Lennox EL280UH110XP60C, EL280UH090P48B, EL280UH135P60D, EL280UH090XP48B, EL280UH070P24A Unit Information

Page 1

© 2012 Lennox Industries Inc.

Corp. 1138−L11

EL280UH(X)

Service Literature

Revised 05/2012

EL280UH(X) SERIES UNITS

EL280UH(X) series units are 80% efficiency gas furnaces
used for upflow or horizontal applications only, manufac­tured with Lennox Duralokt heat exchangers formed of
aluminized steel. EL280UH(X) units are available in heat­ing capacities of 66,000 to 132,000 Btuh and cooling ap­plications up to 5 tons. Product Specifications manual for
proper sizing.

Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. EL280UH(X)
model units are equipped with the SureLight

®

two−stage in­tegrated control. EL280UH(X) unit meets the California Ni­trogen Oxides (NO

x

) Standards and California Seasonal Ef­ficiency requirements. All units use a redundant gas valve to
assure safety shut−off as required by C.S.A.

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 recommendations only and do not consti­tute code.

TABLE OF CONTENTS

Specifications Page 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Blower Data Page 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I Unit Components Page 8. . . . . . . . . . . . . . . . . . . . . . . .

II Installation Page 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

III Start Up Page 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IV Heating System Service Checks Page 19. . . . . . . . .

V Typical Operating Characteristics Page 22. . . . . . . . .

VI Maintenance Page 23. . . . . . . . . . . . . . . . . . . . . . . . . .

VII Wiring and Sequence of Operation Page 26. . . . . .

VIII Field Wiring and DIP Switch Settings Page 28. . . .

IX Troubleshooting Page 30. . . . . . . . . . . . . . . . . . . . . . .

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 installer (or
equivalent), service agency or the gas supplier.

WARNING

Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.

SPECIFICATIONS

Gas
Heating

Model No. - Low Nox - - - EL280UH070XP36A - - -

Performance

High
Fire

Temperature rise range - °F 40 - 70 30 - 60 35 - 65

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

Low
Fire

Temperature rise range - °F 25 - 55 20 - 50 25 - 55

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

High static - in. w.g. Heating 0.5 0.5 0.5

Connections

Flue connection − in. round 4 4 4

in.

Indoor

Wheel nominal diameter x width - in. 10 x 7 10 x 8 10 x 9

Blower

Tons of add-on cooling 1.5 - 2 2 - 3.5 2 - 3.5

Air Volume Range - cfm 560 - 1135 775 - 1620 785 - 1760

Electrical Data Voltage 120 volts - 60 hertz - 1 phase

Blower motor full load amps 3.1 6.1 6.1

Maximum overcurrent protection 15 15 15

Shipping Data lbs. - 1 package 122 126 141

NOTE - Filters and provisions for mounting are not furnished and must be eld provided.

1

Annual Fuel Utilization Efciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized

furnaces.

Model No. EL280UH070P24A EL280UH070P36A EL280UH090P36B

1

AFUE 80% 80% 80%

Input - Btuh 66,000 66,000 88,000

Output - Btuh 52,000 53,000 70,000

3.5 / 10.0 3.5 / 10.0 3.5 / 10.0

Input - Btuh 43,000 43,000 57,000

Output - Btuh 35,000 35,000 46,000

1.7 / 4.9 1.7 / 4.9 1.7 / 4.9

Cooling 0.5 0.5 0.5

Gas pipe size IPS 1/2 1/2 1/2

Motor output - hp 1/5 1/3 1/3

SPECIFICATIONS

Gas
Heating

Model No. - Low Nox EL280UH090XP48B - - -

Performance

High
Fire

Temperature rise range - °F 30 - 60 35 - 65

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

Low
Fire

Temperature rise range - °F 20 - 50 25 - 55

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

High static - in. w.g. Heating 0.5 0.5

Connections

Flue connection − in. round 4 4

in.

Indoor

Wheel nominal diameter x width - in. 10 x 10 10 x 10

Blower

Tons of add-on cooling 3 - 4 3 - 4

Air Volume Range - cfm 1020 - 2030 1050 - 2125

Electrical Data Voltage 120 volts - 60 hertz - 1 phase

Blower motor full load amps 8.2 8.2

Maximum overcurrent protection 15 15

Shipping Data lbs. - 1 package 144 161

NOTE - Filters and provisions for mounting are not furnished and must be eld provided.

1

Annual Fuel Utilization Efciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized

furnaces.

Model No. EL280UH090P48B EL280UH110P48C

1

AFUE 80% 80%

Input - Btuh 88,000 110,000

Output - Btuh 69,000 86,000

3.5 / 10.0 3.5 / 10.0

Input - Btuh 57,000 72,000

Output - Btuh 46,000 58,000

1.7 / 4.9 1.7 / 4.9

Cooling 0.5 0.5

Gas pipe size IPS 1/2 1/2

Motor output - hp 1/2 1/2

Page 2

SPECIFICATIONS

Gas
Heating

Model No. - Low Nox EL280UH110XP60C - - -

Performance

High
Fire

Temperature rise range - °F 30 - 60 35 - 65

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

Low
Fire

Temperature rise range - °F 20 - 50 25 - 55

Gas Manifold Pressure (in. w.g.)

Nat. Gas / LPG/Propane

High static - in. w.g. Heating 0.5 0.5

Connections

Flue connection − in. round 4

in.

Indoor

Wheel nominal diameter x width - in. 11-1/2 x 10 11 x 11

Blower

Tons of add-on cooling 4 - 5 4 - 5

Air Volume Range - cfm 1470 - 2520 1435 - 2750

Electrical Data Voltage 120 volts - 60 hertz - 1 phase

Blower motor full load amps 10 11.5

Maximum overcurrent protection 15 15

Shipping Data lbs. - 1 package 169 188

NOTE - Filters and provisions for mounting are not furnished and must be eld provided.

1

Annual Fuel Utilization Ef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.

Model No. EL280UH110P60C EL280UH135P60D

1

AFUE 80% 80%

Input - Btuh 110,000 132,000

Output - Btuh 87,000 106,000

3.5 / 10.0 3.5 / 10.0

Input - Btuh 72,000 86,000

Output - Btuh 58,000 70,000

1.7 / 4.9 1.7 / 4.9

Cooling 0.5 0.5

2

4

Gas pipe size IPS 1/2 1/2

Motor output - hp 1 1

Page 3 Page 3

OPTIONAL ACCESSORIES - ORDER SEPARATELY

NOTE - FURNACES CANNOT BE TWINNED!

“A” Width

Models

CABINET ACCESSORIES

Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10 51W10

Return Air Base - Upow only 65W75 50W98 50W99 51W00

FILTERS

1

Air Filter and Rack Kit Horizontal (end) 87L95 87L96 87L97 87L98

Size of lter - in. 14 x 25 x 1 18 x 25 x 1 20 x 25 x 1 25 x 25 x 1

Side Return Single 44J22 44J22 44J22 44J22

Ten Pack 66K63 66K63 66K63 66K63

Size of lter - in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1

SERVICE KITS

Night Service Kit 51W04 51W04 51W04 51W04

Universal Service Kit - Switches 89W19 89W19 89W19 89W19

VENTING

Vent Adaptor − 6 in. conn. size upow applications only 18M79 18M79 18M79 18M79

1

Cleanable polyurethane, frame-type lter.

“B” Width

Models

“C” Width

Models

“D” Width

Models

GAS HEAT ACCESSORIES - ORDER SEPARATELY

Natural Gas to

LPG/Propane

Kit

Input

High Altitude

Pressure Switch Kit

0 - 4500 ft. 4501 - 7500 ft. 7501 - 10,000 ft. 0 - 7500 ft. 0 - 7500 ft. 7501 - 10,000 ft. 7501 - 10,000 ft.

070 No Change 91W53 73W35 77W07 77W09 73W37 77W11

090 No Change 91W53 73W35 77W07 77W09 73W37 77W11

110 No Change 91W53 73W35 77W07 77W09 73W37 77W11

135 No Change 73W33 73W34 77W07 77W09 73W37 77W11

LPG/Propane

to Natural Gas

Kit

Natural Gas

High Altitude

Orice Kit

LPG/Propane

High Altitude

Orice Kit

HIGH ALTITUDE DERATE

NOTE - Units may be installed at altitudes up to 4500 ft. above sea level without any modications.

At altitudes above 4500 ft. units must be derated to match information in the shaded area shown below.

NOTE - This is the only permissible derate for these units.

Gas Manifold Pressure (Outlet) in. w.g.

0 - 4500 Feet 4501 -7500 Feet 7501 - 10,000 ft.

Input

Natural Gas LPG/Propane Natural Gas LPG/Propane

High

Fire

Low

Fire

High

Fire

Low

Fire

High

Fire

Low

Fire

High

Fire

Low

Fire

070 3.5 1.7 10 4.9 3.2 1.5 10 4.9 3.5 1.7 10 4.9

090 3.5 1.7 10 4.9 3.2 1.5 10 4.9 3.5 1.7 10 4.9

110 3.5 1.7 10 4.9 3.2 1.5 10 4.9 3.5 1.7 10 4.9

135 3.5 1.7 10 4.9 2.8 1.5 10 4.9 3.5 1.7 10 4.9

1

Natural Gas High Alitude Orice Kit required.

