Lennox O23 Installation and operation manual

Page 1 1995 Lennox Industries Inc.
Litho U.S.A.
Corp. 9535−L8
O23/OHR23
OF23
Service Literature Revised 09/2003
O23 / OHR23 / OF23 SERIES UNITS
O23 (Elite 80) series units are mid−efficiency upflow oil fur
naces manufactured with Beckett oil burners. O23 units are
available in heating capacities of 70,000 to 154,000 Btuh
(20.5 to 45.1 kW) and cooling applications from 2 through 5
tons (7.0 through 17.6 kW). Refer to Engineering Hand
book for proper sizing.
OHR23 (Elite 80) series units are mid−efficiency horizontal /
downflow oil furnaces. The OF23 (Elite 80) series units are
mid−efficiency loboy upflow oil furnaces, which come in front
(OF23) or rear (OF23R) flue openings, both with Beckett oil
burners. The OHR23 and OF23(R) units are available in heat
ing capacities of 105,000 to 154,000 Btuh (30.8 to 45.1 kW)
and cooling applications from 2 through 5 tons (7.0 through
17.6 kW). Refer to Engineering Handbook for proper siz
ing.
The drum type heat exchanger comes with strategically
placed ports allowing easy cleaning, while the oil burner
can be removed for inspection and service. The mainte
nance section gives a detailed description on how this is
done.
Information contained in this manual is intended for use by
experienced HVAC service technicians only. All specifica
tions are subject to change. Procedures outlined in this
manual are presented as a recommendation only and do
not supersede or replace local or state codes.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon
nect switch(es). Unit may have multiple
power supplies.
WARNING
Improper installation, adjustment, alteration, ser
vice or maintenance can cause property damage,
personal injury or loss of life. Installation and service
must be performed by a qualified installer or service
agency.
O23 SHOWN
TABLE OF CONTENTS
General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Indoor Blower Data 4. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Arrangement 5. . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Placement and Installation 16. . . . . . . . . . . . . . . . . . . .
III Start Up 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating Systems Service Checks 22. . . . . . . . . . . . .
V Disassembling Burner 24. . . . . . . . . . . . . . . . . . . . . . . .
VI Typical Operating Characteristics 26. . . . . . . . . . . . . .
VII Maintenance 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VIII Wiring Diagrams 28. . . . . . . . . . . . . . . . . . . . . . . . . .
IX Troubleshooting 31. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 2
SPECIFICATIONS − O23
Model Number O23Q270 O23Q3105/120 O23Q5140/154
InputBtuh (kW) low/high 70,000 (20.5) 105,000 / 120,000(30.8 / 35.2) 140,000 / 154,000(41.0 / 45.1)
Output Btuh (kW) low/high 57,000 (16.7) 85,000 / 97,000 (24.9 / 28.4) 113,000 / 125,000 (33.1 / 36.6)
*A.F.U.E. 83.8% 82.8% (105) / 82.5% (120) 82.5% (140) / 81.4% (154)
Nozzle Rating  gph (L/hr) and spray angle .50 (1.9)  80°hollow .65 (2.5)  80°(105 input) solid
.75 (2.8)  80°(120 input) solid
.85 (3.2)  80°(140 input) solid
1.00 (3.8)  80°(154 input) solid
Flue Size Diameterin. (mm) 6 (152) 6 (152) 6 (152)
Oil Burner Pump 1 Stage 1 Stage 1 Stage
Oil Burner Pump Pressure  psig (Pa) 100 (690) 140 (965) 140 (965)
Blower wheel nominal in. 10 x 6 10 x 8 12 x 9
Blower
wheel
nominal
diameter x width mm 254 x 152 254 x 203 305 x 229
Blower Motor Output  hp (W) 1/3 (249) 1/3 (249) 3/4 (560)
Nominal cooling that can be added
Tons 2 thru 2.5 2 thru 3.5 3 thru 5
Nominal cooling that can be added kW 7.0 thru 8.8 7.0 thru 12.3 10.6 thru 17.6
**Number and size of filtersin. (mm) (1) 16 x 25 x 1 (1) 16 x 25 x 1 (2) 16 x 25 x 1
Shipping weight  lbs. (kg) 1 package 225 (102) 225 (102) 275 (125)
Electrical characteristics 115 volts  60 hertz  1 phase
Optional Accessories (Must Be Ordered Extra) 
Two Stage Oil Pump 65A44
Oil Filter 81P89
*Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and FTC labeling regulations. Isolated combustion system rating for nonweatherized furnaces.
**Cleanable frame type filters. Furnished with unit in Side Filter Adaptor Kit for field installation external to the cabinet.
Requires return air from both sides of cabinet.
Nozzle must be field provided for field conversion to higher heating input.
SPECIFICATIONS − OHR23
Model Number OHR23Q3105/120 OHR23Q5140/154
InputBtuh (kW) low/high 105,000 / 120,000(30.8 / 35.2) 140,000 / 154,000(41.0 / 45.1)
OutputBtuh (kW) low/high 85,000 / 97,000 (24.9 / 28.4) 113,000 / 125,000 (33.1 / 36.6)
*A.F.U.E. (low/high) 81.8% / 81.3% 81.5% / 81.7%
Nozzle RatingU.S. gph (L/hr)
and spray angle
.65 (2.5)  80(105 input) solid
.75 (2.8)  80(120 input) solid
.85(3.2) 80(140 input) solid
1.00 (3.8)  80(154 input) solid
Flue Size Diameterin. (mm) 6 (152) 6 (152)
Oil Burner Pump 1 Stage 1 Stage
Oil Burner Pump Pressure  psig (Pa) 140 (965) 140 (965)
Blower wheel nominal diameter x width  in. (mm) 10 x 10 (254 x 254) 12 x 9 (305 x 229)
Blower motor outputhp (W) 1/2 (373) 3/4 (560)
Nominal cooling that can be added
Tons 2 to 3 3 to 5
Nominal cooling that can be added kW 7.0 to 10.6 10.6 to 17.6
Shipping weightlbs. (kg) 1 package 225 (102) 265 (120)
Electrical characteristics 115 volts  60 hertz  1 phase
Optional Accessories (Must Be Ordered Extra) 
Two Stage Oil Pump 65A44
Filter Kit
Catalog no. 35K01 35K06
Fil
ter
Ki
t
No & size of filters in (mm)
(2)101/4x201/2x1(260x521x25)
(2)113/4x231/2x1(298x597x25)
No. & size of filtersin. (mm) (2) 101/4 x 201/2 x 1 (260 x 521 x 25) (2) 113/4 x 231/2 x 1 (298 x 597 x 25)
Downflo Additive Base 35K07 35K08
Horizontal Venting Kit 62J01
Burner Cover 84H26
Vestibule Cover Kit (full front cover) 37K28 37K29
Oil Filter 81P89
*Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and FTC labeling regulations. Isolated combustion system rating for nonweatherized furnaces.
Nozzle must be field provided for field conversion to higher heating input.

