Push or pull air with inline fan?

Hi All,
should inline fans be used for pushing or pulling air?

I currently have one 6" fan pushing air into space, fan is in the attic above drawing cold air from A/C.

I am adding another fan for 4" exhaust but I need advice about proper placement.

I would like to pull out the air and push it to A/C return with the 2nd fan,
I would like to keep this fan in the attic as well.

does fan belong at either end or is it OK to have it in the middle of a duct run?

any advice??

Peace,
DZ

It should be toward the end and pull air to be most efficient....if its in the middle it has to work pretty hard to push the excess air out, get a inline booster to put in the middle if you think your fan isn't powerful enough...hope this helps

Pull...............