Lennox O23Q3-105, O23Q3-120, O23Q5-140, O23Q5-154, OHR23Q3-105 Unit Information

Corp. 9535−L8

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.

O23/OHR23

OF23

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 1

 1995 Lennox Industries Inc.

Litho U.S.A.

SPECIFICATIONS − O23

Blower wheel nominal

Fil

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

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

diameter x width

Blower Motor Output  hp (W) 1/3 (249) 1/3 (249) 3/4 (560)

Nominal cooling that can be added

**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

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.

in. 10 x 6 10 x 8 12 x 9

mm 254 x 152 254 x 203 305 x 229

Tons 2 thru 2.5 2 thru 3.5 3 thru 5

kW 7.0 thru 8.8 7.0 thru 12.3 10.6 thru 17.6

 Optional Accessories (Must Be Ordered Extra) 

.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

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

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

Shipping weightlbs. (kg) 1 package 225 (102) 265 (120)

Electrical characteristics 115 volts  60 hertz  1 phase

Two Stage Oil Pump 65A44

ter Kit

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.

Catalog no. 35K01 35K06

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)

Tons 2 to 3 3 to 5

kW 7.0 to 10.6 10.6 to 17.6

 Optional Accessories (Must Be Ordered Extra) 

.65 (2.5)  8 0 (105 input) solid

.75 (2.8 )  80 (120 input) solid

.85(3.2) 8 0(140 input) solid

1.00 (3.8)  80 (154 input) solid

Page 2

SPECIFICATIONS − OF23

Blower wheel nominal

External Static

External Static

External Static

Model Number

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)

Nozzle Ratinggph (L/hr) and spray angle

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

diameter x width

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

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.

in. 10 x 8 12 x 9

mm 254 x 203 305 x 229

in. (1) 18 x 19 x 1 (1) 19 x 21 x 1

mm (1) 457 x 483 x 25 (1) 483 x 533 x 25

OF23Q3105/120

OF23Q3105/120R

82.4% / 81.5%

82.5% / 82.4% R Models

.65 (2.5)  80° (105 input)

.75 (2.8)  80° (120 input)

OF23Q5140/154

OF23Q5140/154R

81.8% / 81.5%

82.0% / 81.8% R Models

.85 (3.2)  80° (140 input)

1.00 (3.8)  80° (154 input)

BLOWER PERFORMANCE DATA − O23

O23Q270 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Blower Speeds

High Medium Low

O23Q5140/154 BLOWER PERFORMANCE

External Static

Pressure

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.

O23Q3105/120 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Blower Speeds

High Medium Low

Air Volume at Various Blower Speeds

High Medium Low

Page 3

BLOWER PERFORMANCE DATA − OHR23

External Static

External Static

External Static

External Static

External Static

External Static

OHR23Q3105/120 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Speeds

High Medium Low

BLOWER PERFORMANCE DATA − OF23

FRONT FLUE MODELS

OF23Q3105/120 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Blower Speeds

High Medium Low

OHR23Q5140/154 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Speeds

High Medium Low

OF23Q5140/154 BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Blower Speeds

High Medium Low

OF23Q3105/120R BLOWER PERFORMANCE

External Static

Pressure

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.

Air Volume at Various Blower Speeds

High Medium Low

REAR FLUE MODELS

OF23Q5140/154R BLOWER PERFORMANCE

External Static

Pressure

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 4

Air Volume at Various Blower Speeds

High Medium Low

O23 GENERAL PARTS ORIENTATION

HEAT EXCHANGER

CLEANOUT PORT

LIMIT SWITCH

CONTROL BOX

WITH FAN
CONTROL

BECKETT

AFII BURNER

INDOOR BLOWER

VENT OPENING

CLEANOUT PORT

OBSERVATION PORT

COMBUSTION AIR INTAKE

BLOWER MOTOR

CAPACITOR

FIGURE 1

LIMIT SWITCH

BECKETT

AFII BURNER

COMBUSTION

AIR INTAKE

OBSERVATION

PORT

CLEANOUT

OHR23 GENERAL PARTS ORIENTATION

CLEANOUT PORT

HEAT EXCHANGER

PORT

VENT OPENING

CONTROL BOX

WITH FAN

CONTROL

BLOWER MOTOR

INDOOR BLOWER

FIGURE 2

Page 5

OF23 GENERAL PARTS ORIENTATION

CLEANOUT

PORT

LIMIT SWITCH

CONTROL BOX

WITH FAN
CONTROL

BECKETT

AFII BURNER

FRONT VENT

OPENING (OF23)

