INSTALLATION B
PLENUM COLLECTOR BOX
COLD AIR
RETURN
FILTER BOX
TO EXISTING
DUCT WORK
WARM AIR
EXISTING
FURNACE
MODEL 1321
FURNACE
INSTALLATION C
PLENUM ELBOW
COLD AIR
RETURN
PLENUM TOP
(OPTIONAL) 
FILTER BOX
TO EXISTING
DUCT WORK
WARM AIR
EXISTING
FURNACE
MODEL 1321
FURNACE
21
