Symptoms of outdoor unit being undercharged in heat mode?

[back2space]

-1C here in Leeds and misty, had an engineer out yesterday to replace some lagging on pipes, he also checked refrigerant charge and discovered there was too much gas in it.

He checked with LG the correct charge and it was overcharged with about 300G after the last engineer screwed it up it seems.

So he added the correct ammount in which only required 150grams additional charge.

Indoors it is warm enough & coil seems to freeze up within about 5minutes of defrost running, it isnt even running flat out, only one indoor unit running in heat mode so its drawing about 1.3kw when potential if running flat out it could be drawing 3.0kw.

The defrost cycle works and clears the coil.

Coil is freezing up evenly all over so not just the bottom or top.

Obviously everytime something changes on system performance I panic because so many engineers have been out and each one so far has managed to fix one thing and mess another up etc.

Previously if it wasnt running flat out it would be a while before it starting freezing up, maybe an hour or so.

Thanks.

[Brian_UK]

Lots of variables dictate the defrost timing I believe.

Ambient conditions constantly change which moves the goalposts continually.

Give it time, 24 hours after a engineers visit is, I think, panic on your part.

No offence meant here, but you would be my worst nightmare as a customer; relax, please. ;)

[frank]

If it is -1C in Leeds, then in heating mode, the system would be looking for an evaporating target temp around -7C. This will obviously cause the outdoor coil to frost up. Seems like the defrost is working OK if it clears the coil completely.
I would expect the top of the coil (or small sections) to remain free of frost if the charge was correct as this would indicate that the refrigerant is boiling before heading back to the compressor as a gas.
Difficult to see exactly what is going on from here though.

As Brian says, give it a chance. Monitor temps on and off, inside and outside against ambients, to take the guess work out.

[back2space]

I would expect the top of the coil (or small sections) to remain free of frost if the charge was correct as this would indicate that the refrigerant is boiling before heading back to the compressor as a gas.


The entire coil goes white within about 5-10minutes... wouldnt mind but its only got one indoor unit running so not running anywhere near what it is designed to do so compressor is only jogging along.

Previously with the overcharge in it took the coil probably an hour to go completly frosted over and performance was the same as it is now.

Humidity at the moment is between 93 & 96% humidity.

Tonight I put the unit into cooling.... the outdoor fan runs and the compressor ramps up pretty high before ramping back down again and then the fan goes off and the unit then ramps back up again and the fan comes back on.

Previously the fan always remained on whatever the compressor was running at but rotated very very slowly you could almost count the revolutions.

Now im stressing that he hasnt added the correct refrigerant etc.

Can anyone explain what the unit is doing?

I dont take offence Brian but you can understand where I am coming from, there have been that many "dodgy" guys who have had a go at this unit they have messed up so much I just have no confidence in the kit or A/c any more.

Thanks.

[Gary]

Sounds like it is working perfectly. If it worked any better, we would have to make up a new word to describe it... something like "perfectlyer".

[back2space]

So the fact it was overcharged before would have explained why the fan never cycled off in cooling at low ambient?

[frank]

I'm not sure of the internal working of LG, but quite a few of the systems use a thermal sensor on the liquid line to regulate the speed of the outdoor fan (head pressure control).
If a system is overcharged, then the liquid will become very subcooled as it fills up the bottom of the coil. As the sensor is on the outlet pipe from the coil, it see that the liquid is cold and pulls back on the fan revolutions, even to the extent that the fan switches off.
It's difficult to fault find a system charge in cooling mode with low ambients, it takes skill and a good indoor heat load.

[back2space]

I'm not sure of the internal working of LG, but quite a few of the systems use a thermal sensor on the liquid line to regulate the speed of the outdoor fan (head pressure control).
If a system is overcharged, then the liquid will become very subcooled as it fills up the bottom of the coil. As the sensor is on the outlet pipe from the coil, it see that the liquid is cold and pulls back on the fan revolutions, even to the extent that the fan switches off.
It's difficult to fault find a system charge in cooling mode with low ambients, it takes skill and a good indoor heat load.

Well there is less refrigerant than there was in it before as it was 300g overcharged before and the fan stayed on all the time in cooling despite being overcharged. Now it is cycling off but has the exact charge in it according to lg.

perhaps its just because it was nearlly at 0C outside and the low ambient fan control was coming into effect.

When it was undercharged last time the fan would rotate very fast almost as fast as in heating even though the ambient was about 5C so this was clearly not right.

Now the charge is exact to the pipework length as per lg instruction we are getting the outdoor fan cycling on and off under low cooling load.

Im sure its working fine?

[nike123]

I would say that before this correction of charge fan is been more active due to higher pressure/temperature in outdoor coil.
That could be because now you have correct charge and your condensation temperature is lower because of less backed up liquid in condenser.
And that illustrate how important and critical is correct charge.

