Lennox SL280UHV Installation and operation manual

Page 1
UNIT INFORMATIONUNIT INFORMATION
Service Literature
©2016 Lennox Industries, Inc.
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
To prevent serious injury or death:
1- Lock-out/tag-out before performing maintenance.
2- If system power is required (e.g., smoke detector
maintenance), disable power to blower, remove
fan belt where applicable, and ensure all
controllers and thermostats are set to the “OFF”
position before performing maintenance.
3- Always keep hands, hair, clothing, jewelry, tools,
etc., away from moving parts.
SL280UHV(X) series units are 80% e󰀩ciency gas furnac-
es used for upow or horizontal applications only, man-
ufactured with Lennox Duralok heat exchangers formed
of aluminized steel. SL280UHV(X) units are available in
heating capacities of 66,000 to 132,000 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. SL280UH-
V(X) model units are equipped with a communicating
SureLight® two-stage variable speed integrated control.
SL280UHV(X) unit meets the California Nitrogen Oxides
(NOx) Standards and California Seasonal E󰀩ciency re-
quirements. 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.
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.
TABLE OF CONTENTS
Specications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 3
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . Page 17
II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 47
III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 47
IV Heating System Service Checks . . . . . . . . . Page 48
V Typical Operating Characteristics . . . . . . . . . Page 51
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 52
VII Wiring and Sequence of Operation . . . . . . Page 54
VIII Field Wiring and Jumper Settings . . . . . . . Page 59
IX Program Unit Capacity Size Mode . . . . . . . Page 73
X Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . Page 74
SL280UHV
Corp 1116-L4
Revised 05/2022
LENNOX®COMMUNICATING SL280UHNV SERIES UNITS

Page 2
SPECIFICATIONS
Gas
Heating
Performance
Model No. SL280UH070V36A SL280UH090V36B SL280UH090V48B
Model No. - Low Nox SL280UH070XV36A - - - SL280UH090XV48B
1 AFUE 80% 80% 80%
High
Fire
Input - Btuh 66,000 88,000 88,000
Output - Btuh 52,000 70,000 70,000
Temperature rise range - °F 40 - 70 40 - 70 40 - 70
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10 3.5 / 10 3.5 / 10
Low
Fire
Input - Btuh 43,000 57,000 57,000
Output - Btuh 35,000 47,000 47,000
Temperature rise range - °F 25 -55 25 -55 25 -55
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
1.7 / 4.5 1.7 / 4.5 1.7 / 4.5
High static - in. w.g. Heating 0.8 0.8 0.8
Cooling 1.0 1.0 1.0
Connections
in.
Flue connection − in. round 4 4 4
Gas pipe size IPS 1/2 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width - in. 10 X 8 10 X 9 11-1/2 X 9
Motor output - hp 1/2 1/2 1.0
Tons of add-on cooling 2 - 3 2 - 3.5 2.5 - 4
Air Volume Range - cfm 606 - 1345 498 - 1393 679 - 2002
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 7.7 7.7 12.8
Maximum overcurrent protection 15 15 20
Shipping Data lbs. - 1 package 128 143 154
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.
2 Flue connection on the unit is 4 in. diameter. Most applications will require 5 in. venting and eld supplied 4 x 5 in. adaptor. See Venting Tables in the Installation
Instructions for detailed information.
SPECIFICATIONS
Gas
Heating
Performance
Model No. SL280UH090V60C SL280UH110V60C SL280UH135V60D
Model No. - Low Nox SL280UH090XV60C SL280UH110XV60C - - -
1 AFUE 80% 80% 80%
High
Fire
Input - Btuh 88,000 110,000 132,000
Output - Btuh 70,000 87,000 105,000
Temperature rise range - °F 35 - 65 35 - 65 40 - 70
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0 3.5 / 10.0
Low
Fire
Input - Btuh 57,000 72,000 86,000
Output - Btuh 47,000 58,000 69,000
Temperature rise range - °F 25 -55 25 -55 25 -55
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
1.7 / 4.5 1.7 / 4.5 1.7 / 4.5
High static - in. w.g. Heating 0.8 0.8 0.8
Cooling 1.0 1.0 1.0
Connections
in.
Flue connection − in. round 4 4 2 4
Gas pipe size IPS 1/2 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width - in. 11-1/2 X 10 11-1/2 X 10 11-1/2 X 11
Motor output - hp 1.0 1.0 1.0
Tons of add-on cooling 3 - 5 3 - 5 3.5 - 5
Air Volume Range - cfm 826 - 2305 812 - 2125 828 - 2257
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 12.8 12.8 12.8
Maximum overcurrent protection 20 20 20
Shipping Data lbs. - 1 package 173 181 199
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.
2 Flue connection on the unit is 4 in. diameter. Most applications will require 5 in. venting and eld supplied 4 x 5 in. adaptor. See Venting Tables in the Installation
Instructions for detailed information.

