SERVICE
UNIT
INFORMATION
G17
Corp. 9132-L11
G17 SERIES UNITS
G17 and G17X series units are mid-efficiency gas furĆ
naces manufactured with Duracurve heat exchangers
formed of cold rolled steel. G17 units are available in heatĆ
ing capacities of 50,000 to 125,000 Btuh and cooling apĆ
plications up to 6 tons. Refer to Engineering Handbook for
proper sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. All G17 and
G17X units use electronic (intermittent pilot) ignition. The
G17X unit meets the California Nitrogen Oxides (NO
x
Standards and California Seasonal Efficiency requireĆ
ments. G17X units use only natural gas. All units use a reĆ
dundant gas valve to assure safety shut-off as required by
A.G.A.
A burner box damper assembly located on the intake side of
the burners is featured on G17 series units. A damper door in
the burner box shuts during unit off cycles to retain heat in the
unit. A damper prove switch ensures that damper is open beĆ
fore gas valve is energized. G17 furnaces use atmospheric
burners without an induced draft motor. All G17 units use a
draft hood which allows the use of standard single wall vent
connectors.
SPECIFICATIONS
Model No.
Input Btuh
Output Btuh
*A.F.U.E.
California Seasonal Efficiency - X" Models
Flue connection (in. diameter) round
Temperature rise range
High static certified 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 of filters (in.)
**Optional LPG Conversion Kit
Electrical characteristics
Continuous Low Speed Blower Kit (Optional)
Bottom Return Air
Filter (Optional)
Return Air Cabinet (Optional)
•Not available with LPG.
*Annual Fuel Utilization Efficiency based on D.O.E. test procedures and according to F.T.C. labeling requirements. Isolated combustion system rating for non-weatherized furnaces.
**LPG kit must be ordered extra for field changeover.
***G17Q5/6XĆ100 model furnished with 25 x 26 x 1 filter.
〈°F)
Part No.
Media Cut Size (in.)
G17Q2-50
•G17Q2XĆ50
48,000
38,000
78.0%
72.3% 73.4% 73.7% 72.5% Ć Ć Ć Ć
4
20-50
.50
1/2 (1/2)
9 x 7
1/4
1, 1-1/2, 2Tons of cooling that can be added
120 volts Ċ 60 hertz Ċ 1 phase (less than 12 amps) Ċ All Models
Ć Ć Ć Ć
Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć
RA10Ć16Ć49
All specifications 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 of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommended only and do not constitute
code.
)
G17Q3-75
•G17Q3XĆ75
75,000
59,000
78.0% 78.0% 78.0% 78.0%
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
2-1/2 or 3 5 or 6 5 or 63, 3-1/2 or 4
(1) 16 x 25 x 1
Ć Ć Ć Ć Ć Ć Ć Ć LBĆ62752DA (NonĆX Models)
RA10Ć16Ć49 RA10Ć16Ć53 RA10Ć16Ć53RA10Ć16Ć49
G17Q3/4-100
•G17Q3/4XĆ100
100,000
79,000
LB-62384DB (All Models)
LB-63646A (All Models)
G17Q5/6-100
G17Q5/6-100
•G17Q5/6XĆ100
•G17Q5/6XĆ100
100,000
79,000
***(1) 20 x 25 x 1
25 x 26 x 1
G17Q5/6-125
Litho U.S.A.
