Lennox G17Q2-50 Installation and operation manual

SERVICE G17
UNIT
INFORMATION
Page 1  1992 Lennox Industries Inc.
Corp. 9132-L11 Litho U.S.A.
G17 SERIES UNITS
G17 and G17X series units are mid-e iciency gas urĆ
naces manu actured with Duracurve heat exchangers
ormed o cold rolled steel. G17 units are available in heatĆ
ing capacities o 50,000 to 125,000 Btuh and cooling apĆ
plications up to 6 tons. Re er to Engineering Handbook or
proper sizing.
Units are actory equipped or use with natural gas. A kit is
available or conversion to LPG operation. All G17 and
G17X units use electronic (intermittent pilot) ignition. The
G17X unit meets the Cali ornia Nitrogen Oxides (NOx)
Standards and Cali ornia Seasonal E iciency requireĆ
ments. G17X units use only natural gas. All units use a reĆ
dundant gas valve to assure sa ety shut-o as required by
A.G.A.
A burner box damper assembly located on the intake side o
the burners is eatured on G17 series units. A damper door in
the burner box shuts during unit o cycles to retain heat in the
unit. A damper prove switch ensures that damper is open beĆ
ore gas valve is energized. G17 urnaces use atmospheric
burners without an induced dra t motor. All G17 units use a
dra t hood which allows the use o standard single wall vent
connectors.
All speci ications in this manual are subject to change.
Procedures outlined in this manual are presented as a recĆ
ommendation only and do not supersede or replace local
or state codes. In the absence o local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommended only and do not constitute
code.
Model No.
Input Btuh
Output Btuh
*A.F.U.E.
Flue connection (in. diameter) round
Temperature rise range 〈°F)
High static certi ied by A.G.A.(in wg.)
Gas Piping Size I.P.S. inches - Natural (**LPG)
Blower wheel nominal diameter x width (in.)
Blower motor hp
Number and size o ilters (in.)
Electrical characteristics
**Optional LPG Conversion Kit
G17Q2-50
•G17Q2XĆ50
48,000
38,000
78.0%
4
20-50
.50
1/2 (1/2)
9 x 7
1/4
120 volts Ċ 60 hertz Ċ 1 phase (less than 12 amps) Ċ All Models
1, 1-1/2, 2Tons o cooling that can be added
LB-62384DB (All Models)
75,000
59,000
78.0% 78.0% 78.0% 78.0%
100,000
79,000
100,000
79,000
125,000
98,000
4556
35-65 35-65 25-55 35-65
.50 .50 .75 .50
1/2 (1/2) 1/2 (1/2) 1/2 (1/2) 1/2 (1/2)
10 x 7 10 x 8 12 x 12 12 x 12
1/3 1/2 3/4 3/4
(1) 16 x 25 x 1
2-1/2 or 3 5 or 6 5 or 63, 3-1/2 or 4
•Not available with LPG.
*Annual Fuel Utilization E iciency based on D.O.E. test procedures and according to F.T.C. labeling requirements. Isolated combustion system rating or non-weatherized urnaces.
**LPG kit must be ordered extra or ield changeover.
***G17Q5/6XĆ100 model urnished with 25 x 26 x 1 ilter.
SPECIFICATIONS
Cali ornia Seasonal E iciency - X" Models 72.3% 73.4% 73.7% 72.5% Ć Ć Ć Ć
Continuous Low Speed Blower Kit (Optional)
Bottom Return Air
Filter (Optional)
Return Air Cabinet (Optional)
Part No.
Media Cut Size (in.)
LB-63646A (All Models)
Ć Ć Ć Ć
RA10Ć16Ć49
Ć Ć Ć Ć Ć Ć Ć Ć LBĆ62752DA (NonĆX Models)
25 x 26 x 1
RA10Ć16Ć49 RA10Ć16Ć53 RA10Ć16Ć53RA10Ć16Ć49
Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć
***(1) 20 x 25 x 1
G17Q3 4-100
•G17Q3 4XĆ100
G17Q3-75
•G17Q3XĆ75
G17Q5 6-100
•G17Q5 6XĆ100
G17Q5 6-100
•G17Q5 6XĆ100 G17Q5 6-125

Page 2
FIGURE 1
G17 PARTS IDENTIFICATION
LIMIT
CONTROL
HEAT
EXCHANGER
DRAFT
HOOD
UPPER ACCESS
PANEL
BURNERS
BURNER BOX
bIGNITION
CONTROL
BLOWER
GAS
MANIFOLD
BURNER BOX
DAMPER ASSEMBLY
REAR BAFFLE
TOP STRIP
CABINET
CONTROL BOX
ROLL-OUT
SWITCH
BLOCKED VENT
SHUTOFF
SWITCH
GAS VALVE
PILOT ELECTRODE
ASSEMBLY
LIMIT W RWYTG
90
150
270
210
24V T COM
VALVE
SENSE
G17 CONTROL BOX
BCC2 BLOWER CONTROL CENTER
INB
N1
CABN
XFMRN
N
CAB
L1
A
XFMR
D D H
ACC
FIGURE 2
NEUTRAL
TERMINALS
ACCESSORY
TERMINAL
THERMOSTAT
CONNECTIONS
BLOWER TIME
ADJUSTMENT
JUMPER
HEATING
SPEED TAP
TERMINAL
COOLING
SPEED TAP
TERMINAL
DUMMY
TERMINALS
GROUND
SCREW
DOOR
INTERLOCK
SWITCH
120VAC
24VAC
TRANSFORMER
NOT
USED
TRANSFORMER
LINE
VOLTAGE
DAMPER
MOTOR
TOP VIEW
CF
CONSTANT FAN
TERMINAL
D

Page 3
I-UNIT COMPONENTS (Figures 1)
G17 unit components are shown in igure 1. The blower
controls, gas valve and burners can be accessed by reĆ
moving the upper access panel.