1

Natural Gas LPG/Propane

High

Fire

Low

Fire

High

Fire

Low

Fire

Page 4

BLOWER DATA

EL280UH070P24A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

Air Volume / Watts at Various Blower Speeds

High

Medium-

High

Medium-

Low

cfm Watts cfm Watts cfm Watts cfm Watts

0.10 1073 430 863 332 727 267 657 232

0.20 1076 415 848 324 716 261 641 227

0.30 1060 399 850 315 703 255 634 223

0.40 1039 380 825 301 693 247 624 216

0.50 1004 357 809 289 680 236 608 208

0.60 951 345 778 270 656 227 589 199

0.70 906 320 749 258 630 213 546 188

0.80 836 298 685 239 584 198 492 171

NOTES - All air data is measured external to unit without lter
(not furnished - eld provided)

EL280UH070P36A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

Air Volume / Watts at Various Blower Speeds

High

Medium-

High

Medium-

Low

cfm Watts cfm Watts cfm Watts cfm Watts

0.10 1620 658 1365 568 1115 468 945 374

0.20 1580 621 1355 535 1135 442 960 362

0.30 1520 595 1335 513 1130 423 955 350

0.40 1480 562 1300 478 1100 403 945 335

0.50 1400 520 1270 450 1080 382 925 320

0.60 1340 490 1205 420 1035 358 880 301

0.70 1245 458 1125 393 975 333 835 282

0.80 1160 434 1045 364 915 310 775 262

NOTES - All air data is measured external to unit without lter
(not furnished - eld provided)

Low

Low

EL280UH090P36B PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

Air Volume / Watts at Various Blower Speeds

High

Medium-

High

Medium-

Low

cfm Watts cfm Watts cfm Watts cfm Watts

0.10 1760 730 1435 576 1185 452 970 378

0.20 1725 683 1420 547 1170 440 975 368

0.30 1685 656 1410 525 1170 420 980 356

0.40 1630 625 1370 501 1150 400 955 340

0.50 1535 569 1315 469 1125 391 925 326

0.60 1470 533 1275 440 1085 367 910 309

0.70 1365 490 1185 407 1020 344 840 290

0.80 1255 466 1105 380 935 314 785 266

NOTES - All air data is measured external to unit without lter
(not furnished - eld provided)

EL280UH090P48B PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

Air Volume / Watts at Various Blower Speeds

High

Medium-

High

Medium-

Low

cfm Watts cfm Watts cfm Watts cfm Watts

0.10 2030 804 1780 719 1525 613 1280 518

0.20 1910 740 1740 666 1535 580 1305 493

0.30 1840 698 1705 643 1500 551 1305 474

0.40 1770 664 1635 594 1460 517 1280 445

0.50 1665 625 1560 567 1410 483 1225 420

0.60 1585 595 1470 523 1330 451 1190 391

0.70 1470 561 1365 483 1260 421 1115 368

0.80 1355 514 1230 433 1155 392 1020 338

NOTES - All air data is measured external to unit without lter
(not furnished - eld provided)

Low

Low

EL280UH110P48C PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

NOTES - All air data is measured external to unit without lter
(not furnished - eld provided)

Air Volume / Watts at Various Blower Speeds

High

Medium-

High

Medium-

Low

Low

cfm Watts cfm Watts cfm Watts cfm Watts

0.10 2125 919 1820 747 1555 648 1300 540

0.20 2080 862 1790 705 1540 619 1335 516

0.30 2015 807 1745 652 1545 587 1335 498

0.40 1940 748 1695 629 1505 552 1320 470

0.50 1850 716 1635 581 1470 523 1295 449

0.60 1775 679 1575 560 1395 484 1235 417

0.70 1680 637 1470 508 1320 450 1170 387

0.80 1560 592 1350 469 1205 404 1050 345

Page 5

BLOWER DATA

EL280UH110P60C PERFORMANCE (Less Filter)

Air Volume / Watts at Different Blower Speeds

External

Static

Pressure

in. w.g.

Bottom Return Air, Side Return Air with Optional Return
Air Base, Return Air from Both Sides or Return Air from
Bottom and One Side.

High Medium-High Medium-Low Low High Medium-High Medium-Low Low

cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts

0.10 2520 1359 2250 1034 1860 841 1455 654 2605 1454 2160 1060 1740 848 1430 651

0.20 2465 1329 2230 1018 1870 823 1480 647 2505 1401 2150 1018 1785 838 1450 649

0.30 2385 1307 2180 981 1885 809 1540 646 2435 1349 2115 991 1795 818 1485 638

0.40 2295 1256 2105 942 1865 778 1570 638 2350 1308 2070 965 1805 801 1480 631

0.50 2200 1214 2055 909 1845 762 1570 619 2260 1274 2010 929 1785 775 1480 621

0.60 2130 1186 1985 882 1795 741

1550 604 2175 1228 1955 901 1755 752 1490 611

0.70 2015 1150 1890 848 1720 711 1505 580 2085 1186 1850 853 1710 722 1460 594

0.80 1905 1105 1810 815 1675 687 1470 565 1965 1147 1785 818 1640 689 1425 567

NOTES - All air data is measured external to unit without lter (not furnished - eld provided)

EL280UH135P60D PERFORMANCE (Less Filter)

Air Volume / Watts at Different Blower Speeds

External

Static

Pressure

in. w.g.

Bottom Return Air, Side Return Air with Optional Return
Air Base, Return Air from Both Sides or Return Air from
Bottom and One Side.

High Medium-High Medium-Low Low High Medium-High Medium-Low Low

cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts

0.10 2750 1441 2220 1056 1725 825 1395 625 2725 1463 2180 1075 1715 827 1320 624

0.20 2720 1392 2235 1029 1785 810 1445 618 2640 1400 2180 1051 1720 819 1380 626

0.30 2605 1362 2220 1002 1820 800 1460 623 2575 1374 2165 1005 1790 803 1420 622

0.40 2495 1312 2185 968 1845 779 1485 616 2495 1343 2145 988 1775 791 1450 617

0.50 2420 1275 2135 939 1825 767 1505 605 2405 1292 2105 948 1780 777 1470 610

0.60 2335 1234 2080 909 1825 753

1495 593 2305 1257 2045 914 1775 753 1480 593

0.70 2220 1190 1995 864 1760 716 1475 576 2215 1214 1970 884 1740 727 1455 583

0.80 2120 1157 1890 835 1680 686 1435 558 2110 1170 1890 851 1675 699 1430 565

NOTES - All air data is measured external to unit without lter (not furnished - eld provided)

Single Side Return Air − Air volumes in bold require eld
fabricated transition to accommodate 20 x 25 x 1 in. air lter
in order to maintain proper air velocity.

Single Side Return Air − Air volumes in bold require eld
fabricated transition to accommodate 20 x 25 x 1 in. air lter
in order to maintain proper air velocity.

Page 6

Page 7

FIGURE 1

EL280UH Parts Arrangement

Combustion Air

Pressure Switch

Combustion Air

Inducer

Gas Valve and Manifold

Assembly

Limit Switch

(under collector box)

Collector Box

Heat Exchanger

Integrated Control

Indoor Blower and Motor Assembly

(removed from cabinet)

Indoor Blower and Motor Assembly

(installed in cabinet)

Make Up Box

Transformer

Door Interlock

Switch

Page 8

I−UNIT COMPONENTS

EL280UH(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 compo­nents are in the control box (figure 2) found in the blower
section.
EL280UH(X) units are factory equipped with a bottom return

air panel in place. The panel is designed to be field removed

as required for bottom air return. Markings are provided for

side return air and may be cut out in the field.

CAUTION

Electrostatic discharge can affect 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.

FIGURE 2

CONTROL BOX EL280UH

Transformer

SureLight

®

Integrated Control

Interlock Switch

Circuit Breaker

3. Circuit Breaker (CB8)

A 24V circuit breaker is also located in the control box.
The switch provides overcurrent protection to the trans­former (T1). The breaker is rated 3A at 32V. If the current
exceeds this limit the breaker will trip and all unit opera­tion will shutdown. The breaker can be manually reset
by pressing the button on the face. See figure 3.

FIGURE 3

CIRCUIT BREAKER CB8

PRESS TO RESET

WARNING

Shock hazard.
Disconnect power before servicing. Integrated

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.

4. Integrated Control (A92)

EL280UH units are equipped with the Lennox two−stage
integrated SureLight

®

control. The system consists of a
ignition / blower control (figures 5 and 6) with control pin
designations in tables 2 and 3 and and ignitor. The control
and ignitor work in combination to ensure furnace ignition
and ignitor durability. The SureLight integrated control,
controls all major furnace operations. The control features
a red LED light, for furnace status and troubleshooting.
The LED flashes in X" + Y" codes. For example using
table 4 under PRESSURE SWITCH CODES", if the red
LED flashes 2 times, then off for 2 seconds then flashes 3
times, the low pressure switch is failed open. The control
also has two 120 volt accessory terminals rated at (1) one
amp each and one 24 volt accessory terminal rated at 0.5
an amp.

