Corp. 9728−L12
Service Literature
80UHG series units are mid−efficiency gas furnaces used
for upflow or horizontal applications only, manufactured
with tubular heat exchangers formed of aluminized steel.
80UHG units are available in heating capacities of 45,000
to 120,000 Btuh and cooling applications up to 5 tons. Refer
to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. 80UHG−1 model
units use electronic (direct spark) ignition. 80UHG−2 and −3
model units are equipped with the Lennox SureLight silicon
nitride ignition system. The 80UHGX unit meets the California Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements. All units use a redundant gas
valve to assure safety shut−off as required by A.G.A. or
C.G.A. Units may be installed in upflow or horizontal position.
All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or
state codes. 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.
Revised 01−2002
80UHG
TABLE OF CONTENTS
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data 3−4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Altitude 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification 5−6. . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components 6−15. . . . . . . . . . . . . . . . . . . . . . . . . . .
II Installation 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks 16−17. . . . . . . . . . .
V Typical Operating Characteristics 18. . . . . . . . . . . . . .
VI Maintenance 19−20. . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation 21−28. . . . . . . . .
VIII SureLight Troubleshooting Guide 29−34. . . . . . . . . .
Page 1
© 1999 Lennox Industries Inc.
Litho U.S.A.
SPECIFICATIONS
Blower wheel nominal
g
Nominal cooling
)
Up−Flow/Horizontal Filter and Filter Rack Kits
Single (32J02) Te n Pack (66K64)
Blower wheel nominal
g
Nominal cooling
)
Up−Flow/Horizontal Filter and Filter Rack Kits
Single (46J14) Te n Pack (66K65)
Model No. 80UHG2(X)-45 80UHG2(X)-60 80UHG3(X)-60 80UHG2(X)-75 80UHG3(X)-75 80UHG4(X)-75
Input Btuh (kW) 45,000 (13.2) 60,000 (17.6) 75,000 (22.0)
Output Btuh (kW) 36,900 (10.8) 49,200 (14.4) 61,700 (18.1) 61,700 (18.1)
A.F.U.E. 80.1% 80.5% 80.1% 80.0%
California Seasonal Efficiency 75.4% 76.4% 75.9% 76.8% 76.8% 76.3%
Flue size connection diameter in. (mm) round 3 (76) 4 (102)
Temperature rise range _F (_C) 30 - 60 (17 - 33) 45 - 75 (25 - 42)
High static cert. by A.G.A./C.G.A. in wg. (Pa) .50 (125)
Gas Piping Size I.P.S. Natural or LPG/propane 1/2 (13)
Blower wheel nominal
diameter x width
Blower motor output hp (W) 1/4 (187) 1/3 (224) 1/4 (187) 1/3 (224) 1/2 (373)
Nominal coolin
that can be added
Shipping weight lbs. (kg) 1 package 130 (59) 135 (61) 140 (64)
Electrical Characteristics 120 volts 60 hertz 1 phase (less than 12 amps) All models
LPG/propane kit LB-69845L (38K84)
Twinning Kit 15L38 − 11lbs. (5 kg)
Up−Flow/Horizontal Filter and Filter Rack Kits Single (32J02) Ten Pack (66K64
No. & sizeoffilters− in. (mm)
Sidewall Power Venting Kit 79J15 25 lbs. (11 kg)
Hanging Bracket Kit LB-69957 (46J66) 15 lbs. (8 kg)
in. 9 x 7 10 x 7 9 x 7 10 x 7 12 x 8
mm 229 x 178 254 x 178 229 x 178 254 x 178 305 x 203
Tons 1, 1-1/2 or 2 2, 2-1/2 or 3 1, 1-1/2 or 2 2, 2-1/2 or 3
kW 3.5, 5.3 or 7.0 7.0, 8.8 or 10.6 3.5, 5.3 or7.0 7.0, 8.8 or 10.6
Optional Accessories (Must Be Ordered Extra)
(1) 16 x 20 x 1 (406 x 508 x 25)
2, 2-1/2, 3,
3-1/2 or 4
7.0, 8.8, 10.6,
12.3 or 14.1
SPECIFICATIONS