Page 3
SPECIFICATIONS − OF23
Model Number OF23Q3105/120
OF23Q3105/120R
OF23Q5140/154
OF23Q5140/154R
InputBtuh (kW) low/high 105,000 / 120,000(30.8 / 35.2) 140,000 / 154,000(41.0 / 45.1)
OutputBtuh (kW) low/high 85,000 / 97,000 (24.9 / 28.4) 113,000 / 125,000 (33.1 / 36.6)
*A.F.U.E. (low/high) 82.4% / 81.5%
82.5% / 82.4% R Models
81.8% / 81.5%
82.0% / 81.8% R Models
Nozzle Ratinggph (L/hr) and spray angle .65 (2.5)  80°(105 input)
.75 (2.8)  80°(120 input)
.85 (3.2)  80°(140 input)
1.00 (3.8)  80°(154 input)
Flue Size Diameterin. (mm) 6 (152) 6 (152)
Oil Burner Pump 1 Stage 1 Stage
Oil Burner Pump Pressure  psig (Pa) 140 (965) 140 (965)
Optional 2 Stage Fuel Pump 65A44
Blower wheel nominal in. 10 x 8 12 x 9
Blower
wheel
nominal
diameter x width mm 254 x 203 305 x 229
Blower Motor Outputhp (W) 1/3 (249) 3/4 (560)
Nominal cooling that can be addedTons (kW) 2 thru 3 (7.0 thru 10.6) 3 thru 5 (10.6 thru 17.6)
Number and size of filters
in. (1) 18 x 19 x 1 (1) 19 x 21 x 1
Number and size of filters mm (1) 457 x 483 x 25 (1) 483 x 533 x 25
Shipping weightlbs. (kg) 1 package 255 (116) 290 (132)
Electrical Characteristics 115  60 hertz  1 phase
Optional Accessories (Must Be Ordered Extra) 
Two Stage Oil Pump 65A44
Oil Filter 91P89
*Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and FTC labeling regulations. Isolated combustion system rating for nonweatherized furnaces.
Nozzle must be field provided for field conversion to higher heating input.
BLOWER PERFORMANCE DATA − O23
O23Q270 BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in.w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1260 595 870 410 520 245
.30 75 1205 570 825 390 500 235
.40 100 1135 535 780 370 480 225
.50 125 1050 495 720 340 450 210
.60 150 960 455 660 310 410 195
NOTE  All air data is measured external to the unit with the air filter in place.
O23Q3105/120 BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20. 50 1350 635 1215 575 1080 510
.30 75 1280 605 1180 555 1060 500
.40 100 1210 570 1140 540 1040 490
.50 125 1180 444 1085 510 1000 470
.60 150 1100 520 1025 485 950 450
NOTE  All air data is measured external to the unit with the air filter in place.
O23Q5140/154 BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1950 920 1620 765 1250 590
.30 75 1900 895 1590 750 1230 580
.40 100 1880 885 1560 735 1210 570
.50 125 1850 875 1540 725 1190 560
.60 150 1800 850 1490 705 1155 545
NOTE  All air data is measured external to the unit with the air filter in place.

Page 4
BLOWER PERFORMANCE DATA − OHR23
OHR23Q3105/120 BLOWER PERFORMANCE
External Static Air Volume at Various Speeds
External
Static
Pressure High Medium Low
in w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1470 695 1360 640 1070 505
.30 75 1400 660 1300 615 1040 490
.40 100 1330 630 1230 580 1020 480
.50 125 1260 595 1160 545 980 460
.60 150 1180 555 1085 510 920 435
NOTE  All air data is measured external to the unit with air filter in place.
OHR23Q5140/154 BLOWER PERFORMANCE
External Static Air Volume at Various Speeds
External
Static
Pressure High Medium Low
in w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1950 920 1700 800 1340 630
.30 75 1920 905 1650 780 1300 615
.40 100 1900 895 1600 755 1270 600
.50 125 1870 880 1580 745 1220 575
.60 150 1780 840 1500 710 1170 550
NOTE  All air data is measured external to the unit with air filter in place.
BLOWER PERFORMANCE DATA − OF23
FRONT FLUE MODELS
OF23Q3105/120 BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1490 705 1370 645 1190 560
.30 75 1430 675 1345 635 1180 555
.40 100 1375 650 1280 605 1160 545
.50 125 1300 615 1230 580 1120 530
.60 150 1230 580 1160 545 1080 510
NOTE  All air data is measured external to the unit with the air filter in place.
OF23Q5140/154 BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 2110 995 1850 875 1500 710
.30 75 2035 960 1810 855 1480 700
.40 100 1970 930 1750 825 1450 685
.50 125 1950 920 1690 800 1420 670
.60 150 1880 885 1620 765 1375 650
NOTE  All air data is measured external to the unit with the air filter in place.
REAR FLUE MODELS
OF23Q3105/120R BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 1470 695 1330 630 1150 545
.30 75 1410 665 1295 610 1140 540
.40 100 1340 630 1250 590 1125 530
.50 125 1280 605 1190 560 1080 510
.60 150 1205 670 1130 535 1030 485
NOTE  All air data is measured external to the unit with the air filter in place.
OF23Q5140/154R BLOWER PERFORMANCE
External Static Air Volume at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s cfm L/s cfm L/s
.20 50 2010 950 1765 835 1380 650
.30 75 1960 925 1720 810 1350 635
.40 100 1900 895 1660 785 1330 630
.50 125 1880 885 1600 755 1295 610
.60 150 1800 850 1560 735 1230 580
NOTE  All air data is measured external to the unit with the air filter in place.

Page 5
FIGURE 1
O23 GENERAL PARTS ORIENTATION
LIMIT SWITCH
CONTROL BOX
WITH FAN
CONTROL
BECKETT
AFII BURNER
INDOOR BLOWER
CAPACITOR
BLOWER MOTOR
COMBUSTION AIR INTAKE
OBSERVATION PORT
CLEANOUT PORT
VENT OPENING
HEAT EXCHANGER
CLEANOUT PORT
FIGURE 2
OHR23 GENERAL PARTS ORIENTATION
LIMIT SWITCH
CONTROL BOX
WITH FAN
CONTROL
BECKETT
AFII BURNER
INDOOR BLOWER
BLOWER MOTOR
COMBUSTION
AIR INTAKE
OBSERVATION
PORT
CLEANOUT
PORT
VENT OPENING
HEAT EXCHANGER
CLEANOUT PORT