Electronic Ignition

At the beginning of the heat cycle the SureLight control
monitors the first stage and second stage combustion air
inducer pressure switch. The control will not begin the
heating cycle if the first stage pressure switch is closed (by−
passed). Likewise the control will not begin the second
stage heating cycle if the second stage pressure switch is
closed, and will remain in first stage heat. However, if the
second stage pressure switch closes during the first stage
heat pre−purge, the control will allow second stage heat.
Once the first stage pressure switch is determined to be
open, the combustion air inducer is energized on low (first
stage) heat speed. When the differential in the pressure
switch is great enough, the pressure switch closes and a
15−second pre−purge begins. If the switch is not proven
within 2−1/2 minutes, the control goes into Watchguard−
Pressure Switch mode for a 5−minute re−set period.

Page 9

After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds after which the gas valve opens
for a 4−second trial for ignition. The ignitor energizes during
the 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.

NOTE − During abnormal conditions such as low supply
voltage or low outdoor temperatures and the low fire pres­sure switch does not close, the combustion air inducer will
switch to high fire. After a 15 second pre−purge the high fire
pressure switch will close and the unit will begin operation
on high fire. After 10 to 20 seconds of high fire operation the
unit will switch to low fire.

Two Stage Operation / Thermostat Selection Jumper

The control can be utilized in two modes: SINGLE−STAGE
thermostat or TWO−STAGE thermostat. The thermostat
selection is made using a dip switch (figure 5) and must be
positioned for the particular application. The dip switch is
factory set to OFF" for use with a two−stage thermostat
with two stage heat. Re−position dip switch to ON" for use
with a single stage thermostat with two stage heat.
While in the single−stage thermostat mode (ON DIP switch
setting), the burners will always fire on first−stage heat. The
combustion air inducer will operate on low speed and in­door blower will operate on low heat speed. After a 10 or 15
minute field selectable recognition period, the unit will
switch to second stage heat. While in the two−stage ther­mostat mode (OFF DIP switch setting) the burners will fire
on first−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 first and second stage heat, the unit will fire an first stage
heat and switch to second stage heat after 30 seconds of
operation. See Sequence of Operation flow charts in the
back of this manual for more detail.

DIP Switch Settings
Switch 1 −− Thermostat Selection −− This unit may be used

with either a single−stage or two−stage thermostat. The
thermostat selection is made using a DIP switch which
must be properly positioned for the particular application.
The DIP switch is factory−positioned for use with a two−
stage thermostat. If a single−stage thermostat is to be used,
the DIP switch must be repositioned.

a − Select OFF" for two−stage heating operation con-

trolled by a two−stage heating thermostat (factory set­ting);

b − Select ON" for two−stage heating operation con-

trolled by a single−stage heating thermostat. This set­ting provides a timed delay before second−stage heat
is initiated.

Switch 2 −− Second Stage Delay (Used with Single−
Stage Thermostat Only) −− This switch is used to deter-

mine the second stage on delay when a single−stage ther­mostat is being used. The switch is factory−set in the OFF
position, which provides a 10−minute delay before second−
stage heat is initiated. If the switch is toggled to the ON
position, it will provide a 15−minute delay before second−
stage heat is initiated. This switch is only activated when
the thermostat selector jumper is positioned for SINGLE−
stage thermostat use.

Switches 3 and 4 −− Heating Blower−Off Delay −− The
heating blower−on delay of 30 seconds is not adjustable.
The heating blower−off delay (time that the blower operates
after the heating demand has been satisfied) can be ad­justed by moving switches 3 and 4 on the integrated con­trol. The unit is shipped from the factory with a heating
blower−off delay of 90 seconds. The heating blower off
delay affects comfort and is adjustable to satisfy individual
applications. Adjust the blower off delay to achieve a sup­ply air temperature between 90° and 110°F at the exact
moment that the blower is de−energized. Longer off delay
settings provide lower supply air temperatures; shorter set­tings provide higher supply air temperatures.Table 1 (with
figure 4) provides the blower off timings that will result from
different switch settings.

TABLE 1

Heating Blower−Off Delay Switch Settings

Blower Off Delay

(Seconds)

Switch 3 Switch 4

60 Off On
90

(factorysetting)

Off Off

120 On Off
180 On On

HEAT FAN-OFF TIME IN SECONDS

60sec.

90sec.

120sec.

180sec.

12345 12345

12345 12345

To adjust fan−off timing, flip dip switch to desired setting.

FIGURE 4

Page 10

Switch 5 −− Cooling Blower−Off Delay −− The cooling
blower−off delay (time that the blower operates after the
cooling demand has been satisfied) can be adjusted by
moving switch 5 on the integrated control. The switch is fac­tory−set in the OFF position, which provides a cooling blow­er−off delay of 45 seconds. If the switch is toggled to the ON
position, it will provide a 2−second cooling blower−off delay

On−Board Link W951 Heat Pump (R to O)

On−board link W951 is a clippable connection between ter-

minals R and O on the integrated control. W951 must be cut
when the furnace is installed in applications which include a
heat pump unit and a thermostat which features dual fuel
use. If the link is left intact, terminal O" will remain ener­gized eliminating the HEAT MODE in the heat pump.

On−Board Link W915 2 Stage Compr (Y1 to Y2)

On−board link W915 is a clippable connection between ter­minals Y1 and Y2 on the integrated control. W915 must be
cut if two−stage cooling will be used. If the Y1 to Y2 link is
not cut the outdoor unit will operate in second−stage cooling
only.

TWO−STAGE INTEGRATED CONTROL

THERMOSTAT CONNECTIONS (TB1)

1/4" QUICK CONNECT TERMINALS

DIP SWITCH FUNCTIONS

DIP

SWITCHES

DIAGNOSTIC

LEDs

ON−BOARD

LINKS

1= ERROR CODE RECALL
H= 24V HUMIDIFIER OUTPUT
L= LENNOX SYSTEM OPERATION MONITOR

SENSE = 120 VAC OUTPUT TO FLAME SENSOR
NEUTRALS= 120 VAC NEUTRAL
PARK = DEAD TERMINAL FOR UNUSED BLOWER LEAD
HEAT LOW = 120 VAC OUTPUT TO CIRC BLWR −− LOW HT SPEED & CONT FAN
HEAT HIGH/ COOL LOW = 120 VAC OUTPUT TO CIRC BLWR −−

HIGH HEAT AND LOW COOL SPEED

COOL HIGH = 120 VAC OUTPUT TO CIRC BLWR −− HIGH COOL SPEED

DIP SWITCH(ES) FUNCTION

1 −− 2 Stage T’stat Selects t/stat type (single or two−stage)

2 −− 2nd Stage Delay Second stage ON delay (single−stage t’stat)

3 & 4 −− Heat Off Delay Heating fan OFF delay

5 −− Cool Off Delay Cooling fan OFF delay

W915

W951

FIGURE 5

TABLE 2

SureLight control 5 Pin Terminal Designation

PIN # Function

1 Ignitor

2 Combustion Air Inducer High Speed

3 Combustion Air Inducer Low Speed

4 Combustion Air Inducer Neutral

5 Ignitor Neutral

TABLE 3

SureLight control 12Pin Terminal Designation

PIN # Function

1 Gas Valve High Fire

2 Second Stage pressure Switch

3 Rollout In

4 Ground

5 24V Hot

6 Primary Limit In

7 Gas Valve Low Stage

8 Gas Valve Common

9 24V Neutral

10 Ground

11 Rollout Switch Out

12 1st Stage pressure Switch

Page 11

INTEGRATED CONTROL

FIGURE 6

Page 12

TABLE 4

FLASH CODE

(X + Y)

STATUS / ERROR DESCRIPTION

FLASH CODE DESCRIPTIONS

Pulse A 1/4 second flash followed by four seconds of off time.

Heartbeat Constant 1/2 second bright and 1/2 second dim cycles.

X + Y

LED flashes X times at 2Hz, remains off for two seconds, flashes Y times at 2Hz, remains off for four
seconds, then repeats.

Pulse Power on − Standby.

Heartbeat Normal operation − signaled when heating demand initiated at thermostat.

FLAME CODES

1 + 2 Low flame current −− run mode.

1 + 3 Flame sensed out of sequence −− flame still present.

PRESSURE SWITCH CODES

2 + 3 Low pressure switch failed open.

2 + 4 Low pressure switch failed closed.

2 + 5 High pressure switch failed open.

2 + 6 High pressure switch failed closed.

2 + 7 Low pressure switch opened during ignition trial or heating demand.

LIMIT CODE

3 + 1 Limit switch open.

WATCHGUARD CODES

4 + 1 Watchguard −− Exceeded maximum number of retries.

4 + 2 Watchguard −− Exceeded maximum number of retries or last retry was due to pressure switch opening.