Model No. 80UHG3/4(X)-100 80UHG4/5(X)-100 80UHG3/4(X)-120 80UHG4/5(X)-120
Input Btuh (kW) 100,000 (29.3) 120,000 (35.2)
Output Btuh (kW)
A.F.U.E. 80.1% 80.0% 80.0% 80.1%
California Seasonal Efficiency 76.5% 77.0% Not Available 75.5%
Flue size connection diameter in. (mm) round 4 (102)
Temperature rise range _F (_C) 45 - 75 (25 - 42) 35 - 65 (19 - 36) 45 - 75 (25 - 42)
High static certified by A.G.A./C.G.A. in wg. (Pa) .50 (125) .65 (162) .50 (125)
Gas Piping Size I.P.S. Natural or LPG/propane 1/2 (13)
Blower wheel nominal
diameter x width
Blower motor output hp (W) 1/2 (373) 3/4 (560) 1/2 (373) 3/4 (560)
Nominal coolin
that can be added
Shipping weight lbs. (kg) 1 package 175 (79)
Electrical Characteristics 120 volts 60 hertz 1 phase (less than 12 amps) All models
LPG/propane kit LB-69845K (81J14)
Twinning Kit 15L38 (5 kg)
Up−Flow/Horizontal Filter and Filter Rack Kits Single (46J14) Ten Pack (66K65
No. & sizeoffilters− in. (mm)
Sidewall Power Venting Kit 79J15 25 lbs. (11 kg)
Hanging Bracket Kit LB-69957 (46J66) 15 lbs. (8 kg)
Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
Polyurethane frame type filter is furnished with kit.
in. 12 x 8 12 x 9 12 x 8 12 x 9
mm 305 x 203 305 x 229 305 x 203 305 x 229
Tons 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6
kW 7.0, 8.8, 10.6, 12.3 or 14.1 12.3, 14.1, 17.6 or 21.1 7.0, 8.8, 10.6, 12.3 or 14.1 12.3, 14.1, 17.6or21.1
Optional Accessories (Must Be Ordered Extra)
82,000 (24.0)
(1) 20 x 20 x 1 (508 x 508 x 25)
98,400 (28.8)
Page 2
BLOWER DATA
External Static
External Static
External Static
80UHG2−45, 80UHG2−60 AND 80UHG2−75 BLOWER PERFORMANCE
External Static
Pressure
in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s
0 0 1270 600 980 460 770 365 570 270
.05 12 1245 590 975 460 770 365 565 265
.10 25 1220 575 975 460 770 365 565 265
.15 37 1195 565 965 455 765 360 560 265
.20 50 1170 550 960 455 760 360 560 265
.25 62 1140 540 950 450 760 360 555 260
.30 75 1110 525 940 445 760 360 550 260
.40 100 1060 500 910 430 750 355 545 255
.50 125 990 465 880 415 740 350 540 255
.60 150 900 425 810 380 690 325 530 250
.70 175 800 380 740 350 630 295 520 245
NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table
High Medium-High Medium-Low Low
Air Volume at Various Blower Speeds
80UHG3−60 AND 80UHG3−75 BLOWER PERFORMANCE
External Static
Pressure
in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s
0 0 1425 670 1240 585 1000 470 800 380
.05 12 1415 670 1230 580 995 470 800 380
.10 25 1400 660 1220 575 990 465 795 375
.15 37 1385 655 1200 565 985 465 795 375
.20 50 1370 645 1180 555 980 460 790 375
.25 62 1350 635 1160 545 970 460 780 370
.30 75 1330 630 1140 540 955 450 770 365
.40 100 1280 605 1095 515 925 435 750 355
.50 125 1210 570 1040 490 900 425 720 340
.60 150 1135 535 985 465 860 405 680 320
.70 175 1070 505 920 435 800 380 630 300
NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table
High Medium-High Medium-Low Low
Air Volume at Various Blower Speeds
80UHG4−75, 80UHG3/4−100 AND 80UHG3/4−120 BLOWER PERFORMANCE
External Static
Pressure
in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s
0 0 1830 865 1600 755 1325 625 1070 505 880 415
.05 12 1815 855 1585 750 1320 625 1070 505 880 415
.10 25 1800 850 1570 740 1315 620 1070 505 880 415
.15 37 1875 885 1550 730 1310 620 1065 505 875 415
.20 50 1750 825 1530 720 1300 615 1060 500 875 415
.25 62 1725 815 1515 715 1290 610 1050 495 870 410