[back2space]

I would say that before this correction of charge fan is been more active due to higher pressure/temperature in outdoor coil.
That could be because now you have correct charge and your condensation temperature is lower because of less backed up liquid in condenser.
And that illustrate how important and critical is correct charge.

So the fan when it is running in cooling mode is faster than before but cycles on and off.

Previously with the overcharge the fan would be rotating very slowly but never stop in cooling.

In heating I havent noticed any difference in fan speed as the fans always rotate fast in heating.

So I guess the system is much more happier now.

It is also 0.1C so freezing point and the coil is not freezing up at all. This just shows that when there is no mist/fog in the air the system performs much better.

Indoor temp has gotten upto 22C in matter of half an hour and unit now ticking along happily. That is also with the windows at the back of the house wide open as we have decorators in so in that room its about 5C but the rest of the house is lovely and warm... something central heating radiators would not be able to do!

SO what behaviour would you expect to see the outdoor unit to do in heating mode on an overcharge? The compressor seems to be running the same speeds etc.

[nike123]

SO what behaviour would you expect to see the outdoor unit to do in heating mode on an overcharge? The compressor seems to be running the same speeds etc.

It is hard to tell since it is inverter and condenser in heating mode (indoor units) is divided in more than one part. Electronic control try to maintain set values and adjust compressor speed, electronic valve opening, fan speeds etc.., and it is very hard to find what should we expect wit that much variables, except overall performance degradation. Therefore, it is essential to charge unit to correct amount stated in instalation manual.
They (manufacturer) found it with extensive lab tests and there is no room for much error like in more stupid simple systems like ON-OFF with receiver and TXV.
Like modern and old cars.
They (modern) are fine tuned and when they came to incompetent hands without required tools and instruments, they are nightmare.
Old car was easily tuned (+- margin is much broader) with one screwdriver and trained ear.

[back2space]

It is hard to tell since it is inverter and condenser in heating mode (indoor units) is divided in more than one part. Electronic control try to maintain set values and adjust compressor speed, electronic valve opening, fan speeds etc.., and it is very hard to find what should we expect wit that much variables, except overall performance degradation. Therefore, it is essential to charge unit to correct amount stated in instalation manual.
They (manufacturer) found it with extensive lab tests and there is no room for much error like in more stupid simple systems like ON-OFF with receiver and TXV.
Like modern and old cars.
They (modern) are fine tuned and when they came to incompetent hands without required tools and instruments, they are nightmare.
Old car was easily tuned (+- margin is much broader) with one screwdriver and trained ear.

Thanks for that Nike, what I mean is where does the overcharge of gas go in the system? Is it stored in the outdoor coil? Or is it just squeezed into the pipework?

[nike123]

Thanks for that Nike, what I mean is where does the overcharge of gas go in the system? Is it stored in the outdoor coil? Or is it just squeezed into the pipework?

In the indoor units heat exchangers.

[back2space]

In the indoor units heat exchangers.

Is that in both heating & cooling? How come not in the outdoor, one engineer said it sat in the outdoor units coil.

[frank]

The overcharge will always stay in the condenser as liquid backs up from trying to pass through the metering device -TEV - (which operates to ensure that the evaporator always remains nearly full).

In cooling mode, the outdoor coil is the condenser and in heating mode the indoor coil is the condenser. As the condenser starts to fill up with liquid at the bottom, capacity and efficiency drop off as the useful surface area of the coil is reduced

[back2space]

The overcharge will always stay in the condenser as liquid backs up from trying to pass through the metering device -TEV - (which operates to ensure that the evaporator always remains nearly full).

In cooling mode, the outdoor coil is the condenser and in heating mode the indoor coil is the condenser. As the condenser starts to fill up with liquid at the bottom, capacity and efficiency drop off as the useful surface area of the coil is reduced

Ok that explains a lot then I guess! So the fact the fan is now cycling off in cooling on the outdoor unit is a good thing as apposed to it just slowly running?

[nike123]

I presumed that question is where it goes in heating mode, but Frank leave no doubt where it is at all time.;)

[nike123]

Ok that explains a lot then I guess! So the fact the fan is now cycling off in cooling on the outdoor unit is a good thing as apposed to it just slowly running?
It mean that temperature which guide fan is dropped. That is probably result of more efficient condenser due to less backed liquid in it.

[Gary]

Ok that explains a lot then I guess! So the fact the fan is now cycling off in cooling on the outdoor unit is a good thing as apposed to it just slowly running?


You seem fixated upon the outdoor fan operation, as if you thought it told you something important about the system.

Can an overcharge cause the fan to run more than it should? Yes.

If the fan is running more than it should, does that mean the system is overcharged? Probably not. There can be any number of causes, most of them normal.

And this begs the question. How much should it run? This depends upon a long list of variable conditions, both indoors and outdoors, any of which can change from moment to moment, as well as control settings, accuracy of sensors, etc., etc. etc.

The outdoor fan operation tells you absolutely nothing about the relative health of the system.