4 + 3 Watchguard −− Exceeded maximum number of retries or last retry was due to flame failure.

4 + 5 Watchguard −− Limit remained open longer than three minutes.

4 + 6 Watchguard −− Flame sensed out of sequence; flame signal gone.

4 + 7 Ignitor circuit fault −− Failed ignitor or triggering circuitry.

4 + 8 Low line voltage.

HARD LOCKOUT CODES

5 + 1 Hard lockout −− Rollout circuit open or previously opened.

5 + 2 Control failed self check, internal error (control will restart if error recovers).

5 + 3 No Earth ground (control will restart if error recovers).

5 + 4 Reversed line voltage polarity (control will restart if the error recovers).

5 + 6 Low secondary (24VAC) voltage.

Error Code Storage

The ignition control stores the last ten error codes in
memory. The codes are retained in case of power loss.

Error Code Review

1 − Short R (2) to (1). Within 1/2 second, the STATUS LED

will stay lit continuously to indicate that the short was
sensed.

2 − Continue to hold the short between R (2) to (1). After 5

seconds, STATUS LED will go from being continuously
lit to off. This indicates that error code review is pend­ing.

3 − Remove R (2) to (1) short within ten seconds of STA-

TUS LED turning off. This activates error code review.

4 − Last ten error codes will be flashed on the STATUS

LED.

5 − After final error code is indicated, STATUS LED will

flash to indicate normal operation.

Clearing Error Codes

1 − Short R (2) to (1). Within 1/2 second, the STATUS LED

will stay lit continuously to indicate that the short was
sensed.

2 − Continue to hold the short between R (2) to (1). After 5

seconds, STATUS LED will go from being continuously
lit to off.

3 − Continue to hold the short between R (2) to (1) beyond

ten seconds after STATUS LED has turned off. STA­TUS LED will turn on, indicating that error codes have
been cleared.

4 − Remove R (2) to (1) short. STATUS LED will flash to in-

dicate normal operation.

Page 13

B− Indoor Blower

5. Blower Motors and Capacitors

All EL280UH(X) units use direct drive blower motors. All mo­tors are 120V permanent split capacitor motors to ensure
maximum efficiency. Ratings for capacitors will be on motor
nameplate. See SPECIFICATIONS section for motor speci­fications.

C− Heating Components

1. Ignitor

The SureLight

®

ignitor is made of durable silicon nitride. Ig­nitor longevity is enhanced by controlling voltage to the ig­nitor. The integrated control provides a regulated 120 volts
to the ignitor for a consistent ignition and long ignitor life.
Ohm value should be 39 to 70. See figure 7 for ignitor loca­tion and figure 9 for ignitor check out.

NOTE − The EL280UH(X) furnace contains electronic com­ponents that are polarity sensitive. Make sure that the fur­nace is wired correctly and is properly grounded.

2. Flame Sensor

A flame sensor is located on the left side of the burner sup­port. See figure 7. The sensor protrudes into the flame en­velope of the left−most burner. The sensor 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. A microamp DC meter is needed to check the
flame signal on the integrated control. See figure 8 and
table 5 for flame signal check and measurement.

3. Gas Valve

The two−stage gas valve (figure 12) is internally redundant
to assure safety shut−off. If the gas valve must be replaced,
the same type valve must be used.

24VAC terminals and ON/OFF switch are located on the
valve. A wire harness connects the terminals from the gas
valve to the electronic ignition control. 24V applied to the termi­nals energizes the valve.

Inlet and outlet pressure taps are located on the valve. A regu­lator adjustment screw is located on the valve.

LPG change over kits are available from Lennox. Kits include
burner orifices.

4. Flame Rollout Switches (S47)

The EL280UH is equipped with two rollout switches. See
figure 7 for location. The limits are a N.C. SPST manual-re­set limit. When S47 senses rollout, the circuit breaks and
the ignition control immediately stops ignition and closes
the gas valve. Rollout can be caused by a blocked heat ex­changer, flue or lack of combustion air. The switches are
factory set to trip (open) at 210°F and cannot be adjusted. To
manually reset a tripped switch, push the reset button located
on the control.

5. Burners

All units use inshot burners. Burners are factory set and re­quire no adjustment. Always operate the unit with the burner
box front panel in place. Each burner uses an orifice that is
precisely matched to the burner input. Burners can be re­moved as a one piece assembly for service. If burner assem­bly has been removed, it is critical to align center of each
burner to the center of the clamshell when re−installing. See
more detail in Section VI− MAINTENANCE sub−section E−
Heat Exchanger and Burners.

6. Primary Limit Control (S10)

The primary limit (S10) is located in the heating vestibule pan­el. When excess heat is sensed in the heat exchanger, the
limit will open. If the limit is open, the furnace control energizes
the supply air blower and closes the gas valve. The limit auto­matically resets when unit temperature returns to normal. The
switch must reset within three minutes or the SureLight control
will go into Watchguard for one hour. The switch is factory
set and cannot be adjusted. The switch may have a different
set point for each unit model number. See Lennox Repair
Parts Handbook if limit switch must be replaced,

Page 14

EL280UH HEATING COMPONENTS

FIGURE 7

Gas Valve

Gas Orifices

Sensor

Ignitor

Burners

Rollout Switches

Page 15

To Measure Flame Signal − Integrated Control:

Use a digital readout meter capable of reading DC micro­amps. S e e f i g ure 8 an d table 5 for flame signal check.

1 − Set the meter to the DC amps scale.
2 − Turn off supply voltage to control.
3 − Disconnect integrated control flame sensor wire from

the flame sensor.
4 − Connect (−) lead to flame sensor.
5 − Connect (+) lead to the ignition control sensor wire.

6 − Turn supply voltage on and close thermostat contacts to

cycle system.

7 − When main burners are in operation for two minutes, take

reading.

TABLE 5

Flame Signal in Microamps

Normal

Low Drop Out

1.9 or greater 1.4 or less .20

FIGURE 8

Measuring Flame Signal

Set dial to measure

DC microamps

(+)

To Flame

Terminal

DIGITAL METER

Red Collar
Indicates
Positive Leads

(+) To Control

Sensor Terminal

Flame
Sensor

Flame Sensor

Wire

Integrated
Control

Remove Sensor Wire from
Integrated Control and
Connect Alligator Clip (−)
to Frame Sensor Lead

Flame Sensor

Terminal

Remove Sensor Wire from

Integrated Control and

Connect Alligator Clip (+)

to Terminal on Control

(+)

Page 16

FIGURE 9

EL280UH Ignitor Check Out

Meter

(set to ohms)

Test 1 Checking resistance of ignitor circuit

Remove 5−pin plug from integrated control.
Check Ohms reading across terminal 1 and 5.
Reading should be between 39 and 70 ohms. If
value is correct, this is the only test needed. If
the meter reading is not correct ("0" or ifinity),
then a second test is needed.

Integrated control detail

Test 2 Checking the resistance of the ignitor

Seperate the 2−pin jack plug near the manifold and check
resistance of the ignitor. Reading should be betwenn 39
and 70 ohms. If reading is correct, then there is a problem
with the wiring between the jack plug anf the control. If
reading is not correct, the issue is the ignitor.

Meter

(set to ohms)

Test 3 Checking voltage to ignitor

Insert meter probes into terminals 1 and 5.
(use small diameter probes in order to not
damage plug). Check voltage during 20
second ignitor warm up period. Voltage
should read 120 volts + or − 10%. If voltage
is above or below these values, check for
correct supply voltage to furnace.

Meter

(set to AC volts)

Integrated control detail

Integrated control detail

Page 17

7. Combustion Air Inducer (B6)

All EL280UH(X) units use a two−stage combustion air in­ducer to move air through the burners and heat exchanger
during heating operation. The blower uses a 120VAC mo­tor. The motor operates during all heating operation and is
controlled by integrated control A92. The inducer also op­erates for 15 seconds before burner ignition (pre-purge)
and for 5 seconds after the gas valve closes (post-purge).
The inducer operates on low speed during first−stage heat,
then switches to high speed for second stage heat.

NOTE − Each furnace model uses a unique CAI. Refer to
Lennox Repair Parts listing for correct inducer for replace­ment.

A pressure switch connected to the combustion air inducer
orifice plate is used to prove inducer operation. The combus­tion air inducer orifice will be different for each model. See
table 6 for orifice sizes. The switch monitors air pressure in
the inducer housing. During normal operation, the pressure in
the housing is negative. If pressure becomes less negative
(signifying an obstruction in the flue) the proving switch
opens. When the proving switch opens, the furnace control
(A92) immediately closes the gas valve to prevent burner op­eration.

TABLE 6

EL280UH(X) Unit

C.A.I. Orifice Size (in)

−070 1.375

−09036B 1.625

−090(X)48B 1.690

−110 1.875

−135 1.940

8. Combustion Air Inducer
pressure Switch (S18)

EL280UH(X) series units are equipped with a dual combus­tion air pressure switch (first and second stage) located on
the combustion air inducer orifice bracket. See figure 10.
The switch is connected to the combustion air inducer hous­ing by means of a flexible silicone hose. It monitors negative
air pressure in the combustion air inducer housing.

