Lennox G41UF?24B?045, G41UF?36B?070, G41UF?36B?045, G41UF?48C?090, G41UF?60C?090, G41UF?48C?110, G41UF?60C?110, G41UF?60D?135, G41UF?36C?090 Service Literature
Specifications and Main Features
Frequently Asked Questions
User Manual
Corp. 0303−L2
Service Literature
G41UF SERIES UNITS
G41UF series units are high−efficiency upflow gas fur
naces manufactured with Lennox DuralokPlust alumi
nized primary and stainless steel secondary clamshelltype
heat exchangers. G41UF units are available in heating
input capacities of 44,000 to 132,000 Btuh (12.9 to 38.6 kW)
and cooling applications from 2 through 5 tons (7.0 through
17.6 kW). 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 G41UF
units are equipped with the Lennox SureLight® hot sur
face ignition system. The gas valve is redundant to as
sure safety shut−off as required by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
Information contained in this manual is intended for use by
qualified service technicians only. All specifications are sub
ject to change. Procedures outlined in this manual are pre
sented as a recommendation only and do not supersede or
replace local or state codes.
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
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.
Side Return Air Filter & Rack Kit − Number & size of
filters
EZ Filter
Base
Number and size of field provided filter − in. (mm)16 x 25 x 1 (406 x 635 x 25)20 x 25 x 1 (508 x 635 x 25)
Condensate
eat
Cable
Heat Cable
ape
6
High Altitude Orifice Kit − Natural Gas47M8247M8247M8247M8247M82
3
High Altitude
Pressure Switch Kit
LPG/Propane Kit
5
Termination
ts
Twinning Kit15L3815L3815L3815L3815L38
1
Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for nonweatherized
furnaces.
3
Required for proper operation at altitudes over 4500 ft. (1370 m).
4
Cleanable polyurethane frame type filter.
5
Kits contain enough parts for two installations. Determine from venting tables proper exhaust pipe size and termination kit required.
6
Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
Catalog Number − Shipping Weight73P56 − 7 lbs. (3 kg)73P57 − 8 lbs. (4 kg)
Dimensions − H x W x D − in. (mm)4 x 17−5/8 x 28−5/8 (102 x 448 x 727)
50 ft. (15.2 m) long26K7026K7026K7026K7026K70
Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)
Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m)
4501−7500 ft. (1372−2286 m)
7501−10,000 ft. (2286−3048 m)
0−7500 ft. (0−2286 m)47M8347M8347M8347M8347M83
7501−10,000 ft. (2286−3048 m)47M8147M8147M8147M8147M81
Roof − 2 inch (51 mm)
Roof − 3 inch (76 mm)
Wall Ring − 2 inch (51 mm)15F7415F7415F7415F7415F74
Air Filter and Rack Kit − Number & size of filtersSingle 44J22 or Ten Pack 66K63 − (1) 16 x 25 x 1 (406 x 635 x 25)
EZ Filter
Base
Condensate
eat
Cable
Heat Cable
ape
7
High Altitude Orifice Kit − Natural Gas Only47M8247M8247M8247M82
3
High Altitude
Pressure Switch Kit
RAB Return Air BaseRAB60C (12M71)− − − −RAB60D (12M72)RAB60D (12M72)
LPG/Propane Kit
5
Termination
ts
Twinning Kit15L3815L3815L3815L38
1
Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for nonweatherized
furnaces.
3
Required for proper operation at altitudes over 4500 ft. (1370 m).
4
Cleanable polyurethane frame type filter.
5
Kits contain enough parts for two installations. Determine from venting tables proper exhaust pipe size and termination kit required.
6
Not for use with RAB Return Air Base or with 60C and 60D size units with air flow requirements of 1800 cfm (850 L/s) or greater. See Blower Performance
tables for additional information.