125,000
98,000
Page 1
1992 Lennox Industries Inc.
G17 PARTS IDENTIFICATION
UPPER ACCESS
PANEL
MANIFOLD
GAS VALVE
BURNER BOX
DAMPER ASSEMBLY
TOP STRIP
GAS
DRAFT
HOOD
bIGNITION
CONTROL
ROLL-OUT
SWITCH
PILOT/ELECTRODE
ASSEMBLY
BLOCKED VENT
SHUTOFF
SWITCH
BURNER BOX
BURNERS
REAR BAFFLE
HEAT
EXCHANGER
LIMIT
CONTROL
BLOWER
CABINET
CONTROL BOX
G17 CONTROL BOX
NEUTRAL
TERMINALS
INB
DAMPER
MOTOR
N1
CABN
N
XFMRN
SPEED TAP
LINE
VOLTAGE
CAB
COOLING
TERMINAL
A
L1
120VAC
CONSTANT FAN
XFMR
TERMINAL
NOT
USED
D
TRANSFORMER
BCC2 BLOWER CONTROL CENTER
24VAC
VALV E
SENSE
LIMIT W RWYTG
FIGURE 1
TOP VIEW
TERMINALS
SPEED TAP
TERMINAL
DDH
CF
270
150
210
90
24V T COM
DUMMY
HEATING
ACC
ACCESSORY
TERMINAL
BLOWER TIME
ADJUSTMENT
TRANSFORMER
GROUND
SCREW
JUMPER
DOOR
INTERLOCK
SWITCH
THERMOSTAT
CONNECTIONS
FIGURE 2
Page 2
I-UNIT COMPONENTS (Figures 1)
G17 unit components are shown in figure 1. The blower
controls, gas valve and burners can be accessed by reĆ
moving the upper access panel.
G17 units are factory equipped with bottom return air panels
and bottom side return air panels in place. The panels are deĆ
signed to be field removed as required for bottom air return or
side air return. All X models are factory 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 for serĆ
vice access by removing two securing screws, one located
on either side. At the top right corner of the control box is the
door interlock switch (S51).
Housed in the control box are the unit transformer (T1) and
BCC2-2 blower control (A15).
G17 CONTROL BOX Ć FRONT VIEW
DOOR
DAMPER
DOOR
INTERLOCK
S51
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, factory preset on" fan timĆ
ing. Fan off" timings are adjustable. The board is divided
into two sections, 120 and 24VAC. Line voltage comes into
the board on the 120VAC side. See figure 2.
CAB" and XFMR " send 120VAC to the damper motor and
transformer, respectively. The active cooling and heating
blower speed terminals and three dummy D" terminals are
located on the 120VAC side of the BCC2-2. Also located on
the 120VAC side of the control are neutral terminals and a
terminal for accessories such as an electronic air cleaner.
24VAC comes from the transformer into terminal 24V" on
the 24VAC side of the BCC2-2. Thermostat connections
and safety circuit terminals are also located on the 24VAC
side of the control. Fan off" timings may be adjusted by
changing the position of a jumper across terminal pins.
The CF" terminal provides 120VAC power for continuous
fan option or other accessories.
Later production units are equipped with a 3A fuse located
inline between the transformer and terminal XFMR on the
blower control. The fuse 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.
FANĆOFF TIME ADJUSTMENT
TIMING
JUMPER
To adjust fan-off timings:
Remove jumper from BCC2 and select
one of the other pin combinations to
achieve the desired time.
BCC2-2
CONTROL
A15
BLOWER
FIGURE 3
1- Control Transformer (T1)
A transformer located inside the control box provides powĆ
er to the low voltage section of the unit. Transformers 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
TRANSFORMER
T1
Page 3
TIMING PINS
(seconds)
270
210
Leave jumper off to
achieve
330 second fan-off timing.
150 90
FIGURE 4
NOTEĊIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 to trip reĆ
sulting in frequent cycling of blower. If this occurs, adĆ
just blower to longer time setting.
Fan off" timings (time that the blower operates after the
heat demand has been satisfied) are determined by the arĆ
rangement of a jumper across pins on the BCC2-2 blower
control board. See figure 2. To adjust fan off " timings, gentĆ
ly disconnect jumper and reposition across pins correĆ
sponding with new timing. Fan on" time is factory set at 45
seconds and is not adjustable.
Figure 4 shows the various fan off" timings and how jumpĆ
er should be positioned. Unit is shipped with a factory fan
off" setting of 90 seconds. Fan off" time will affect comfort
and efficiency and is adjustable to satisfy 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 efficiency. See table1 for ratings.
