Lennox EL280UHE Service manual

Page 1
UNIT INFORMATIONUNIT INFORMATION
Service Literature
©2016 Lennox Industries, Inc.
OFF
ONON
CCCC
HIHI
IIII
LOLO
HIHI
WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause property damage,
personal injury or loss of life. Installation and service
must be performed by a licensed professional HVAC
installer (or equivalent), 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 disconnect switch(es). Unit may have multiple
power supplies.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal
injury. Take care while handling this equipment and
wear gloves and protective clothing.
EL280UHE(X) series units are 80% e󰀩ciency gas furnac-
es used for upow or horizontal applications only, manu-
factured with Lennox Duralok heat exchangers formed of
aluminized steel. Units are available in heating capacities
of 44.000 to 110,000 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. EL280UHE(X)
model units are equipped with the SureLight® two-stage
integrated control. EL280UHE(X) unit meets the California
Nitrogen Oxides (NOx) Standards and California Season-
al E󰀩ciency requirements. All units use a redundant gas
valve to assure safety shut-o󰀨 as required by C.S.A.
All specications in this manual are subject to change.
Procedures outlined in this manual are presented as a
recommendation only and do not supersede or replace lo-
cal or state codes. In the absence of local or state codes,
the guidelines and procedures outlined in this manual (ex-
cept where noted) are recommendations only and do not
constitute code.
TABLE OF CONTENTS
Specications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Blower Performance Data . . . . . . . . . . . . . . . . . . Page 5
Parts Identication. . . . . . . . . . . . . . . . . . . . . . . . Page 7
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . Page 8
II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . Page 25
III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 25
IV Heating System Service Checks . . . . . . . . . Page 25
V Typical Operating Characteristics . . . . . . . . . Page29
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 30
VII Wiring and Sequence of Operation . . . . . . Page 34
VIII Field Wiring and DIP Switch Settings . . . . Page 37
IX Troubleshooting Flow Chart . . . . . . . . . . . . . Page 41
EL280UHE(X)
Corp 1901-L1
EL280UHE(X) SERIES UNITS

Page 2
SPECIFICATIONS
Gas
Heating
Performance
Model No. EL280UH045E36A EL280UH070E36A
Model No. - Low NOx - - - EL280UH070XE36A
1 AFUE 80% 80%
High
Fire
Input - Btuh 44,000 66,000
Output - Btuh 35,000 53,000
Temperature rise range - °F 30 - 60 30 - 60
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0
Low
Fire
Input - Btuh 29,000 43,000
Output - Btuh 23,000 35,000
Temperature rise range - °F 20 - 50 20 - 50
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
1.7 / 4.5 1.7 / 4.5
High static - in. w.g. Heating 0.5 0.5
Cooling 0.5 0.5
Connections
in.
Flue connection − in. round 4 4
Gas pipe size IPS 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width - in. 10 x 8 10 x 8
Motor output - hp 1/2 1/2
Tons of add-on cooling 1.5 - 3.5 2 - 3.5
Air Volume Range - cfm 250 - 1500 350 - 1375
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.1 6.1
Maximum overcurrent protection 15 15
Shipping Data lbs. - 1 package 111 121
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
SPECIFICATIONS
Gas
Heating
Performance
Model No. EL280UH090E36B EL280UH090E48B
Model No. - Low NOx - - - EL280UH090XE48B
1 AFUE 80% 80%
High
Fire
Input - Btuh 88,000 88,000
Output - Btuh 70,000 69,000
Temperature rise range - °F 35 - 65 30 - 60
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0
Low
Fire
Input - Btuh 57,000 57,000
Output - Btuh 46,000 46,000
Temperature rise range - °F 25 - 55 20 - 50
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
1.7 / 4.5 1.7 / 4.5
High static - in. w.g. Heating 0.5 0.5
Cooling 0.5 0.5
Connections
in.
Flue connection − in. round 4 4
Gas pipe size IPS 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width - in. 10 x 9 10 x 10
Motor output - hp 1/2 3/4
Tons of add-on cooling 2 - 3.5 3 - 4
Air Volume Range - cfm 350 - 1600 765 - 1800
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.1 8.2
Maximum overcurrent protection 15 15
Shipping Data lbs. - 1 package 136 140
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Page 3
SPECIFICATIONS
Gas
Heating
Performance
Model No. EL280UH110E48C EL280UH110E60C
Model No. - Low NOx - - - EL280UH110XE60C
1 AFUE 80% 80%
High
Fire
Input - Btuh 110,000 110,000
Output - Btuh 86,000 87,000
Temperature rise range - °F 35 - 65 30 - 60
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0
Low
Fire
Input - Btuh 72,000 72,000
Output - Btuh 58,000 58,000
Temperature rise range - °F 25 - 55 20 - 50
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
1.7 / 4.5 1.7 / 4.5
High static - in. w.g. Heating 0.5 0.5
Cooling 0.5 0.5
Connections
in.
Flue connection − in. round 4 4
Gas pipe size IPS 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width - in. 10 x 10 11-1/2 x 10
Motor output - hp 3/4 1
Tons of add-on cooling 3 - 4 4 - 5
Air Volume Range - cfm 865 - 1780 1100 - 2200
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 8.2 10
Maximum overcurrent protection 15 15
Shipping Data lbs. - 1 package 152 156
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized
furnaces.