G17 units are actory equipped with bottom return air panels
and bottom side return air panels in place. The panels are deĆ
signed to be ield removed as required or bottom air return or
side air return. All X models are actory equipped with the botĆ
tom return air panel removed.
DANGER
Possibility of exhaust gas recirculation.
X models are factory equipped with bottom return
air panel removed. If opening is not used and if
not properly sealed, exhaust gases can recircuĆ
late through the opening and enter supply air
stream resulting in personal injury or death.
A-Control Box Components(Figure 3)
On G17 series units the unit control box is located in the
blower compartment between the burner box and the blowĆ
er housing. The hinged control box can be lowered or serĆ
vice access by removing two securing screws, one located
on either side. At the top right corner o the control box is the
door interlock switch (S51).
Housed in the control box are the unit trans ormer (T1) and
BCC2-2 blower control (A15).
G17 CONTROL BOX Ć FRONT VIEW
DAMPER
DOOR
BLOWER
BCC2-2
CONTROL
A15
TRANSFORMER
T1
FIGURE 3
DOOR
INTERLOCK
S51
1- Control Transformer (T1)
A trans ormer located inside the control box provides powĆ
er to the low voltage section o the unit. Trans ormers on all
models are rated 30VA with a 120V primary and a 24V secĆ
ondary.
2- BCC2-2 Blower Control (A15)
All G17 units utilize the BCC2-2 blower control. The
BCC2-2 is a printed circuit board which controls the blower
and monitors primary limit and gas valve operation. The
control has a non-adjustable, actory preset on" an timĆ
ing. Fan o " timings are adjustable. The board is divided
into two sections, 120 and 24VAC. Line voltage comes into
the board on the 120VAC side. See igure 2.
CAB" and XFMR " send 120VAC to the damper motor and
trans ormer, respectively. The active cooling and heating
blower speed terminals and three dummy D" terminals are
located on the 120VAC side o the BCC2-2. Also located on
the 120VAC side o the control are neutral terminals and a
terminal or accessories such as an electronic air cleaner.
24VAC comes rom the trans ormer into terminal 24V" on
the 24VAC side o the BCC2-2. Thermostat connections
and sa ety circuit terminals are also located on the 24VAC
side o the control. Fan o " timings may be adjusted by
changing the position o a jumper across terminal pins.
The CF" terminal provides 120VAC power or continuous
an option or other accessories.
Later production units are equipped with a 3A use located
inline between the trans ormer and terminal XFMR on the
blower control. The use provides overcurrent protection
to all components located in the low voltage control circuit.
Fan Timings
DANGER
Shock hazard. Avoid control damage or personĆ
al injury. Make sure to disconnect power before
changing fan off" timings.
FIGURE 4
FANĆOFF TIME ADJUSTMENT
270 210
150 90
To adjust fan-off timings:
Remove jumper from BCC2 and select
one of the other pin combinations to
achieve the desired time.
TIMING
JUMPER
TIMING PINS
(seconds)
Leave jumper off to
achieve
330 second fan-off timing.
NOTEĊIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S 0 to trip reĆ
sulting in frequent cycling of blower. If this occurs, adĆ
just blower to longer time setting.

Page 4
Fan o " timings (time that the blower operates a ter the
heat demand has been satis ied) are determined by the arĆ
rangement o a jumper across pins on the BCC2-2 blower
control board. See igure 2. To adjust an o " timings, gentĆ
ly disconnect jumper and reposition across pins correĆ
sponding with new timing. Fan on" time is actory set at 45
seconds and is not adjustable.
Figure 4 shows the various an o " timings and how jumpĆ
er should be positioned. Unit is shipped with a actory an
o " setting o 90 seconds. Fan o " time will a ect com ort
and e iciency and is adjustable to satis y individual apĆ
plications.
3-Door Interlock Switch (S51)
A door interlock switch rated 16A at 125VAC is located beĆ
hind the blower access panel. The switch is wired in series
with line voltage. When the blower door access panel is reĆ
moved the unit will shut down.
B-Blower Motors and Capacitors
All G17 units use direct drive blower motors. All motors
used are 120V permanent split capacitor motors to ensure
maximum e iciency. See table1 or ratings.