Page 6
FIGURE 3
OF23 GENERAL PARTS ORIENTATION
LIMIT SWITCH
CONTROL BOX
WITH FAN
CONTROL
BECKETT
AFII BURNER
INDOOR BLOWER
COMBUSTION
AIR INTAKE OBSERVATION PORT
CLEANOUT PORT
FRONT VENT
OPENING (OF23)
HEAT EXCHANGER
CLEANOUT
PORT
FILTER
REAR VENT
OPENING (OF23R)
FIGURE 4
BCC2 / BCC3 BLOWER CONTROL BOARD
NEUTRAL
TERMINALS ACCESSORY
TERMINAL
THERMOSTAT TERMINAL STRIP TB1
(DETACHABLE ON EARLY −1 AND −2
MODELS ONLY)
BLOWER TIME
ADJUSTMENT
JUMPER
HEATING SPEED
TAP TERMINAL
COOLING
SPEED TAP
TERMINAL
CONTINUOUS FAN
TERMINAL
To Remove Terminal Strip,
Grasp Ends of Block Between
Thumb and Forefinger. Push
Block Down and Out.
(Jack / Plug 94)
120VAC
TRANSFORMER
COMMON
120VAC LINE
VOLTAGE IN
24VAC IN FROM
PRIMARY LIMIT
24VAC OUTPUT
TO BURNER
(HEAT DEMAND)
24VAC THERMOSTAT
DEMAND OUTPUT
24VAC INPUT
FROM TRANSFORMER
24VAC COMMON
FROM TRANSFORMER

Page 7
I−UNIT COMPONENTS
General parts orientation for the O23, OHR23 and OF23 are
shown in figures 1, 2 and 3 respectively. The O23 and OF23
control box, burner, limit switch and cleanout ports may be ac
cessed by removing the front access panel, while the OHR23
components are exposed. The blower can be accessed in the
O23 and OF23 by removing the blower access panel, while in
the OHR23 units two 1/4" screws must be removed before the
blower access panel can be removed.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during unit instal
lation and service to protect the unit’s electronic
controls. Precautions will help to avoid control
exposure to electrostatic discharge by putting
the unit, the control and the technician at the
same electrostatic potential. Neutralize electro
static charge by touching hand and all tools on an
unpainted unit surface before performing any
service procedure.
A−Blower Control Board
BCC2 Blower Control Board (Figure 4)
−1 and −2 units
All O23, OHR23 and OF23−1 and −2 oil units utilize the BCC2
(A15) blower control manufactured by Heatcraft. The BCC2 is
a printed circuit board which controls the supply air blower and
monitors the limit controls and oil burner operation. The control
has a nonadjustable, factory preset fanon" timing. Fan off"
timing is adjustable. The board is divided into two sec
tions, 120 and 24VAC. Line voltage comes into the board
on the 120VAC side. See figure 4. See table 1 for BCC2
terminal designations.
DANGER
Shock hazard. Avoid personal injury. Make sure to
disconnect power before changing fan off" timing.
Blower Operation and Timing
Blower off" timing (time that the blower operates after the heat
demand has been satisfied) is determined by the arrange
ment of a jumper across pins on the BCC2 blower control
board. See figure 4. To adjust fan off " timing, gently discon
nect jumper and reposition across pins corresponding with
new timing. Fan on" time is factory set at 45 seconds and is
not adjustable.
NOTEIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 or auxilary
limit S21 to trip resulting in frequent cycling of blower. If
this occurs, adjust blower to longer time setting.
Figure 5 shows the various fan off" timings and how
jumper should be positioned. Unit is shipped with a fac
tory fan off" setting of 150 seconds. Fan off" time will
affect comfort and efficiency and is adjustable to satisfy
individual applications. The fan off" timing is initiated
after a heating demand but not after a blower or cooling
demand (that is, when indoor thermostat switch is
changed from ON to AUTO and heating/cooling demand
is not present, the blower stops immediately).
FIGURE 5
FANOFF TIME ADJUSTMENT
270 210
150 90
To adjust fan−off timings:
Remove jumper from BCC2
and select one of the other pin com
binations to achieve the
desired time.
TIMING
JUMPER
TIMING PINS (seconds)
Leave jumper off to achieve
330 second fan−off timing.
Fanoff timing is factory
set at 150 seconds
Thermostat Connection
Thermostat wires are connected to terminal strip TB1 found
on the BCC2 control board. The terminal strip is clearly
marked with the corresponding thermostat designation.
The terminal strip (jack / plug 94) is simply removed by
grasping the ends of the block and rotating down while pull
ing away (see figure 4).
TABLE 1
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
Terminal Type Function
WDetachable
Screw Strip Heating Demand
RDetachable
Screw Strip 24VAC to Thermostat
YDetachable
Screw Strip Cooling Demand
CDetachable
Screw Strip 24VAC Common To Indoor Thermostat
GDetachable
Screw Strip Blower Demand
NEUTRAL 1/4" Spade 120VAC Neutral
L1 1/4" Spade 120VAC Line Voltage In
A1/4" Spade Switched 120VAC
to Blower Cooling Tap
XFMRN 1/4" Spade 120VAC Transformer Common
CF 1/4" Spade Switched 120VAC to
Continuous Blower Tap
H1/4" Spade Switched 120VAC to
Blower Heating Tap
ACC 1/4" Spade Switched 120VAC to Accessory (Electronic Air Cleaner,
Humidifier, Etc. 1 amp rating.)
VALVE SENSE 3/16" Spade 24VAC Output To Burner
LIMIT 1/4" Spade
24VAC In From Primary Limit.
Limit Open: Stops Burner and Turns
On Blower
Limit Closed: Allows Burner
Operation
WI 1/4" Spade 24VAC Thermostat
Demand Output
24V 1/4" Spade 24VAC Input
From Transformer
COM 1/4" Spade 24VAC Common
From Transformer

