Page 25
31-5000731 Rev. 0
Typical Operating Characteristics
Blower Operation and Adjustment
NOTE:
The following is a generalized procedure and does
not apply to all thermostat controls.
1.
Blower operation is dependent on thermostat control
system.
2.
Generally, blower operation is set at thermostat
subbase fan switch. With fan switch in ON position,
blower operates continuously. With fan switch in
AUTO position, blower cycles with demand or runs
continuously while heating or cooling circuit cycles.
3.
Depending on the type of indoor thermostat, blower
and entire unit will be off when the system switch is in
OFF position.
Temperature Rise
Temperature rise for NF80UV units depends on unit input,
blower speed, blower horsepower and static pressure as
marked on the unit rating plate. The blower speed must be
set for unit operation within the range of “TEMP. RISE °F”
listed on the unit rating plate.
Supply Air
Return Air
Supply Duct Temperature
Return Duct Temperature
_
Temperature Rise =
Figure 23. Temperature Rise
External Static Pressure
1.
Tap locations shown in Figure 24.
2.
Punch a 1/4” diameter hole in supply and return air
plenums. Insert manometer hose flush with inside
edge of hole or insulation. Seal around the hose with
permagum. Connect the zero end of the manometer to
the discharge (supply) side of the system. On ducted
systems, connect the other end of manometer to the
return duct as above.
3.
With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blower
motor speed to deliver the air desired according to the
job requirements. For heating speed external static
pressure drop must not be more than 0.5” W.C. For
cooling speed external static pressure drop must not
be more than 0.8” W.C.
4.
Seal the hole when the check is complete.
Supply Duct Static
Return Duct
Total Duct Static =
(dry coil)
Supply Air
Return Air
-
+
or
High
Low
Figure 24. External Static Pressure