Page 3
BLOWER DATA
SL280UH070V36A BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1045 1145
+18% 985 1080
+12% 940 1035
+6% 880 960
Factory Default 850 925
–6% 785 875
–12% 745 815
–18% 680 745
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1045 1139 1219 1372
Factory Default 695 734 797 883 943 1005 1114 1260
–645 674 720 815 847 922 991 1144
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 250 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 250 cfm.
SL280UH070V36A BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 32 55 70 94 111 131 152 174 194 100 123 144 170 196 232 260 266 299 306 343
Med-Low 43 66 87 103 128 147 167 190 217 134 153 185 211 241 266 291 316 342 367 384
Med-High 53 74 97 120 143 165 184 209 228 181 198 234 261 289 316 342 367 390 411 436
High 77 101 123 148 175 194 218 242 266 259 282 318 339 375 402 430 457 489 507 536
Factory Default
Cooling
Speed
Low 26 44 61 78 94 114 138 152 163 66 86 112 139 160 174 199 223 247 270 296
Med-Low 27 49 66 83 106 126 147 169 182 87 107 134 158 182 206 232 258 274 302 319
Med-High 37 57 78 104 122 138 167 186 203 127 150 173 207 237 267 288 313 340 360 390
High 60 85 101 123 148 167 193 211 236 197 218 249 277 306 333 358 388 412 434 454
– Setting
Cooling
Speed
Low 19 34 54 69 86 105 119 144 149 45 66 91 105 138 150 176 189 213 237 266
Med-Low 23 41 56 75 90 112 132 144 159 61 86 103 132 150 172 193 217 233 262 291
Med-High 24 45 63 82 102 121 139 161 183 84 107 139 153 178 204 234 259 280 304 325
High 38 59 81 104 123 145 170 188 208 136 158 190 213 236 268 290 318 339 367 390

Page 4
BLOWER DATA
SL280UH070V36A BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1050 1165
+18% 1000 1110
+12% 940 1040
+6% 895 975
Factory Default 820 935
–6% 775 855
–12% 735 805
–18% 685 750
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1035 1122 1248 1360
Factory Default 704 725 793 899 949 1029 1135 1257
–642 680 717 812 874 933 1021 1133
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 250 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 250 cfm.
SL28UH070V36A BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 36 54 73 95 113 130 147 170 186 90 112 138 159 190 213 236 263 284 305 329
Med-Low 40 61 80 99 124 139 164 182 201 125 136 166 193 218 243 270 271 292 320 340
Med-High 52 74 98 116 140 162 182 207 226 163 181 217 246 274 311 331 358 382 410 430
High 77 100 123 144 165 187 213 234 259 236 259 290 327 354 381 413 448 467 496 519
Factory Default
Cooling
Speed
Low 22 42 63 74 98 119 135 158 174 68 90 107 134 157 175 202 222 239 260 286
Med-Low 30 49 68 83 111 126 139 160 184 86 109 135 153 178 204 232 258 273 292 321
Med-High 32 53 74 92 116 136 154 177 199 115 137 165 197 221 247 272 300 326 348 370
High 55 74 97 120 143 165 181 203 224 172 192 227 257 281 310 342 372 391 422 435
– Setting
Cooling
Speed
Low 17 31 48 69 82 97 111 131 146 48 67 89 110 129 152 172 194 215 231 251
Med-Low 22 43 57 74 84 109 130 140 163 62 84 103 124 151 173 196 212 233 258 277
Med-High 28 49 64 78 104 117 136 156 176 87 112 132 151 180 203 228 251 273 292 317
High 36 56 72 99 118 139 164 177 194 114 137 162 198 221 247 279 302 328 352 374