.30 75 1700 800 1500 710 1275 600 1040 490 870 410
.40 100 1650 780 1460 690 1245 590 1020 480 860 405
.50 125 1600 755 1420 670 1210 570 1000 470 840 395
.60 150 1550 730 1380 650 1170 550 980 460 820 385
.70 175 1480 700 1330 630 1130 535 960 455 790 375
NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table
High Medium-High Medium Medium-Low Low
Air Volume at Various Blower Speeds
Page 3
BLOWER DATA
External Static
80UHG4/5-100 AND 80UHG4/5-120 BLOWER PERFORMANCE
External Static
Pressure
in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s
0 0 2450 1155 2160 1020 1970 930 1700 800 1500 710
.05 12 2440 1150 2155 1015 1965 925 1695 800 1500 710
.10 25 2430 1145 2150 1015 1960 925 1690 800 1495 705
.15 37 2415 1140 2135 1010 1950 920 1685 795 1495 705
.20 50 2400 1135 2120 1000 1940 915 1680 795 1490 705
.25 62 2380 1125 2105 995 1930 910 1675 790 1480 700
.30 75 2360 111 5 2090 985 1915 905 1670 790 1470 695
.40 100 2310 1090 2050 965 1870 880 1650 780 1440 680
.50 125 2260 1065 2000 945 1810 855 1610 760 1410 665
.60 150 2180 1030 1950 920 1750 825 1560 735 1370 645
.70 175 2100 990 1890 890 1700 800 1520 715 1330 630
NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table
High Medium-High Medium Medium-Low Low
Air Volume at Various Blower Speeds
FILTER AIR RESISTANCE
cfm (L/s) in. w.g. (Pa)
0 (0) 0.00 (0)
200 (95) 0.01 (2)
400 (185) 0.03 (7)
600 (280) 0.04 (10)
800 (375) 0.06 (15)
1000 (470) 0.09 (22)
1200 (560) 0.12 (30)
1400 (655) 0.15 (37)
1600 (750) 0.19 (47)
1800 (845) 0.23 (57)
2000 (935) 0.27 (67)
2200 (1030) 0.33 (82)
2400 (1125) 0.38 (95)
2600 (1220) 0.44 (110)
Refer to table below for manifold pressure settings for
Installations at different altitudes and different fuels.
NOTE−In Canada, certification for installations over
4500 ft. (1372m) above sea level is the jurisdictionof
the local authorities.
Manifold Absolute Pressure in. w.c. (kPa)
ALTITUDE ft. (m)
FUEL
NAT 3.5 (0.87) 3.4 (0.85) 3.3 (0.82) 3.2 (0.80)
LP 9.5 (2.36) 9.2 (2.29) 8.9 (2.21) 8.6 (2.14)
0−4500
(0−1372)
4500−5500
(1372−1676)
5500−6500
(1676−1981)
HIGH ALTITUDE DERATE
The combustion air inducer prove switches are factory
set and are not to be adjusted.
At elevations of 4500 ft. (1372m) or greater, change factory
installed pressure switch to switch listed in table below.
6500−7500
(1982−2286)
Page 4
UNIT MODEL
80UHG−45 NO CHANGE
80UHG−60 NO CHANGE
80UHG−75 88J8001
80UHG−100 18L2401
80UHG−120 18L2401
PRESSURE SWITCH
PART NUMBER
80UHG PARTS IDENTIFICATION
FLUE BOX
VENT ADAPTER
HEAT EXCHANGER
ASSEMBLY
CABINET TOP
COMBUSTION AIR
INDUCER
FRONT ACCESS
PANEL
ROLLOUT SWITCH (2)
PROVE
SWITCH
BURNER
ASSEMBLY
TRANSFORMER
CONTROL
BOARD
DOOR INTERLOCK SWITCH
SECONDARY
LIMITS
BLOWER ASSEMBLY
FIGURE 1
HEATING COMPONENTS (shown in horizontal position)
80UHG
CABINET
CABINET
BOTTOM
PRIMARY LIMIT
COMBUSTION AIR
PROVE SWITCH
MANIFOLD
BURNERS
GAS VALVE
COLLECTOR
FIGURE 2
Left
Bottom
Front
Right
HEAT EXCHANGER
COMBUSTION AIR INDUCER
Back
To p
Page 5
80UHG BURNER ASSEMBLY (shown in upflow position)
−2 MODEL SHOWN
SURELIGHT
IGNITOR
BURNER BOX
TOP
UPPER
BURNER
MOUNTING
RAIL
LOWER
BURNER
MOUNTING
RAIL
FLAME
SENSOR
ORIFICE
MANIFOLD
ROLLOUT
SWITCHES
FIGURE 3
I−UNIT COMPONENTS (Figures 1, 2, 3)
80UHG unit components are shown in figure 1. The gas
valve, combustion air inducer and burners can be accessed by removing the burner access panel. Electrical
components are mounted to the blower housing.