TABLE 1
G17 BLOWER RATINGS 120V 1PH
BLOWER MOTOR HP
Q2
Q3
Q3/4
CAP
1/2
1/3
1/4 5MFD 370V
5MFD 370V
7.5MFD 370V
Q5/6
Q4
Q4/5
1/2 7.5MFD 370V
3/4 40MFD 370V
3/4 40MFD 370V
C-Blocked Vent Shutoff Switch (S62)
The blocked vent shuto switch or spill switch (S62) is loĆ
cated on the right side o the dra t diverter. The switch is a
high temperature N.C. SPST manualĆreset limit conĆ
nected in series with ignition control A3. The switch opens
when excess heat is sensed in the dra t diverter. Excess
heat in the dra t diverter can be caused by a blocked vent
or reversed dra t (outside air coming down the lue). Limits
on early production units open at 300_F+12_F (149° C) on
a temperature rise. Later production units use a limit
which opens at 262_F+12_F (128° C). It cannot be adĆ
justed.
D-Flame Rollout Switch (S47)
Flame rollout switch is a high temperature limit located on
top o the burner box. The limit is a N.C. SPST manualĆreset
limit connected in series with the ignition control A3. When
S47 senses rollout, the ignition control immediately stops
ignition and closes the gas valve. I unit is running and lame
rollout is detected, the gas valve will close and ignition conĆ
trol will be disabled. Rollout can be caused by a reverse
dra t, blocked lue or lack o combustion air. The switch is
actory set and cannot be adjusted. See table 2. The switch
can be manually reset. To manually reset a tripped switch,
push the red reset button located on the control.
TABLE 2
FLAME ROLLOUT SWITCH SETPOINTS
HEATING INPUT KBTUH SETPOINT
50, 75
100, 125
260°F + 12°F
300°F + 12°F
E-Limit Control (S10)
The primary limit (S10) on G17 units is located in the middle o
the heating vestibule wall. When excess heat is sensed in the
heat exchanger, the limit will open and interrupt current to the
gas valve. I the limit is tripped, the BCC2-2 energizes the
blower. The limit automatically resets when unit temperature
returns to normal. Table 3 shows the temperatures at which
the limit trips on a temperature rise and then closes on a temĆ
perature all.
TABLE 3
UNIT MODEL NO. TEMP. RISE TEMP. FALL
G17Q2-50 Series
G17Q3-75 Series
G17Q3/4-100 Series
G17Q5/6-100 Series
G17Q5/6-125 Series
130°F + 5°F 100°F + 10°F
180°F + 5°F 150°F + 8°F
180°F + 5°F 150°F + 10°F
250°F + 5°F 220°F + 8°F
180°F + 5°F 150°F + 10°F
PRIMARY LIMIT TEMPERATURES
INSULATING COVER (s)
FIGURE 5
G17 SERIES UNITS
LIMIT CONTROL FOR
SPADE CONNECTORS
INSULATING COVER
LIMIT
LIMIT
F-Robertshaw Electronic Ignition
The Robertshaw electronic ignition is an intermittent pilot
ignition control module located on the vestibule panel. See
igure 1. When there is a call or heat, the control generates
a spark to ignite the pilot, a ter which the control senses the
lame. I the lame current is too weak (less than 1 microĆ
amp) the control will shutdown and de-energize the gas
valve. Flame current should be between 1 and 5 microĆ
amps. See igure 6.
DANGER
Shock hazard.
Spark related components contain high voltage.
disconnect power before servicing. Control is
not field repairable. If control is inoperable, simĆ
ply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.

Page 5
ROBERTSHAW IGNITION CONTROL
FIGURE 6
MAIN AND PILOT
VALVE COMMON
24VAC OUTPUT
TO MAIN VALVE
24VAC OUTPUT TO PILOT
24VAC INPUT FROM BCC2-2
MICROAMP SIGNAL
FROM FLAME
SENSOR
COMMON
HIGH VOLTAGE
TO SPARK IGNITOR
TRIGN SENSE TH MV MV/PVPV
G-Gas Valve
The G17 uses a gas valve manu actured by Robertshaw or
Honeywell. The valve is internally redundant to assure sa ety
shut-o . I the gas valve must be replaced, the same type
valve must be used.
24VAC terminals and gas control knob are located on top o
the valve. All terminals on the gas valve are connected to
wires rom the electronic ignition control. 24V applied to termiĆ
nal P" energizes the pilot valve. An orange sensing wire rom
terminal V"(marked VALVE SENSE) o the BCC2-2 control
rides piggy back" on the P" terminal connection. 24V applied
to terminal M" energizes the main valve. Terminal C" proĆ
vides 24V common.
Inlet and outlet pressure taps are located on the valve. A
pilot adjusting screw and regulator adjustment screw ( igĆ
ures 7 and 9) are located on the valve. Re er to igure 8 or
exact location o valve eatures.
FIGURE 7
(Robertshaw 7200 gas valve shown)
GAS VALVE
SELECTOR
ARM
IN OFF
POSITION
REGULATOR
COVER SCREW
ADJUSTING
SCREW
SPRING
TYPICAL ACCESS TO REGULATOR
FOR ADJUSTMENT AND L.P. CHANGEOVER
An LPG changeover kit is available rom Lennox. The kit inĆ
cludes main and pilot burner ori ices, burner air adjustment
shutters and a regulating conversion kit.
