Is there any kits to make A/c hotter in cold weather

[Chris2005]

Hi All

I fitted an LG FM40AH mps inverter system in my house with four artcool mirror units about 2 years ago.

There is nothing wrong with the units they work fine apart from when the outside temp gets to about -1.5c or -2c they put out hardly any heat.

Is there anything can be done to cure this problem .

Thanks chris

The

[nike123]

Hi All

I fitted an LG FM40AH mps inverter system in my house with four artcool mirror units about 2 years ago.

There is nothing wrong with the units they work fine apart from when the outside temp gets to about -1.5c or -2c they put out hardly any heat.

Is there anything can be done to cure this problem .

Thanks chris

The

Yes, recover and weigh refrigerant and check if its amount is correct.

[Abby Normal]

the heat capcity will start dropping off when it gets below freezing.

Get the installer back and have him check to performance. Do they not keep up or does it just bother you the supply air temp drops when the outside air temp drops?

[Chris2005]

Hi all

I am a refrigeration engineer myself it was me installed the units.

The heat out of the units are great when the outside temp is not below freezing ,
just thought some of you that do alot of Aircon might no of a few tricks or bit of kit that could be fitted in colder countries to get round the problem of low outdoor temps.

I was thinking of something like making a ground loop system but was hoping there would be a handier solution.

Thanks chris

[Peter_1]

Chris, or your machine is lacking gas or your system was undersized since the original install.
If it's undersized, then you have to add additional evaporators and a ground coil is indeed a very good idea. How you would connect this to the machine is something different, what about the electronics?

[Abby Normal]

Hi all

I am a refrigeration engineer myself it was me installed the units.

The heat out of the units are great when the outside temp is not below freezing ,
just thought some of you that do alot of Aircon might no of a few tricks or bit of kit that could be fitted in colder countries to get round the problem of low outdoor temps.

I was thinking of something like making a ground loop system but was hoping there would be a handier solution.

Thanks chris

in cold climates heat pumps will often utilize auxiliary heat, like electric to work on top of what the heat pump can do, or fossil fuel systems that take over once the heat pump cannot keep up with the heat load of the space. They go for a balance point temperature for when to switch over to the fossil fuel heat.

I did ground source heat pumps in Canada from the mid 80s to the mid 90s. You could size them for the full heat load, however it became diminishing returns when you looked at the yearly cost of a small amount of electric heat vs the cost of more excavating, more pipe in the ground, more antifreeze and a larger unit.

In places more humid than where I was from in Canada, oversized heat pumps would have a hard time keeping up with the humidity in the ambient air in the cooling mode and you could be prone to high indoor RH with a heat pump sized to do the entire heating load.

I had no problem with RH being driven up in Canada as the ambient air did not get all that humid and the homes the heat pumps were installed in were fairly air tight and not prone to high infiltrations. Such houses needed ventialtion air in the winter to keep windows from condensating.

Houses that need humidifiers in the winter have a lot of infiltration. A dry house is a drafty house

[nike123]

Hi all

I am a refrigeration engineer myself it was me installed the units.

The heat out of the units are great when the outside temp is not below freezing ,
just thought some of you that do alot of Aircon might no of a few tricks or bit of kit that could be fitted in colder countries to get round the problem of low outdoor temps.

I was thinking of something like making a ground loop system but was hoping there would be a handier solution.

Thanks chris

Acording to this table of capacity for your unit you have full capacity when outdoor temperature is around -2°C WB and indoor is 22°C DB.





Also, it is clear that unit should work easy and to have almost 80% of nominal capacity at -15°C WB (if you have 100% connected capacity of indoor units).
So, I would first check, as I already said, refrigerant amount! And, if that is not the cause, continue with troubleshooting the unit.

[multisync]

That is assuming it was sized for heating and not just cooling. We recently installed a 3.5kw Daikin into a converted garage where only 1.5kw cooling was needed. We managed to convince the customer that the heat duty was more important and that those quoting 2kw cooling will leave him cold during the real cold winter

Suffice to say he's delighted and wrote a letter to say as much

Multisync
london

[Chris2005]

The only thing i notice in the cold weather is the outdoor coil is covered in ice and takes it quite a while before it goes on a defrost mode and clears the coil.

Is there anyway of adjusting the outdoor unit so it goes on a defrost more often.

Thanks chris

[nike123]

The only thing i notice in the cold weather is the outdoor coil is covered in ice and takes it quite a while before it goes on a defrost mode and clears the coil.

Is there anyway of adjusting the outdoor unit so it goes on a defrost more often.

Thanks chris

Check sensors for proper values!

[paul_h]

It will only allow itself to go on defrost every 45-50min generally.
So if you have poor installation (not very good outdoor unit airflow, lots of air recycling), low on refrigerant, restriction, or if the indoor unit has poor airflow (overheats, short cycles air, ie jammed up too high or in a corner which causes the ouside fan to cycle off a lot), It will ice up very quickly and lose capacity, but can't do anything about it for 45min.