80UHG units are factory equipped with bottom return air panels in place. The panels are designed to be field removed as
required for bottom air return. Knockout panels are provided
for side return air.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
BURNER
VEST PANEL
HEAT EXCHANGER
GAS VALVE
BURNER BOX
PRIMARY LIMIT
Left
Front
To p
Back
Right
Bottom
1− Control Transformer (T1)
A transformer located on the blower housing provides
power to the low voltage section of the unit. Transformers
on all models are rated 30VA with a 120V primary and a
24V secondary.
2−Door Interlock Switch (S51)
A door interlock switch rated 16A at 125VAC is wired in series with line voltage. When the blower door is removed the
unit will shut down.
DANGER
CAUTION
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 technician at the same electrostatic potential. Neutralize 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.
Shock hazard.
Spark related components contain high voltage.
Disconnect power before servicing. Control is
not field repairable. If control is inoperable, simply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
Page 6
3− Furnace Control (A3)
80UHG−2, −3 Models
80UHG−2 and −3 model units are equipped with the Lennox SureLight ignition system. The system consists of
ignition control board (figure 6 with control terminal designations in table 4) and ignitor (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 (4) four amps. See table 3 for troubleshooting diagnostic codes. Table 1 and 2 show jack plug terminal designations. Units equipped with the SureLight
board can be used with either electronic or electro−mechanical thermostats without modification. 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
successfully light the burner, thus increasing the life of the
ignitor. Each time power is applied to the furnace, the SureLight board performs a selfcheck including energizing
the combustion air blower for a period of 1 second.
TABLE 1
SureLight BOARD J156 (J2) TERMINAL
PIN # FUNCTION
1 Combustion Air Inducer Line
2
3
4
SureLight BOARD J58 (J1) TERMINAL
PIN # FUNCTION
1 Primary Limit / Pressure Switch Out
2
3
4
5
6
7
8
9
10
11
12
DESIGNATIONS
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
DESIGNATIONS
Secondary Limit
24V
Not Used
Rollout Switch In
24V
Primary Limit In
Ground
Gas Valve In
Pressure Switch In
Rollout Switch Out
Gas Valve Out
a−Electronic Ignition (See Figure 5)
On a call for heat the SureLight control monitors the combustion air inducer pressure 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 combustion 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 Watchguard−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 for the first second of the 4−second
trial. 80UHG units equipped with control 10M9301: ignitor
remains 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−minute reset period, the control will begin the ignition
sequence again.
The SureLight control board has an added feature that
prolongs 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.
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 flipping the dip
switches located on the SureLight integrated control. The
unit is shipped with a factory fan off setting of 90 seconds.
Fan off time will affect comfort and is adjustable to satisfy
individual applications. See figure 4.
FAN-OFF TIME ADJUSTMENT
60sec. 90sec. 120sec. 180sec.
To adjust fan−off timing, flip dip switch to desired setting.
FIGURE 4
Page 7
The SureLight board is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 3.
TABLE 3
DIAGNOSTIC CODES
MAKE SURE TO ID LED’S CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT.
LED #1 LED #2 DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS FAST
FLASH
SLOW FLASH ON
OFF SLOW FLASH
ALTERNATING SLOW
FLASH
SLOW FLASH OFF
ON SLOW FLASH
ON
ON
OFF
FAST FLASH SLOW FLASH
SLOW FLASH FAST FLASH
ALTERNATING FAST
FLASH
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS FAST
ALTERNATING SLOW
ALTERNATING FAST
FLASH
FLASH
ON
OFF
ON
FLASH
Also signaled during cooling and continues fan.
Normal operation − signaled when heating demand initiated at thermostat.