TABLE 1
BLOWER MOTOR HP
Q2
Q3
Q3/4
Q4
Q4/5
Q5/6
G17 BLOWER RATINGS 120V 1PH
1/4 5MFD 370V
1/3
1/2
1/2 7.5MFD 370V
3/4 40MFD 370V
3/4 40MFD 370V
5MFD 370V
7.5MFD 370V
CAP
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
50, 75
100, 125
SETPOINT
260°F + 12°F
°F + 12°F
300
E-Limit Control (S10)
The primary limit (S10) on G17 units is located in the middle of
the heating vestibule wall. When excess heat is sensed in the
heat exchanger, the limit will open and interrupt current to the
gas valve. If 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 fall.
TABLE 3
PRIMARY LIMIT TEMPERATURES
UNIT MODEL NO. TEMP. RISE TEMP. FALL
130
G17Q2-50 Series
G17Q3-75 Series
G17Q3/4-100 Series
G17Q5/6-100 Series
G17Q5/6-125 Series
INSULATING COVER
SPADE CONNECTORS
°F + 5°F 100°F + 10°F
°F + 5°F 150°F + 8°F
180
°F + 5°F 150°F + 10°F
180
°F + 5°F 220°F + 8°F
250
180
°F + 5°F 150°F + 10°F
LIMIT CONTROL FOR
G17 SERIES UNITS
LIMIT
C-Blocked Vent Shutoff Switch (S62)
The blocked vent shutoff switch or spill switch (S62) is loĆ
cated on the right side of the draft 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 draft diverter. Excess
heat in the draft diverter can be caused by a blocked vent
or reversed draft (outside air coming down the flue). 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 of 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. If unit is running and flame
rollout is detected, the gas valve will close and ignition conĆ
trol will be disabled. Rollout can be caused by a reverse
draft, blocked flue or lack of combustion air. The switch is
factory set and cannot be adjusted. See table 2. The switch
LIMIT
INSULATING COVER (s)
FIGURE 5
F-Robertshaw Electronic Ignition
The Robertshaw electronic ignition is an intermittent pilot
ignition control module located on the vestibule panel. See
figure 1. When there is a call for heat, the control generates
a spark to ignite the pilot, after which the control senses the
flame. If the flame 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 figure 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 4
ROBERTSHAW IGNITION CONTROL
MAIN AND PILOT
VALVE COMMON
24VAC OUTPUT
TO MAIN VALVE
24VAC OUTPUT TO PILOT
24VAC INPUT FROM BCC2-2
MICROAMP SIGNAL
FROM FLAME
SENSOR
TRIGN SENSE TH MV MV/PVPV
COMMON
HIGH VOLTAGE
TO SPARK IGNITOR
FIGURE 6
G-Gas Valve
The G17 uses a gas valve manufactured by Robertshaw or
Honeywell. The valve is internally redundant to assure safety
shut-off. If the gas valve must be replaced, the same type
valve must be used.
24VAC terminals and gas control knob are located on top of
the valve. All terminals on the gas valve are connected to
wires from the electronic ignition control. 24V applied to termiĆ
nal P" energizes the pilot valve. An orange sensing wire from
terminal V"(marked VALVE SENSE) of 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 (figĆ
ures 7 and 9) are located on the valve. Refer to figure 8 for
exact location of valve features.
TYPICAL GAS VALVE COMPONENTS
(Robertshaw 7100 gas valve shown)
ON
OFF
GAS VALVE KNOB SHOWN IN
OFF POSITION
INLET
PRESSURE
TAP
VALV E
INLET
PRESSURE
OUTLET
PCM
TOP VIEW
TAP
FRONT
VIEW
ADJUSTMENT SCREW
PILOT
PRESSURE REGULATOR
ADJUSTMENT SCREW
FIGURE 8
TYPICAL ACCESS TO REGULATOR
FOR ADJUSTMENT AND L.P. CHANGEOVER
(Honeywell VR8204 series gas valve shown)
ON
VALV E
OUTLET
TYPICAL ACCESS TO REGULATOR
FOR ADJUSTMENT AND L.P. CHANGEOVER
(Robertshaw 7200 gas valve shown)
REGULATOR
COVER SCREW
GAS VALVE
SELECTOR
ARM
IN OFF
POSITION
ADJUSTING
SCREW
SPRING
FIGURE 7
An LPG changeover kit is available from Lennox. The kit inĆ
cludes main and pilot burner orifices, burner air adjustment
shutters and a regulating conversion kit.
