USSC Hotblast 1321 Owner's Manual page 20

COLD AIR
RETURN
FILTER BOX
INSTALL GRAVITY-TYPE BACKDRAFT DAMPERS IN THE 8" ROUND HEAT
OUTLET PIPES FOR SUPPLEMENTARY INSTALLS.
COMBINED STATIC PRESSURE IN OUTLET PLENUM MUST NOT EXCEED
0.25 INCHES WATER COLUMN WITH BOTH FURNACE'S FANS RUNNING.
APPENDIX
INSTALLATION A
MODEL 1321
FURNACE
NOTE:
NOTE:
20
TO EXISTING
DUCT WORK
WARM AIR
EXISTING
FURNACE