The expansion tank can be installed on either side of the low loss header as long as its on the suction side of the pump. You never want to have your pump pumping into or preloading the expansion tank. Please reference Idronics 15 where you will find a lot of information and concept drawings showing systems and expansion tank positioning. Page 42 has a great display of where to or not to install the expansion tank.
The expansion tank can be installed on either side of the low loss header as long as its on the suction side of the pump. You never want to have your pump pumping into or preloading the expansion tank. Please reference Idronics 15 where you will find a lot of information and concept drawings showing systems and expansion tank positioning. Page 42 has a great display of where to or not to install the expansion tank.