Page 8
BCC3 Blower Control Board (Figure 4)
−3 and −4 units
All O23, OHR23 and OF23−3 and −4 oil units utilize the BCC3
(A15) blower control manufactured by Heatcraft. The BCC3 is
a printed circuit board which controls the supply air blower and
monitors the limit controls and oil burner operation. The control
has a nonadjustable, factory preset fanon" timing. Fan off"
timing is adjustable. The board is divided into two sec
tions, 120 and 24VAC. Line voltage comes into the board
on the 120VAC side. See figure 4. See table 2 for BCC3
terminal designations.
DANGER
Shock hazard. Avoid personal injury. Make sure to
disconnect power before changing fan off" timing.
Blower Operation and Timing
Blower off" timing (time that the blower operates after the heat
demand has been satisfied) is determined by the arrange
ment of a jumper across pins on the BCC3 blower control
board. See figure 4. To adjust fan off " timing, gently discon
nect jumper and reposition across pins corresponding with
new timing. Fan on" time is factory set at 45 seconds and is
not adjustable.
NOTEIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 or auxilary
limit S21 to trip resulting in frequent cycling of blower. If
this occurs, adjust blower to longer time setting.
Figure 5 shows the various fan off" timings and how
jumper should be positioned. Unit is shipped with a fac
tory fan off" setting of 150 seconds. Fan off" time will
affect comfort and efficiency and is adjustable to satisfy
individual applications. The fan off" timing is initiated
after a heating demand but not after a blower or cooling
demand (that is, when indoor thermostat switch is
changed from ON to AUTO and heating/cooling demand
is not present, the blower stops immediately).
FIGURE 6
FANOFF TIME ADJUSTMENT
270 210
150 90
To adjust fan−off timings:
Remove jumper from BCC2
and select one of the other pin com
binations to achieve the
desired time.
TIMING
JUMPER
TIMING PINS (seconds)
Leave jumper off to achieve
330 second fan−off timing.
Fanoff timing is factory
set at 150 seconds
Thermostat Connection
Thermostat wires are connected to terminal strip TB1 found
on the BCC3 control board. The terminal strip is clearly
marked with the corresponding thermostat designation.
The terminal strip (jack / plug 94) is simply removed by
grasping the ends of the block and rotating down while pull
ing away (see figure 4).
TABLE 2
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
Terminal Type Function
WDetachable
Screw Strip Heating Demand
RDetachable
Screw Strip 24VAC to Thermostat
YDetachable
Screw Strip Cooling Demand
CDetachable
Screw Strip 24VAC Common To Indoor Thermostat
GDetachable
Screw Strip Blower Demand
NEUTRAL 1/4" Spade 120VAC Neutral
L1 1/4" Spade 120VAC Line Voltage In
A1/4" Spade Switched 120VAC
to Blower Cooling Tap
XFMRN 1/4" Spade 120VAC Transformer Common
CF 1/4" Spade Switched 120VAC to
Continuous Blower Tap
H1/4" Spade Switched 120VAC to
Blower Heating Tap
ACC 1/4" Spade Switched 120VAC to Accessory (Electronic Air Cleaner,
Humidifier, Etc. 4 amp rating.)
VALVE SENSE 3/16" Spade 24VAC Output To Burner
LIMIT 1/4" Spade
24VAC In From Primary Limit.
Limit Open: Stops Burner and Turns
On Blower
Limit Closed: Allows Burner
Operation
WI 1/4" Spade 24VAC Thermostat
Demand Output
24V 1/4" Spade 24VAC Input
From Transformer
COM 1/4" Spade 24VAC Common
From Transformer

Page 9
ST9103A Blower Control Board (Figure 8)
−5 units
All O23, OHR23 and OF23 −5 oil units utilize the ST9103A
(A15) blower control manufactured by Honeywell. The
ST9103A is a printed circuit board which controls the supply
air blower and monitors the limit controls and oil burner opera
tion. The control has a nonadjustable, factory preset fanon"
timing. Fan off" timing is adjustable. See figure 8 and
table 3 for ST9103A terminal designations
DANGER
Shock hazard. Avoid personal injury. Make sure to
disconnect power before changing fan off" timing.
Blower Operation and Timing
The fan on time of 30 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by moving the delay
switches on the fan control board. Fan off time will affect
comfort and is adjustable to satisfy individual applications.
See figure 7. Set the heat fan off delay switches to either
60, 90, 120, or 150 seconds. The factory setting is 90 sec
onds.
NOTEIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 or auilary
limit S21 to trip resulting in frequent cycling of blower. If
this occurs, adjust blower to longer time setting.
Thermostat Connection
Thermostat wires are connected directly to the terminlas on
the ST9103A board. See figure 8.
Continuous Blower
If the ST9103A blower control board is wired for continuous
blower, the blower will energized on low speed and remain
energized when heat or cool demand is satisfied. Continuous
blower will also energized when indoor thermostat is left in the
OFF mode.
150 sec
Figure 7
Fan Off Delay Switch Settings
120 sec90 sec60 sec
ONON ON ON
Figure 8
ST9103A Blower Control Board
thermostat
terminal strip
fan off
delay switches
120V
TABLE 3
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
J58 Pin # Function
1Limit S10
2L1 120V
3T1 24V
4L2 Common
5Jumpered to Pin 4
6T2 24V
7Combustion Air Inducer
120V
8Jumpered to Pin 7
9Limit S21 (if used)
Thermostat Connections
GBlower Demand
WHeating Demand
R 24V
YCooling Demand
C Common
24 VAC CONNECTIONS
X24V Transformer
CCommon Transformer
120 VAC
S2 Line
S3 120V To Transformer
N, 2, 3, 4, 6, 7 Neutral
CONT Continuous Blower
COOL Cool Tap
HEAT Heat Tap

Page 10
−1THROUGH −4 UNIT OIL BURNER PARTS ARRANGEMENT
FIGURE 9
FB–HEAD
HEAD
INSULATOR
CLIP
RETAINING
FB HEADS
ASSY FOR
AIR TUBE
CONNECTOR
ASSY.
ELECTRODE HEAD
NOZZLE LINE
ADAPTER
NOZZLE
AIR SCOOP
INLET
WHEEL
BLOWER
FLANGE
GASKET
DOOR GASKET
REAR ACCESS
COUPLING
OIL PUMP
PLATE
ESCUTCHEON
NUT
SPLINED
DOOR ASSY
REAR ACCESS
ASSY
HOUSING
MAIN
HOLE PLUG
SCREWS
AIR TUBE
FLANGE
ASSY
ELECTRODE
6
5
4
3
7
0
8
TUBE
ELECTRONIC IGNITION
TRANSFORMER
BURNER
CONTROL
AIR
ADJUSTMENT
DIAL
ELECTRONIC IGNITION
TRANSFORMER RESET
BUTTON
COMBUSTION AIR
MOTOR
VIEW PORT

Page 11
−5 UNIT BURNER PARTS ARRANGEMENT
FIGURE 10
FB−HEAD
HEAD
INSULATOR
CLIP
RETAINING
1/4" HEX
HEAD SCREW
FB HEADS
ASSY FOR
AIR TUBE
ASSY.
ELECTRODE HEAD
NOZZLE LINE
PEDESTAL
ADAPTER
NOZZLE
AIR SCOOP
INLET
WHEEL
BLOWER
FLANGE
GASKET
MOTOR
4X4
BOX
IGNITOR
DOOR GASKET
REAR ACCESS
COUPLING
FUEL PUMP
PLATE
ESCUTCHEON
NUT
SPLINED
DOOR ASSY
REAR ACCESS
ASSY
HOUSING
MAIN
SCREWS
AIR TUBE
FLANGE
ASSY
ELECTRODE
6
5
4
3
7
0
8
ELECTRONIC IGNITION
TRANSFORMER
PRIMARY
CONTROL
AIR
ADJ.
DIAL
CONNECTOR
TUBE
PREMOUNTED PRE−PURGE VALVE

Page 12
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A100 psig (689.5 kPa) FB0
105 35K75 AFII 85 4.0 84,000 BTU
(24.6 kW) 0.65 X 80B140 psig 965.3 kPa) FB3
120 35K75 AFII 85 4.5 105,000 BTU
(30.8 kW) 0.75 X 80B140 psig 965.3 kPa) FB3
140 35K76 AFII 150 6.0 112,000 BTU
(32.8 kW) 0.85 X 80B140 psig 965.3 kPa) FB6
154 35K76 AFII 150 6.5 125,000 BTU
(36.6 kW) 1.00 X 80B140 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 startup 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.