Page 5
BLOWER DATA
SL280UH090V36B BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1300 1420
+18% 1250 1335
+12% 1185 1285
+6% 1145 1240
Factory Default 1070 1170
–6% 1015 1100
–12% 970 1035
–18% 880 980
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1018 1197 1291 1399
Factory Default 571 698 767 886 909 1083 1197 1284
–489 627 681 812 834 968 1081 1179
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 250 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 250 cfm.
SL280UH090V36B BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 13 29 43 62 73 86 105 122 137 63 85 105 134 159 186 207 230 252 275 292
Med-Low 27 46 64 84 102 119 137 159 177 112 136 157 193 224 247 277 300 321 350 372
Med-High 43 59 80 104 119 143 159 178 191 145 163 199 233 264 289 316 345 374 397 417
High 57 78 103 125 148 181 202 219 245 190 219 254 273 310 351 377 408 442 467 489
Factory Default
Cooling
Speed
Low 12 25 42 55 65 86 93 115 123 51 70 97 113 139 155 176 199 221 242 261
Med-Low 22 38 52 70 89 108 121 135 150 77 99 129 152 184 206 231 264 283 307 333
Med-High 27 46 64 85 103 123 141 157 179 112 136 157 193 224 247 277 300 321 350 372
High 51 68 90 110 136 150 172 198 211 145 164 197 232 257 290 320 351 362 396 411
– Setting
Cooling
Speed
Low 9 21 35 45 60 74 89 100 119 41 59 80 96 116 136 159 176 195 204 230
Med-Low 16 29 46 64 78 93 106 121 138 58 80 104 124 150 175 192 221 238 260 284
Med-High 22 40 54 68 90 108 125 141 153 73 94 125 152 177 203 228 258 279 304 326
High 36 53 72 91 112 131 150 169 185 99 125 154 182 207 234 266 296 320 344 369

Page 6
BLOWER DATA
SL280UH090V36B BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1305 1425
+18% 1250 1350
+12% 1195 1290
+6% 1135 1230
Factory Default 1070 1165
–6% 995 1100
–12% 935 1030
–18% 870 960
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1160 1274 1376
Factory Default 575 674 748 870 889 1075 1160 1270
–519 604 691 786 808 952 1056 1147
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 250 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 250 cfm.
SL280UH090V36B BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 10 27 41 57 72 88 105 123 135 55 82 99 123 148 173 199 220 244 266 290
Med-Low 23 44 59 80 99 119 138 158 177 103 129 151 184 214 235 264 290 316 342 368
Med-High 37 56 75 95 114 135 153 174 189 147 167 205 230 264 285 317 347 365 394 423
High 54 81 95 120 144 170 191 217 234 189 219 249 273 312 339 379 404 431 459 485
Factory Default
Cooling
Speed
Low 824 34 50 70 83 96 110 124 39 63 85 105 131 147 174 193 214 243 264
Med-Low 16 36 50 68 86 106 121 144 159 73 92 123 148 173 203 221 249 266 297 317
Med-High 23 43 61 81 106 123 144 160 182 103 129 151 184 214 235 264 290 316 342 368
High 43 62 88 107 123 145 169 189 209 149 170 199 234 259 291 311 334 367 389 412
– Setting
Cooling
Speed
Low 4 18 29 45 59 74 86 98 113 31 52 67 92 113 129 156 175 197 209 232
Med-Low 11 29 44 58 79 93 111 129 141 50 76 97 116 141 159 185 206 235 250 282
Med-High 15 36 52 67 86 108 126 144 161 68 89 121 139 167 192 219 243 269 292 310
High 32 53 70 94 109 129 153 174 189 95 118 144 178 198 226 256 278 302 328 352

Page 7
BLOWER DATA
SL280UH090V48B BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1280 1410
+18% 1220 1340
+12% 1155 1270
+6% 1095 1205
Factory Default 1035 1135
–6% 970 1070
–12% 910 1000
–18% 845 930
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1030 1335 1550 1755
Factory Default 605 815 965 1090 940 1205 1405 1,600
–525 690 850 985 795 1060 1260 1435
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 380 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 380 cfm.
SL280UH090V48B BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 40 56 75 86 105 128 141 157 173 93 125 144 161 182 209 237 258 286 307 338
Med-Low 64 86 105 122 146 169 187 207 227 167 196 240 262 299 328 367 398 433 467 492
Med-High 93 119 141 163 189 213 237 261 286 259 287 321 374 410 451 481 518 555 581 611
High 128 156 188 219 248 281 308 338 366 372 407 465 493 558 604 661 706 726 764 817
Factory Default
Cooling
Speed
Low 35 51 64 79 92 107 122 138 159 81 105 122 139 159 186 200 221 247 263 286
Med-Low 50 65 85 114 130 148 173 179 200 112 142 173 206 234 271 300 323 356 395 419
Med-High 75 98 117 136 159 177 187 207 244 189 221 254 289 335 362 400 431 458 504 526
High 98 122 149 180 194 230 252 278 300 288 321 372 398 433 470 507 554 598 623 653
– Setting
Cooling
Speed
Low 32 44 57 71 82 95 107 121 132 74 94 112 130 147 174 189 206 226 245 264
Med-Low 43 60 76 91 109 127 143 159 176 86 119 134 161 185 212 236 257 290 320 342
Med-High 55 70 94 116 132 157 171 190 206 138 170 194 226 269 295 325 357 384 414 442
High 80 100 123 147 166 187 210 231 253 204 235 269 312 342 376 425 450 482 516 546