Page 4
OPTIONAL ACCESSORIES - ORDER SEPARATELY
“A” Width
Models
“B” Width
Models
“C” Width
Models
CABINET
Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10
Return Air Base - Upow only 65W75 50W98 50W99
High Performance Economizer (Commercial only) 10U53 10U53 10U53
CONTROLS
iComfort®E30 Smart Wi-Fi Thermostat 20A65 20A65 20A65
Remote Outdoor Temperature Sensor X2658 X2658 X2658
Furnace Twinning Kit 16W72 16W72 16W72
FILTERS
1Air Filter and Rack Kit Horizontal (end) 87L95 87L96 87L97
Size of lter - in. 14 x 25 x 1 18 x 25 x 1 20 x 25 x 1
Side Return Single 44J22 44J22 44J22
Ten Pack 66K63 66K63 66K63
Size of lter - in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1
NIGHT SERVICE KIT
Night Service Kit 17B59 17B59 17B59
VENTING
Vent Adaptor − 6 in. conn. size upow applications only 18M79 18M79 18M79
1 Cleanable polyurethane, frame-type lter.

Page 5
EL280UH045E36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1500 300 1220 175 1050 114 850 65 800 48
0.10 1485 311 1200 179 1025 118 810 68 790 50
0.20 1460 323 1170 188 980 125 725 73 580 53
0.30 1420 334 1140 195 930 133 670 76 455 54
0.40 1395 343 1095 203 890 138 600 86 375 60
0.50 1355 355 1050 212 840 149 550 93 325 64
0.60 1325 368 1020 222 790 158 495 96 275 67
0.70 1290 369 980 228 745 164 420 103 238 69
0.80 1260 381 945 238 700 172 380 107 - - - - - -
EL280UH070E36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1375 340 1350 240 1110 190 970 93 780 50
0.10 1350 346 1325 254 1100 194 940 104 725 57
0.20 1330 346 1310 264 1080 200 895 113 680 64
0.30 1315 353 1280 272 1060 204 860 118 610 70
0.40 1300 368 1250 283 1040 212 810 125 550 76
0.50 1285 369 1220 293 1010 222 765 132 510 78
0.60 1260 384 1190 301 975 227 725 140 460 83
0.70 1240 391 1150 314 950 236 680 147 400 89
0.80 1210 399 1120 319 915 244 640 152 355 95
EL280UH090E36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1605 313 1475 240 1320 173 1,050 99 865 60
0.10 1565 323 1430 251 1270 185 995 108 800 68
0.20 1515 334 1380 264 1225 196 935 115 730 76
0.30 1475 347 1340 275 1170 207 870 124 645 83
0.40 1435 360 1300 285 1120 215 805 133 550 91
0.50 1395 369 1250 295 1065 225 715 140 470 98
0.60 1355 378 1205 307 1010 235 655 147 395 101
0.70 1305 391 1160 318 935 246 560 156 345 107
0.80 1265 404 1105 329 875 254 510 162 300 112