Primary or Secondary limit open. Units with board 12L69: Limit must close within
5 trials for ignition or board goes into one hour limit Watchguard. Units with board
56L84: Limit must close within 3 minutes or board goes into one hour limit Watch-
Pressure switch open or has opened 5 times during a single call for heat; OR:
Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch
closed prior to activation of combustion air blower.
Flame sensed without gas valve energized.
Rollout switch open. OR: 9 pin connector improperly attached.
Circuit board failure or control wired incorrectly.
Main power polarity reversed. Switch line and neutral.
Low flame signal. Measures below 0.2 microAmps. Replace flame sense rod.
Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR:
Power − Normal operation
guard.
Watchguard − burners fail to ignite.
Open ignitor circuit.
NOTE − Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second). Drop out flame sense current < 0.15 microAmps
SureLight Control Ignition Sequence
(Control 56L8401 ONLY)
15
ON
OFF
DEMAND
CA
B
IGNITOR
GAS VALVE
INDOOR BLOWER
*Blower on time will be 45 seconds after ignition. Blower off time will depend on OFF TIME" Setting.
Pre −Purge Ignitor Warmup Trial for
341
35
Ignition
38
Blower On"
Delay
5 SEC80
Post
Purge
FIGURE 5
Page 8
SURELIGHT INTEGRATED CONTROL BOARD
XFMR−N
Flame
sense
COOL−H
TERMINAL DESIGNATIONS
HEAT−H
EAC−H
HUM−H
XFMR−H
LINE−H
LINE−N
HUM−N
EAC−N
XFMR−N
CIR−N
PARK
(FLAME SENSE)
SURELIGHT IGNITOR
TABLE 4
Blower − Cooling Speed (120VAC)
Blower − Heating Speed (120VAC)
Electronic Air Cleaner (120VAC)
Humidifier (120VAC)
Transformer (120VAC)
Input (120VAC)
Input (Neutral)
Humidifier (Neutral)
Electronic Air Cleaner (Neutral)
Transformer (Neutral)
Not Used
SureLight Ignitor
FIGURE 6
4−Flame Sensor 80UHG −2 models
A flame sensor is located on the left side of the burner support. See figure 8. The sensor is mounted on a bracket in
the burner support and the tip protrudes into the flame envelope of the left−most burner. The sensor is fastened to
burner supports and can be removed for service without
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 80UHG furnace contains electronic components that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
BURNER
NORMAL FLAME SIGNAL u 0.2 MICROAMPS
LOW FLAME SIGNAL v 0.2 MICROAMPS
MINIMUM FLAME SIGNAL v 0.15 MICROAMPS
1/4 in. 7 mm
1/32 in. 0.79
mm
3/16 in.
4.7 mm
FLAME
SIDE VIEW END VIEW
SENSOR
11/16 in. 18 mm
1/32 in. 0.79
FIGURE 8
mm
Page 9
5− Furnace Control (A3) 80UHG−1 Model
80UHG units are equipped with an integrated ignition/blower
control (EGC-2) which controls ignition, safety circuits,
blower operation, fan off timing, and allows for thermostat
connection and troubleshooting. The EGC-2 is a printed
circuit board which is divided into two sections, 120 and
24VAC. Line voltage comes into the board on the 120VAC
side. See figure 10. Terminal designations are listed in
tables 6 and 7.
Ignition Control
80UHG units use the EGC−2 direct spark integrated
ignition control. The EGC−2 controls and monitors the
entire sequence of operation. On a call for heat from the
thermostat the control monitors the combustion 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 combustion
air inducer is energized. When the differential in pressure
across the prove switch is great enough, the prove switch
closes and a 15 second pre-purge period begins. If the
prove switch does not close within 2 1/2 minutes, the control goes into 5 minute watchguard. After the pre-purge period, the gas valve will open and ignition (spark) will be attempted for 10 seconds. After ignition, the control initiates a
ten second flame stabilization period. The flame stabilization period allows the burners to heat up and the
flame to stabilize. Once flame is established, the control will
constantly monitor the burner flame using flame rectification.
Flame failure response time is 0.8 seconds.
If the initial attempt for ignition fails, the sequence is repeated up to five times. After the fifth trial, the control goes into
Watchguard"*. During watchguard mode, the entire unit will
be de-energized for one hour. After one hour the control will
repeat the ignition sequence. Watchguard may be manually
reset by breaking and remaking thermostat demand.