The switches are a single-pole single-throw proving switch
electrically connected to the integrated control. The purpose
of the switch is to prevent burner operation if the combustion
air inducer is not operating or if the flue becomes obstructed.

On heat demand (first or second stage) the switch senses
that the combustion air inducer is operating. It closes a cir­cuit to the integrated control when pressure inside the com­bustion air inducer decreases to a certain set point.
Set points vary depending on unit size. See table 7. The
pressure sensed by the switch is negative relative to atmo­spheric pressure. If the flue becomes obstructed during op­eration, the switch senses a loss of negative pressure
(pressure becomes more equal with atmospheric pres­sure) and opens the circuit to the furnace control and gas
valve. A bleed port on the switch allows relatively dry air in
the vestibule to purge switch tubing, to prevent condensate
build up.

FIGURE 10

COMBUSTION AIR PRESSURE SWITCH

Ta p

High Fire

Switch

Low Fire

Switch

Bracket

3/16" terminals

1/4 terminals

NOTE − The switch is factory set and is not field adjustable.
It is a safety shut-down control in the furnace and must not
be by−passed for any reason. If switch is closed or by−
passed, the control will not initiate ignition at start up.

TABLE 7

0 − 4500 ft

EL280UH(X) Unit

Set Point Low
Heat (in w.c.)

Set Point High Heat

(in w.c.)

−070 0.35 0.68

−090P36B 0.35 0.68

−090P48B 0.30 0.68

−090XP48B 0.35 0.68

−110P48C/60C 0.30 0.68

−110XP60C 0.35 0.68

−135 0.35 0.75

NOTE − See table 11 for high altitude pressure switch kits.

Page 18

Multiple Venting

The EL280UH(X) furnace can vent in multiple positions.

See figure 11.

The make up box may be removed and the combustion air

inducer may be rotated clockwise or counterclockwise 90°

to allow for vertical or horizontal vent discharge in a vertical

or horizontal cabinet position. Remove the four mounting

screws, rotate the combustion air inducer and gasket
(pressure switch should be above the combustion air in­ducer in all positions), then reinstall the mounting screws.
See unit Installation Instructions for more detail.

IMPORTANT

The combustion air pressure switch must be moved
for horizontal discharge air left position.

FIGURE 11

FLOW

AIR

vent pipe

In all positions route the wires away from moving parts and the heat of the inducer
motor to prevent damage to the wires. The pressure switch must be installed above
the CAI to prevent moisture from collecting in the hoses or switch.

FLOW

AIR

Vent Pipe

FLOW

AIR

Vent Pipe

Vent Pipe

Vent Pipe

vent pipe

Page 19

II−PLACEMENT AND INSTALLATION

Make sure unit is installed in accordance with installation
instructions and applicable codes.

III−START-UP

A−Preliminary and Seasonal Checks

1 − Inspect electrical wiring, both field and factory installed

for loose connections. Tighten as required.

2 − Check voltage at disconnect switch. Voltage must be

within range listed on the nameplate. If not, consult the
power company and have voltage condition corrected
before starting unit.

B−Heating Start-Up

WARNING

Shock and burn hazard.

EL280UH(X) units are equipped with a hot surface
ignition system. Do not attempt to light manually.

1 − STOP! Read the safety information at the beginning of

this section.

2 − Set the thermostat to the lowest setting.

3 − Turn off all electrical power to the unit.

4 − This furnace is equipped with an ignition device which

automatically lights the burners. Do not try to light the
burners by hand.

5 − Remove the access panel.

6 − Turn switch on gas valve to OFF. Do not force. See

figure 12.

7 − Wait five minutes to clear out any gas. If you then smell

gas, STOP! Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s instruc­tions. If you do not smell gas go to next step.

FIGURE 12

GAS VALVE SHOWN IN ON POSITION

INLET PRESSURE POST

HIGH FIRE ADJUSTMENT

SCREW

(under cap)

MANIFOLD

PRESSURE POST

White Rodgers Gas Valve

8 − Move switch on gas valve to ON. Do not force. See fig-

ure 12.

9 − Replace the access panel.

10− Turn on all electrical power to to the unit.

11− Set the thermostat to desired setting.

NOTE − When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.

Turning Off Gas To Unit

1 − Set thermostat to lowest setting.
2 − Turn off all electrical power to unit if service is to be per-

formed.

3 − Remove access panel.
4 − Move switch on valve to OFF. Do not force.
5 − Replace access panel.

Failure To Operate

If the unit fails to operate, check the following:
1 − Is the thermostat calling for heat?
2 − Are access panels securely in place?
3 − Is the main disconnect switch closed?
4 − Is there a blown fuse or tripped circuit breaker?
5 − Is the filter dirty or plugged? Dirty or plugged filters will

cause the limit control to shut the unit off.
6 − Is gas turned on at the meter?
7 − Is the manual main shut-off valve open?
8 − Is the gas valve ON/OFF switch in the ON position?
9 − Is the unit ignition system in lock out? If the unit locks out

again, call the service technician to inspect the unit for

blockages.
10 −Is pressure switch closed? Obstructed flue will cause

unit to shut off at pressure switch. Check flue and outlet

for blockages.
11 −Are flame rollout switches tripped? If flame rollout

switches are tripped, call the service technician for in-

spection.

C−Safety or Emergency Shutdown

Turn off unit power. Close manual and main gas valves.

D−Extended Period Shutdown

Turn off thermostat or set to UNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guaran­tee no gas leak into combustion chamber. Turn off power to
unit. All access panels and covers must be in place and se­cured.

IV−HEATING SYSTEM SERVICE CHECKS

A−CSA Certification

All units are CSA design certified without modifications.
Refer to the EL280UH(X) Installation Instruction.

B−Gas Piping

CAUTION

If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet.

WARNING

Do not exceed 600 in−lbs (50 ft−lbs) torque when
attaching the gas piping to the gas valve.

Gas supply piping should not allow more than 0.5"W.C. drop
in pressure between gas meter and unit. Supply gas pipe
must not be smaller than unit gas connection.

Page 20

Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.

C−Testing Gas Piping

IMPORTANT

In case emergency shutdown is required, turn off
the main shut-off valve and disconnect the main
power to unit. These controls should be properly
labeled by the installer.

When pressure testing gas lines, the gas valve must be dis­connected and isolated. Gas valves can be damaged if
subjected to more than 0.5 psig (14" W.C.). See figure 13. If
the pressure is greater than 0.5psig (14"W.C.), use the
manual shut−off valve before pressure testing to isolate fur­nace from gas supply.

FIGURE 13

MANUAL MAIN SHUT−OFF VALVE

WILL NOT HOLD TEST PRESSURE

IN EXCESS OF 0.5 PSIG (14"W.C.)

GAS VALVE

CAP

GAS PIPING TEST PROCEDURE

1/8 NPT PLUG

When checking piping connections for gas leaks, use pre­ferred means. Kitchen detergents can cause harmful corro­sion on various metals used in gas piping. Use of a specialty
Gas Leak Detector is strongly recommended. It is available
through Lennox under part number 31B2001. See Corp.
8411−L10, for further details.

Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.

D−Testing Gas Supply Pressure

A threaded plug on the inlet side of the gas valve provides
access to the supply pressure tap. Remove the threaded
plug, install a field−provided barbed fitting and connect a
manometer to measure supply pressure. See table 10 for
supply line pressure. Replace the threaded plug after mea­surements have been taken.

E−Check Manifold Pressure

After line pressure has been checked and adjusted, check
manifold pressure. Checks of manifold pressure are made
as verification of proper regulator adjustment. Manifold pres­sure for the EL280UH(X) can be measured at any time the
gas valve is open and is supplying gas to the unit.

IMPORTANT

For safety, connect a shut-off valve between the ma­nometer and the gas tap to permit shut off of gas
pressure to the manometer.

The gas valve is factory set and should not require adjust­ment. All gas valves are factory regulated.

Manifold Adjustment Procedure:

NOTE − Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.

1 − Connect test gauge to manifold pressure post (figure

12) on gas valve.

2 − Ignite unit on high fire and let run for 5 minutes to allow

for steady state conditions.

3 − After allowing unit to stabilize for 5 minutes, record

manifold pressure and compare to value given in table

10.

4 − If necessary, make adjustments. Figure 12 show loca-

tion of high fire adjustment screw.

5 − If an adjustment is made on high fire, re−check man-

ifold pressure on low fire. Do not adjust low fire man-
ifold pressure. If low fire manifold pressure is more
than 1/2" above or below value specified in table 10,
replace valve.

NOTE − Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to replace
pressure tap plug.

F− Proper Gas Flow (Approximate)

Furnace should operate at least 5 minutes before check­ing gas flow. Determine time in seconds for two revolu­tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time
in table 8 below. If manifold pressure matches table 10
and rate is incorrect, check gas orifices for proper size and
restriction.