Page 8
BLOWER DATA
SL280UH090V48B BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1280 1410
+18% 1220 1340
+12% 1155 1270
+6% 1095 1205
Factory Default 1035 1135
–6% 970 1070
–12% 910 1000
–18% 845 930
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1005 1295 1500 1670
Factory Default 570 780 930 1040 895 1160 1345 1500
–530 700 810 955 795 1050 1210 1405
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 380 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 380 cfm.
SL280UH090V48B BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 34 54 68 85 102 120 142 159 177 79 107 133 148 172 201 226 253 274 301 327
Med-Low 64 85 105 124 145 166 186 206 227 151 179 214 247 276 312 339 370 399 433 464
Med-High 85 112 135 157 184 208 233 258 284 230 261 305 348 379 421 453 490 523 565 602
High 110 139 172 201 234 270 294 326 352 478 369 414 462 506 547 597 643 691 735 781
Factory Default
Cooling
Speed
Low 30 46 59 77 87 106 118 143 152 70 93 115 134 153 172 195 219 242 260 286
Med-Low 36 56 76 95 120 136 162 175 196 100 132 163 192 214 244 276 307 338 368 402
Med-High 64 88 106 130 149 173 198 222 238 166 192 231 266 303 342 370 410 444 462 493
High 87 118 141 161 194 223 248 275 302 245 273 333 365 396 432 460 503 546 579 635
– Setting
Cooling
Speed
Low 28 43 53 70 83 97 110 120 135 53 72 88 112 133 150 175 191 205 230 245
Med-Low 37 56 72 86 106 124 141 158 176 84 111 134 154 185 215 235 260 284 311 336
Med-High 51 69 90 109 129 152 168 187 205 119 152 182 210 244 276 307 338 370 401 432
High 71 94 119 138 158 181 207 233 250 180 211 248 284 316 355 385 419 450 487 521

Page 9
BLOWER DATA
SL280UH090V48B BLOWER PERFORMANCE (less lter)
SIDE RETURN AIR WITH OPTIONAL RETURN AIR BASE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1295 1425
+18% 1235 1355
+12% 1170 1290
+6% 1110 1220
Factory Default 1045 1150
–6% 980 1080
–12% 920 1010
–18% 855 945
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 985 1290 1495 1675
Factory Default 600 760 930 1045 905 1125 1345 1525
–535 700 850 970 815 1040 1225 1385
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 380 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 380 cfm.
SL280UH090V48B BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 34 54 65 84 101 122 138 156 169 75 104 128 146 170 193 224 244 266 300 326
Med-Low 57 74 97 120 137 158 177 197 216 124 160 189 216 254 287 319 351 385 416 449
Med-High 76 102 125 147 174 200 223 248 272 208 238 279 319 350 391 422 457 489 529 564
High 106 134 165 193 224 259 283 313 340 302 346 386 426 470 510 554 596 640 680 722
Factory Default
Cooling
Speed
Low 31 47 59 74 89 105 123 139 150 64 88 107 131 150 173 196 217 241 263 285
Med-Low 43 61 82 101 118 144 158 177 194 94 123 150 183 213 243 279 300 331 353 393
Med-High 62 85 104 130 151 173 196 216 239 150 180 219 250 294 333 368 399 428 463 497
High 81 113 131 151 187 211 238 264 291 235 263 312 349 387 426 455 489 522 568 608
– Setting
Cooling
Speed
Low 29 40 53 69 83 93 104 122 129 50 69 85 107 127 149 169 187 201 222 237
Med-Low 32 50 66 84 101 116 136 153 172 78 105 126 146 174 199 223 247 272 295 319
Med-High 46 65 86 109 127 146 167 187 207 105 135 166 195 227 262 289 319 348 380 411
High 69 92 112 134 156 175 200 221 245 161 195 230 264 298 334 367 401 434 469 503