7
Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
Catalog Number − Shipping Weight73P57 − 8 lbs. (4 kg)73P58 − 10 lbs. (5 kg)
Dimensions − H x W x D 4 x 21−5/8 x 28−5/8 in. (102 x 549 x 727 mm)
Number and size of field provided filter20 x 25 x 1 in. (508 x 635 x 25 mm)24 x 24 x 1 in. (610 x 610 x 25 mm)
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
012255804851000470365820385290
751120530415945445325780365260
150955450355835395285695325225
2257153353000600285220435205170
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
545435970460340805380265
480375865405295740350240
390320695330245545255185
G41UF−36B−045 PERFORMANCE
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00
0.10251515715605138565555511905604851020480415
0.20501470
0.30
0.40100135064053512505904651120530410980465360
0.501251290
0.60
0.7017511455404601080510400975460345860405300
0.802001050
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
251555735630141066558511905605201030485435
751410665555131062049511555454401000470385
150122057548511455404201020480365905430320
225945445410900425345825390305730345270
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
695580134563552011705504551010475400
61050512055704501080510390950450345
495425985465365870410320785370285
G41UF−36B−070 PERFORMANCE
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00
0.10251600755635139566055011605454601000470385
0.20501540
0.30
0.40100142067054512756054801125530395965455345
0.501251360
0.60
0.7017511705554651085515385965430335860405295
0.802001080
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
01640775660141566557511605454851005475410
75149570558013456355051145540425990465365
150127560049011655504101025485350900425305
225945445400840395320765360275710 335245
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
72560513706505251160545445995470375
64052512455904501080510375945445325
5104401010475360865410310775365270
G41UF−36C−090 PERFORMANCE
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00
0.10251680795700139065058511855604801005475395
0.20501645
0.30
0.40100156073561513456355151155545425990465360
0.501251495
0.60
0.70175133063050512055704351035490360890420300
0.802001255
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
01705805730139566060511955554951010475410
75160075563513656455351165550445995470375
150141566554012706004751080510375940445320
22511355354501020480365830390300760360260
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
775675138065056011755554651000470390
70558013056155001125530400970460345
5904851120530400955450330840395280
Air Volume / Watts at Different Blower Speeds
MediumLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Page 4
BLOWER PERFORMANCE
External Static
External Static
External Static
External Static
G41UF−48C−090 PERFORMANCE
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00
0.102521351005885182586075015107106101275600495
0.20502085
0.30
0.401001940915760173582065014807005351250590440
0.501251865
0.60
0.701751645775640147569552012906104501105520375
0.802001540
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
021801030930183586579015207156301280605510
752030955800177583568515007055651265595460
1501740820670159075057513806504751175555410
225133563054011705554401070505375950450330
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
985840181085572015057105801270600475
880725166078560014306755051215575425
725600134063046511755554051020480355
G41UF−60C−090 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00
0.10252460116011452310109097020959908251780840660
0.20502395
0.30
0.40100222510501050211099588019509207451720810620
0.501252135
0.60
0.701751950920950186588079017508256751535725555
0.802001845
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
025101185116023501110990214510108501785845670
752325109510902175102591020159507751735820630
1502025955975195092082018208607001600755575
2251730815885164077572015557356251340630510
HighMedium−HighMedium−LowLow
113011252240106094020609708051760830650
10101015205096585519008957251665785600
870915176083075516407756501450685530
G41UF−60C−090 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from
Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
02575121512352360111 5103020509658751790845720
752375112011402215104595519959408151740820680
150214010101030205597089518758857551665785635
2251905900970178584580016407756751495705570
High
115511702270107098520259558401755830695
10451075209098590019159057751700800650
9451010189089083017308157051565740595
G41UF−48C−110 PERFORMANCE
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
0.00021601020880188089075514907056021235580485
0.10252100990850185587573014807005851230580475
0.20502035960805181586069014756955601225580460
0.30
0.401001885890725171581062514656905101215575430
0.501251780
0.60
0.701751575745620141066550512105704051035490350
0.802001375
0.90
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
751965925750175583065014756955451220575445
150169080066015507355501360640460111 0525380
225122558052011205304151050495365885420310
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High
840680163077058014206704901150540400
65055012305804501125530380970460325
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Page 5
BLOWER PERFORMANCE
External Static
External Static
External Static
External Static
G41UF−60C−110 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
025501205130023451105108020559708951740820715
752350111 011902175102596519459208051690795670
15020759801065195592587517858457351585750630
2251770835975164077577015357256451415670565