NOTE− To obtain accurate reading, shut off all other gas
appliances connected to meter.

TABLE 8

GAS METER CLOCKING CHART

Input

Seconds for One Revolution
Natural LP

1 cu ft

Dial

2 cu ft

Dial

1 cu ft

Dial

2 cu ft

DIAL

−045 80 160 200 400

−70 55 110 136 272

−90 41 82 102 204

−110 33 66 82 164

−135 27 54 68 136

Natural−1000 btu/cu ft LP−2500 btu/cu ft

Page 21

IMPORTANT

For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.

G− Proper Combustion

Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com­bustion. See sections E− and F−. Take combustion sample
beyond the flue outlet. Table 9 shows acceptable combus­tion for ALL EL280UH models. The maximum carbon

monoxide reading should not exceed 50 ppm.

TABLE 9

Firing Rate

CO2%

For Nat

CO2%

For L.P.

High Fire 6.0 − 7.5 7.0 − 8.5

Low Fire 5.0 − 6.5 5.8 − 7.3

H− High Altitude

The manifold pressure may require adjustment and com­bustion air pressure switch may need replacing to ensure
proper combustion at higher altitudes. Refer to table 10 for
manifold pressure and table 11 for pressure switch change
and gas conversion kits.

TABLE 10

Manifold Pressure Settings at all Altitudes

Unit

Input

Gas

Manifold

Pressure in.wg.

0−4500 ft.

Manifold

Pressure in.wg.

4501−7500 ft.

1

Manifold

Pressure in.wg.

7501 − 10,000 ft.

2

Supply Line

Pressure

in. w.g.

Low Fire High Fire Low Fire High Fire Low Fire High Fire Min Max

070

Natural 1.7 3.5 1.5 3.2 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

090

Natural 1.7 3.5 1.5 3.2 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

110

Natural 1.7 3.5 1.5 3.2 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

135

Natural 1.7 3.5 1.5 2.8 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

1

This is the only permissible derate for these units.

2

Natural gas high altitude orifice kit required.

3

A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion

procedure.

NOTE − Units may be installed at altitudes up to 4500 ft. above sea level without modifications.

TABLE 11

Pressure Switch and Gas Conversion Kits at all Altitudes

Unit

Input

High Altitude Pressure Switch Kit

High Altitude

Natural Gas Kit

LP/Propane Gas Kit

LP/Propane to

Natural Kit

0 − 4500 ft. 4501 − 7500 ft. 7501 − 10,000 ft. 7501 − 10,000 ft. 0 − 7500 ft 7501 − 10,000 ft. 0 − 7500 ft.Min

070

No Change

91W53 73W35

73W37 77W07 77W11 77W09

090 91W53 73W35

110 91W53 73W35

135 73W33 73W34

NOTE − A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion
procedure.

Page 22

V−TYPICAL OPERATING CHARACTERISTICS

A−Blower Operation and Adjustment

1 − Blower operation is dependent on thermostat control

system.

2 − Generally, blower operation is set at thermostat sub-

base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO position,
blower cycles with demand or runs continuously while
heating or cooling circuit cycles.

3 − Depending on the type of indoor thermostat, blower

and entire unit will be off when the system switch is in
OFF position.

B−Temperature Rise (Figure 14)

Temperature rise for EL280UH units depends on unit input,
blower speed, blower horsepower and static pressure as
marked on the unit rating plate. The blower speed must be
set for unit operation within the range of TEMP. RISE °F"
listed on the unit rating plate.

FIGURE 14

Supply Air

Return Air

TEMPERATURE RISE

Supply Duct Temperature ________

Return Duct Temperature

_

_____

Temperature Rise = ________

C−External Static Pressure

1 − Tap locations shown in figure 15.
2 − Punch a 1/4" diameter hole in supply and return air ple-

nums. Insert manometer hose flush with inside edge of
hole or insulation. Seal around the hose with perma­gum. Connect the zero end of the manometer to the
discharge (supply) side of the system. On ducted sys­tems, connect the other end of manometer to the return
duct as above.

3 − With only the blower motor running and the evaporator

coil dry, observe the manometer reading. Adjust blow­er motor speed to deliver the air desired according to
the job requirements. For heating speed external static
pressure drop must not be more than 0.5" W.C. For
cooling speed external static pressure drop must not
be more than 0.8" W.C.

4 − Seal the hole when the check is complete.

FIGURE 15

EXTERNAL STATIC PRESSURE

Supply Duct Static ________

Return Duct Static + _____

Total Duct Static = ________
(dry coil)

Supply Air

Return Air

−+

or

Page 23

VI−MAINTENANCE

WARNING

Disconnect power before servicing unit.

CAUTION

Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dan­gerous operation. Verify proper operation after ser­vicing.

At the beginning of each heating season, a qualified techni-

cian should check the system as follows:

A−Blower

Check the blower wheel for debris and clean if necessary.

The blower motors are prelubricated for extended bearing

life. No further lubrication is needed.

WARNING

The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal inju­ry or death.

B−Filters

All EL280UH(X) filters are installed external to the unit. Fil-

ters should be inspected monthly. Clean or replace the fil-

ters when necessary to ensure that the furnace operates

properly. Replacement filters must be rated for high veloc-

ity airflow.

C−Flue and Chimney

Check the flue pipe, chimney and all connections for tight-

ness and to make sure there is no blockage.

A Disconnected Vent" warning sticker should be attached

to a visible area of the plenum near the vent pipe. If the

sticker is not legible or missing, order kit 66W04 for re-

placement stickers.

D−Electrical

1 − Check all wiring for loose connections.

2 − Check for the correct voltage at the furnace (furnace

operating). Correct voltage is 120VAC +

10%

3 − Check amp−draw on the blower motor with inner blow-

er access panel in place.
Motor Nameplate__________Actual__________

E−Heat Exchanger and Burners

Cleaning the Heat Exchanger and Burners

NOTE − Use papers or protective covering in front of the fur­nace during cleaning.

1 − Turn off both electrical and gas power supplies to fur-

nace.

2 − Remove flue pipe and top cap (some applications top

cap can remain) from the unit.

3 − Label the wires from gas valve, rollout switches, prima-

ry limit switch and make−up box then disconnect them.

4 − Remove the screws that secure the combustion air in-

ducer/pressure switch assembly to the collector box.

Carefully remove the combustion air inducer to avoid

damaging blower gasket. If gasket is damaged, it must

be replaced to prevent leakage.

5 − Remove the collector box located behind the combus-

tion air inducer. Be careful with the collector box gas-

ket. If the gasket is damaged, it must be replaced to

prevent leakage.

6 − Disconnect gas supply piping. Remove the screw se-

curing the burner box cover and remove cover. Re-

move the four screws securing the burner manifold as-

sembly to the vestibule panel and remove the assem-

bly from the unit.

7 − Remove screws securing burner box and remove

burner box.

8 − NOX units only − Remove screw securing NOX insert.

Remove NOX insert. See figure 2.

9 − Remove screws from both sides, top and bottom of

vestibule panel.

10 −Remove heat exchanger. It may be necessary to

spread cabinet side to allow more room. If so, remove

five screws from the left side or right side of cabinet.

See figure 3.

11 − Backwash using steam. Begin from the burner opening

on each clam. Steam must not exceed 275°F.

12 −To clean burners, run a vacuum cleaner with a soft brush

attachment over the face of burners. Visually inspect in-

side the burners and crossovers for any blockage

caused by foreign matter. Remove any blockage. Figure

1 shows burner detail.

13 − To clean the combustion air inducer visually inspect and

using a wire brush clean where necessary. Use com-

pressed air to clean off debris and any rust.

14 −Reinstall heat exchanger in vestibule. (Replace the

five screws in the cabinet from step 10 if removed).

15 −NOx units only − Replace NOx inserts.

16 − Reinstall collector box and combustion air assembly.

Reinstall all screws to the collector box and combustion

air inducer. Failure to replace all screws may cause

leaks. Inspect gaskets for any damage and replace if

necessary.

17 − Reinstall burner box, manifold assembly and burner box

cover.

Page 24

EL280UH BURNER, COMBUSTION AIR INDUCER ASSEMBLY &

HEAT EXCHANGER REMOVAL

FIGURE 1

Heat Exchanger

Manifold And Gas Valve

Retention Rings

Cross Over

Ignitor

Sensor

Rollout

Switches

Gasket

Collector Box

Orifice Plate

Flue Transition

Pressure Switch

Combustion Air Inducer

EL280UH NOx INSERTS

FIGURE 2

NOx Insert

Page 25

FIGURE 3

Remove 5 screws if necessary

(either side of cabinet)

1

2

3

4

5

18 −Reconnect all wires.

19 −Reconnect top cap and vent pipe to combustion air in-

ducer outlet.

20 −Reconnect gas supply piping.

21 −Turn on power and gas supply to unit.

22 −Set thermostat and check for proper operation.

23 −Check all piping connections, factory and field, for gas

leaks. Use a leak detecting solution or other preferred

means.