Page 10
BLOWER DATA
SL280UH090V60C BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1420 1565
+18% 1355 1490
+12% 1285 1415
+6% 1215 1335
Factory Default 1145 1260
–6% 1080 1185
–12% 1010 1110
–18% 940 1035
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1680 1575 1740 2000 2305
Factory Default 1005 1100 1280 1545 1440 1595 1820 2125
–890 1015 1125 1380 1295 1450 1610 1930
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH090V60C BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 89 113 136 159 182 204 228 251 275 218 245 291 327 372 398 436 474 505 532 579
Med-Low 104 133 163 184 214 245 266 304 328 298 333 382 412 450 488 541 576 612 648 681
Med-High 162 191 227 262 294 333 354 391 422 440 476 527 576 636 686 741 777 820 857 892
High 279 316 355 394 432 473 509 547 584 772 808 877 946 1000 1056 1089 1146 1190 1255 1266
Factory Default
Cooling
Speed
Low 70 92 108 134 159 174 196 215 242 160 195 228 265 291 340 364 397 442 469 500
Med-Low 89 115 135 156 185 207 227 250 281 241 267 305 347 384 413 445 477 519 542 573
Med-High 122 149 183 206 234 269 297 324 350 330 370 414 452 500 542 593 634 675 702 747
High 214 241 277 318 350 388 423 449 469 553 591 655 713 781 819 868 922 967 1026 1066
– Setting
Cooling
Speed
Low 54 70 91 110 129 154 166 185 200 107 151 177 206 245 272 298 332 398 423 449
Med-Low 73 94 112 135 151 175 189 214 235 173 201 244 272 304 337 368 393 437 465 498
Med-High 93 120 141 160 191 221 244 261 288 246 271 310 353 395 433 466 492 528 557 593
High 149 185 217 251 284 314 352 386 422 410 456 505 543 595 635 692 729 777 829 867

Page 11
BLOWER DATA
SL280UH090V60C BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR − Air volumes in bold 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.
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1360 1500
+18% 1295 1425
+12% 1230 1355
+6% 1165 1280
Factory Default 1100 1210
–6% 1030 1135
–12% 965 1065
–18% 900 990
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1620 1515 1680 1915 2225
Factory Default 955 1060 1215 1480 1390 1545 1735 2060
–840 945 1090 1290 1220 1385 1580 1825
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH090V60C BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 75 104 122 142 163 189 214 239 264 219 243 283 317 363 384 424 441 484 511 543
Med-Low 98 128 150 181 205 236 259 289 317 289 333 351 405 444 490 523 564 604 636 668
Med-High 144 172 205 242 279 306 344 367 396 417 451 507 557 605 655 694 733 788 824 867
High 245 272 307 359 386 421 447 473 520 709 743 795 855 906 955 1009 1049 1095 1131 1165
Factory Default
Cooling
Speed
Low 66 88 109 127 150 165 189 209 236 157 185 219 259 290 328 353 394 425 452 480
Med-Low 79 104 127 147 173 201 225 248 268 222 246 284 328 370 397 416 460 490 519 555
Med-High 106 137 164 190 215 250 278 307 333 307 349 387 435 463 505 553 599 634 674 714
High 192 224 260 298 338 365 400 438 467 563 597 664 717 756 820 881 907 972 1007 1039
– Setting
Cooling
Speed
Low 44 65 80 103 121 142 163 180 199 114 141 173 200 230 259 289 318 347 374 401
Med-Low 63 82 105 125 145 166 188 203 227 159 187 226 252 288 323 353 388 419 444 475
Med-High 82 108 131 151 178 203 229 253 274 236 263 302 344 382 420 443 478 514 548 583
High 127 159 187 213 252 281 305 338 371 361 393 450 494 537 586 616 672 711 752 787

Page 12
BLOWER DATA
SL280UH110V60C BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1690 1855
+18% 1605 1765
+12% 1525 1675
+6% 1445 1585
Factory Default 1360 1495
–6% 1280 1405
–12% 1200 1315
–18% 1115 1230
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1565 1535 1710 1910 2210
Factory Default 970 1075 1180 1430 1400 1565 1715 2015
–875 980 1070 1255 1260 1400 1560 1815
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH110V60C BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 89 116 144 159 201 222 245 274 298 234 259 304 360 385 408 451 484 530 553 596
Med-Low 108 135 170 196 228 259 286 320 343 297 340 380 409 459 502 539 570 616 660 702
Med-High 136 164 202 236 269 300 331 370 392 390 420 497 530 585 630 677 727 777 815 854
High 252 275 329 366 396 441 472 493 537 702 734 780 841 907 957 1013 1048 1100 1124 1148
Factory Default
Cooling
Speed
Low 71 98 118 139 166 184 207 237 262 179 203 244 281 329 356 388 425 453 480 519
Med-Low 86 118 138 154 187 212 237 266 291 223 251 288 342 377 399 449 474 513 548 578
Med-High 99 132 160 184 222 254 277 308 343 299 341 384 420 472 497 540 599 632 674 709
High 192 227 258 299 333 376 409 434 471 493 540 591 653 705 760 829 869 919 965 1005
– Setting
Cooling
Speed
Low 60 78 104 122 144 168 187 205 226 133 162 191 225 262 289 324 357 385 410 436
Med-Low 68 94 116 132 150 177 203 220 251 163 189 224 263 292 333 364 392 431 458 473
Med-High 80 109 128 151 174 204 229 252 279 224 251 293 326 370 398 439 467 491 531 570
High 131 165 196 226 265 300 336 356 397 365 406 460 511 558 603 643 705 743 792 835

