LG Multisplit ongoing issue... slowly getting there I think!

[back2space]

It's difficult without knowing the system equipment layout but we'll have a go...

Cooling Mode -
Outdoor unit - Solenoid valve - pipework - indoor unit EEV - indoor coil - pipework - outdoor unit.
Indoor EEV has liquid feed from outdoor unit and expands liquid into the indoor coil.

Heating Mode -
Outdoor unit - pipework - indoor unit coil - indoor unit EEV - pipework - outdoor unit solenoid valve.
Hot gas runs through the indoor coil before being arrested by the EEV. EEV may not have a liquid seal on it so will bleed vapour.

Short pipes have not provided sufficient resistance to the hot gas so coil operates at higher pressure/temperature.

I could be wrong though.

I should have said the EEVs are in the outdoor unit.

Just done a little test, disconnected the fan motor on the 2mtr run unit so that at thermostat off the fan cannot run. Now normally with the fan running the unit furthest away the coil will drop to about 38C and match the 2mtr run unit with the same air off, now having the fan motor disconnected on the 2mtr run so the coil retains its heat means the unit furthest away maintains its coil temp of 47C and didnt drop at all.

I also notice that with this 2 mtr run in heating mode the refrigerant is noisy when it circulates through the indoor unit when it is turned off as if theres too much velocity in the pipework.

I think your onto something, the short piperun isnt providing sufficient resistance so its all flowing to its easiest route the 2mtr run and then causing performance drop off on the unit furthest away.

We know for certain there is nothing wrong with the EEV as this works fine in cooling so it must be the pipe run that is not making any resistance to hold back the gas so its just flowing through the indoor unit fast at which the indoor units response is to get rid of the heat from the coil.

The wall mount unit at thermostat off keeps the fans off no matter how hot the coil is so if I had wall mounts in the other rooms then there would never have been this problem as the software in the unit does not run the fans unless its thermostat on.

Engineer coming back on Friday to hopefully install 6mtr worth of pipe work to the short one and hopefully this will resolve our problems once and for all.

Shame on LG though at the beginning and the installing engineer for saying thats how it was supposed to operate!