FIGURE 15
STATIC PRESSURE
TEST
MANOMETER
G17 UNIT
Page 9
FLAME SIGNAL TEST
FIGURE 14
IGNITION
CONĆ
TROL
SENSE"
TERMINAL
SENSOR
WIRE
D.C. MICROAMP
METER
FLAME
SENSOR
Flame signal may rise above 5 microamps for the first few
seconds after ignition and then level off within the range.
WARNING
Fire and explosion hazard.
These instructions MUST be followed exactly.
Can cause a fire or explosion resulting in property
damage, personal injury or loss of life.
VI-TYPICAL OPERATING CHARACTERISTICS
A-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 subĆ
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO posiĆ
tion, blower cycles with demand or runs continuously
while heating or cooling circuit cycles.
3- In all cases, blower and entire unit will be off when the
system switch is in OFF position.
B-Temperature Rise
Temperature rise for G17 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 AIR TEMP. RISE
°
F" listed on the unit rating plate.
To Measure Temperature Rise:
1- Place plenum thermometers in the supply and return
air plenums. Locate supply air thermometer in the first
horizontal run of the warm air plenum where it will not
pick up radiant heat from the heat exchanger.
2- Set thermostat to highest setting.
3- After plenum thermometers have reached their highĆ
est and steadiest readings, subtract the two readings.
The difference should be in the range listed on the unit
rating plate. If the temperature is too low, decrease
blower speed. If temperature is too high, first check
the firing rate. Provided the firing rate is acceptable, inĆ
crease blower speed to reduce temperature. To
change blower speed taps see the Blower Speed Taps
section in this manual.
C-External Static Pressure
1- Measure tap locations as shown in figure 15.
2- Punch a 1/4" diameter hole
in supply and return air pleĆ
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perĆ
magum. Connect the zero
end of the manometer to the
discharge (supply) side of the system. On ducted sysĆ
tems, connect the other end of manometer to the reĆ
turn duct as above. For systems with non-ducted reĆ
turns, leave the other end of the manometer open to
the atmosphere.
3- With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blowĆ
er motor speed to deliver the air desired according to
the job requirements.
4- External static pressure drop must not be more than
0.5" W.C.
5- Seal around the hole when the check is complete.
D-Blower Speed Taps
Blower speed tap selection is accomplished by changing the
taps at the blower motor harness connector. Disconnect harĆ
ness connector from motor to expose speed selectors.
Blower speed selections are listed in table 7.
To Change Blower Speed:
1- Turn off electric power to furnace.
2- Remove upper access panel and filter access door.
See figure 1.
3- Lift left side filter over left support angle. For easy hanĆ
dling, hold filter at center bottom.
4- Rotate filter sideways and pull it through the blower
access panel opening.
5- Pull the second filter out the same way as the first.
6- Grasp blower motor harness connector located on
back on motor. Depress lock tab and pull connector
from motor.
Blower Speed Taps
7- Pull harness connector and wires through blower acĆ
cess panel opening.
8- Select desired speeds for heating and cooling. (Red =
heating, Black = cooling, White = common). See table
7.