Page 13
5−Burner Control (A3) & Transformer (T1)
−1 through −4 units
The burner control, along with the matching cad cell, proves
flame and controls the burner. After the cad cell closes a circuit
to the burner control, the burner control de−energizes the safe
ty switch heater to allow the unit to operate normally. The
burner control allows 45 seconds for the cad cell to close. If the
cad cell remains open after the 45 second time frame, the
burner control locks out. The burner control must be manually
reset by depressing the red reset button on top of the burner
control.
Transformer (T1) is part of the burner control. T1 provides
24VAC to the low voltage components in the unit and to the
thermostat.
6−Burner Control (A3) −5 units
All O 23, OHR23 and OF23 −5 units are equipped with a burn
er control R7184B manufactured by Honeywell. The burner
control, along with the matching cad cell, proves flame and
controls the burner. An LED on the control shows unit status.
See table 5 for status codes. After the cad cell closes a circuit
to the burner control, the burner control de−energizes the safe
ty switch heater to allow the unit to operate normally. When
there is a call for heat the control performs a 2 to 6 second
delay safety check. Once this is established a 15 second pre−
puge will follow. The valve then opens for a 15 second trial for
ignition. If flame is not sensed during the 15 second trial, the
control shuts down and must be manual re−set. After three
consecutive lockouts the control goes into restricted lockout.
Once flame is established after 10 seconds of run time, the ig
niiton shuts off.
If flame is lost during the heat cycle the control will shut
down the burner and begin a 60 second recycle delay. Af
ter 60 seconds the control repeats the ignition process. If
flame is lost three consecutive times during a single ther
mostat demand the control goas into restricted lockout.
Reset button
If the control lockouts three consecutive times the control
will go into restricted lockout. To reset control hold down
the reset button for 30 seconds until the LED flashes twice.
At any time the burner motor is energized, press and hold
the reset button to disable the buner. The burner will re
main disabled as long as the reset button is held and return
to operational once the button is released.
TABLE 5
LED STATUS
On Flame sensed
Off Flame not sensed
Flashing
(1/2 sec on1/2 sec off)
Lockout /
Restricted Lockout
Flashing
(2 sec on 2 sec off) Recycle
7−Heat Shutoff Relay (K125)
−1 and −2 units only
Heat shutoff relay K125 is a SPST N.O. relay, with a 24V
coil. K125 is located on the vestibule and wired in series
with the burner. When secondary limit S21 or primary limit
S10 open, the circuit breaks opening K125 contacts which
in turn de−energizes the burner.
8−Cad Cell (R26)
Together the cad cell and the burner control prove flame.
The cad cell senses the presence of burner light (less re
sistance) to close a circuit to the burner control.
IMPORTANT−Burner should not be installed so it is ex
posed to direct sunlight or electric bulb light. If the cell
is exposed to light on start up, the burner will not oper
ate.
O23, OHR23 & OF23 −5 Units Only
Resistance for the cad cell can be checked while the burn
er is firing and after ignition is off. Press (1/2 second or
less) and release the reset button. The LED will flash 1 to 4
times depending on the cad cell resistance. The cad cell
resistance should read less than 1600 Ohms. See table 6.
TABLE 6
O23, OHR23 & OF23 −5 UNITS
LED FLASHES RESISTANCE
10 − 400Ohms
2400 − 800 Ohms
3800 − 1600 Ohms
41600 Ohms

Page 14
9−Electronic Ignitor (A73)
The electronic ignitor provides the needed hot spark at the
electrodes to ignite the fuel mixture. The ignitor is a solid
state transformer . O23, OHR23 and OF23−1 through −4
units have 115V primary and 14,000V secondary wind
ings. O23, OHR23 and OF23−5 units have 120V primary
and 20,000V secondary windings. The center of the sec
ondary winding is grounded. Each secondary terminal is
7000V to ground and the total voltage between the elec
trodes is 14,000V.
NOTE−The leads for the solid state transformer are re
placeable and are available in a kit form.
NOTE−When testing the solid state transformer, do not
use a transformer tester designed for iron magnet trans
formers. Damage to the tester may result.
Testing the Ignitor
WARNING
SHOCK HAZARD
Do not touch ignitor or any metal touching ignitor
when ignitor is energized. Can result in serious per
sonal injury.
If the ignitor fails it will not produce a spark. Looking and
listening for the arc is a simple way to check. The most sure
way is to perform the screwdriver check. By placing the
blade of an insulated screwdrivere across the ignitor termi
nal leads will test for an arc. First, remove power from the
burner and disconnect the oil supply from nozzle. The cad
cell will not let the control energize the ignitor if the cad cell
senses light. Therefore remove one lead of the cad cell
from the burner control, or remove the cad cell all together
(do not forget to put back when test is complete). Place the
screwdriver blade across the terminals and slowly raise
one end of the blade off the terminal while the other re
mains in contact with the other terminal. There should be
an arc from terminal to the blade up to 3/4" away. If not re
place the ignitor. If an arc is present then place one end of
the screwdriver on one terminal and the other end with the
grounded baseplate. Raise the blade from the baseplate
and draw an arc. Repeat with the other terminal. If the arc
from the baseplate to one terminal is weaker than the arc
from the baseplate to the other terminal, replace the ignitor.
10−Gun Assembly
The gun assembly receives oil from the oil pump and feeds
it to the nozzle. The nozzle converts liquid oil into a fog−like
mist that is discharged through the flame retention head
into the combustion chamber.
11−Flame Retention Heads
The stainless steel flame retention head (see figure 11)
is used to swirl (cone) the foglike oil and air mixture as it
enters the combustion chamber. Three different heads
are used in the O23/OHR23/OF23. The firing rate dic
tates which head is used. See table 4. The greater the
FB number the larger the slots on the head. When com
bustion takes place, the flame will be cylindrical com
pact shaped as a result.
FLAME RETENTION HEAD
FB3 SHOWN
FIGURE 11
C−Primary Limit Control (S10)
The primary limit on all O23, OHR23, and OF23 units, is
located on the vestibule panel (see figures 1 through 3 for
location and figure 12 for type). When excess heat is
sensed in the heat exchanger, the limit will open. If the limit
is tripped, the blower control deenergizes the thermostat,
in turn shutting down the unit. The limit automatically re
sets when unit temperature returns to normal. The switch is
factory set and cannot be adjusted. The switch has a different
setpoint for each unit model number (see table 7). The set
point is printed on the face plate of the limit.

