In my house the air enters under the door through vents into a plenum and then goes up through the filter the fan the furnace and the a c evaporator.
Furnace closet door requirements.
Mark the two sides of the door frame on the chalk line of the wall where the doors will be located.
Once your combustion vents have been installed and the ceiling in the closet has been finished out you will want to close off any vents in the door.
The door when shut sealed against the inlet to the air handler.
If you have this arrangement the door must be vented.
Measure the width of the framing of the pre hung double interior doors.
A furnace malfunction can cause a deadly carbon monoxide co buildup.
The heat can safely escape if there is space around the furnace.
So the florida building code fbc g2406 and international residential code irc do not allow furnace installation in a bedroom bathroom or an any adjoining closet unless it meets these specifications that essentially isolate the furnace from the room.
The heat that the furnace radiates may lead to a fire hazard.
Cut off the bottom few inches of the door with a circular saw to create a gap that allows air to vent into the furnace room.
Be sure to caulk around the seams to make a tight seal.
This is where ventilation become important not the ventilation of the furnace itself but the ventilation of the closet space.
Furnaces in basements.
Unscrew the hinges from the furnace room door with a screwdriver.
Close off vents in door.
Jim stewart oct 22 18 at 1 32.
A furnace can be installed various places in a house in a basement an attic a garage a ground floor utility room or outside the walls.
Do not install your furnace in a storage closet.
How to build a furnace enclosure.