Last time on a flight I came to the strange situation @ FL350 where pack temps were around 20C, FWD and CONT CAB temp was around that too while AFT temp was a little over 40C. All switches on AUTO, PACKs on, TRIM AIR on, RECIRC fans on. TAT was around -10C. Just don't get what's happening even after reading the FCOM. The way I understand is if the PACK temperatures are around 20C then FWD and AFT cabin temperatures should not be much higher. Can anyone enlighten me what I'm doing wrong? Thanks,

Pack temperature is the working temperature of the ACM (air cycle machine). The packs can only generate cold air, as this is the working principle. To warm it the system uses hot bleed air. This flow is not sensed by the pack temp. sensor. The mixed air temperature is sensed by duct sensors.For pilots the only needed temperature during flight (in normal condition) is the cabin temperature that is sensed by 2 sensors that are inside the overhead bins, one forward, one aft.There is no indication about the control cabin temperature, but there is a sensor needed by the packs controllers to work properly.The temperature on the packs will be always lower or equal of the cabin temp, the duct temperature can be from 2°C to 88° (duct overheat) normally lower than 65/70°C. The amount of hot or cold air depends on the curve calculated by the pack controllers.Imagine a hot cabin, at 40°, the pack will work creating as much cold as they can (with their limitation), the duct temp will slowly reach low values of 10, 8°, but the cabin will never reach this temperature as the cabin is big, is heated by the sun etc...In flight, at FL350, TAT says -10 but SAT will be much lower, we can have -50° at these altitudes. The packs will be almost bypassed by the hot air that must warm the plane because uotside temp want to freeze the airplane. So duct temp will be 40 or higher, all depends on the capacity of the plane to insulate its cabin from the outside.I'm loading flight sim and I will check this right now.

Ok, over 10 minutes at cruise altitude:All temperatures from left to right of the selector:Supply duct:CONT CAB: 20°FWD : 26°AFT: 34° Cabin temperature:FWD: 25°AFT: 26° Pack temp:RH: 18°LH: 24° Flight level 350. temperature were 15°C on ground (standard)This is the switch configuration.