Daikin REYQ10M7W1B problem

[sparkatan]

I am working on a system with a Daikin REYQ10M7W1B outdoor. In heating mode the outdoor unit continually defrosts and the fan coils never achieve a decent off coil temp. The hot gas outlet to the indoor units leaving the outdoor is reaching 65+ degrees C but the return is never any better than about 20C. Would refrigerant shortage make the unit continually defrost? Ambient is only 9C.

[The Viking]

Well, it's worth checking the outdoor unit's temp sensors.
(Ambient air, coils and liquid lines)
But after you checked them you will have to verify the charge.

Out of interest, what temperature does the compressor's discharge line get up to when the system is in heating?

[sparkatan]

Compressor discharge between 65 and 70C

[VRVIII]

The min time between deforsts is 40min, are you sure the system is not entering equalisation due to BS change over requests? usually caused by an indoor sensor being influenced (recirc of indoor discharge air etc).

Have you checked the discharge pipe temps entering BS boxes and pipe temps entering indoors?