Small Stacks of items on convey rail wont cool

item chunks <1g do not exchange heat

Items below 1g do not exchange heat. 

Frankly, they should remove the items <1 g (maybe do an average and round up/down). They don't have any real value in the game and just put additional load on CPU. 

There is no option in the game to limit the minimum load on a rail so at least the sweeper can be set to a minium package of 1g to avoid such scenarios.