ON
OFF
FIGURE 8
(Robertshaw 7100 gas valve shown)
GAS VALVE KNOB SHOWN IN
OFF POSITION
PCM
PRESSURE REGULATOR
ADJUSTMENT SCREW
TOP VIEW
FRONT
VIEW
PILOT
ADJUSTMENT SCREW
INLET
PRESSURE
TAP
VALVE
INLET
VALVE
OUTLET
OUTLET
PRESSURE
TAP
TYPICAL GAS VALVE COMPONENTS
FIGURE 9
TYPICAL ACCESS TO REGULATOR
FOR ADJUSTMENT AND L.P. CHANGEOVER
ON
OFF
(Honeywell VR8204 series gas valve shown)
GAS VALVE SHOWN IN OFF POSITION
INLET
PRESSURE
TAP
CAP SCREW
(Black)
ADJUSTING SCREW
(White)
SPRING
Tapered End
Down
(Red)
GAS INLET
PRESSURE
REGULATOR

Page 6
H-Pilot Tube, Ignition Wire and Flame Rod
The pilot tube rom the gas valve and the lame sensor and
ignition wires rom the ignition control enter through the top
o the burner box to the pilot burner assembly.
Figure 10 shows the clearance between top o pilot burner
head and the top o the main burner sur ace.
FLAME SENSOR
WIRE
IGNITION WIRE
PILOT ASSEMBLY LOCATION
5 16"
PILOT
HOOD
FIGURE 10
BURNER
SURFACE
II-BURNER BOX ASSEMBLY
A-Burner Box Damper Door
A damper motor is located on the right side o the burner box.
On the le t side o the burner box, behind a protective plate is
the damper prove switch. Re er to igure 12. The top o the
burner box top is removable or service.
When there is a call or heat, the damper motor is enerĆ
gized and damper door opens as the damper motor axle
begins to rotate.
B-Damper Prove Switch (S64)
A spring, which is held by a notch in the burner box rame,
activates the damper prove switch as the damper door
opens. See igure 11. The damper door axle rotates the
damper door to open position. As the axle turns, the spring
winds backwards to make contact with the damper prove
switch. The protective cover plate is removable (two screws)
and the spring may be unclipped or service to the damper
door or burner box. The spring must be removed in order to
remove the damper door.
A ter service is complete, the spring must rest snugly in
notch or damper prove switch to unction properly. Do not
orce door open, damage to the spring and motor may ocĆ
cur. Take care to open damper door slowly.
DAMPER
PROVE
SWITCH
SPRING SPRING FITS
SNUGLY IN NOTCH
FIGURE 11
AXLE DAMPER
DOOR
DAMPER PROVE SWITCH ASSEMBLY
MANIFOLD
Axle rotates and
opens the door, slot in
le t end o axle pulls
spring back to activate
damper prove switch.
III-PLACEMENT AND INSTALLATION
Make sure unit is installed in accordance with installation
instructions and applicable does.
IV-STARTĆUP
A-Preliminary and Seasonal Checks
1- Inspect electrical wiring, both ield and actory
installed or loose connections. Tighten as required.
2- Check voltage at disconnect switch. Voltage must be
within range listed on the nameplate. I not, consult the
power company and have voltage condition corrected
be ore starting unit.
B-Heating StartĆUp
1- Set thermostat to OFF position. Close manual knob on
gas valve.
2- Wait 5 minutes.
3- Open manual knob on gas valve, replace burner acĆ
cess door and turn on unit electrical supply.
FIGURE 12
DAMPER
MOTOR
GEAR
PATCH PLATE
PATCH
PLATE
SPRING
DAMPER
SWITCH
DAMPER SWITCH
COVER
OBSERVATION PORT
COVER
ROLL-OUT
SWITCH DAMPER BURNER
BOX
DAMPER BOX PARTS ARRANGEMENT
REMOVABLE
BURNER BOX TOP

Page 7
WARNING
Shock and burn hazard.
G17 units are equipped with an intermittent pilot
ignition system. Do not attempt to light manually.
4- Set an switch to AUTO or ON and move system
selection switch to HEAT. Adjust thermostat to a setĆ
ting above room temperature.
5- I unit does not light the irst time, it will attempt one
more ignition be ore locking out.
6- I lockout occurs, repeat steps 1, 2, 3 and 4.
C-Safety or Emergency Shutdown
Turn o unit power. Close manual and main gas valves.
D-Extended Period Shutdown
Turn o thermostat or set to UNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guaranĆ
tee no gas leak into combustion chamber. Turn o power
to unit. All access panels, covers and vent caps must be in
place and secured.
V-HEATING SYSTEM SERVICE CHECKS
A-A.G.A. Applications and Requirements
All units are A.G.A. design certi ied without modi ications.
Re er to the G17 Operation and Installation Instruction
Manual In ormation.
B-Gas Piping
Gas supply piping should not allow more than 0.5"W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection.
Compounds used on gas piping threaded joints should be
resistant to action o lique ied petroleum gases.
