LG heat pump problem

[paul_h]

I have to admit I've never come across that situation and don't think it's possible. The faster the indoor fan runs, the further it blows the air away from the unit, the more the ambient (not heated) air comes into contact with the room thermistor and the less likely the air thermistor will sample any of the discharge air, short cycle or think the room in down to temp etc and wind down or slow down on safetys.

Normally short cycling is caused by low airflow, ie the air thrown out of the indoor is at low velocity (dirty filters or low fan speed) so it's not blown far away out of the unit, so ends up coming back into the units intake a lot quicker than high speed air blown out away from the unit.

Low speed air is more likely to make the unit short cycle, and the evap over heats, the pressures are high, the compressor draws more current, the power bills are higher, the system's protections are kicked in, the outdoor ices up more etc etc.
Try running a unit with dirty filter, see how much trouble that has with efficiency and effectiveness. Running a split on heat on low fan speed is almost as bad, does that make sense? If so then you'll agree that high speed fan is the best, and if you still have problems, then something is wrong with the equipment or install.

Running a split in heat mode on low indoor fan is worse than running a split in cooling mode with a blocked filter. Both drop efficency, but nothing is harmed with a blocked filter is cool mode, the room just doesn't get cold. With heat mode though, everything is under stress at higher temps and pressure, which means more load, more consumption, more safetys kicking in. Increasing airflow will reduce that load because it can blow away heat further away.

Your situation may be unique as far as a possible falt in the equipment or installation though.
But if a lot more air was being blown through the indoor coil, the indoor coil would be cooler, the pressure would be lower, the compressor woudn't have to work so hard, the temps would be lower so the protections wouldn't have to work so hard etc etc.

edit: It's like saying: What would happen if you put your outdoor unit in your sealed up garage? On a hot day while running on cool mode, eventually your garage is going to get hotter and hotter until the unit can't reject heat anymore and breaks down. The lack of cooler outside fresh air coming into the condenser means the system won't work.
Not only is your indoor unit smaller than the outdoor unit, but it also has to work in similar closed up enviroments that we would never expect the outdoor unit to work in. That's why heaeting draws more power, needs safetys, and why it benefits from the largest supply of ambient air (high fan) that you can possible give it.

[back2space]

i will have to look into it tmrw when i'm home as it seems that high fan speed heats the room quicker as then its running design capacity. If i have been out all day i put the unit on high fan speed as it takes ages to bring the room temp up from very cold on low. Then once its reached set point i switch on to low for the evening the unit then maintains that. I assume it would be the same.