Over the weekend one of the guys on call was sent to look at an aircon problem at a restaurant. He looked at the controller and found it flashing P8 02, he reset the fault and i was sent up there today to try and figure out the problem.

As i arrived on site i found 9 indoor units and 5 controllers, i worked out that there were 4 twins and one single split.

The indoors were all running as were the condensors. I found the P8 was an abnormal pipe temperature fault. I would normally associate this with a possibility of lack of refrigerant so i put the indoors on cooling and then heating and they worked fine.
I checked for cross wiring but everything seemed in order.

I then checked the resistance of TH1 TH2 and TH5 which were the return air sensor, Liquid line pipe temp and evap temperature of both units and they were all fine.
I rang mitsubishi up and they seemed to be going down the route that they could be undersized something which i can't beleive.

Has anyone come across a P8 fault on the new Mitsi Electrics?

The model number indoor PLA-RP125BA
outdoor is a PUHZRP250YHA2