High
1140122522201050100020009458401715810695
10351115203596091018408707601630770650
8951005177083581016157656751475695580
G41UF−60C−110 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from
Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
025801215134023301100110020459659501760830745
7523751120122522001040101519659258351715810710
150213010051105202595593018258607701600755650
2251820860980173081581515557356601430675580
High
1155125522551065104020059458551735820730
10401135208598595518708807801660785670
9101025182586085016507806951500710600
G41UF−60D−135 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
025501205134023301100114520359609551725815775
752355111 0123521801030103519559208551700800715
15021009901110198593593518158557801600755660
22518158551005173582083516057556901420670580
High
1145128522301050106519909408901715810740
10401160207097598018658808051645775675
9001050184587087516707907201490705605
G41UF−60D−135 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from
Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g.PacfmL/sWattscfmL/sWattscfmL/sWattscfmL/sWatts
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
02585122013702355111 0116020759809851730820765
7524101135126022301050106020109508901715810725
150219010351155204596596018508758051615765660
22518608801020175082583516357707201425670580
High
1170130022951085109020509709201730815745
107511902120100099519159058301650780685
9451080185587589017158107451500710615
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Air Volume / Watts at Different Blower Speeds
Medium−HighMedium−LowLow
Page 6
G41UF PARTS IDENTIFICATION
BURNER BOX
ASSEMBLY
GAS VALVE AND
MANIFOLD
COMBUSTION AIR
PROVE
(PRESSURE)
SWITCH
FLUE
COLLAR
COMBUSTION AIR
INDUCER
DuralokPlus
HEAT EXCHANGER
ASSEMBLY
TM
TOP CAP
CABINET
WARM HEADER
(COLLECTOR)
BOX
BURNER
ACCESS
PANEL
BLOWER
ACCESS
DOOR
SIGHT
GLASS
DOOR
INTERLOCK
SWITCH
CONTROL BOX
CONDENSER COIL
PRIMARY LIMIT
COLD HEADER
(COLLECTOR)
BOX
FIGURE 1
Page 7
I−UNIT COMPONENTS
G41UF unit components are shown in figure 1. The com
bustion air inducer, gas valve and burners can be accessed
by removing the burner access panel. The blower and con
trol box can be accessed by removing the blower access
door. G41UF units are designed for bottom and side re
turn air.
A−MakeUp Box (Figure 2)
A field makeup box is provided for line voltage wiring. Line
voltage wiring to unit is routed from the make up box. The
hot" wire is connected to the door switch and then from the
switch to the SureLight board. The make−up box may be
installed inside or outside the unit and on the unit left or right
side (right side shown figure 2).
INTERIOR MAKE−UP BOX INSTALLATION
MAKE−UP
BOX
Right Side
CLAMP LOCATION
FIGURE 2
B−Control Box Components (Figure 3)
Unit transformer (T1) and SureLight control (A92) are lo
cated in the control box. In addition, a door interlock switch
(S51) is located in the control box.
DOOR INTERLOCK
SWITCH (S51)
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage 24 volt section of the unit. Transformers on
all models are rated 40VA with a 120V primary and a 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located on
the control box. The switch is wired in series with line volt
age. When the blower door is removed the unit will shut
down.
WARNING
Shock hazard.
Disconnect power before servicing. Control is
not field repairable. If control is inoperable, sim
ply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
3. Furnace Control (A92)
All G41UF model units are equipped with the Lennox Sur
eLight ignition system. The system consists of ignition
control board (figure 5 with control terminal designations
in table 3), ignitor (figure 6) and sensor (figure 7). The
board and ignitor work in combination to ensure furnace
ignition and ignitor durability. The SureLight integrated
board controls all major furnace operations. The board
also features two LED lights for troubleshooting and two
accessory terminals rated at (1) one amp. Tables 1 and 2
show jack plug terminal designations. See table 4 for trou
bleshooting diagnostic codes. The SureLight ignitor is
made of durable silicon−nitride. Ignitor longevity is also
enhanced by voltage ramping by the control board. The
board finds the lowest ignitor temperature which will suc
cessfully light the burner, thus increasing the life of the ig
nitor.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
SURELIGHT
CONTROL
BOARD
(A92)
FIGURE 3
TRANSFORMER
(T1)
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace’s
electronic controls. Precautions will help to avoid
control exposure to electrostatic discharge by
putting the furnace, the control and the techni
cian at the same electrostatic potential. Neutral
ize electrostatic charge by touching hand and all
tools on an unpainted unit surface, such as the
gas valve or blower deck, before performing any
service procedure.
Page 8
TABLE 1
SureLight BOARD J156 (J2) TERMINAL
DESIGNATIONS
PIN #FUNCTION
1Combustion Air Inducer Line
2
3
Combustion Air Inducer Neutral
4
Ignitor Line
Ignitor Neutral
TABLE 2
SureLight BOARD J58 (J1) TERMINAL
DESIGNATIONS
PIN #FUNCTION
1High Limit Output
2
3
4
5
6
7
8
9
10
11
12
Not Used
24V Line
Not Used
Rollout Switch In
24V Neutral
High Limit Input
Ground
Gas Valve In
Pressure Switch Out
Rollout Switch Out
Gas Valve Out
a−Electronic Ignition (See Figure 8)
On a call for heat the SureLight control monitors the com
bustion air inducer prove switch. The control will not begin
the heating cycle if the prove switch is closed (by−passed).
