I have a detailed question please bear with me. I have a Trane XL 90 model TDC060B930AC furnace (downflow/horizontal). With a matching XE 800 model TTJ724A100BO A/C condenser unit. The evaporator unit sits bellow the furnace. The air intake is on my ceiling and the coil sits on a raised duct system, which sits on the floor (cement slap construction). The duct system then returns up into the attic. Once in the attic, each room is feed and the air is blown down from the ceiling vents. My opinion is that there was no planning with this set up. It should of just been an upflow to start with.
I want to move the furnace into my attic. I want to draw the return air from the floor, through a duct, to the attic. Then, have the furnace blow the air through the ceiling.
The return air draw for the furnace is 17” x 20 ¼”, drawing about 1200 CFM. My confusion starts here. The hole coming out of the furnace is only 14 ¼” x 16 ½”, which is sitting right on top of the A/C coil. The A/C coil openings on both sides are 17” x 20 ¼”, same as the return air. Problem is, the air is only in direct contact with half of the coil. 3” on the sides and 4” on one end is missed.
Here’s the question(s); Couldn’t I mount the A/C coil in the return duct before it goes into the attic? Electric furnaces and Air Handlers have the A/C coil mounted before the blower. They draw the air through them instead of blowing the air through them. If the blower, blows 1200 CFM through it, then isn’t it safe to figure the it has to Draw 1200 CFM? If the return air duct was sealed air tight except through the return filter. The duct insulated on the inside and on the out side. Wouldn’t this work just as well or good as the coil mounted on the outlet side of the furnace? Plus I would have all of the air going through the coil instead of just 2/3eds.
The system is a good quality and working system 92%+AFUE, although the A/C is only SEER 10. I haven’t discussed this idea with a contractor as of yet. I don’t want to sound stupid or be taken . With the way that it’s set up now I have questions of reliability for the craftsmen in this area. My reasoning for this set up are for easier access to the freon lines, charging, checking Superheat. The freon lineset wouldn’t need an oil trap, condensation blockage wouldn’t destroy my ceiling and the A/C coil would have total air flow through.
I would like to make my own decisions of the work I want done before I contract someone to do it.
Any replies are welcome, thank you for your time.