The supply ductwork is to be field installed and sized properly for the cfm of the unit.
Under sizing of plenums and ductwork can relate to excessive static pressure and poor
airflow causing multiple problems to occur. When replacing a competitor’s unit, the
ductwork supply may require an alteration.
Proper air flow is required for the correct operation of this furnace. Too little air flow can
cause erratic operation and can damage the heat exchanger. The duct system must carry
the correct amount of air for heating and cooling. Position the unit to minimize long runs and
runs that require many turns and elbows.
Size the ducts according to acceptable industry standards and methods. The total static
pressure drop (including evaporator coil, if used) of the entire system should not exceed
0.5” w.c. Be sure to have adequate space for unit filter.
NOTE:
Airflow external static pressure measurements do not include filter or coil.
IMPORTANT: Some high efficiency filters have a greater than normal resistance to
air flow. This can adversely affect furnace operation. BE SURE TO CHECK AIR FLOW
if using any filter other than the factory provided filter.
Installation/Instruction Manual for Architects & Engineers
21.