C-Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn off
the main shutĆoff valve and disconnect the main
power to unit. These controls should be properly
labeled by the installer.
When pressure testing gas lines, the gas valve must be
disconnected and isolated. Gas valves can be damaged i
subjected to more than 0.5psig (14" W.C.). See igure 13. I
the pressure is equal to or less than 0.5psig (14"W.C.), use
the manual shut-o valve be ore pressure testing to isoĆ
late urnace rom gas supply.
FIGURE 13
MANUAL MAIN SHUT-OFF VALVE
WILL NOT HOLD TEST PRESSURE
IN EXCESS OF 0.5 PSIG (14"W.C.)
GAS VALVE
CAP
GAS PIPING TEST PROCEDURE
FIELD PROVIDED
LINE PRESSURE TAP
When checking piping connections or gas leaks, use preĆ
erred means. Kitchen detergents can cause harm ul corroĆ
sion on various metals used in gas piping. Use o a specialty
Gas Leak Detector is strongly recommended. It is available
through Lennox under part number 31B2001. See Corp.
8411-L10, or urther details.
Do not use matches, candles, lame or any other source o
ignition to check or gas leaks.
D-Testing Gas Supply Pressure
When testing supply gas pressure, connect test gauge to
inlet pressure tap ( ield provided). See igure 13. Check
gas line pressure with unit iring at maximum rate. Low
pressure may result in erratic operation or under ire. High
pressure can result in permanent damage to gas valve or
over ire. For natural gas units, operating pressure at unit
gas connection must be between 4.5" W.C. and 10.5" W.C.
For L.P. gas units, operating pressure at unit gas connecĆ
tion must be between 10.5" W.C. and 13.5" W.C.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply presĆ
sure must all within range listed in previous paragraph.
E-Check Manifold Pressure
A ter line pressure has been checked and adjusted, check
mani old pressure. Checks o mani old pressure are made
as veri ication o proper regulator adjustment. Mani old presĆ
sure or the G17 can be measured at any time the gas valve
is open and is supplying gas to the unit. Normal mani old
pressure or natural gas units is 3.5 in. w.c. For LP/propane
gas the correct mani old pressure is 9.5 in. w.c. See tables 5
and 6 or derated mani old pressure values in high altitude
application or both natural and LP gases. Move pressure
gauge to outlet pressure tap located on unit gas valve
(GV1). See igure 8 or location o pressure tap on gas
valve.

Page 8
IMPORTANT
For safety, connect a shutĆoff valve between the
manometer and the gas tap to permit shut off of
gas pressure to the manometer.
Operating Pressure (outlet) in. W.C.
TABLE 4
GAS VALVE REGULATION
3.5 +0 -0.3Natural
L.P. 9.5 + 0.5
Unit (Fuel)
The gas valve is actory set and should not require adjustĆ
ment. All gas valves are actory regulated. See table 4.
Manifold Adjustment Procedure:
1- Connect a test gauge to outlet pressure tap on gas
valve. Start unit and allow 5 minutes or unit to reach
steady state.
2- While waiting or the unit to stabilize, notice the lame.
Flame should be stable and should not li t rom burner.
Natural gas should burn blue. L.P. gas should burn
mostly blue with some orange streaks.
3- A ter allowing unit to stabilize or 5 minutes, record
mani old pressure and compare to values given in
table 4.
NOTE-Shut unit off and remove manometer as soon as
an accurate reading has been obtained. Take care to
replace pressure tap plug.
F- Proper Gas Flow
To check or proper gas low to combustion chamber, deterĆ
mine Btuh input rom unit rating plate or table or the speci iĆ
cations tables on pages 1 and 2. Divide input rating by Btuh
per cubic oot o available gas. Result is the number o cubic
eet per hour required. Determine low o gas through gas
meter or two minutes. Multiply by 30 to get hourly low o
gas to burner.
NOTE- To obtain accurate reading, shut off all other
gas appliances connected to meter.
G-High Altitude Derate
C.G.A. certi ied units used in high altitude applications are
actory equipped with modi ications that eliminate the
need or mani old pressure adjustment to obtain proper
heat input. Check the unit rating plate to make sure unit is a
high altitude unit.
A.G.A. certi ied units must be derated when installed at an
elevation o 2,000 t. (610 m) or more above sea level.
Tables 5 and 6 show the derated mani old pressure or
high altitude operation with both natural and LP/Propane
gas. Operating this appliance at the mani old pressure
speci ied on the tables will ensure proper unit heat input at
high altitude. Consult your gas utility or the local natural
gas heating value.
2.25" wc
Altitude *Heating Value (Btu Ft#)
(Ft.) 900 950 1000 1050 1100
0
1000
2000
3000
4000
5000
6000
4.32" wc
4.32" wc
3.65" wc
3.35" wc
3.05" wc
2.77" wc
2.50" wc
3.88" wc
3.88" wc
3.30" wc
3.00" wc
2.75" wc
2.48" wc
3.50" wc
3.50" wc
2.95" wc
2.70" wc
2.45" wc
2.25" wc
3.17" wc
3.17" wc
2.70" wc
2.45" wc
2.25" wc
2.89" wc
2.89" wc
2.45" wc
2.25" wc
HIGH ALTITUDE MANIFOLD PRESSURE
DERATE FOR NATURAL GAS UNITS
*Heating value based on atmospheric pressure of 30" mercury and
temperature of 60°F ( 6°C).
