Skyjob,as i wrote:
Did i write that the fans influence the packs flow schedule directly?NO, but indirectly yes.
As of now,my boeing technical pilot source(boeing team) seems to agree that an increase in bleed demand for same thrust setting,(pack work load increases as less cool air into the manifold,therefore an indirect increase in fuel consumption due to the recirc fans off.
He will ask confirmation to his ops engineering and will get back to me in the morning.
Concerning the original question,why during both pack remaining illuminated,the kept fan is off and right fan is left in auto,he will confirm it tomorrow as well.
Concerning :
It's like the air is standing still in the cabin (it won't be standing still, but move too slowly). Lowering the temperature won't help, except cold stuffy air seems more comfortable than normal temperature. Still the O2/CO2 levels will be uncomfortable (but not in anyway dangerous), which may make pax and cabin crew tired/cause headache etc. Like I compared already, it's like being a lot of people in a small room without opening the window occasionally to let in fresh air.
Boeing guy wrote:
Selecting recirculation fan (s) off will result in lower cabin humidity levels, but the total fresh air remains unchanged unless the packs are selected to HIGH flow. Also, cabin temperature gradients may be affected by selecting the recirc fans off inflight. Selecting the recirc fans off may prevent the cabin air from circulating in the normal manner, creating pockets of slightly colder areas within the cabin. Selecting high flow will not necessarily improve this situation