CAUTION

Some soaps used for leak detection are corrosive to
certain metals. Carefully rinse piping thoroughly af­ter leak test has been completed. Do not use
matches, candles, flame or other sources of ignition
to check for gas leaks.

24 −If a leak is detected, shut gas and electricity off and

repair leak.

25 −Repeat steps 24 and 26 until no leaks are detected.

26 −Replace access panel.

Page 26

VII− Wiring and Sequence of Operation

120V
EAC

FACTORY DEFAULT IS FOR A 2 STAGE THERMOSTAT

9

9

1

2

3

4

5

6

7

8

9

10

11

12

TERMINAL #1 IS USED FOR ERROR CODE RECALL ONLY.
SEE INSTALLATION INSTRUCTIONS FOR DETAILS.

K1

K4

K9

K6

K8

HI

HEAT

LO

HEAT

K10

K11

24V POWER IS PROVIDED FOR OPTIONAL
HUMIDIFIER DURING HEAT DEMAND

2011

EL280UH110P60C
EL280UH135P60D
EL280UH070XP36A
EL280UH090XP48B
EL280UH110XP60C

.50 AMP
.43 AMP

070P24A
070P36A
090P36B
090P48B
110P48C
110P60C
135P60D

070XP36A
090XP48B
110XP60C

EL280UH070P24A
EL280UH070P36A
EL280UH090P36B
EL280UH090P48B
EL280UH110P48C

BROWN

BLACK
BLACK

BLACK
BLACK
BLACK

BLACK
BLACK

BLACK
BLACK

BLACK

BROWN

BROWN

BROWN

BROWN

YELLOW

YELLOW

YELLOW
YELLOW
YELLOW
YELLOW
YELLOW

RED

RED

RED

RED

RED

RED

RED

RED

RED

RED

YELLOW

YELLOW

YELLOW

BROWN

BROWN

BROWN

BROWN

BROWN

0112

BURNER

ASSY GND

8

8

DELAY

G

WHITE RODGERS VALVE

BLACK

WHITE

GRN/YLW

JUMPER W915 FROM Y1 TO Y2, LABELED ”2 STAGE
COMPR”, IS FACTORY INSTALLED AT A92 CONTROL
BOARD. LEAVE IN FOR ONE STAGE COOL
THERMOSTAT, CUT JUMPER FOR TWO STAGE COOL
THERMOSTAT.

Page 27

Integrated Control Self Check

When there is a call for heat, the integrated control runs a
self check. The control checks for S10 primary limit, S21
secondary limit (s) and S47 rollout switch normally closed
contacts. The control also checks for S102 high heat and
S128 low heat pressure switch normally open contacts.
Once self check is complete and all safety switches are op­erational, heat call can continue.

Two−Stage Thermostat, Two Stage Heat. Dip Switch

set at OFF".

1− SureLight

®

control energizes combustion air inducer
B6 on low heat speed. Combustion air inducer runs
until S128 low heat pressure switch contacts close
(switch must close within 2 1/2 minutes or control goes
into Watchguard Pressure Switch mode. High heat
pressure switch S102 may also close). A 15 second
pre−purge follows once S128 closes.

NOTE − If the low fire pressure switch does not close the
combustion air inducer will switch to high fire. After a 15
second pre−purge the high fire pressure switch will close
and the unit will begin operation on high fire. After 10 to 20
seconds of high fire operation the unit will switch to low fire.

NOTE − If the furnace is operating on continuous fan mode
(terminal R" and G" are energized), the combustion air in­ducer will energize on high speed, the gas valve will ener­gize on second−stage heat and the furnace will operate on
high fire. Furnace will stay on high fire for 60 seconds then
switch to low fire.

2− SureLight

®

control begins 20 second ignitor warm up
period.

3− Gas valve opens on first stage for a 4 second trial for

ignition. Ignitor stays energized during the trial or until
flame sensed.

4− Flame is sensed, gas valve remains on first stage heat,

ignitor de−energizes.

5− After 30 second delay, indoor blower B3 is energized

on low heat speed.

The furnace will stay in this mode until first stage de­mand is satisfied OR a second stage heat demand is
initiated.

6− Second stage heat demand initiated. A 30 second sec-

ond stage recognition period begins.

7− The combustion air inducer ramps up to high heat

speed.

8− S102 high heat pressure switch closes and the gas

valve energizes second stage heat.

9− B3 indoor blower switches to high heat speed.

Single−Stage Thermostat, Two Stage Heat. Dip

Switch set at ON"

1− SureLight control energizes combustion air inducer B6

on low heat speed. Combustion air inducer runs until
S128 low heat pressure switch contacts close (switch
must close within 2 1/2 minutes or control goes into
Watchguard Pressure Switch mode. High heat pres­sure switch S102 may also close). A 15 second pre−
purge follows once S128 closes.

NOTE − If the low fire pressure switch does not close the
combustion air inducer will switch to high fire. After a 15
second pre−purge the high fire pressure switch will close
and the unit will begin operation on high fire. After 10 to 20
seconds of high fire operation the unit will switch to low fire.

NOTE − If the furnace is operating on continuous fan mode
(terminal R" and G" are energized), the combustion air in­ducer will energize on high speed, the gas valve will ener­gize on second−stage heat and the furnace will operate on
high fire. Furnace will stay on high fire for 60 seconds then
switch to low fire.

2− SureLight control begins 20 second ignitor warm up

period.

3− Gas valve opens on first stage for a 4 second trial for

ignition. Ignitor stays energized during the trial or until
flame sensed.

4− Flame is sensed, gas valve remains on first stage heat,

ignitor de−energizes.

5− After 30 second delay, indoor blower B3 is energized

on low heat speed.

6− A 10 minute (factory set) or 15 minute (field set) second

stage heat delay period begins.

7− After the delay the combustion air inducer ramps up to

high heat speed.

8− S102 high heat pressure switch closes and the gas

valve energizes second stage heat.

9− B3 indoor blower switches to high heat speed.

Page 28

VIII− Field Wiring and DIP Switch Settings

TABLE 12

Field Wiring Applications

Thermostat

DIP Switch Settings and On−Board Links (See figure 6)

Wiring Connections

DIP Switch 1

W915

Two−Stage

Cooling

W951

Heat Pumps

1 Heat / 1 Cool

NOTE − Use DIP
switch 2 to set sec­ond−stage heat ON
delay.
OFF10 minutes.
ON−15 minutes.

ON Intact Intact

S1

T’STAT

CONTROL

TERM. STRIP

OUTDOOR

UNIT

1 Heat / 2 Cool

NOTE − Use DIP
switch 2 to set sec­ond−stage heat ON
delay.
OFF−10 minutes.
ON−15 minutes.

ON Cut Intact

S1

T’STAT

CONTROL

TERM. STRIP

OUTDOOR

UNIT

Page 29

TABLE 12

Field Wiring Applications (Continued)

Thermostat

DIP Switch Settings and On−Board Links (See figure 6)

Wiring Connections

DIP Switch 1

W915

Two−Stage

Cooling

W951

Heat Pumps

2 Heat / 2 Cool OFF Cut Intact

S1

T’STAT

CONTROL

TERM. STRIP

OUTDOOR

UNIT

2 Heat / 1 Cool OFF Intact Intact

S1

T’STAT

CONTROL

TERM. STRIP

OUTDOOR

UNIT

Page 30

IX− Troubleshooting

Troubleshooting: Heating Sequence of Operation

HEATING SEQUENCE OF OPERATION

NORMAL AND ABNORMAL HEATING MODE

CONTROL SELF−CHECK OKAY?

YES

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF. (RESET CONTROL BY

TURNING MAIN POWER OFF.)

NO

POLARITY REVERSED.

STATUS ERROR CODE 5 + 4.

POWER ON

POLARITY OKAY?

SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED.

STATUS ERROR CODE 5 + 3.

IS THERE A

PROPER GROUND?

NO

YES

A

NORMAL OPERATION:

STATUS LED −− PULSE

B

THERMOSTAT CALLS FOR HEAT:

STATUS LED −− HEARTBEAT

YES

PRIMARY AND SECONDARY LIMIT

SWITCHES CLOSED?

YES

NO

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER ON. HAS PRIMARY OR

SECONDARY LIMIT RESET WITHIN 3 MINUTES?

STATUS ERROR CODE 3 + 1.

ROLLOUT SWITCH CLOSED?

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER ON.

STATUS ERROR CODE 5 + 1.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS
RESET AND MAIN POWER IS INTERRUPTED OR

T’STAT IS CYCLED OFF/ON FOR 3 SEC. MINIMUM.

NO

YES

FIRST (LOW) STAGE PRESSURE SWITCH

CONTACTS OPEN?

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF. CONTROL REMAINS UNTIL

PRESSURE SWITCH IS DETECTED OPEN.

STATUS ERROR CODE 2 + 4

YES

GAS VALVE OFF.

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF.

CONTROL WILL NOT ATTEMPT SECOND−STAGE

OPERATION DURING THIS HEAT DEMAND.

FIRST−STAGE OPERATION WILL BE ATTEMPTED.

STATUS ERROR CODE 2 + 6.