Page 5
GAS VALVE SHOWN IN OFF POSITION
PRESSURE
REGULATOR
ADJUSTING SCREW
(White)
OFF
CAP SCREW
(Black)
SPRING
Tapered End
Down
(Red)
INLET
PRESSURE
TAP
GAS INLET
FIGURE 9
H-Pilot Tube, Ignition Wire and Flame Rod
The pilot tube from the gas valve and the flame sensor and
ignition wires from the ignition control enter through the top
of the burner box to the pilot burner assembly.
Figure 10 shows the clearance between top of pilot burner
head and the top of the main burner surface.
force door open, damage to the spring and motor may ocĆ
cur. Take care to open damper door slowly.
DAMPER PROVE SWITCH ASSEMBLY
PILOT ASSEMBLY LOCATION
IGNITION WIRE
BURNER
SURFACE
PILOT
HOOD
5/16"
FLAME SENSOR
WIRE
FIGURE 10
II-BURNER BOX ASSEMBLY
A-Burner Box / Damper Door
A damper motor is located on the right side of the burner box.
On the left side of the burner box, behind a protective plate is
the damper prove switch. Refer to figure 12. The top of the
burner box top is removable for service.
When there is a call for 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 frame,
activates the damper prove switch as the damper door
opens. See figure 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 for service to the damper
door or burner box. The spring must be removed in order to
remove the damper door.
After service is complete, the spring must rest snugly in
notch for damper prove switch to function properly. Do not
MANIFOLD
DAMPER
PROVE
SWITCH
Axle rotates and
opens the door, slot in
left end of axle pulls
spring back to activate
damper prove switch.
AXLE
SPRING
DAMPER
DOOR
SPRING FITS
SNUGLY IN NOTCH
FIGURE 11
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 field and factory
installed for loose connections. Tighten as required.
2- Check voltage at disconnect switch. Voltage must be
within range listed on the nameplate. If not, consult the
power company and have voltage condition corrected
before 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.
OBSERVATION PORT
COVER
ROLL-OUT
SWITCH
REMOVABLE
BURNER BOX TOP
DAMPER SWITCH
COVER
DAMPER BOX PARTS ARRANGEMENT
DAMPER
SWITCH
SPRING
DAMPER
PATCH PLATE
PATCH
PLATE
FIGURE 12
Page 6
BURNER
BOX
DAMPER
MOTOR/
GEAR
WARNING
Shock and burn hazard.
G17 units are equipped with an intermittent pilot
ignition system. Do not attempt to light manually.
4- Set fan switch to AUTO or ON and move system
selection switch to HEAT. Adjust thermostat to a setĆ
ting above room temperature.
5- If unit does not light the first time, it will attempt one
more ignition before locking out.
6- If lockout occurs, repeat steps 1, 2, 3 and 4.
C-Safety or Emergency Shutdown
Turn off unit power. Close manual and main gas valves.
D-Extended Period Shutdown
Turn off 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 off 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 certified without modifications.
Refer to the G17 Operation and Installation Instruction
Manual Information.
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 of liquefied 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 if
subjected to more than 0.5psig (14" W.C.). See figure 13. If
the pressure is equal to or less than 0.5psig (14"W.C.), use
the manual shut-off valve before pressure testing to isoĆ
late furnace from gas supply.
