Issue with a ducted Mitsubishi unit

[Salmon81]

Hi all, new to the forum and wondered if someone could either help with what issues I could have or say it’s normal.
I have a 6kw ducted Mitsubishi heavy motor industries unit (R32) think it’s an fdum60vh
It has 4 supply and 4 return 6” ducts
Pipe run is 15m (no additional charge added)
The issue I have is the following:
Outdoor temp is showing around 28°c
Indoor temp showing around 30°c
A/c set point 18°c

Supply air will vary from around 20°c to 2°c going up and down every few minutes, with the room temp still well above the set point the compressor and condenser fan will ramp up then cut out (not sure if this corresponds with the supply air temp rise) also the air through the condenser doesn’t seem as warm as another 6kw wall mount we have (same outdoor units)
I’ve had someone look at it and checked the charge and he believes it all looks fine, I have a feeling it’s not working as it should but not sure why.
If anyone has any suggestions I’d be very grateful

[Brian_UK]

There are an awful lot of possibilities as to what is causing the problem.

My initial thought would be a shortage of refrigerant, believing the charge looks fine does not really confirm anything other than it needs looking at.
To confirm tthat the charge is correct means recovering the existing charge to weight it and then weighing in the design charge when refilled.

With the air off temperature dropping to around 2'C this is normallly caused by lack of refrigerant which then triggers safety shutdown modes.

Have any fault code shown up on the remote control or in the outdoor unit history?

[Salmon81]

Thanks for the reply,
Hi be checked for any error codes on the wired remote and none are showing, but not sure how to check the outdoor unit.
Looking at the info on the remote the evap temp (heat exchange temp) is sometimes showing as low as 0°C
I’m not sure how critical the charge would be as it is exactly 15m pipe run so would a small amount being lost during install (whilst removing gauges) be enough to cause this issue as it’s precharged to 15m?