cold air return

[chris vance]

Is it ever ok to bring the cold air return into the back of the furnace instead of the sides? If not why.

[dash]

Don't no of any that say you can in the instructions.

Why not? Most if not all have the blower positioned to "pull' air from the sides or bottom.Pulling from the rear the space for air to get into the blower is too small on the ones I've seen,this will reduce air flow,likely below the required minimum in some cases.