GAS PIPING TEST PROCEDURE
MANUAL MAIN SHUT-OFF VALVE
WILL NOT HOLD TEST PRESSURE
IN EXCESS OF 0.5 PSIG (14"W.C.)
GAS VALVE
LINE PRESSURE TAP
FIGURE 13
When checking piping connections for gas leaks, use preĆ
ferred means. Kitchen detergents can cause harmful corroĆ
sion on various metals used in gas piping. Use of a specialty
Gas Leak Detector is strongly recommended. It is available
through Lennox under part number 31B2001. See Corp.
8411-L10, for further details.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
CAP
FIELD PROVIDED
D-Testing Gas Supply Pressure
When testing supply gas pressure, connect test gauge to
inlet pressure tap (field provided). See figure 13. Check
gas line pressure with unit firing at maximum rate. Low
pressure may result in erratic operation or underfire. High
pressure can result in permanent damage to gas valve or
overfire. 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 fall within range listed in previous paragraph.
E-Check Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Checks of manifold pressure are made
as verification of proper regulator adjustment. Manifold presĆ
sure for the G17 can be measured at any time the gas valve
is open and is supplying gas to the unit. Normal manifold
pressure for natural gas units is 3.5 in. w.c. For LP/propane
gas the correct manifold pressure is 9.5 in. w.c. See tables 5
and 6 for derated manifold pressure values in high altitude
application for both natural and LP gases. Move pressure
gauge to outlet pressure tap located on unit gas valve
(GV1). See figure 8 for location of pressure tap on gas
valve.
Page 7
IMPORTANT
For safety, connect a shutĆoff valve between the
manometer and the gas tap to permit shut off of
gas pressure to the manometer.
Unit (Fuel)
GAS VALVE REGULATION
L.P. 9.5 +
The gas valve is factory set and should not require adjustĆ
ment. All gas valves are factory 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 for unit to reach
steady state.
2- While waiting for the unit to stabilize, notice the flame.
Flame should be stable and should not lift from burner.
Natural gas should burn blue. L.P. gas should burn
mostly blue with some orange streaks.
3- After allowing unit to stabilize for 5 minutes, record
manifold 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 for proper gas flow to combustion chamber, deterĆ
mine Btuh input from unit rating plate or table or the specifiĆ
cations tables on pages 1 and 2. Divide input rating by Btuh
per cubic foot of available gas. Result is the number of cubic
feet per hour required. Determine flow of gas through gas
meter for two minutes. Multiply by 30 to get hourly flow of
gas to burner.
NOTE- To obtain accurate reading, shut off all other
gas appliances connected to meter.
G-High Altitude Derate
C.G.A. certified units used in high altitude applications are
factory equipped with modifications that eliminate the
need for manifold pressure adjustment to obtain proper
heat input. Check the unit rating plate to make sure unit is a
high altitude unit.
A.G.A. certified units must be derated when installed at an
elevation of 2,000 ft. (610 m) or more above sea level.
Tables 5 and 6 show the derated manifold pressure for
high altitude operation with both natural and LP/Propane
TABLE 4
Operating Pressure (outlet) in. W.C.
3.5 +0 -0.3Natural
0.5
gas. Operating this appliance at the manifold pressure
specified on the tables will ensure proper unit heat input at
high altitude. Consult your gas utility for the local natural
gas heating value.
TABLE 5
HIGH ALTITUDE MANIFOLD PRESSURE
DERATE FOR NATURAL GAS UNITS
Altitude
(Ft.)
0
1000
2000
3000
4000
5000
6000
*Heating value based on atmospheric pressure of 30" mercury and
temperature of 60
900 950 1000 1050 1100
4.32" wc
4.32" wc
3.65" wc
3.35" wc
3.05" wc
2.77" wc
2.50" wc
*Heating Value (Btu/Ft#)
3.88" wc
3.88" wc
3.30" wc
3.00" wc
2.75" wc
2.48" wc
2.25" wc
°F (16°C).
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
_ _
_ _
NOTE-This is the only permissible field derate for this
appliance.