COMBUSTION

AIR INTAKE

FILTER

INDOOR BLOWER

REAR VENT

OPENING (OF23R)

HEAT EXCHANGER

CLEANOUT PORT

OBSERVATION PORT

FIGURE 3

NEUTRAL

TERMINALS

24VAC OUTPUT

TO BURNER

(HEAT DEMAND)

24VAC IN FROM

PRIMARY LIMIT

24VAC THERMOSTAT

DEMAND OUTPUT

BCC2 / BCC3 BLOWER CONTROL BOARD

120VAC LINE

VOLTAGE IN

THERMOSTAT TERMINAL STRIP TB1

(DETACHABLE ON EARLY −1 AND −2

MODELS ONLY)

COOLING

SPEED TAP

TERMINAL

TRANSFORMER

120VAC

COMMON

FROM TRANSFORMER

CONTINUOUS FAN

TERMINAL

BLOWER TIME

ADJUSTMENT

JUMPER

24VAC INPUT

HEATING SPEED

TAP TERMINAL

ACCESSORY

TERMINAL

To Remove Terminal Strip,

Grasp Ends of Block Between

Thumb and Forefinger. Push

Block Down and Out.

(Jack / Plug 94)

24VAC COMMON

FROM TRANSFORMER

FIGURE 4

Page 6

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).

FANOFF TIME ADJUSTMENT

TIMING

JUMPER

270

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.

Leave jumper off to achieve

210

330 second fan−off timing.

TIMING PINS (seconds)

Fanoff timing is factory

set at 150 seconds

FIGURE 5

Thermostat Connection

Thermostat wires are connected to terminal strip TB1 found
on the BCC2 control board. The terminal strip is c l early
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

Term inal Type Function

W

R

Y

C

G

NEUTRAL 1/4" Spade 120VAC Neutral

L1 1/4" Spade 120VAC Line Voltage In

A 1/4" Spade

XFMRN 1/4" Spade 120VAC Transformer Common

CF 1/4" Spade

H 1/4" Spade

ACC 1/4" Spade

VALVE SENSE 3/16" Spade 24VAC Output To Burner

LIMIT 1/4" Spade

WI 1/4" Spade

24V 1/4" Spade

COM 1/4" Spade

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Heating Demand

24VAC to Thermostat

Cooling Demand

24VAC Common

To Indoor Thermostat

Blower Demand

Switched 120VAC

to Blower Cooling Tap

Switched 120VAC to

Continuous Blower Tap

Switched 120VAC to

Blower Heating Tap

Switched 120VAC to Accessory

(Electronic Air Cleaner,

Humidifier, Etc. 1 amp rating.)

24VAC In From Primary Limit.

Limit Open: Stops Burner and Turns

On Blower

Limit Closed: Allows Burner

Operation

24VAC Thermostat

Demand Output

24VAC Input

From Transformer

24VAC Common

From Transformer

Page 7

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).

FANOFF TIME ADJUSTMENT

TIMING

JUMPER

To adjust fan−off timings:

Remove jumper from BCC2

and select one of the other pin com

binations to achieve the

desired time.

Thermostat Connection

Thermostat wires are connected to terminal strip TB1 found
on the BCC3 control board. The terminal strip is clea r ly
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

Term inal Type Function

W

R

Y

C

G

NEUTRAL 1/4" Spade 120VAC Neutral

L1 1/4" Spade 120VAC Line Voltage In

A 1/4" Spade

XFMRN 1/4" Spade 120VAC Transformer Common

CF 1/4" Spade

H 1/4" Spade

ACC 1/4" Spade

VALVE SENSE 3/16" Spade 24VAC Output To Burner

LIMIT 1/4" Spade

WI 1/4" Spade

24V 1/4" Spade

COM 1/4" Spade

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Detachable
Screw Strip

Heating Demand

24VAC to Thermostat

Cooling Demand

24VAC Common

To Indoor Thermostat

Blower Demand

Switched 120VAC

to Blower Cooling Tap

Switched 120VAC to

Continuous Blower Tap

Switched 120VAC to

Blower Heating Tap

Switched 120VAC to Accessory

(Electronic Air Cleaner,

Humidifier, Etc. 4 amp rating.)

24VAC In From Primary Limit.