Page 13
BLOWER DATA
SL280UH110V60C BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR − Air volumes in bold 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.
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1640 1805
+18% 1560 1715
+12% 1480 1630
+6% 1400 1545
Factory Default 1325 1455
–6% 1245 1370
–12% 1165 1280
–18% 1085 1195
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1550 1505 1690 1855 2125
Factory Default 940 1050 1155 1400 1375 1525 1685 1935
–835 945 1020 1250 1235 1380 1505 1730
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH110V60C BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 84 116 131 156 193 216 238 265 292 218 245 293 336 378 415 454 488 516 557 601
Med-Low 99 128 156 195 216 245 280 309 335 292 333 381 412 454 490 535 577 618 662 704
Med-High 128 157 193 226 266 293 321 360 387 373 412 475 518 573 617 661 710 771 800 857
High 238 274 303 354 388 413 460 493 524 675 717 786 854 898 983 1017 1071 1112 1157 1186
Factory Default
Cooling
Speed
Low 73 96 121 140 154 184 206 228 255 166 192 237 271 319 345 382 419 459 480 515
Med-Low 81 108 133 156 175 207 230 253 285 220 248 290 328 372 405 447 474 513 540 577
Med-High 92 123 148 185 209 246 277 302 331 290 328 374 415 452 487 536 576 605 653 701
High 175 202 247 285 327 364 388 426 457 477 511 590 647 690 739 789 843 901 947 998
– Setting
Cooling
Speed
Low 56 74 98 116 141 157 179 199 216 129 157 198 221 259 298 325 354 387 418 451
Med-Low 69 92 111 132 155 174 197 214 243 166 186 232 268 289 339 365 389 429 454 479
Med-High 78 107 128 149 172 203 230 249 278 204 225 282 312 353 383 406 452 489 519 552
High 124 157 186 220 261 291 321 352 386 326 372 427 464 526 566 608 658 706 762 808

Page 14
BLOWER DATA
SL280UH135V60D BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1875 2065
+18% 1785 1965
+12% 1695 1865
+6% 1605 1765
Factory Default 1515 1665
–6% 1425 1565
–12% 1330 1465
–18% 1240 1365
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1650 1500 1600 1840 2235
Factory Default 965 1015 1180 1490 1420 1510 1700 2110
–875 930 1060 1350 1225 1320 1505 1840
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH135V60D BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 72 99 123 145 177 204 228 253 277 180 208 244 299 334 374 408 432 478 511 539
Med-Low 80 108 137 164 194 224 252 280 308 214 249 291 340 384 422 450 493 530 579 619
Med-High 119 154 180 227 259 298 328 363 392 309 359 404 464 509 560 622 661 715 757 809
High 239 271 320 370 394 439 477 513 559 655 683 774 832 888 957 1022 1053 1122 1161 1206
Factory Default
Cooling
Speed
Low 52 79 95 120 147 167 188 215 238 127 161 197 238 277 316 349 386 412 457 493
Med-Low 63 87 116 137 158 188 210 239 262 160 194 229 280 317 350 395 431 451 502 540
Med-High 86 115 152 174 203 236 270 298 328 227 266 333 369 373 405 445 541 579 601 642
High 160 194 229 278 318 359 394 429 455 468 521 580 647 716 763 819 872 934 994 1053
– Setting
Cooling
Speed
Low 45 65 87 107 128 152 170 191 210 103 133 167 199 235 268 294 325 366 391 425
Med-Low 50 70 95 120 140 166 185 208 228 109 143 178 213 247 283 320 359 380 421 455
Med-High 71 97 123 147 175 204 228 254 279 171 203 235 294 328 370 401 439 478 515 543
High 127 160 196 232 265 299 334 369 403 294 343 402 457 510 576 619 673 720 781 835