[back2space]

I have put a post up about my LG air con a few days ago with pictures and a video of the out door unit (FM25ah) in defrost mode.

Its the same situation today, were at 0C at night and we have snow on the ground and the indoor temp when I got in was 14C it is now 4hours later and we have just got up to 22C. Its struggling to get above 22.5C though and I think thats due to it being so cold outside. Should it be able to heat up any higher than this? When the central heating is on, the central heating will only manage to get the indoor temp upto about 21 after being on for the same ammount of time.

[back2space]

Ur air off temps when the outdoor temp is -0.5 should be about 36C. This is if the unit is maintaining yourset point if its still trying to achieve and there is a difference of 3c, the inverter tells the compressor to run at full speed, i have noticed air off temps of about 39-40C when i set the remote to 30c.

[NoNickName]

Note that data are referred to wet bulb not to dry bulb. This is because manufacturers take advantage of the latent heat of vaporisation in the air, what should be FORBIDDEN, and include this heat in the evaporating coil heat transfer.
That means that a heat pump would initially give more capacity if the weather is damp, but shortly after will start defrosting... and of course performances are measured while the coil is clean...

[back2space]

I find that when the unit is defrosting particulary the first time the unit was used in heat mode the water that ran out the bottom was dirty, the 2nd time it happened the water was clear. I guess the ice brings off some of the surface dirt.

[paul pursehouse]

Interesting problem,I feel you may be trying to achieve to high a winter inside temperature,I have recently purchased a heat load program that was recognised by the ARC and CSIRO in Aust and it uses 21 deg C winter and 24 deg C summer
So now the question - at what design temp was the installation sized.Is the system fully charged
Is the system capable of performing at the low ambient.I use MHI Inverter splits and they are rated at full capacity down to - 15c

[Sledge]

I have never seen these units in Toronto...but I have a question: Is it possible to speed up the outdoor fan? I am thinking more air flow, gives more heat, which in turn should slow down frosting of the coil.

[paul_h]

That's what I alluded to before. If the indoor coil temp is too high (above 50C), it will actually turn off the outdoor fan completely, increasing the ice on the outdoor unit. It does this to protect itself, ie brings the suction temp down to lower the indoor temp.
So a poorly set up unit, or a unit with a problem, or less than ideal installation will always switch off the outdoor fan excessively as the indoor coil temp gets too hot, causing excess ice ups and a drop in performance.

I see it all the time when units have too short a pipe run for the precharge amount, or the outdoor unit has lots of air recirculation because it's too close to walls, or the indoor unit is high up in a corner or oversized, or the owner doesn't keep their filters clean and always sets the thermostat to 30C and the indoor fan on quiet/super low speeds.

[sinewave]

I know of a little 2.6kW Fujitsu Inverter I fitted last year in a Static Caravan while a self build is going on which easily attains 28 degrees C at outside temps as low as -10C.

[Electrocoolman]

Chris,
What is the total capacity of the indoor units compared to the capacity of the outdoor unit? Do the sums add up? Sometimes the indoor unit are oversized (diversity factor).
Have you tried running just one or two of the indoor units (as opposed to all 4) and see if that makes a difference....this might point to refrigerant charge if the capacity sums are OK.

I assume that you have checked that the filters on the indoor units are clean...if the 'condenser' (ie indoor coil) can't get rid of the heat, the sensor on the coil will step the system back (ie reduce the output), thus you will not get the expected output.

Also have you cleaned the outdoor coil? Coils will build up ice more readily when dirty. I see you are in N.I. ....Are you near the sea (salt air)....have you examined the outdoor coil for deterioration.

[Chris2005]

Hi Elecrocoolman

The units are working fine they just loose some of there effeciency in the cold weather about -2c.

I leave them on now all day now when the weather is very cold set for 20c where as before i was turning them on at night when i came home and the house was about 15c,

AT the time of my first post I was just wondering if there was anything to stop them loosing any of there effeciency in the very cold weather as this is when full heat output is most needed.

But with the electronics on the unit a ground loop system seems to be out of the question,.. IT was just a thought.

Chris.

[back2space]

I find that if I keep the units switched on all the time in cold weather and at night or when im not at home set the units to 19C the units happily tick over and maintain room temp. However if the units are asked to heat a room up after being off all day/night they will struggle just as any heating system would. The room temp will drop to about 13C overnight or during the day when its very cold out, and when the units are switched back on the air wont feel as warm coming out the unit as it would if the room was already at a reasonable temp. Its all to do with the rate at which your house loses heat, plus if you are heating the room up from 15C all the objects in the room are also going to need to heated up too, and they will absorb the heat from the air so it will feel like the units have lost capacity when really they are working fine. For instance if you fill your fridge up with ambient temp beer its going to take a while before the beers are chilled but the fridge will be working hard.

Chris do you find that your units dont monitor the temp of the air after thermo off unless one of the other units is operating in thermo on and blowing warm air. If all units are thermo off the units dont actually monitor the temp of the air.

[back2space]

Did you resolve this issue Chris?