TABLE 5
_ _ _ _ _ _
_ _
_ _
_ _
NOTE-This is the only permissible field derate for this
appliance.
ALTITUDE
(Ft.)
MANIFOLD
PRESSURE
HIGH ALTITUDE MANIFOLD PRESSURE
DERATE FOR LP PROPANE GAS UNITS
0 1000 2000 3000 4000 5000 6000
9.5"
w.c.
8.0"
w.c.
7.2"
w.c.
6.5"
w.c.
5.9"
w.c.
5.3"
w.c.
TABLE 6
9.5"
w.c.
IMPORTANT
For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
H-Flame Signal
A 50 microamp DC meter is needed to check the lame sigĆ
nal on the primary ignition control.
Flame (microamp) signal is an electrical current which
passes rom the ignition control through the sensor elecĆ
trode during unit operation. Current passes rom the senĆ
sor through the lame to ground to complete a sa ety cirĆ
cuit.
To Measure Flame Signal:
1- Place meter in series between ignition control and
sensor wire. Connect the positive (+) lead o meter to
the ignition control sensor connection and the negaĆ
tive (-) lead o the meter to the sensor wire. See igure
14.
2- Set thermostat or a heating demand and check lame
signal with unit operating. For G17 series, a reading o
1 to 5 microamps DC should occur.

FIGURE 15
STATIC PRESSURE
TEST
MANOMETER
G17 UNIT
Page 9
FLAME SIGNAL TEST
FIGURE 14
IGNITION
CONĆ
TROL
SENSE"
TERMINAL
SENSOR
WIRE
D.C. MICROAMP
METER
FLAME
SENSOR
Flame signal may rise above 5 microamps or the irst ew
seconds a ter ignition and then level o within the range.
WARNING
Fire and explosion hazard.
These instructions MUST be followed exactly.
Can cause a fire or explosion resulting in property
damage, personal injury or loss of life.
VI-TYPICAL OPERATING CHARACTERISTICS
A-Blower Operation and Adjustment
NOTE- The following is a generalized procedure and
does not apply to all thermostat controls.
1- Blower operation is dependent on thermostat control
system.
2- Generally, blower operation is set at thermostat subĆ
base an switch. With an switch in ON position, blower
operates continuously. With an switch in AUTO posiĆ
tion, blower cycles with demand or runs continuously
while heating or cooling circuit cycles.
3- In all cases, blower and entire unit will be o when the
system switch is in OFF position.
B-Temperature Rise
Temperature rise or G17 units depends on unit input,
blower speed, blower horsepower and static pressure as
marked on the unit rating plate. The blower speed must be
set or unit operation within the range o AIR TEMP. RISE
°F" listed on the unit rating plate.
To Measure Temperature Rise:
1- Place plenum thermometers in the supply and return
air plenums. Locate supply air thermometer in the irst
horizontal run o the warm air plenum where it will not
pick up radiant heat rom the heat exchanger.
2- Set thermostat to highest setting.
3- A ter plenum thermometers have reached their highĆ
est and steadiest readings, subtract the two readings.
The di erence should be in the range listed on the unit
rating plate. I the temperature is too low, decrease
blower speed. I temperature is too high, irst check
the iring rate. Provided the iring rate is acceptable, inĆ
crease blower speed to reduce temperature. To
change blower speed taps see the Blower Speed Taps
section in this manual.
C-External Static Pressure
1- Measure tap locations as shown in igure 15.
2- Punch a 1/4" diameter hole
in supply and return air pleĆ
nums. Insert manometer
hose lush with inside edge
o hole or insulation. Seal
around the hose with perĆ
magum. Connect the zero
end o the manometer to the
discharge (supply) side o the system. On ducted sysĆ
tems, connect the other end o manometer to the reĆ
turn duct as above. For systems with non-ducted reĆ
turns, leave the other end o the manometer open to
the atmosphere.
3- With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blowĆ
er motor speed to deliver the air desired according to
the job requirements.
4- External static pressure drop must not be more than
0.5" W.C.
5- Seal around the hole when the check is complete.
D-Blower Speed Taps
Blower speed tap selection is accomplished by changing the
taps at the blower motor harness connector. Disconnect harĆ
ness connector rom motor to expose speed selectors.
Blower speed selections are listed in table 7.
To Change Blower Speed:
1- Turn o electric power to urnace.
2- Remove upper access panel and ilter access door.
See igure 1.
3- Li t le t side ilter over le t support angle. For easy hanĆ
dling, hold ilter at center bottom.
4- Rotate ilter sideways and pull it through the blower
access panel opening.
5- Pull the second ilter out the same way as the irst.
6- Grasp blower motor harness connector located on
back on motor. Depress lock tab and pull connector
rom motor.
Blower Speed Taps
7- Pull harness connector and wires through blower acĆ
cess panel opening.
8- Select desired speeds or heating and cooling. (Red =
heating, Black = cooling, White = common). See table
7.