Limit Open: Stops Burner and Turns

On Blower

Limit Closed: Allows Burner

Operation

24VAC Thermostat

Demand Output

24VAC Input

From Transformer

24VAC Common

From Transformer

270

150 90

Leave jumper off to achieve

210

330 second fan−off timing.

TIMING PINS (seconds)

Fanoff timing is factory

set at 150 seconds

FIGURE 6

Page 8

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

ST9103A Blower Control Board

120V

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.

Fan Off Delay Switch Settings

ONON ON ON

120 sec90 sec60 sec

Figure 7

150 sec

fan off

delay switches

thermostat

terminal strip

Figure 8

TABLE 3

BLOWER CONTROL A15 TERMINAL DESIGNATIONS

J58 Pin # Function

1 Limit S10

2 L1 120V

3 T1 24V

4 L2 Common

5 Jumpered to Pin 4

6 T2 24V

7 Combustion Air Inducer

120V
8 Jumpered to Pin 7

9 Limit S21 (if used)

Thermostat Connections

G Blower Demand

W Heating Demand

R 24V

Y Cooling Demand

C Common

24 VAC CONNECTIONS

X 24V Transformer

C Common 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 9

RETAINING

CLIP

HEAD

INSULATOR

−1THROUGH −4 UNIT OIL BURNER PARTS ARRANGEMENT

AIR TUBE
SCREWS

HOLE PLUG

ELECTRONIC IGNITION

TRANSFORMER

MAIN

HOUSING

ASSY

ESCUTCHEON

PLATE

CONNECTOR

TUBE

AIR TUBE

ASSY FOR

FB HEADS

FB–HEAD

NOZZLE

ADAPTER

NOZZLE LINE

ELECTRODE HEAD

FLANGE

GASKET

ASSY.

FLANGE

ELECTRODE

ASSY

REAR ACCESS

DOOR GASKET

VIEW PORT

REAR ACCESS

DOOR ASSY

OIL PUMP

SPLINED

NUT

ELECTRONIC IGNITION

TRANSFORMER

BURNER

CONTROL

RESET

BUTTON

AIR

ADJUSTMENT

0

3
4
5

6
7
8

DIAL

COUPLING

COMBUSTION AIR

MOTOR

BLOWER

FIGURE 9

Page 10

WHEEL

INLET

AIR SCOOP

−5 UNIT BURNER PARTS ARRANGEMENT

RETAINING

CLIP

HEAD

INSULATOR

AIR TUBE

ASSY FOR

FB HEADS

1/4" HEX

HEAD SCREW

FB−HEAD

NOZZLE

ADAPTER

ELECTRODE HEAD

FLANGE

GASKET

NOZZLE LINE

ASSY.

ELECTRODE

FLANGE

ASSY

AIR TUBE
SCREWS

ELECTRONIC IGNITION

TRANSFORMER

ESCUTCHEON

CONNECTOR

PEDESTAL

PREMOUNTED PRE−PURGE VALVE

MAIN

HOUSING

ASSY

PLATE

TUBE

REAR ACCESS

DOOR ASSY

SPLINED

NUT

FUEL PUMP

COUPLING

REAR ACCESS

DOOR GASKET

MOTOR

IGNITOR

PRIMARY

CONTROL

BLOWER

WHEEL

4X4

BOX

0

3
4
5

6
7
8

AIR
ADJ.
DIAL

INLET

AIR SCOOP

FIGURE 10

Page 11

TABLE 4

FURNACE / BURNER SPECIFICATIONS

Unit

70 35K74 AFII 85 3.0

105 35K75 AFII 85 4.0

120 35K75 AFII 85 4.5

140 35K76 AFII 150 6.0

154 35K76 AFII 150 6.5

*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.

Lennox Burner

Part Number

Burner

Model

*Initial
Air Dial
Setting

Output

57,000 BTU

(16.7 kW)

84,000 BTU

(24.6 kW)

105,000 BTU

(30.8 kW)

112,000 BTU

(32.8 kW)

125,000 BTU

(36.6 kW)

Nozzle Size

(Delevan)

0.50 X 80A

0.65 X 80B

0.75 X 80B

0.85 X 80B

1.00 X 80B

Pump

Pressure

100 psig

(689.5 kPa)

140 psig

965.3 kPa)

140 psig

965.3 kPa)

140 psig

965.3 kPa)

140 psig

965.3 kPa)

Head

FB0

FB3

FB3

FB6

FB6

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 12