I have a RZQ200 on a OEM coil in an AHU which starts a defrost at an ambient of -5°C, Te at -11°C every 27 to 30 minutes but there's not a single drop of ice on the coil. The defrost then lasts >15 minutes and it takes then +/- 7 to 10 minutes before coil is hot enoiugh to start the fans.
What triggers faulty the defost in this case? Charge is OK.
We've taken IR-scan during the defrost and after 5 to 6 minutes, the whole coil still is at -1°C. I have pictures of it.