*NOTE−If flame is established beyond the 10 second flame
stabilization period then lost, the control resets for five more
ignition trials. The control can be reset five times during one
unsatisfied thermostat demand, providing a maximum
of 25 trials for ignition.
Safety Circuits
During the entire heating demand the control monitors the
safety circuits. If the primary or secondary heating limits
open, the control de-energizes the main gas valve and
combustion air blower while the indoor blower remains energized. When the limit automatically resets, the ignition sequence also resets. If either of the limits trip five consecutive times during one unsatisfied thermostat demand, the
control will go into watchguard for one hour.
The control monitors main valve voltage. If voltage is sensed
when no voltage should be present, the control de-energizes
the combustion air inducer which terminates voltage to the
valve. The system goes into hard lock-out which is reset only
by removing power to the unit.
If flame is sensed when no flame should be present, the control will energize the combustion and indoor blowers. The
unit will remain locked in this sequence until the flame is no
longer sensed or the main power is turned off to reset the
control.
The roll-out circuit is also monitored by the EGC-2 control. If
the switch opens, the control will de-energize the gas
valve, combustion air inducer, and indoor blower. The
unit will remain de-energized until the switch is manually reset.
DANGER
Shock hazard. Avoid personal injury. Make sure to
disconnect power before changing fan off" timing.
Blower Operation / Fan Off Timings
Fan off" timing (time that the blower operates after the heat
demand has been satisfied) can be adjusted by moving the
jumper on the EGC-2 blower control board. Figure 9 shows
the various fan off" timings and how jumper should be positioned. To adjust fan off " timing, gently disconnect jumper
and reposition across pins corresponding with new timing.
Unit is shipped with a factory fan off" setting of 180 seconds.
Fan on" time is factory set at 45 seconds following the
opening of the main gas valve and is not adjustable.
Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. The fan off" timing is initiated after a heating demand but not after a cooling demand.
NOTEIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 to trip, resulting in frequent cycling of blower. If this occurs, adjust
blower to longer fan off" time setting.
FAN-OFF TIME ADJUSTMENT
TIMING
JUMPER
180
120 90
60
FIGURE 9
To adjust fan-off timing:
Remove jumper from EGC-2 and select
one of the other pin combinations to
achieve the desired time.
TIMING PINS
(seconds)
Leave jumper off for
240 second fan-off timing.
Page 10
Thermostat Connection
Thermostat wires are connected to the terminal strip
found on the EGC-2 control board.
Troubleshooting
The EGC-2 control board is equipped with two diagnostic
green LEDs to indicate the mode of failure. The LED lights
are marked DIAG #1 and DIAG #2. The codes are given in
table 5.
A slotted edge connector is also provided for the Lennox
Diagnostic Module (part number 11K75). See figure 10.
When connected to the EGC-2 control board, the module displays (in words) the diagnostic condition.
80UHG−1 MODEL INTEGRATED CONTROL (EGC−2)
(Shown as installed in horizontal left hand application)
(See tables 6 and 3 for terminal designations)
TABLE 5
EGC-2 DIAGNOSTIC CODES
DIAG #2 DIAG #1 DIagnostic Condition
Simultaneous
Flash
On Flash
Flash Off
Alternate
Flash
Off Flash
Flash On
Continuous
On
Simultaneous
Flash
Alternate Flash
Continuous On
Power ON". Normal Operation. In-
creased flash rate indicates there
is a heating demand.
Primary or Secondary
Limit Switch Open.
Auto-Reset Switch.
Pressure Switch Watchguard,
pressure switch opened during
Circuit board self-check failure or
operation.
Watchguard, burners
failed to ignite.
Flame sensed without
valve energized.
Roll-out Switch Open.
Manual-Reset Switch.
ignition/blower control
is wired incorrectly.
DIAGNOSTIC MODULE
DIAGNOSTIC LEDS
BLOWER TIME
ADJUSTMENT
JUMPER
THERMOSTAT
TERMINAL STRIP
(DETACHABLE)
EDGE
CONNECTION
8 9 10 11 12 13 15
7
6
5
4
1
7
2
8
5
14
PLUG P20
24VAC
346
9
DIAGNOSTIC CODE ERASE JUMPER
(Remove power to control and short pins for
10 seconds to erase previous code.)
FIGURE 10
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