Page 15
BLOWER DATA
SL280UH135V60D BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR − Air volumes in bold 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.
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
HEATING
1Heating Speed
DIP Switch
Settings
First Stage Heating Speed - cfm Second Stage Heating Speed - cfm
+24% 1850 2035
+18% 1760 1935
+12% 1670 1835
+6% 1580 1740
Factory Default 1490 1640
–6% 1400 1540
–12% 1310 1445
–18% 1225 1345
COOLING
1Cooling Speed
DIP Switch
Settings
First Stage Cooling Speed - cfm Second Stage Cooling Speed - cfm
Low Medium-Low Medium-High 2High Low Medium-Low Medium-High 2High
[phone] 1635 1525 1600 1840 2255
Factory Default 960 1005 1175 1480 1355 1435 1635 2035
–845 925 1050 1340 1240 1315 1520 1850
1 Cooling and heating speeds are based on a combination of DIP switch settings on the furnace control. Refer to Installation Instructions for specic DIP Switch Settings.
2 Factory default setting.
NOTES - The e󰀨ect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position.
Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm.
Lennox iHarmony® Zoning System Applications - Minimum blower speed is 450 cfm.
SL280UH135V60D BLOWER MOTOR WATTS (COOLING)
1Cooling Speed
DIP Switch
Settings
Motor Watts @ Various External Static Pressures - in. wg.
First Stage Second Stage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
+ Setting
Cooling
Speed
Low 66 97 120 138 165 195 220 245 279 189 220 259 298 333 378 410 441 486 517 543
Med-Low 82 111 140 161 190 218 255 269 306 224 255 298 354 389 422 455 499 549 571 616
Med-High 114 148 177 218 254 288 320 359 381 317 359 418 459 511 557 615 655 701 747 795
High 233 268 307 357 396 430 475 503 544 668 704 766 831 898 941 995 1048 1103 1144 1176
Factory Default
Cooling
Speed
Low 49 76 97 121 146 170 198 223 246 130 166 200 238 281 318 350 398 425 462 490
Med-Low 58 89 109 130 161 193 221 238 267 163 185 240 290 318 347 398 432 460 500 538
Med-High 76 109 135 170 200 231 268 290 324 233 281 333 368 408 456 499 539 591 644 693
High 162 195 230 282 318 356 391 425 457 484 529 603 651 721 783 832 898 951 994 1051
– Setting
Cooling
Speed
Low 41 60 86 104 129 149 169 190 212 94 130 161 189 221 259 288 317 355 390 421
Med-Low 50 72 96 120 139 160 184 201 235 114 147 177 211 256 290 330 354 385 422 453
Med-High 73 101 123 147 167 196 221 250 274 177 207 245 291 331 370 413 431 475 509 543
High 118 151 181 231 261 303 327 363 399 328 369 431 477 535 580 638 683 723 777 827

Page 16
FIGURE 1
HEAT EXCHANGER
CABINET
COMBUSTION AIR INDUCER
BLOWER
ASSEMBLY
BURNER BOX
INNER BLOWER
ACCESS PANEL
ACCESS PANEL
SIGHT GLASS
COMBUSTION AIR INDUCER
PRESSURE SWITCH
GAS VALVE
CONTROL BOX
(with blower drive in
some units. Not to scale)
SECONDARY LIMITS
(2 switches)
PRIMARY LIMIT
Parts Arrangement

Page 17
I-UNIT COMPONENTS
SL280UHV(X) unit components are shown in FIGURE 1.
The gas valve, combustion air inducer and burners can be
accessed by removing the access panel. Electrical com-
ponents are in the control box (FIGURE 2) found in the
blower section.
SL280UHV(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)
An interlock switch rated 14A at 125VAC is wired in series
with line voltage. When the indoor blower access panel is
removed the unit will shut down.
CONTROL BOX
Door Interlock Switch
Circuit Breaker
Blower Drive
(some units)
Tw-Stage Variable Speed
Ignition Control
Transformer
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 FIGURE 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 a communicating enabled Sure-
Light ® two-stage, variable speed integrated control. This
control is used with a communicating thermostat as part
of a communicating comfort system. The control can also
operate with a non-communicating conventional single or
two-stage thermostat. The system consists of a ignition
/ blower control (FIGURE 4 103130-XX and FIGURE 5
107045-XX) with control pin designations in TABLE 1, TA-
BLE 2, TABLE 3 and ignitor (FIGURE 15). The control and
ignitor work in combination to ensure furnace ignition and
ignitor durability. The control provides gas ignition, safety
checks and indoor blower control with two-stage gas heat-
ing. The furnace combustion air inducer, gas valve and in-
door 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-seg-
ment LED display, indicating furnace status (including in-
door blower) and error codes. The LED ashes in single
digits. For example using 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” con-
tacts for a humidier and a 120 volt accessory terminal.
Both rated at (1) one amp each. See “Ignition Control Di-
agnostic Modes” on page 22, “Ignition Control 103130-
XX Diagnostic Codes” on page 23 and “Ignition Control
107045-XX Diagnostic Codes” on page 29.