TABLE 6
HIGH ALTITUDE MANIFOLD PRESSURE
DERATE FOR LP/PROPANE GAS UNITS
ALTITUDE
(Ft.)
MANIFOLD
PRESSURE
0 1000 2000 3000 4000 5000 6000
9.5"
9.5"
w.c.
w.c.
8.0"
w.c.
7.2"
w.c.
6.5"
w.c.
5.9"
w.c.
5.3"
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 flame sigĆ
nal on the primary ignition control.
Flame (microamp) signal is an electrical current which
passes from the ignition control through the sensor elecĆ
trode during unit operation. Current passes from the senĆ
sor through the flame to ground to complete a safety cirĆ
cuit.
To Measure Flame Signal:
1- Place meter in series between ignition control and
sensor wire. Connect the positive (+) lead of meter to
the ignition control sensor connection and the negaĆ
tive (-) lead of the meter to the sensor wire. See figure
14.
2- Set thermostat for a heating demand and check flame
signal with unit operating. For G17 series, a reading of
1 to 5 microamps DC should occur.
Page 8
D.C. MICROAMP
METER
FLAME
SENSOR
IGNITION
CONĆ
TROL
SENSOR
WIRE
SENSE"
TERMINAL
FIGURE 14
Flame signal may rise above 5 microamps for the first few
seconds after ignition and then level off 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 fan switch. With fan switch in ON position, blower
operates continuously. With fan 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 off when the
system switch is in OFF position.
B-Temperature Rise
Temperature rise for 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 for unit operation within the range of 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 first
horizontal run of the warm air plenum where it will not
pick up radiant heat from the heat exchanger.
2- Set thermostat to highest setting.
3- After plenum thermometers have reached their highĆ
est and steadiest readings, subtract the two readings.
The difference should be in the range listed on the unit
rating plate. If the temperature is too low, decrease
blower speed. If temperature is too high, first check
the firing rate. Provided the firing rate is acceptable, inĆ
FLAME SIGNAL TEST
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 figure 15.
2- Punch a 1/4" diameter hole
in supply and return air pleĆ
nums. Insert manometer
hose flush with inside edge
STATIC PRESSURE
TEST
MANOMETER
of hole or insulation. Seal
around the hose with perĆ
magum. Connect the zero
end of the manometer to the
G17 UNIT
FIGURE 15
discharge (supply) side of the system. On ducted sysĆ
tems, connect the other end of manometer to the reĆ
turn duct as above. For systems with non-ducted reĆ
turns, leave the other end of 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 from motor to expose speed selectors.
Blower speed selections are listed in table 7.
To Change Blower Speed:
1- Turn off electric power to furnace.
2- Remove upper access panel and filter access door.
See figure 1.
3- Lift left side filter over left support angle. For easy hanĆ
dling, hold filter at center bottom.
4- Rotate filter sideways and pull it through the blower
access panel opening.
5- Pull the second filter out the same way as the first.
6- Grasp blower motor harness connector located on
back on motor. Depress lock tab and pull connector
from motor.
Blower Speed Taps
7- Pull harness connector and wires through blower acĆ
cess panel opening.
8- Select desired speeds for heating and cooling. (Red =
heating, Black = cooling, White = common). See table
7.
Page 9
TABLE 7
BLOWER SPEED SELECTION
UNIT
G17Q2-50*
G17Q3-75
G17Q3/4-100
G17Q5/6-100
G17Q5/6-125
SPEE
D
TAPS
◊
*DO NOT USE LOW SPEED TAP ON Q2-50
MOTOR PLUG SPEED TAP DESIGNATION
◊
Factory Connected
Speed Taps
Cool Heat
23 3
24 4
24 4
35 5
34 5
BLOWER SPEED SELECTION
HI LOW
◊
234
◊
2345
23456
Motor Speeds
Available
3
4
5
9- Depress harness connector tab to release wire termiĆ
nal. Select connector location for new speed (refer to
unit wiring diagram). Insert wire terminal until it is seĆ
curely in place. See figure 16.