Page 15
TABLE 7
PRIMARY LIMIT CONTROL (S10)
UNIT ACTUATES
ON TEMP. RISE
ACTUATES
ON TEMP. FALL
O23Q2−70 210F (99C) 180F (82C)
O23Q3−105/120 220F (104C) 190F (88C)
O23Q5−140/154 210F (99C) 180F (82C)
OHR23Q3−105/120 240F (116C) 210F (99C)
OHR23Q5−140/154 190F (88C) 160F (71C)
OF23Q3−105/120
OF23Q3−105/120R 240F (116C) 210F (99C)
OF23Q5−140/154
OF23Q5−140/154R 210F (99C) 180F (82C)
FIGURE 12
INSULATING COVER
LIMIT CONTROL (S10)
SPADE CONNECTORS
LIMIT
D−Blower Compartment (Figure 13)
Blower motor (B3), capacitor (C4), and secondary limit con
trol (S21) are located in the blower compartment. The blow
er compartment can be accessed by removing the blower
access panel.
FIGURE 13
BLOWER COMPARTMENT
(OHR23 SIDE VIEW SHOWN)
BLOWER
MOTOR
CAPACITOR
(C4)
SECONDARY LIMIT
CONTROL (S21)
(OHR23 ONLY)
(BACK SIDE)
BLOWER MOTOR
(B3)
1.Blower Motor (B3) and Capacitor (C4)
All O23, OHR23, and OF23 series units use single phase
direct drive blower motors. All motors used are 115V perma
nent split capacitor motors to ensure maximum efficiency.
See SPECIFICATIONS tables for horsepower and motor
nameplate for capacitor rating.The blower motor is con
nected to the blower control board via the blower motor
plug P43.
2.Secondary Limit Control (S21)
The secondary limit (S21) is used on the OHR23 series unit
only. The N.C. limit is mounted on the side and toward the
back of the blower housing. See figure 13 for location and fig
ure 14 for type. When excess heat is sensed in the blower
compartment, the limit will open. If the limit is tripped, the blow
er control deenergizes the thermostat, inturn shutting down
the unit. The limit automatically resets when unit tempera
ture returns to normal. The switch opens at 150F + 5F
(65.5C + 2.8C) on a temperature rise and resets at
140F + 5F (60.0C + 2.8C) on a temperature fall. The
switch is factory set and cannot be adjusted. The set
point is printed on the face plate of the limit.
FIGURE 14
SECONDARY LIMIT CONTROL (S21)
E−Optional Accessories
Optional accessories are available from Lennox for the O23,
OHR23, and OF23 series units. Some accessories are in kit
form which come with instructions.
1.Low Speed On − Off Switch (S68)
The low speed on  off switch is a kit (catalog # 67H91) which
permits continuous low speed blower operation. The switch is
a DPDT toggle switch.
2.Economizer Relay (K43)
The economizer relay (catalog # 65G40) is used to energize
the economizer if used. The relay is a 120V coil, single pole
contact which is energized by the accessory terminal of the
blower control board.

Page 16
II−PLACEMENT AND INSTALLATION
Make sure unit is installed in accordance with installation in
structions and applicable codes.
A−Piping
The piping system and it’s components (oil filter, safety valves,
shutoff valves, etc.) must be designed to provide clean, air
free fuel to the burner.
An oil filter is required for all models. Use an oil filter of gener
ous capacity for all installations. Install filter inside the building
between the tank shut−off valve and the burner. Locate filter
close to burner for easy servicing. The GAR−Ber 11BV−R or
equivalent filter (with the below specifications) is recom
mended.
Maximum Firing Rate: 10GPH (38LPH)
Micron Removal: 10
Filtering Area: 500 in.2(3225.8 cm2)
Working Pressure: 15 PSI (103.4 kPa)
Inlet/Outlet Dimension: 3/8" (9.5 mm) NPT
Flow Rate: 45GPH (171LPH)
Care must be taken to ensure the restriction of the piping sys
tem, plus any lift involved, does not exceed the capabili
ty of the oil pump. Each installation will be different. Use
the following guide lines when determining to use a single or
two stage pump.
When using a single pipe system with the fuel supply level
with or above the burner (see figure 15) and a vacuum of 6"
(152 mm) Hg or below, a single stage fuel unit with a supply
line and no return line should be adequate. Manual bleeding of
the fuel unit is required on initial start up. Failure to bleed air
from the pump could result in an air lock/oil starvation condi
tion.
NOTE−As an extra precaution, cycle heating on and off
ten times after bleeding air from the pump. This will elim
inate air in the gun assembly.
When using a two pipe system with the fuel supply level
below the level of the burner (see figure 16) a single
stage fuel unit should be used in lift conditions of up to
10 feet (3 m) and/or a vacuum of 10" (254 mm) Hg or be
low. A two stage fuel unit should be used when lift ex
ceeds 10 feet (3 m) and/or a vacuum of 10" (254 mm) Hg
to 15" (381 mm) Hg. Both conditions require the use of a re
turn line that purges the fuel unit of air by returning it to the fuel
tank. Use table 8 when determining the run and lift for piping.
Before converting a onepipe system to a twopipe sys
tem the pump must be converted to a twopipe system.
To convert the pump, install the bypass plug according
to the instructions. Notice in the twopipe system the re
turn line must terminate 3" (76 mm) to 4" (102 mm)
above the supply inlet. Failure to do this may introduce
air into the system and could result in loss of prime.
NOTE−If using an outside tank in cold climates a number one
fuel or an oil treatment is strongly recommended.
FIGURE 15
OIL PIPING
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
Air Vent
Fill
Pipe
Oil
Tank
Fuel
Unit Aux
Filter
Shut−off
Valve
8 ft (2.4 m)
Maximum
One Pipe Lift
ONEPIPE SYSTEM
FIGURE 16
OIL PIPING
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
Fuel
Unit Aux
Filter
Return
Line
Fill
Pipe
Air Vent
Oil
Tank
Inlet
Return
Line
H
3"−4"
(76mm −102mm)
R
OUTSIDE TANK FUEL UNIT ABOVE BOTTOM OF TANK.
TWOPIPE SYSTEM
TABLE 8
TWO−PIPE MAXIMUM LINE LENGTH (H + R)
3450 RPM − 3 GPH (11.4 LPH)
Lift H"
Figure 15
3/8" (10 mm) OD
Tubing
1/2" (12 mm) OD
Tubing
g
Single
Stage
Two
Stage
Single
Stage
Two
Stage
0’
(0.0 m)
84’
(25.6 m)
93’
(28.3 m)
100’
(30.5 m)
100’
(30.5 m)
2’
(0.6 m)
73’
(22.3 m)
85’
(25.9 m)
100’
(30.5 m)
100’
(30.5 m)
4’
(1.2m)
63’
(19.2 m)
77’
(23.5 m)
100’
(30.5 m)
100’
(30.5 m)
6’
(1.8m)
52’
(15.8 m)
69’
(21.0 m)
100’
(30.5 m)
100’
(30.5 m)
8’
(2.4m)
42’
(12.8 m)
60’
(18.3 m)
100’
(30.5 m)
100’
(30.5 m)
10’
(3.0m)
31’
(9.4 m)
52’
(15.9 m)
100’
(30.5 m)
100’
(30.5 m)
12’
(3.7m)
21’
(6.4 m)
44’
(13.4 m)
83’
(25.3 m)
100’
(30.5 m)
14’
(4.3m) −−− 36’ (11.0 m)
41’
(12.5 m)
100’
(30.5 m)
16’
(4.9m) −−− 27’ (8.2 m) −−− 100’ (30.5 m)
18’
(5.5m) −−− −−− −−− 76’ (23.2 m)