Page 18
Electronic Ignition
At the beginning of the heat cycle the integrated control
monitors the rst stage and second stage combustion air
inducer prove switch. The control will not begin the heating
cycle if the rst stage prove switch is closed (by-passed).
Likewise the integrated control will not begin the second
stage heating cycle if the second stage prove switch is
closed, and will remain in rst stage heat. However, if the
second stage prove switch closes during the rst stage
heat pre-purge, the control will allow second stage heat.
Once the rst stage prove switch is determined to be open,
the combustion air inducer is energized on low (rst stage)
heat speed. When the di󰀨erential in the prove switch is
great enough, the prove switch closes and a 15-second
pre-purge begins.
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 re. After a 15 second pre-purge the high
re pressure switch will close and the unit will begin op-
eration on high re. After 10 to 20 seconds of high re
operation the unit will switch to low re.
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 energiz-
es 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.
Two Stage Operation / Thermostat Selection DIP
Switch
The control can be utilized in two modes: SINGLE-STAGE
thermostat or TWO-STAGE thermostat. The thermostat
selection is made using a DIP switch and must be posi-
tioned 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 burners
will always re on rst-stage heat. The combustion air in-
ducer will operate on low speed and indoor blower will
operate on low heat speed. The unit will switch to second
stage heat after a “recognition period”. DIP switch 2, la-
beled 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 secondstage
heat.
While in the two-stage thermostat mode (two DIP switch
setting) the burners will 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 on call from the indoor thermostat. If
there is a simultaneous call for rst and second stage heat,
the unit will re an rst stage heat and switch to second stage
heat after 30 seconds of operation. See Sequence of Oper-
ation 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 Neu-
tral
5 Ignitor Neutral
TABLE 2
SureLight® Control 12 Pin Terminal Designation
PIN# Function
1Gas Valve High Fire
2Second Stage Prove Switch
3 Rollout In
4 Ground
5 24V Hot
6 Primary Limit In
7 Gas Valve Low Stage
8Gas Valve Common
9 24V Neutral
10 Ground
11 Rollout Switch Out
12 1st Stage Prove Switch
TABLE 3
SureLight®Control 6 Pin Terminal Designation
PIN# Function
1Data Input From Motor
2Common
3 Not Used
4 Data Output To Motor
5 5 Volt Bias Supply
6 Not Used

Page 19
IGNITION CONTROL 103130-XX
THERMOSTAT CONNECTIONS (TB1)
1/4” QUICK CONNECT TERMINALS
RS-BUS LINK (TB82, future use)
I+ = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
RS-BUS OUTDOOR (TB83)
R = 24VAC
I + = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
C = 24VAXC COMMON
RS-BUS INDOOR (TB84)
R = 24VAC
I + = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
C = 24VAXC COMMON
FLAME SENSE
DIP SWITCHES
OUTDOOR AIR
SENSOR
TERMINALS
DISCHARGE AIR
SENSOR
TERMINALS
INDOOR
BLOWER
CONNECTOR
NEUTRAL
DIAGNOSTIC
PUSH BUTTON
TB83
COMMUNICATING
OUTDOOR
EQUIPMENT
TB84
COMMUNICATING
INDOOR
THERMOSTAT
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 = USE ONLY WITH A COMMUNICATING THERMOSTAT
AND A NON-COMMUNICATING OUTDOOR UNIT
DH = DEHUMIDIFICATION OUTPUT COMMUNICATING
THERMOSTAT ONLY
HUM = UNPOWERED NORMALLY OPEN (DRY) CONTACTS
XMFR = 120 VAC OUTPUT TO TRANSFORMER
LI = 120 VAC INPUT TO CONTROL
ACC = 120 VAC OUTPUT TO OPTIONAL ACCESSORY
NEUTRALS = 120 VAC NEUTRAL
W915 Y1 TO Y2
2 STAGE COMPR
W951 R TO O
HEAT PUMP
W914 R TO DS
DEHUM OR
HARMONY
W1 W2 G Y2 Y1 CCRDHL ODS
RI +I- CRI +I- C
7 SEGMENT LED
ACC
LINE 1
HUM
12 PIN LOW
VOLTAGE
CONNECTOR
NON-COMMUNICATINGNG
24V TERMINALS
HS/ CAI
FIGURE 4

Page 20
IGNITION CONTROL 107045-XX
THERMOSTAT CONNECTIONS (TB1)
1/4” QUICK CONNECT TERMINALS
RS-BUS LINK (TB82, future use)
I+ = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
R = 24VAC
I + = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
C = 24VAC COMMON (ground)
RS-BUS INDOOR (TB84)
R = 24VAC
I + = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
C = 24VAC COMMON
A2L=A2L REFRIGERANT
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 = DEHUMIDIFICATION OUTPUT COMMUNICATING
THERMOSTAT ONLY
HUM = UNPOWERED NORMALLY OPEN (DRY) CONTACTS
XMFR = 120 VAC OUTPUT TO TRANSFORMER
LI = 120 VAC INPUT TO CONTROL
ACC = 120 VAC OUTPUT TO OPTIONAL ACCESSORY
NEUTRALS = 120 VAC NEUTRAL
H = LOW VOLTAGE (24 VAC) HUMIDIFICATION
.............
FIGURE 5