10- Replace harness connector to motor .
BLOWER SPEED TAP SELECTION
HARNESS
CONNECTOR
Filters must be cleaned or replaced when dirty to assure
proper unit operation. Replace with same hogshair-type
filter material cut to specific measurements for each unit
as outlined in the specification table in this manual.
The factory supplied filter can be washed with cold water.
Direct water through filters in the opposite direction of air
flow. When dry, replace filter and reconnect springs. Refer
to figure 17 for spring position.
FILTER RETENTION SPRING LOCATION
FOR BOTTOM RETURN AIR OPENING
CRIMP THIS END
OF SPRING
FINGER
LOOPS
CABINET
FILTER RETENTION SPRING LOCATION
FOR SIDE RETURN AIR OPENING
FINGER
LOOP
CRIMP THIS END
OF SPRING
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.
MOTOR
FIGURE 16
VII-MAINTENANCE
At the beginning of each heating season, the system
should be checked as follows:
A-Filters and Filter Springs
G17 units use a cleanable hogshair-type filter. Holding springs
lock filter in place by securing hook in holes provided in unit.
G17 units are factory shipped for side air return. Bottom filter
applications for use on G17Q5/6-100 and G17Q5/6-125 reĆ
quire an optional kit available from Lennox. G17X models are
factory equipped for use with bottom return air only. If side reĆ
turn air is desired, an optional kit is available. See figure 17.
FINGER
LOOP
CABINET
FIGURE 17
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 off both electrical
and gas power supplies
to furnace. Refer to figĆ
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 flue pipe and draft hood.
CLEANING HEAT
EXCHANGER
Connect chain to rod and drop chain
down through top of heat exchanger.
Connect at bottom to another rod. Move
rods up and down, back and forth to
clean heat exchanger.
FIGURE 18
Page 10
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 flue restrictor over flue outlet (Ć50 only).
7- Gas manifold, gas valve and burners do not need to be
removed and can be left in place.
8- Insert a 2 ft. steel rod with a 20 in. length of chain atĆ
tached to one end into top opening of heat exchanger.
Refer to figure 18.
9- Shake rod to drop chain through clamshell into burner
cavity in bottom of heat exchanger.
10- Attach bottom of chain to 2 ft. (600 mm) rod.
11- Push and pull the rods back and forth and up and down
with a vigorous motion. The chain will dislodge the soot
and scale deposits inside the heat exchanger. Repeat
for each clamshell.
12- With a shop vacuum or rags, clean out soot and scale
deposits from bottom of heat exchanger.
To clean burners:
1- Disconnect gas piping.
2- Remove screws
holding gas manĆ
ifold in place and
pull burners from
heat exchanger.
3- Clean top of burnĆ
er ports with a wire
brush. See figure 19.
4- Clean burner ports
by inserting a cleanĆ
ing tool (made from
a piece of sheet
metal cut to fit the
burner ports) and
work in and out of
each port. See figure 20.
5- Clean inside of
each burner
with a bottle
cleaning
brush. See figĆ
ure 21.
6- Replace burners making sure to fully engage in rear
CLEANING INSIDE
CLEANING TOP
FIGURE 19
CLEANING
PORTS
FIGURE 20
FIGURE 21
receiving slot in heat exchanger. See figure 22. ReseĆ
cure gas manifold and supply piping.
7- Resecure damper
assembly, damper
prove switch cover
and burner box
top. Carefully 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 flue restrictor (Ć50 models only).
9- Before replacing draft hood, flue pipe and access
panels, inspect draft hood gasket. Replace gasket if
necessary.
10- Carefully check all piping connections (factory and
field) for gas leaks. Use a leak detecting solution or othĆ
er preferred means.
11- Turn on gas and electrical supply.
BURNER SLOT ENGAGEMENT
ENGAGE
BURNER
IN SLOT
FIGURE 22
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 further lubrication.
