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TABLE 4
FURNACE / BURNER SPECIFICATIONS
Unit
Lennox Burner
Part Number
Burner
Model
*Initial
Air Dial
Setting
Output
Nozzle Size
(Delevan)
Pump
Pressure
Head
70
35K74
AFII 85
3.0
57,000 BTU
(16.7 kW)
0.50 X 80
A
100 psig
(689.5 kPa)
FB0
105
35K75
AFII 85
4.0
84,000 BTU
(24.6 kW)
0.65 X 80
B
140 psig
965.3 kPa)
FB3
120
35K75
AFII 85
4.5
105,000 BTU
(30.8 kW)
0.75 X 80
B
140 psig
965.3 kPa)
FB3
140
35K76
AFII 150
6.0
112,000 BTU
(32.8 kW)
0.85 X 80
B
140 psig
965.3 kPa)
FB6
154
35K76
AFII 150
6.5
125,000 BTU
(36.6 kW)
1.00 X 80
B
140 psig
965.3 kPa)
FB6
*NOTE: The initial air dial setting is provided to get unit started. The air dial setting
MUST
be adjusted after startup to
achieve proper combustion.
B−Burner (Figures 9 & 10)
The O23, OHR23, and OF23 oil furnaces use the Beckett AFII
burner. The oil burner provides an atomized oil vapor mixed
with the correct proportion of air when it is ignited in the com
bustion chamber. Oil burner minimum and maximum ratings
are listed on the unit nameplate. Proper air adjustment for
these ratings is achieved through the air adjustment dial. Set
air dial to the initial air dial setting (see table 4). After start up
adjust air dial to achieve proper combustion. Remember to
tighten set screw on air dial.
The AFII burner is available in five sizes with either a single
or two stage pump. Table 4 identifies the burners used in
Lennox units. Figures 9 and 10 show the typical layout of the
burner assembly.
1−Combustion Air Blower / Pump Motor (B6)
The burner is activated by the primary control. A com
bustion air blower is mounted on the motor shaft. The
motor shaft also connects to the direct drive oil pump
through a coupler. The burner motor turns both the com
bustion air blower and the oil pump. The motor operates
at 3500 RPM.
Burner motors are overload protected. In the event of
excess motor temperature or current, the overload
opens to de−energize the motor. The overload automat
ically resets after temperature has returned to normal.
Keep motor clean to prevent starting switch from sticking.
All AFII motors are permanently lubricated. No further oiling is
required.
2−Combustion Air Blower / Pump Fuse (F22)
(−140 and −154 CSA units only)
In the −140 and −154 Canadian units an in line fuse (F22) is
used between the line voltage from the BCC2 blower con
trol and the blower / pump motor. The fuse is rated at 300
volts and 15 amps.
3− Pump (−1 through −4 units)
The O23, OHR23, and OF23 oil furnaces use a single
stage, 3450 RPM pump. A two stage pump is available
as an option (catalog # 65A44). The oil burner is shipped
from factory for use in a single line system. To convert the
pump to a two line system, install the bypass plug pro
vided in the attached bag according to the accompany
ing instructions.
4− Pump (−5 units only)
The O23, OHR23 and OF23−5 units all utilize the Cleancut
Fuel Unit manufactured by Becket. This pump uses a sole
noid valve to control the piston cut−on cut−off operation
instead of a cone valve and diaphram used by other con
ventional pumps. The solenoid works with the R7184B
Honeywell burner control to provide cut−on cut−off opera
tion while the burner motor is at full speed.
At startup the pump shaft is brought to full speed before the
solenoid is energized. At this time low pressure oil
(approximatley 20−25 psi) from the gearset circulates
around the pressure regulator piston which is closed and
through the open solenoid valve. The solenoid valve re
turns the oil to either the cover cavity (one pipe) or return
line (two pipe). When the solenoid vavle is energized, it
closes (and remains closed while energized) blocking the
return path to the cover cavity and return line creating pres
sure build up in the piston cavity. The piston opens and reg
ulates pressure and delivers pressurized oil to the nozzle.
At shutdown the solenoid valve will de−energize and open
before the pump shaft rotation stops. When the solenoid
valve opens the oil by−passes the cover cavity and return
line causing a pressure drop in the piston cavity. The piston
closes blocking oil to the nozzle while the burner motor is
running at full speed.
