Typical Operating Characteristics; Blower Operation And Adjustment; Temperature Rise; External Static Pressure - Lennox G26 series User Manual

4 − Connect (+) lead of transducer to ignition control sen-
sor connection. See figure 47.
5 − Connect (−) lead of the transducer to sensor wire. See
figure 47.
6 − Turn supply voltage on and close thermostat contacts
to cycle system.
7 − When unit lights, read voltage on meter display. Re-
member 1 DC volt = 1 DC microamp.
TABLE 11
FLAME SIGNAL MICROAMPS
G26 −1 and −2 G26 1 and 2
models
Minimum
G26 3 4 5 G26 −3, −4, −5
and −6 models and −6 models
Minimum
FLAME SIGNAL TEST
TRANSDUCER
DIGITAL
METER
(+)
(−)
SENSOR
WIRE
FLAME SENSOR
FIGURE47
V−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 sub-
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO posi-
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 G26 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 plenum where it will not pick up ra-
diant heat from the heat exchanger.
Normal 0.25
0.15
u0.7
Normal
v0.7
Low
0.15
IGNITION
CONTROL
(G776 SHOWN)
SENSE" TERMINAL
2 − Set thermostat to highest setting.
3 − After plenum thermometers have reached their high-
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, in-
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 48.
2 − Punch a 1/4" diameter hole
in supply upstream of evap-
orator and return air ple-
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with per-
magum. 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. For
systems with non−ducted returns, 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 blow-
er motor speed to deliver the air desired according to
the job requirements.
4 − Pressure drop must not exceed 0.5" W.C.
5 − Seal around the hole when the check is complete.
D−Blower Speed Taps Leadless Motors
−1, −2, −3 and −4 Models
Blower speed tap selection on unleaded motors is accom-
plished by changing the taps at the blower motor harness
connector. Disconnect harness connector from motor to ex-
pose speed selectors. Blower speed selections are listed on
table 12.
To Change Blower Speed Uleaded Motors
1 − Turn off electric power to furnace.
2 − Remove blower access door.
3 − Disconnect blower motor harness from motor.
4 − Pull harness connector and wires through blower ac-
cess panel opening.
5 − Select desired speeds for heating and cooling. (Red =
heating, Black = cooling, White = common).
6 − Depress harness connector tab to release wire termi-
nal. Select connector location for new speed (refer to
unit wiring diagram). Insert wire terminal until it is se-
curely in place. See figure 50.
7 − Replace harness connector to motor .
Page 32
STATIC PRESSURE
TEST
MANOMETER
G26 UNIT
FIGURE 48