A - Flue and Chimney
Flue must conform to all AGA/GAMA venting requireĆ
ments for Category I Central Furnaces." Flue pipe deteriĆ
orates from the inside out and must be disconnected in orĆ
der to check thoroughly. Check flue pipe, chimney and all
connections for tightness and to make sure there is no
blockage or leaks.
B - Electrical
1 - Check all wiring for loose connections.
2 - Check for correct voltage.
3 - Check amp-draw on blower motor.
Page 11
3
8
10
2
5
7
6
9
7
1
5
OPERATION SEQUENCEG17 SERIES
1- When disconnect is closed, 120V feeds to line voltage
side of the blower control (A15). Door interlock switch
(S51) must be closed for A15 to receive voltage.
2- A15 supplies 120V to transformer (T1).
3- T1 supplies 24VAC to terminal 24" on A15. In turn,
terminal R" of A15 supplies 24VAC to terminal RC"
of the thermostat (S1).
4- When there is a call for heat, W1 of the thermostat enĆ
ergizes W of the blower control with 24VAC.
5- CAB of the blower control energizes the damper motor
(B17) which opens the damper door. When door is in
full open position, damper prove switch (S64) closes.
6- When S64 closes, assuming the flame rollout switch
(S47) and blocked vent shutoff switch (S62) are
9
closed, 24VAC is supplied to the TH" terminal of the
electronic control (A3).
7- Through the electronic control, the pilot valve P" of
the gas valve opens. The spark electrode ignites the
pilot and the flame sensor senses the pilot.
8- When flame is sensed the main gas valve opens and
supplies the burners with gas.
9- Terminal V" (Valve Sense) of the blower control
senses that the gas valve is energized and initiates a
45 second time delay. At the end of the 45 seconds the
blower, (B3) is energized.
10- When the heat demand has been satisfied, W1 of 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 for a designated period (90-330 sec.) as set by
jumper on blower control.
Page 12
START
BCC2-1
TROUBLESHOOTING
FLOWCHART
REPLACE
BCC2-1
NO
(REMOVE R & G JUMPER)
NO
IS
120VAC ACROSS
N1 & ACC?
YES
JUMPER ACROSS
R &W
IS
DAMPER MOTOR
ON?
YES
YES
YES
DOES UNIT
OPERATE?
NO
IS
24VAC ACROSS
R & T?
YES
JUMPER ACROSS
SCREWS R & G
IS
BLOWER
RUNNING ON HIGH
SPEED?
ARE
BURNERS
LIT?
YES
NO
NO
CHECK:
1-UNIT POWER
2-INTERLOCK SWITCH
3-TRANSFORMER
4-LIMIT SWITCH
NO
IS
120VAC ACROSS
N1 & A?
YES
CHECK BLOWER
WIRING AND
BLOWER
CHECK:
1-DAMPER MOTOR
2-IGNITION CONTROL
3-GAS VALVE
4-IGNITOR
5-LIMIT SWITCHES
6-PROVE SWITCH
NO
REPLACE
BCC2-1
NO
REPLACE
BCC2-1
END OF TEST
IS
120VAC ACROSS
N1 & CAB?
NO
REPLACE
BCC2-1
YES
YES
IS
120VAC ACROSS
N1 & ACC?
YES
REMOVE
R & W JUMPER
AFTER
THE SELECTED
TIME, DOES THE
BLOWER TURN
OFF?
CHECK
DAMPER MOTOR
WIRING AND
DAMPER MOTOR
YES
NO
IS BLOWER
RUNNING ON LOW
SPEED, 45 SEC.
AFTER FURNACE
LIGHTS?
REPLACE
BCC2-1
FIGURE 15
Page 13
NO
IS
120VAC ACROSS
N1 & H?
NO
IS
24VAC ACROSS
T & V?
NO
CHECK
WIRING
YES
CHECK BLOWER
WIRING AND
BLOWER
REPLACE
YES
BCC2-1
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