I recently had a 2.5 ton carrier system installed in my approx. 1350sqft ranch. The finished basement is about 380 sqft out of the total 1350. We have one supply going to the basement and it is not cooling or dehumidifying the basement to a comfortable level. As mentioned in my previous post the contractor is coming out on 7/9 to fix some other initial istall problems and I would like to be able to ask them about adding a return from the basement.

First, I spoke with the salesman and he said adding a return in the basement would not help and possibly hurt the system because it would be sucking up the cold air from the supply. Does this make sense? My thought is that the basement needs a few more supplies and a return. It seems like the main return is the hallway is not getting the air up from the basement. I leave the door open.

So, would it make sense to add a return to in the basement or would just adding more supplies be better or maybe both.
Again, does it make any sense about what he is saying about
the basement return being bad. Another contractor was going to add a return in the basement. I'm confused.
The salesman did do a manual J load.

Thanks in advance. Also, thanks for everyones previous responses