At last succeded with quoting.) I find it reasonable to suggest that such a (more precise) system should take into calculation the rate at which a conditioned space (might) lose /acquire heat - depending on temp difference between inside and outside - factoring this value into the room control. (But this might be not the case with A/Cs altogether, however, so forget it).

[AbsoluteWDJ]

They have yes, despite the control strategy above as long as you dont need fine control of temps then you would be fine, would suit conservatories or larger heat gain rooms where there is less chance of them needing to cycle off.

Plenty of cool/heat output.

THe only reason selling is because want better temp control from Mitsis which im prepared to pay for.

I'm only pulling your leg my friend....

Peace

[back2space]

I'm only pulling your leg my friend....

Peace

:eek:
Oh dont lol, ive had so much messing around with this system its unbelievable!

;)

[back2space]

(At last succeded with quoting.) I find it reasonable to suggest that such a (more precise) system should take into calculation the rate at which a conditioned space (might) lose /acquire heat - depending on temp difference between inside and outside - factoring this value into the room control. (But this might be not the case with A/Cs altogether, however, so forget it).

Maybe very expensive systems certainly not LG.

However I know it has a fan control on the outdoor unit but purely for fan speed on o/d unit.

[headgasket]

my dad brought a new fridge once, after two weeks he told me the fridge runs for 10 mins, then off for 6 mins, the point. its only effecting you, you do not have a close control a/c system installed, and you said it is over sized, there you have it i am afraid.a/c works well in a square box, or office, or work shop

[back2space]

my dad brought a new fridge once, after two weeks he told me the fridge runs for 10 mins, then off for 6 mins, the point. its only effecting you, you do not have a close control a/c system installed, and you said it is over sized, there you have it i am afraid.a/c works well in a square box, or office, or work shop


Im not saying its short cycling, it will run for about 20 mins at thermo on, but in that time its not RAMPING DOWN far enough!

The control strategy is poor.