CLEANING HEAT
EXCHANGER
FIGURE 18
Connect chain to rod and drop chain
down through top o heat exchanger.
Connect at bottom to another rod. Move
rods up and down, back and orth to
clean heat exchanger.
Page 10
BLOWER SPEED SELECTION
G17Q3/4-100
G17Q2-50*
G17Q3-75
G17Q5/6-100
G17Q5/6-125
UNIT
Factory Connected
Speed Taps Motor Speeds
Available
Cool Heat
23 3
24 4
24 4
34 5
35 5
*DO NOT USE LOW SPEED TAP ON Q2-50
BLOWER SPEED SELECTION
HI LOW
2345
23456
SPEE
D
TAPS
4
5
TABLE 7
◊
◊
◊
MOTOR PLUG SPEED TAP DESIGNATION
234
◊3
9- Depress harness connector tab to release wire termiĆ
nal. Select connector location or new speed (re er to
unit wiring diagram). Insert wire terminal until it is seĆ
curely in place. See igure 16.
10- Replace harness connector to motor .
FIGURE 16
BLOWER SPEED TAP SELECTION
HARNESS
CONNECTOR
MOTOR
DEPRESS TAB TO RELEASE
WIRE TERMINAL. SELECT
CONNECTOR LOCATION
FOR NEW SPEED (REFER TO
UNIT WIRING DIAGRAM). INĆ
SERT WIRE UNTIL IT IS SEĆ
CURELY IN PLACE.
VII-MAINTENANCE
At the beginning o each heating season, the system
should be checked as ollows:
A-Filters and Filter Springs
G17 units use a cleanable hogshair-type ilter. Holding springs
lock ilter in place by securing hook in holes provided in unit.
G17 units are actory shipped or side air return. Bottom ilter
applications or use on G17Q5/6-100 and G17Q5/6-125 reĆ
quire an optional kit available rom Lennox. G17X models are
actory equipped or use with bottom return air only. I side reĆ
turn air is desired, an optional kit is available. See igure 17.
Filters must be cleaned or replaced when dirty to assure
proper unit operation. Replace with same hogshair-type
ilter material cut to speci ic measurements or each unit
as outlined in the speci ication table in this manual.
The actory supplied ilter can be washed with cold water.
Direct water through ilters in the opposite direction o air
low. When dry, replace ilter and reconnect springs. Re er
to igure 17 or spring position.
CRIMP THIS END
OF SPRING
FILTER RETENTION SPRING LOCATION
FOR BOTTOM RETURN AIR OPENING
CRIMP THIS END
OF SPRING
FILTER RETENTION SPRING LOCATION
FOR SIDE RETURN AIR OPENING
FIGURE 17
FINGER
LOOPS
FINGER
LOOP
FINGER
LOOP
CABINET
CABINET
B-Cleaning Heat Exchanger and Burners
NOTE-Use papers or protective covering in front of furĆ
nace while cleaning furnace.
To clean heat exchanger:
1- Turn o both electrical
and gas power supplies
to urnace. Re er to igĆ
ures 1 and 12 during disĆ
assembly and reassembĆ
ly procedures.
2- Remove upper and lower
access panels.
3- Remove screws holding
burner box damper in
place and remove burner
box damper assembly and damper prove switch covĆ
er.
4- Remove screws securing removable burner box covĆ
er and remove burner box cover.
5- Remove lue pipe and dra t hood.

CLEANING TOP
FIGURE 19
CLEANING
PORTS
FIGURE 20
CLEANING INSIDE
FIGURE 21
FIGURE 22
BURNER SLOT ENGAGEMENT
ENGAGE
BURNER
IN SLOT
Page 11
CAUTION
Potential for unit damage.
Use extreme care when opening damper door to
prevent permanent damage to the damper door.
Can cause damage to damper motor resulting in
improper furnace operation.
6- Remove lue restrictor over lue outlet (Ć50 only).
7- Gas mani old, gas valve and burners do not need to be
removed and can be le t in place.
8- Insert a 2 t. steel rod with a 20 in. length o chain atĆ
tached to one end into top opening o heat exchanger.
Re er to igure 18.
9- Shake rod to drop chain through clamshell into burner
cavity in bottom o heat exchanger.
10- Attach bottom o chain to 2 t. (600 mm) rod.
11- Push and pull the rods back and orth and up and down
with a vigorous motion. The chain will dislodge the soot
and scale deposits inside the heat exchanger. Repeat
or each clamshell.
12- With a shop vacuum or rags, clean out soot and scale
deposits rom bottom o heat exchanger.
To clean burners:
1- Disconnect gas piping.
2- Remove screws
holding gas manĆ
i old in place and
pull burners rom
heat exchanger.
3- Clean top o burnĆ
er ports with a wire
brush. See igure 19.
4- Clean burner ports
by inserting a cleanĆ
ing tool (made rom
a piece o sheet
metal cut to it the
burner ports) and
work in and out o
each port. See igure 20.
5- Clean inside o
each burner
with a bottle
cleaning
brush. See igĆ
ure 21.
