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V-TYPICAL OPERATING CHARACTERISTICS
A-Blower Operation and Adjustment
1 - Blower operation is dependent on thermostat control
system.
2 - Generally, blower operation is set at thermostat sub
base 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.
B-Temperature Rise (Figure 51)
Temperature rise for SL297UHNV units depends on unit in
put, 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.
FIGURE 51
TEMPERATURE RISE
Supply Duct Temperature ________
Return Duct Temperature
_
_____
Temperature Rise = ________
SUPPLY
AIR
Temperatures
RETURN AIR
C-External Static Pressure
1 - Tap locations shown in figure 52.
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 blow
er motor speed to deliver the air desired according to
the job requirements. For heating speed (second
stage heat speed) external static pressure drop must
not be more than 0.8” W.C. For cooling speed (second
stage cool speed) external static pressure drop must
not be more than 1.0” W.C.
4 - Seal the hole when the check is complete.
FIGURE 52
EXTERNAL STATIC PRESSURE
Supply Duct Static ________
Return Duct _____
Total Duct Static = ________(dry coil)
Duct Static
or
Supply
Air
Return Air
VI-MAINTENANCE
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or
property damage.
Improper servicing could result in dangerous opera
tion, serious injury, death, or property damage.
Before servicing, disconnect all electrical power to
furnace.
When servicing controls, label all wires prior to dis
connecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
At the beginning of each heating season, system should be
checked as follows by a qualified service technician:
Blower
Check the blower wheel for debris and clean if necessary.
The blower motors are prelubricated for extended bearing
life. No further lubrication is needed.
WARNING
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal inju
ry or death.