Page 17
B−Venting Considerations
WARNING
Combustion air openings in front of the furnace
must be kept free of obstructions. Any obstruction
will cause improper burner operation and may re
sult in a fire hazard or injury.
WARNING
The barometric shall be in the same atmospheric
pressure zone as the combustion air inlet to the
furnace. Deviation from this practice will cause im
proper burner operation and may result in a fire
hazard or injury.
CAUTION
Do not store combustible materials near the fur
nace or supply air ducts. The material (such as
paint, motor oil, gasoline, paint thinner, etc.) may
ignite by spontaneous combustion creating a fire
hazard.
WARNING
This furnace is certified for use with type L" vent.
B" vent must not be used with oil furnaces.
NOTE−Oil burning equipment may be vented into an ap
proved masonry chimney or type L vent. (Type L vent is
similar in construction to type B gas vent except it carries a
higher temperature rating and is constructed with an inner
liner of stainless steel rather than aluminum).
Prior to installation of unit, make a thorough inspection of the
chimney to determine whether repairs are necessary. Make
sure the chimney is properly constructed and sized accord
ing to the requirements of the National Fire Protection Asso
ciation. The smallest dimensions of the chimney should be
at least equal to the diameter of the furnace vent connector.
Make sure the chimney will produce a steady draft sufficient
to remove all the products of combustion from the furnace.
A draft of at least .04" w.c. (9.9 Pa) is required during burner
operation.
1− Local building codes may have more stringent instal
lation requirements and should be consulted before
installation of unit.
2− The vent connector should be as short as possible to
do the job.
3− The vent connector should not be smaller than the
outlet diameter of the vent outlet of the furnace.
4− Pipe should be at least 24 gauge galvanized.
5− Single wall vent pipe should not run outside or through
any unconditioned space.
6− Chimney should extend 3 feet (0.9 m) above the high
est point where the vent passes through the roof, and 2
feet (0.6 m) higher than any portion of a building within
a horizontal distance of 10 feet (3 m).
7− The vent must not pass through a floor or ceiling. Clear
ances to single wall vent pipe should be no less than 6"
(152 mm); more if local codes require it.
8− The vent may pass through a wall where provisions have
been made for a thimble as specified in the Standards of
the National Board of Fire Underwriters. See figure 17.
9− The vent pipe should slope upward toward the chim
ney on horizontal run at least 1/4 inch (6 mm) to the
foot (0.3 m) and should be supported by something
other than the furnace, such as isolation hangers. See
figure 18.
10− Extend the vent pipe into the chimney so that it is flush
with the inside of the vent liner. Seal the joint between
the pipe and the liner.
11− The furnace shall be connected to a factory built
chimney or vent complying with a recognized stan
dard, or masonry or concrete chimney lined with a
lining material acceptable to the authority having
jurisdiction.
WALL THIMBLE
FIGURE 17
THIMBLE
VENT PIPE
COMBUSTIBLE
WALL

Page 18
MASONRY CHIMNEY
BAROMETRIC
CONTROL*
(IN EITHER
LOCATION)
CLEANOUT
CLEANOUT
LINER
MASONRY
CHIMNEY
FIGURE 18
*Barometric control may be installed in either vertical or horizontal
section of vent pipe within 18" (457 mm) of vent outlet of furnace.
12− When two or more appliances vent into a common vent,
the area of the common vent should not be less than the
area of the largest vent or vent connection plus 50% of
the areas of the additional vent or vent connection. Chim
ney must be able to sufficiently vent all appliances oper
ating at the same time.
13− The vent pipe shall not be connected to a chimney vent
serving a solid fuel appliance or any mechanical draft
system.
14− All unused chimney openings should be closed.
15− All vent pipe run through unconditioned areas or outside
shall be constructed of factory built chimney sections.
See figure 19.
16− Where condensation of vent gas is apparent, the vent
should be repaired or replaced. Accumulation of con
densation in the vent is unacceptable.
FACTORY−BUILT CHIMNEY
BAROMETRIC
CONTROL*
(IN EITHER
LOCATION)
FACTORY
BUILT
CHIMNEY
FIGURE 19
*Barometric control may be installed in either vertical or horizontal
section of vent pipe within 18" (457 mm) of vent outlet of furnace.
17− Vent connectors serving this appliance shall not be
connected into any portion of mechanical draft sys
tems operating under positive pressure.
18− Keep the area around the vent terminal free of snow,
ice and debris.
NOTE−If vent pipe needs to exit from side of cabinet, use the
cross hairs (located on either side of the unit) to cut a 6" (152
mm) round hole. Attach finishing plate (provided) with four
sheet metal screws to cover rough edges.
Combustion and Ventilation Air
(Confined and Unconfined Spaces)
Until recently, there was no problem in bringing in suffi
cient amounts of outdoor air for combustion −− infiltration
provided all the air that was needed and then some. In
today’s homes built with energy conservation in mind,
tight construction practices make it necessary to bring in
air from outside for combustion. Consideration must also be
given to the use of exhaust fans, appliance vents, chimneys
and fireplaces because they force additional air that could
be used for combustion out of the house. Unless outside
air is brought into the home for combustion, negative
pressure (pressure outside is greater than inside pres
sure) will build to the point that a down draft can occur in
the furnace vent pipe or chimney. Combustion gases enter
the living space creating a potentially dangerous situa
tion.
The importance of the previous paragraph cannot be
overstated. Users may inadvertently block fresh air in
takes after installation.
In the absence of local codes concerning air for combus
tion and ventilation, the following section outlines guide
lines and recommends procedures for operating oil fur
naces in a manner that ensures efficient and safe
operation. Special consideration must be given to com
bustion air needs as well as requirements for exhaust vents
and oil piping.
Combustion Air Requirements
CAUTION
Insufficient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also
cause excess water in the heat exchanger result
ing in rusting and premature heat exchanger fail
ure. It can also cause property damage.
All oil−fired appliances require air to be used for the com
bustion process. If sufficient amounts of combustion air are not
available, the furnace or other appliance will operate in an inef
ficient and unsafe manner. Enough air must be provided to
meet the needs of all fuel−burning appliances, as well as ap
pliances such as exhaust fans which force air out of the home.
When fireplaces, exhaust fans, or clothes dryers are used at
the same time as the furnace, much more air is required
to ensure proper combustion and to prevent a down−
draft situation. Insufficient amounts of air also cause in

