Combustion Air Inducer (B6); Horizontal Applications; Surelight Board 18M99 & 49M59 Sensor; Surelight Board 100870 Sensor - Lennox G60UHV Service Manual

SureLight Board 18M99 & 49M59 Sensor
NORMAL FLAME SIGNAL > 0.23 MICROAMPS
LOW FLAME SIGNAL
DROP OUT SIGNAL
5/16"
FIGURE 14

SureLight Board 100870 Sensor

NORMAL FLAME SIGNAL > 1.50 MICROAMPS
LOW FLAME SIGNAL
DROP OUT SIGNAL
5/16"
FIGURE 15

9. Combustion Air Inducer (B6)

All G60UHV(X) units use a two−stage combustion air induc-
er to move air through the burners and heat exchanger dur-
ing heating operation. The blower uses a 120VAC motor.
The motor operates during all heating operation and is con-
trolled by furnace / blower control A92. The inducer also
operates for 15 seconds before burner ignition (pre-purge)
and for 5 seconds after the gas valve closes (post-purge).
The inducer operates on low speed during first−stage heat,
then switches to high speed for second stage heat.
A proving switch connected to the combustion air inducer ori-
fice plate is used to prove inducer operation. The combustion
air inducer orifice will be different for each model. See table
25 for orifice sizes. The switch monitors air pressure in the in-
ducer housing. During normal operation, the pressure in the
housing is negative. If pressure becomes less negative (sig-
nifying an obstruction) the proving switch opens. When the
proving switch opens, the furnace control (A92) immediately
closes the gas valve to prevent burner operation.
< 0.22 MICROAMPS
= 0.16 MICROAMPS
< 1.40 MICROAMPS
= 0.20 MICROAMPS
Page 29
TABLE 25
G60UHV(X) Unit
−070
−090
−110
−135

Horizontal Applications

The G60UHV(X) furnace can be installed in horizontal ap-
plications.
The combustion air inducer may be rotated clockwise or
counterclockwise by 90° to allow for vertical vent discharge
in a horizontal application. Remove the four mounting
screws, rotate the assembly (assembly consists of orifice
plate, proving switch, gasket and combustion air inducer),
then reinstall the mounting screws. See figure 16. Use the
provided wire tie to bundle the pressure switch wires with
the inducer motor power leads. Route the wires away
from moving parts and the heat of the inducer motor to
prevent damage to the wires. Use sheet metal shears to
remove the cut out from the side of the cabinet. See figure
17. Use the two provided sheet metal screws to install the
cut out on the top cap to cover the original flue outlet open-
ing.
Combustion Air Inducer
90°
(Upflow Position)
Flue Transition
(Do not remove
)
Mounting Screws
(Remove)
FIGURE 16
C.A.I. Orifice Size
1.5"
1.75"
2.0"
2.25"
90°
MOUNTING SCREWS
(Remove)
Power Leads