Page 6
EL280UH090E48B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1800 370 1555 260 1425 207 1370 172 1240 131
0.10 1765 381 1525 272 1390 218 1320 184 1190 144
0.20 1725 397 1485 283 1350 229 1255 195 1130 157
0.30 1685 416 1450 296 1310 241 1205 206 1075 165
0.40 1635 425 1390 312 1260 250 1165 217 1015 174
0.50 1600 438 1350 322 1205 263 1100 230 955 185
0.60 1560 453 1300 332 1140 270 1050 239 905 193
0.70 1520 467 1255 344 1110 284 1000 249 840 202
0.80 1470 474 1215 352 1050 294 935 258 765 211
EL280UH110E48C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1780 349 1570 248 1465 190 1370 169 1250 131
0.10 1750 365 1540 260 1420 205 1330 177 1205 140
0.20 1720 382 1500 271 1365 220 1280 187 1155 150
0.30 1675 397 1460 279 1330 228 1250 197 1110 159
0.40 1645 407 1415 291 1290 241 1200 211 1070 166
0.50 1605 424 1395 307 1250 249 1165 219 1015 177
0.60 1580 432 1345 316 1205 258 1105 228 960 186
0.70 1565 448 1300 328 1165 271 1060 237 915 194
0.80 1525 449 1270 339 1125 283 1025 246 865 203
EL280UH110E60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Di󰀨erent Blower Speeds
Bottom Return Air, Side Return Air from Both Sides or
Return Air from Bottom and One Side.
Single Side Return Air - Air volumes in bold (over
1800 cfm) require Optional Return Air Base and eld
fabricated transition to accommodate 20 x 25 x 1 in. air
lter in order to maintain proper air velocity.
High
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
High
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2175 590 2050 410 1850 310 1695 275 1510 195 2175 605 1930 420 1785 320 1675 260 1500 195
0.10 2158 607 1943 421 1778 328 1650 283 1461 205 2129 628 1892 441 1733 345 1627 288 1458 209
0.20 2131 620 1897 436 1719 345 1591 299 1405 215 2091 649 1838 458 1691 360 1586 297 1407 220
0.30 2085 639 1847 456 1678 354 1563 308 1351 228 2072 660 1806 471 1631 371 1529 313 1353 232
0.40 2055 652 1806 466 1641 371 1499 317 1297 238 2014 677 1772 485 1591 385 1485 327 1302 243
0.50 2030 668 1767 476 1588 387 1462 333 1256 254 1977 690 1742 498 1554 395 1444 337 1252 256
0.60 1976 686 1724 495 1550 399 1419 348 1215 265 1960 707 1696 511 1511 410 1412 348 1204 265
0.70 1949 700 1685 510 1512 408 1371 357 1168 271 1913 720 1661 525 1480 424 1351 359 1149 274
0.80 1896 716 1649 527 1473 419 1332 372 1121 287 1873 738 1617 538 1440 437 1313 371 1117 285

Page 7
EL280UHE(X) Parts Arrangement
Combustion Air
Pressure Switch
Combustion Air
Inducer
Gas Valve and Manifold
Assembly
Limit Switch
(under collector box)
Collector Box
Heat Exchanger
Indoor Blower and Motor Assembly
(installed in cabinet)
Make Up Box
Constant Torque Indoor Blower Motor
(removed from cabinet)
Two-Stage Integrated Control
Figure 1

Page 8
I-UNIT COMPONENTS
EL280UHE(X) unit components are shown in gure 1. The
gas valve, combustion air inducer and burners can be ac-
cessed by removing the access panel. Electrical compo-
nents are in the control box (gure 2) found in the blower
section.
EL280UHE(X) units are factory equipped with a bottom
return air panel in place. The panel is designed to be eld
removed as required for bottom air return. Markings are
provided for side return air and may be cut out in the eld.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can a󰀨ect
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
A- Control Box
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage 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 is wired in series with line voltage.
When the inner blower access panel is removed the unit
will shut down.
CONTROL BOX
Transformer
SureLight®Integrated Control
Interlock Switch
Circuit Breaker
Figure 2
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box.
The switch provides overcurrent protection to the trans-
former (T1). The breaker is rated 3A at 32V. If the current
exceeds this limit the breaker will trip and all unit opera-
tion will shutdown. The breaker can be manually reset by
pressing the button on the face. See gure 3.
CIRCUIT BREAKER CB8
PRESS TO RESET
Figure 3
WARNING
Shock hazard.
Disconnect power before servicing. Integrated
control is not eld repairable. If control is inoperable,
simply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
4. Integrated Control (A92)
Units are equipped with the SureLight® two-stage, inte-
grated control. The system consists of a ignition / blower
control (gures 4 and 5) with control pin designations in
tables 1 and 2 and ignitor. The control and ignitor work in
combination to ensure furnace ignition and ignitor durabil-
ity. The control provides gas ignition, safety checks and
indoor blower control with two-stage gas heating. The fur-
nace combustion air inducer, gas valve and indoor blower
are controlled in response to various system inputs such
as thermostat signal, pressure and limit switch signal and
ame signal. The control features a seven-segment LED
display, indicating furnace status and error codes. The
LED ashes in single digits. For example using table 4
under LIMIT CODE, an “E” followed by “2” followed by “5”
followed by “0”, the limit switch circuit is open. The control
also has two unpowered (dry) 1/4” contacts for a humid-
ier and a 120 volt accessory terminal. Both rated at (1)
one amp each.
Electronic Ignition
At the beginning of the heat cycle the integrated control
monitors the rst stage and second stage combustion air
inducer pressure switch. The control will not begin the
heating cycle if the rst stage pressure switch is closed
(bypassed). Likewise the integrated control will not be-
gin the second stage heating cycle if the second stage
pressure switch is closed, and will remain in rst stage
heat. However, if the second stage pressure switch closes
during the rst stage heat pre-purge, the control will allow
second stage heat. Once the rst stage pressure switch
is determined to be open, the combustion air inducer is
energized on low (rst stage) heat speed. When the di󰀨er-
ential in the pressure switch is great enough, the pressure
switch closes and a 15-second pre-purge begins.