Page 19
complete combustion which can result in sooting. Require
ments for providing air for combustion and ventilation depend
largely on whether the furnace is installed in an uncon
fined or confined space.
Unconfined Space
An unconfined space is an area such as a basement or
large equipment room with a volume greater than 50 cu
bic feet (1.4 cubic meters) per 1,000 Btu (293 W) per
hour of the combined input rating of all appliances
installed in that space. This space also includes adjacent
rooms which are not separated by a door. Though an area
may appear to be unconfined, it might be necessary to bring in
outdoor air for combustion if the structure does not provide
enough air by infiltration. If the furnace is located in a
building of tight construction with weather stripping and
caulking around the windows and doors, follow the proce
dures outlined for using air from the outside for combus
tion and ventilation.
Confined Space
A confined space is an area with volume less than 50 cu
bic feet (1.4 cubic meters) per 1,000 Btu (293 W) per
hour of the combined input rating of all appliances
installed in that space. This definition includes furnace closets
or small equipment rooms.
When the furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside the space con
taining the furnace, the return air must be handled by ducts
which are sealed to the furnace casing and which terminate
outside the space containing the furnace. This is especially
important when the furnace is mounted on a platform in a con
fined space such as a closet or small equipment room. Even a
small leak around the base of the unit at the platform or at the
return air duct connection can cause a potentially dangerous
negative pressure condition. Air for combustion and ventilation
can be brought into the confined space either from inside the
building or from outside.
Air from an Adjacent Space
If the confined space housing the furnace adjoins space
categorized as unconfined, air can be brought in by pro
viding two permanent openings between the two
spaces. Each opening must have a minimum free area
of 1 square inch (6.4 square centimeters) per 1,000 Btu
(293 W) per hour of the total input rating of all fuel−fired
equipment in the confined space. Each opening must
be at least 100 square inches (614.5 square centime
ters). One opening shall be within 12" (305 mm) of the
top of the enclosure and one opening within 12" (305
mm) of the bottom (See figure 20).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM INSIDE
CHIMNEY OR
OIL VENT
WATER
HEATER
OPENINGS
(To Adjacent Room)
FIGURE 20
NOTE−Each opening shall have a free area of at least 1 square inch
(6.4 square centimeters) per 1,000 Btu (293 W) per hour of the total
input rating of all equipment in the enclosure, but not less than 100
square inches (614.5 square centimeters).
OIL
FURNACE
Air from Outside
If air from outside is brought in for combustion and ven
tilation, the confined space shall be provided with two
permanent openings. One opening shall be within 12"
(305 mm) of the top of the enclosure and one within 12"
(305 mm) of the bottom. These openings must communicate
directly or by ducts with the outdoors or spaces (crawl or attic)
that freely communicate with the outdoors or indirectly
through vertical ducts. Each opening shall have a minimum
free area of 1 square inch (6.4 square centimeters) per 4,000
Btu (1172 W) per hour of total input rating of all equipment in
the enclosure (See figures 21 and 22). When communicating
with the outdoors through horizontal ducts, each opening
shall have a minimum free area of 1 square inch (6.4
square centimeters) per 2,000 Btu (586 W) per total input
rating of all equipment in the enclosure (See figure 23).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and
Outlet Air to Ventilated Attic)
NOTE−The inlet and outlet air openings shall each have a free area of
at least one square inch (6.4 square centimeters) per 4,000 Btu (1172
W) per hour of the total input rating of all equipment in the enclosure.
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR WATER
HEATER
INLET
AIR
CHIMNEY
OR OIL
VENT
VENTILATION
LOUVERS
(For unheated
crawl space)
FIGURE 21
OIL
FURNACE

Page 20
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
NOTE−The inlet and outlet air openings shall each have a free area of at
least one square inch (6.4 square centimeters) per 4,000 Btu (1172 W)
per hour of the total input rating of all equipment in the enclosure.
CHIMNEY
OR OIL
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12" above
bottom)
FIGURE 22
OIL
FURNACE
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR OIL
VENT
FIGURE 23
NOTE−Each air duct opening shall have a free area of at least one
square inch (6.4 square centimeters) per 2,000 Btu (586 W) per hour
of the total input rating of all equipment in the enclosure. If the equip
ment room is located against an outside wall and the air openings
communicate directly with the outdoors, each opening shall have a
free area of at least one square inch (6.4 square centimeters) per
4,000 Btu (1172 W) per hour of the total input rating of all other equip
ment in the enclosure.
OIL
FURNACE
When ducts are used, they shall be of the same cross−sec
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3" (76 mm). In calculating free area, the
blocking effect of louvers, grilles, or screens must be con
sidered. If the design and free area of protective covering is
not known for calculating the size opening required, it may
be assumed that wood louvers will have 20 to 25 per
cent free area and metal louvers and grilles will have 60
to 75 percent free area. Louvers and grilles must be
fixed in the open position or interlocked with the equip
ment so that they are opened automatically during equip
ment operation.
CAUTION
Combustion air openings in the front of the furnace
must be kept free of obstructions. Any obstruction
will cause improper burner operation and may result
in a fire hazard or injury.
CAUTION
The barometric shall be in the same atmospheric
pressure zone as the combustion air inlet to the
furnace. Deviation from this practice will cause
improper burner operation and may result in a fire
hazard or injury.
Direct Connection of Outdoor Air for Combustion
The Beckett AFII burner was designed to allow for direct air
intake piping (4" [102 mm]). The maximum equivalent
length of pipe is 70 feet (21.3 m). A 90elbow equals
6feet (1.8 m).
To convert the AFII burner from confined space to out
side combustion air, simply remove the three screws at
taching the inlet air scoop to the burner and insert 4"
(102 mm) direct air intake piping.
The use of a barometric relief placed in the intake pipe is
recommended when outdoor combustion air is directly
connected to the burner. This will allow confined space
air to be used as combustion air in the event that the
opening to the outdoor air becomes blocked. Using a
barometric relief in the intake will reduce the chance of
sooting.
CAUTION
DO NOT USE a barometric draft relief in exhaust
vent pipe if outdoor combustion air is connected
directly to the burner. The only exception are baro
metric draft reliefs as required by FIELD or TJERN
LUND power vents.
Removal of Unit from Common Venting System
In the event that an existing furnace is removed from a venting
system commonly run with separate appliances, the venting
system is likely to be too large to properly vent the remaining
attached appliances. The following test should be conducted
while each appliance is in operation and the other ap
pliances not in operation remain connected to the com
mon venting system. If venting system has been installed
improperly, the system must be corrected as outlined in the
previous section.
1− Seal any unused openings in the common venting sys
tem.
2− Visually inspect venting system for proper size and hori
zontal pitch and determine there is no blockage or restric
tion, leakage, corrosion or other deficiencies which could
cause an unsafe condition.