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H−Flame Signal
A microamp DC meter is needed to check the flame signal
on the ignition control.
Flame (microamp) signal is an electrical current which passes
from the furnace control through the sensor during unit opera-
tion. Current passes from the sensor through the flame to
ground to complete a safety circuit.
To Measure Flame Signal − Ignition Control:
A
transducer
(Part
#78H5401 available from
Lennox Repair Parts) is
required to measure flame
signal if meter used will not
read a low micro amp sig-
nal.
See figure 21. The
transducer converts mi-
croamps to volts on a 1:1 conversion. See figure 14 or 15 for
flame signal. A digital readout meter must be used. The
transducer plugs into most meters. See figure 22 for
proper use of transducer.
1 − Set the volt meter to the DC voltage scale. Insert
transducer into the VDC and common inputs. Ob-
serve correct polarities. Failure to do so results in
negative (−) values.
2 − Turn off supply voltage to control.
3 − Disconnect ignition control flame sensor wire from the
flame sensor.
4 − Connect (−) lead of the transducer to flame sensor.
5 − Connect (+) lead of transducer to the ignition control sen-
sor wire.
6 − Turn supply voltage on and close thermostat contacts to
cycle system.
7 − When main burners are in operation for two minutes, take
reading. Remember 1 DC volt = 1 DC microamp.
(+)
(−)
FLAME SENSOR
(+) TO
IGNITION
CONTROL
SENSOR
WIRE
FIGURE 22
TRANSDUCER
(PART #78H5401)
FIGURE 21
NOTE−MUST USE DIGITAL METER
SET DIAL TO MEASURE
VDC
RED COLLAR
INDICATES
POSITIVE
LEAD
(−) TO
V−TYPICAL OPERATING CHARACTERISTICS
A−Blower Operation and Adjustment
When the thermostat is set to FAN ON," the indoor
blower will run continuously at approximately 38% of
the second−stage cooling speed when there is no cool-
ing or heating demand.
When the G60UHV(X) is running in the heating mode,
the indoor blower will run on the heating speed desig-
nated by the positions of dip switches 11 and 12.
When there is a cooling demand, the indoor blower will
run on the cooling speed designated by the positions
of dip switches 5 and 6.
B−Temperature Rise
Temperature rise for G60UHV(X) 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.
To Measure Temperature Rise:
1 − Place plenum thermometers in the supply and return air
plenums. Locate supply air thermometer in the first hori-
zontal run of the 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 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 − Tap locations shown in figure 23.
2 − Punch a 1/4" diameter hole
in supply and return air ple-
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perma-
gum. Connect the zero end
of the manometer to the dis-
charge (supply) side of the system. On ducted sys-
tems, 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 at-
mosphere.
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 − External static pressure drop must not be more than
0.8" W.C.
5 − Seal around the hole when the check is complete.
Page 35
STATIC PRESSURE TEST
FIGURE 23
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