6- Replace burners making sure to ully engage in rear
receiving slot in heat exchanger. See igure 22. ReseĆ
cure gas mani old and supply piping.
7- Resecure damper
assembly, damper
prove switch cover
and burner box
top. Care ully open
damper by hand to
ensure that the
damper spring
closes damper
correctly and that
the damper prove
switch is engaged
when damper is open.
8- Install lue restrictor (Ć50 models only).
9- Be ore replacing dra t hood, lue pipe and access
panels, inspect dra t hood gasket. Replace gasket i
necessary.
10- Care ully check all piping connections ( actory and
ield) or gas leaks. Use a leak detecting solution or othĆ
er pre erred means.
11- Turn on gas and electrical supply.
CAUTION
Potential for gas leaks, fire or explosion.
Some soaps used for leak detection are corrosive
to certain metals. Carefully clean piping thorĆ
oughly after leak detection has been completed.
Can cause damage to piping resulting in gas
leaks, fire or explosion.
C-Supply Air Blower
1- Check and clean blower wheel.
2- Motors used on the Lennox G17 series units are permaĆ
nently lubricated and need no urther lubrication.
A - Flue and Chimney
Flue must con orm to all AGA/GAMA venting requireĆ
ments or Category I Central Furnaces." Flue pipe deteriĆ
orates rom the inside out and must be disconnected in orĆ
der to check thoroughly. Check lue pipe, chimney and all
connections or tightness and to make sure there is no
blockage or leaks.
B - Electrical
1 - Check all wiring or loose connections.
2 - Check or correct voltage.
3 - Check amp-draw on blower motor.

Page 12
2
1
3
5
6
7
8
9
10
7
5
9
OPERATION SEQUENCE-
G17 SERIES
1- When disconnect is closed, 120V eeds to line voltage
side o the blower control (A15). Door interlock switch
(S51) must be closed or A15 to receive voltage.
2- A15 supplies 120V to trans ormer (T1).
3- T1 supplies 24VAC to terminal 24" on A15. In turn,
terminal R" o A15 supplies 24VAC to terminal RC"
o the thermostat (S1).
4- When there is a call or heat, W1 o the thermostat enĆ
ergizes W o the blower control with 24VAC.
5- CAB o the blower control energizes the damper motor
(B17) which opens the damper door. When door is in
ull open position, damper prove switch (S64) closes.
6- When S64 closes, assuming the lame rollout switch
(S47) and blocked vent shuto switch (S62) are
closed, 24VAC is supplied to the TH" terminal o the
electronic control (A3).
7- Through the electronic control, the pilot valve P" o
the gas valve opens. The spark electrode ignites the
pilot and the lame sensor senses the pilot.
8- When lame is sensed the main gas valve opens and
supplies the burners with gas.
9- Terminal V" (Valve Sense) o the blower control
senses that the gas valve is energized and initiates a
45 second time delay. At the end o the 45 seconds the
blower, (B3) is energized.
10- When the heat demand has been satis ied, W1 o the
thermostat de-energizes the gas valve and damper
spring closes the damper door. As the damper door
closes, the damper prove switch opens. The blower
runs or a designated period (90-330 sec.) as set by
jumper on blower control.

Page 13
CHECK:
1-UNIT POWER
2-INTERLOCK SWITCH
3-TRANSFORMER
4-LIMIT SWITCH
START
IS
24VAC ACROSS
R & T?
YES
JUMPER ACROSS
SCREWS R & G
YES
DOES UNIT
OPERATE?
NO
NO
IS
BLOWER
RUNNING ON HIGH
SPEED?
NO IS
120VAC ACROSS
N1 & A?
REPLACE
BCC2-1
NO
YES
YES
CHECK BLOWER
WIRING AND
BLOWER
IS
120VAC ACROSS
N1 & ACC?
NO
REPLACE
BCC2-1
YES
JUMPER ACROSS
R &W
(REMOVE R & G JUMPER)
IS
DAMPER MOTOR
ON?
NO
REPLACE
BCC2-1
NO IS
120VAC ACROSS
N1 & CAB?
CHECK
DAMPER MOTOR
WIRING AND
DAMPER MOTOR
YES
YES ARE
BURNERS
LIT?
NO
CHECK:
1-DAMPER MOTOR
2-IGNITION CONTROL
3-GAS VALVE
4-IGNITOR
5-LIMIT SWITCHES
6-PROVE SWITCH
YES
IS BLOWER
RUNNING ON LOW
SPEED, 45 SEC.
AFTER FURNACE
LIGHTS?
NO IS
120VAC ACROSS
N1 & H?
YES
IS
24VAC ACROSS
T & V?
REPLACE
BCC2-1
NO
NO
CHECK
WIRING
YES
IS
120VAC ACROSS
N1 & ACC?
YES
REMOVE
R & W JUMPER
AFTER
THE SELECTED
TIME, DOES THE
BLOWER TURN
OFF?
YES NO
YES
REPLACE
BCC2-1
END OF TEST
BCC2-1
TROUBLESHOOTING
FLOWCHART
NO
REPLACE
BCC2-1 CHECK BLOWER
WIRING AND
BLOWER
FIGURE 15