[Karl Hofmann]

Jesus H Christ Back 2 Space!..... Please! For your own sanity, stop sitting in the garden with a torch, stop watch and notepad and take yourself off down the pub for a pint and a bag of pork scratchings.....

[frank]

take yourself off down the pub for a pint and a bag of pork scratchings.....
I didn't think they were called PINTS anymore..... everyone in the medical profession & Insurance business keeps asking me how many UNITS I drink a week.....:confused:

........just off down the pub myself for a few UNITS :D:D:D

[eggs]

The outdoor fan operation tells you absolutely nothing about the relative health of the system.

According to your book, "If you ain't got airflow, you aint got $hit"

Care to explain? T= calling for cooling/heating, E=evap fans running, C=cond fan running (oh, this isn't important anymore), H= heat measurements.

So if the condenser fan is playing up surely we can not move on to heat measurements???? or is my understanding of your TECH method not as it should be?

Eggs

[eggs]

Jesus H Christ Back 2 Space!..... Please! For your own sanity, stop sitting in the garden with a torch, stop watch and notepad and take yourself off down the pub for a pint and a bag of pork scratchings.....

Karl, I tried getting him to do that a while ago, apparently he has a sore foot. :)

Eggs

[Gary]

According to your book, "If you ain't got airflow, you aint got $hit"

Care to explain? T= calling for cooling/heating, E=evap fans running, C=cond fan running (oh, this isn't important anymore), H= heat measurements.

So if the condenser fan is playing up surely we can not move on to heat measurements???? or is my understanding of your TECH method not as it should be?

Eggs

Now who is picking nits? :p

[Brian_UK]

According to your book, "If you ain't got airflow, you aint got $hit"

Care to explain? T= calling for cooling/heating, E=evap fans running, C=cond fan running (oh, this isn't important anymore), H= heat measurements.

So if the condenser fan is playing up surely we can not move on to heat measurements???? or is my understanding of your TECH method not as it should be?

Eggs
I think what Gary is trying to say is that without intimate knowledge of exactly what the moden AC control software is doing, by the second, then watching a fan go round doesn't tell you a lot.

On a simple system watching the head pressure being controlled by a simple FSC might show something but only if it is related to pressures and temperatures. Also, unless you have a speed indicator who's to say how fast the fan is spinning?

[eggs]

Now who is picking nits? :p

Ahhhh, that must be the PLuS part of the book that went tits up when inverters were born. :)

Seriously though, brilliant book. Only useful for fridges and coldrooms now though. How about an update for A/C's with inverters?

Eggs

[eggs]

I think what Gary is trying to say is that without intimate knowledge of exactly what the moden AC control software is doing, by the second, then watching a fan go round doesn't tell you a lot.

On a simple system watching the head pressure being controlled by a simple FSC might show something but only if it is related to pressures and temperatures. Also, unless you have a speed indicator who's to say how fast the fan is spinning?

I think we were typing at the same time Brian. I know this and Gary knows this. ;)

How about we have a whip round and buy B2S a decent A/C system so that we can put an end to his bl00dy LG woes.
Jeeezuz every self respecting engineer stopped fitting them years ago. Even Hendrag give up on them.

Eggs

[Brian_UK]

^^ I know Eggs but we have B2S reading also. :D

[back2space]

Ahhhh, that must be the PLuS part of the book that went tits up when inverters were born. :)

Seriously though, brilliant book. Only useful for fridges and coldrooms now though. How about an update for A/C's with inverters?

Eggs

Yes how about it haha

[eggs]

B2S.

Please read this and understand.

You are going through what myself and most small business owners were going through 10 years ago. There is no logic to LG controls, I repeat, there is no logic to LG controls.
If it is heating when you want warmth, accept it. If it cools when you want cooling, accept it. But leave it at that. Any more information will drive you daft (I suspect it has already)

When Lg first came to play in about 2001/2002 ish (my memory is not what it was) I put them in for fun, their sales spiel said "it would give me back my margins" what a load of bllx, the only people who profited where Hitachi, my system of choice at that time. The reason was that I skipped every faulty LG system and replaced it with some quality........at my expense.
Perhaps that is why we are thriving during this downturn, I don't know, maybe I should thank LG for being crap.

But the fact is, your LG blows warm air when you want heating, what is the problem? You are lucky to get this.

Eggs

[al]

set up a paypal account, 1 euro/pound from each member, soon have a nice mitsubishi/hitachi/fugitsu installed......:p

alec

[lomb]

I think the motto should be if the fan even turns Lifes Good:D

[eggs]

I think the motto should be if the fan even turns Lifes Good:D

Saying that, I tried one of those Eco V units the other week.

What an excellent piece if kit, who makes them? :p

Eggs

[olddog]

My memory isnt what it used to be :confused: but didnt I see shelves of LG kit in Arthurs lockup in a recent Minder rerun ?