Page 9
After the 15-second pre-purge period, the SureLight®ig-
nitor warms up for 20 seconds after which the gas valve
opens for a 4-second trial for ignition. The ignitor remains
energized during the trial until ame 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 ve 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.
NOTE - During abnormal conditions such as low supply
voltage or low outdoor temperatures and the low re pres-
sure switch does not close, the combustion air inducer will
switch to high speed. After the low & high pressure switch
close, the unit will proceed with a 15 sec pre-purge, fol-
lowed by a 20 sec ignitor warm up, then ignition on high-
re. After 10 to 20 seconds of high re operation the unit
will switch to low re.
Two Stage Operation / Thermostat Selection DIP
Switch
The control can be utilized in two modes: SINGLE-STAGE
thermostat or TWO-STAGE thermostat. The thermo-
stat selection is made using a DIP switch and must be
positioned for the particular application. DIP switch 1,
labeled T”STAT HEAT STAGE is factory-set in the OFF
position for use with a two-stage thermostat. Move the
DIP switch to ON for use with a single stage thermostat.
While in the single-stage thermostat mode, the burn-
ers will always re on rst-stage heat. The com-
bustion air inducer will operate on low speed and
indoor blower will operate on low heat speed.
The unit will switch to second stage heat after a “recog-
nition period”. DIP switch 2, labeled SECOND STAGE
DELAY, is factory set in the OFF position for a 7 minute
recognition period. The switch can be moved to the ON
position for a 12 minute recognition period, after which
time the unit will switch to second-stage heat. While in the
two-stage thermostat mode, the burners will re on rst-
stage heat. The combustion air inducer will operate on low
speed and indoor blower will operate on low heat speed.
The unit will switch to second-stage heat on call from the
indoor thermostat. If there is a simultaneous call for rst
and second stage heat, the unit will re on rst stage heat
and switch to second stage heat after 30 seconds of oper-
ation. See Sequence of Operation ow charts in the back
of this manual for more detail.
TABLE 1
SureLight®Control 5 Pin Terminal Designation
Pin # Function
1Ignitor
2Combustion Air Inducer High Speed
3 Combustion Air Inducer Low Speed
4 Combustion Air Inducer Neutral
5Ignitor Neutral
TABLE 2
SureLight® Control 12 Pin Terminal Designation
Pin # Function
1Gas Valve Second Stage
2Pressure Switch Second Stage
3 Rolout Switch
4 Ground
524V Hot
6Primary Limit In
7 Gas Valve First Stage
8Gas Valve Common
9 24V Neutral
10 Ground
11 Primary Limit Out
12 Pressure Switch First Stage

Page 10
INTEGRATED CONTROL
THERMOSTAT CONNECTIONS (TB1)
1/4” QUICK CONNECT TERMINALS
DS = DEHUMIDIFICATION SIGNAL
W2 = HEAT DEMAND FROM 2ND STAGE T/STAT
W1 = HEAT DEMAND FROM 1ST STAGE T/STAT
R = CLASS 2 VOLTAGE TO THERMOSTAT
G = MANUAL FAN FROM T'STAT
C = THERMOSTAT SIGNAL GROUND CONNECTED TO
TRANSFORMER GRD (TR) & CHASIS GROUND (GRD)
Y1 = THERMOSTAT 1ST STAGE COOL SIGNAL
Y2 = THERMOSTAT 2ND STAGE COOL SIGNAL
O = THERMOSTAT SIGNAL TO HEAT PUMP
REVERSING VALVE
L = NOT USED
DH = NOT USED
HUM = UNPOWERED NORMALLY OPEN (DRY) CONTACTS
LI = 120 VAC INPUT TO CONTROL
A
CC = 120 VAC OUTPUT TO OPTIONAL ACCESSORY
NEUTRALS = 120 VAC NEUTRAL
3/16” QUICK CONNECT TERMINALS
FLAME SENSE SIGNAL
HI COOL 24VAC
HI HEAT 24VAC
LO COOL 24VAC
LO HEAT 24VAC
PARK
PARK
COMMON 24VAC
Flame Sense
S4 DIP Switches
24VAC Indoor
Blower Terminals
HUM ACC
Ignitor and Combustion
Air Inducer
Neutrals
On Board Links
LED
Diagnostic Push
Button
Figure 4