Once the prove switch is determined to be open, the com
bustion air inducer is energized. When the differential in the
prove switch is great enough, the prove switch closes and a
15−second pre−purge begins. If the prove switch is not
proven within 2−1/2 minutes, the control goes into Watch
guard−Pressure Switch mode for a 5−minute re−set period.
After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds during which the gas valve opens
at 19 seconds for a 4−second trial for ignition. The ignitor
stays energized during the 4 second trial until flame is
sensed. If ignition is not proved during the 4−second period,
the control will try four more times with an inter purge and
warm−up time between trials of 35 seconds. After a total of
five trials for ignition (including the initial trial), the control
goes into Watchguard−Flame Failure mode. After a 60−min
ute reset period, the control will begin the ignition sequence
again.
The SureLight control board has an added feature that pro
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again. Each time
120V is removed and then re−applied, the control re−starts
the learning process.
b−Fan Time Control
The fan on time of 45 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by setting the dip
switches located on the SureLight integrated control. The
unit is shipped with a factory fan off setting of 90 seconds.
For customized comfort, monitor the supply air tempera
ture once the heat demand is satisfied. Note the supply air
temperature at the instant the blower is de−energized. Ad
just the fan−off delay to achieve a supply air temperature
between 90° − 110° at the instant the blower is de−ener
gized. (Longer delay times allow for lower air temperature,
shorter delay times allow for higher air temperature). See
figure 4.
FANOFF TIME ADJUSTMENT
60sec.90sec.
OFF
ON
1
2
OFF
ON
OFF
1
2
(Black square indicates switch position)
To adjust fan−off timing, flip dip switch to desired setting.
120sec.
OFFOFFOFF
ON
OFF
180sec.
1
OFF
2
ON
1
2
FIGURE 4
Page 9
SURELIGHT INTEGRATED CONTROL BOARD
XFMR–N
J156
4. Ignitor (Figure 6)
The SureLight ignitor is made of durable silicon nitride. Ig
nitor longevity is enhanced by controlling voltage to the ig
nitor. The board finds the lowest ignitor temperature which
will successfully light the burner, thus increasing the life of
the ignitor. Due to this feature of the board, voltage cannot
be measured so ignitor must be ohmed. Ohm value should
be 10.9 to 19.7
SureLight Ignitor Location
MEASUREMENT IS TO I.D.
5/8"
OF RETENTION RING
13/32’
J58
FIGURE 5
TABLE 3
TERMINAL DESIGNATIONS
COOL−H 120V HOTBlower Cooling Speed (120VAC)
HEAT−HBlower Heating Speed−(120VAC)
EAC−HElectronic Air Cleaner (120VAC)
HUM−HHumidifier (120VAC)
XFMR−HTransformer (120VAC)
LINE−HInput (120VAC)
LINE−N 120V NEUTInput (Neutral)
HUM−NHumidifier (Neutral)
EAC−NElectronic Air Cleaner (Neutral)
XFMR−NTransformer (Neutral)
CIR−NBlower (Neutral)
PARKAlternate Blower Speeds (dead)
(FLAME SENSE)Flame Sensor
BRACKET
IGNITOR
BURNERS FRONT VIEW
FIGURE 6
5. Flame Sensor (Figure 7)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the bottom burner box plate
and the tip protrudes into the flame envelope of the left−
most burner. The sensor can be removed for service with
out removing any part of the burners. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The SureLight control allows the gas
valve to remain open as long as flame signal is sensed.
NOTE − The G41UF furnace contains electronic com
ponents that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
NORMAL FLAME SIGNAL > 0.18 MICROAMPS
LOW FLAME SIGNAL <
DROP OUT SIGNAL = 0.15 MICROAMPS
5/16"
0.17 MICROAMPS
FIGURE 7
Page 10
The SureLight board is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 4.
y
TABLE 4
DIAGNOSTIC CODES
Make sure to Identify LED’S Correctly.
Refer to Installation Instructions for control board layout.
LED #1LED #2DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
SLOW FLASHON
OFFSLOW FLASH
ALTERNATING
SLOW FLASH
SLOW FLASHOFFFlame sensed without gas valve energized.