NO

TWO−STAGE OR SINGLE−STAGE THERMOSTAT

CALL FOR HEAT

COMBUSTION AIR INDUCER ON LOW SPEED.

STATUS LED −− HEARTBEAT

CONTINUED ON NEXT PAGE

NO

NO

60−MINUTE LIMIT WATCHGUARD MODE.

GAS VALVE OFF, COMBUSTION AIR INDUCER

OFF, INDOOR BLOWER OFF WITH DELAY.

STATUS ERROR CODE 4 + 5.

YES

NO

YES

SECOND (HIGH) STAGE PRESSURE SWITCH

CONTACTS OPEN?

NO

YES

1

1

If the furnace is operating on continuous fan mode (terminals R" and G" are energized), the combustion
air inducer will energize on high speed, the gas valve will energize on second−stage heat and the furnace

will operate on high fire. Furnace will stay on high fire 60 seconds then switch to low fire.

Page 31

Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE OF OPERATION

FIRST−STAGE (LOW FIRE) PRESSURE

SWITCH CLOSED WITHIN 2.5 MINUTES?

GAS VALVE OFF. COMBUSTION AIR INDUCER

OFF. INDOOR BLOWER OFF. UNIT WILL RETRY

AFTER 5−MINUTE WAIT PERIOD.

STATUS ERROR CODE 2 + 3.

YES

NO

15−SECOND COMBUSTION AIR INDUCER

PRE−PURGE INITIATED BY CLOSED FIRST−STAGE

PRESSURE SWITCH (or 15 SECOND

INTER−PURGE PERIOD.)

STATUS LED −− HEARTBEAT.

IGNITOR WARM−UP (20 SECONDS)

STATUS LED −− HEARTBEAT.

IS VOLTAGE ABOVE 90 VOLTS?

NO

COMBUSTION AIR INDUCER OFF, IGNITOR OFF.

SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 95

VOLTS. STATUS ERROR CODE 4 + 8.

YES

NO

COMBUSTION AIR INDUCER OFF, IGNITOR OFF.

SIGNAL HOLDS UNTIL IGNITOR IS REPLACED

OR RECONNECTED.

STATUS ERROR CODE 4 + 7.

YES

AT END OF IGNITOR 20 SECOND WARM UP

PERIOD, 4−SECOND TRIAL FOR IGNITION.

GAS VALVE OPENS, IGNITOR ENERGIZED DURING

4−SECOND TRIAL UNTIL FLAME SENSED.

YES

4−SECOND FLAME STABILIZATION PERIOD.

FLAME RECTIFICATION CURRENT CHECK

CAN FLAME BE PROVEN WITHIN 4

SECONDS AFTER GAS VALVE OPENS?

(u0.19 microamps)

GAS VALVE OFF. COMBUSTION AIR

INDUCER ON. INDOOR BLOWER OFF.

STATUS LED −− HEARTBEAT.

HAS CONTROL FAILED TO SENSE

FLAME FOR FIVE CONSECUTIVE TRIES

DURING A SINGLE HEAT DEMAND?

YES

THERMOSTAT CALLS FOR HEAT

STATUS LED − HEARTBEAT.

(Refer to box A on previous page)

YES

FLAME PRESENT?

NO

HAS CONTROL RESET IGNITION SEQUENCE

FOUR (4) TIMES?

WATCHGUARD MODE.

STATUS ERROR CODE 4 + 3.

YES

CONTINUED ON NEXT PAGE

YES

NO

NO

CONTINUED

IS IGNITOR INTACT AND CONNECTED?

WATCHGUARD MODE. GAS VALVE OFF,

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF.

STATUS ERROR CODE 4 + 1.

IS 60−MINUTE RESET PERIOD COMPLETE?

NO

YES

1

1

1

If the furnace is operating on continuous fan mode (terminals R" and G" are energized), the combustion
air inducer will energize on high speed, the gas valve will energize on second−stage heat and the furnace

will operate on high fire. Furnace will stay on high fire 60 seconds then switch to low fire.

2

2

If combustion air inducer is operating on high speed and gas valve is energized on second−
stage heat, 20 seconds after flame is sensed furnace will switch to low fire.

COMBUSTION AIR INDUCER
ENERGIZED ON HIGH SPEED

LOW AND HIGH

PRESSURE SWITCH

CLOSED WITHIN 30

SECONDS

YES

NO

Page 32

Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE OF OPERATION

LOW FLAME SIGNAL

(Does not affect control operation)

STATUS ERROR CODE 1 + 2.

FLAME SIGNAL ABOVE

(u1.40 microamps)

NO

YES

CONTINUED ON NEXT PAGE

YES

SINGLE−STAGE THERMOSTAT MODE

(DIP SWITCH SET AT ON")

TWO STAGE THERMOSTAT MODE

(DIP SWITCH SET AT OFF")

YES

YES

START SECOND−STAGE RECOGNITION

ON DELAY (10 OR 15 MINUTES).

STATUS LED −− HEARTBEAT

45−SECOND INDOOR BLOWER ON DELAY BEGINS.

STATUS LED −− HEARTBEAT.

YES

YES

PRIMARY & SECONDARY LIMIT SWITCHES

CLOSED?

GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,

INDOOR BLOWER ON.

STATUS ERROR CODE 3 + 1.

HAS PRIMARY OR SECONDARY LIMIT
SWITCH CLOSED WITHIN 3 MINUTES?

(Indoor blower on low speed during 3−minute period)

FIRST−STAGE (LOW FIRE)

PRESSURE SWITCH CLOSED?

LIMIT SWITCH WATCHGUARD MODE.

GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,

INDOOR BLOWER OFF WITH DELAY.

STATUS ERROR CODE 4 + 5

IS 60−MINUTE RESET PERIOD COMPLETE?

THERMOSTAT CALLS FOR HEAT.

STATUS LED −− HEARTBEAT.

SEE BOX A.

NO

YES

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER OFF AFTER DELAY.

STATUS ERROR CODE 2 + 3. CONTROL RESTARTS

IGNITION SEQUENCE IF PRESSURE SWITCH

CLOSES WITHIN 2−1/2 MINUTES.

NO

YES

FIRST−STAGE HEAT DEMAND SATISFIED?

GAS VALVE OFF, COMBUSTION AIR INDUCER

OFF FOLLOWING POST PURGE.

INDOOR BLOWER OFF WITH DELAY

STATUS LED −− PULSE

YES

SECOND−STAGE HEAT DEMAND.

SECOND−STAGE HEAT DEMAND REQUIRED?

NO

SECOND STAGE PRESSURE SWITCH CLOSED?

ABNORMAL FLASH CODE.

NOTE − IF SECOND−STAGE PRESSURE SWITCH

WAS ORIGINALLY FOUND CLOSED,

ABNORMAL CODE WILL FLASH.

SECOND−STAGE PRESSURE SWITCH CLOSED

AT BEGINNING OF HEAT DEMAND?

STATUS ERROR CODE 2 + 6.

YES

NO

SECOND−STAGE 30−SECOND DELAY ON BEGINS.

STATUS LED −− HEARTBEAT.

SECOND−STAGE COMBUSTION AIR INDUCER

ON. SECOND−STAGE GAS VALVE ON. HIGH

HEAT INDOOR BLOWER SPEED ON.

STATUS LED −− HEARTBEAT.

YES

SECOND−STAGE PRESSURE SWITCH CLOSED

IN LESS THAN TEN (10) SECONDS?

STATUS LED −− HEARTBEAT

YES

NO

RETURNS TO FIRST−STAGE HEAT MODE WHICH
CONTINUES UNTIL SECOND−STAGE PRESSURE

SWITCH CAN BE PROVEN or HEAT DEMAND IS

SATISFIED. FIVE (5) MINUTE WAIT PERIOD

INITIATED BEFORE RETRY. WERE 5 ATTEMPTS

MADE FOR SECOND−STAGE HEAT?

YES

CONTINUES FIRST−STAGE HEATING DEMAND.

WILL NOT REATTEMPT SECOND−STAGE

HEATING DEMAND.

STATUS ERROR CODE 2 + 5.

SECOND STAGE HEAT DEMAND

STATUS LED −− HEARTBEAT.

NO

YES

NO

YES

CONTINUED

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER ON.

STATUS ERROR CODE 5 + 1. SEQUENCE HOLDS

UNTIL ROLLOUT SWITCH IS RESET AND MAIN

POWER IS INTERRUPTED OR THERMOSTAT

IS CYCLED OFF/ON FOR 3 SECOND MINIMUM.

ROLLOUT SWITCHES CLOSED?

NO

YES

YES

NO

YES

YES

Page 33

Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE OF OPERATION

SEE BOX B

THERMOSTAT CALLS FOR HEAT.

SEE BOX A

NORMAL OPERATION.

YES

NO

RETURN TO FIRST−STAGE HEAT MODE.

FIRST−STAGE CONTINUES UNTIL SECOND−

STAGE PRESSURE SWITCH CAN BE PROVEN

or HEAT DEMAND IS SATISFIED. A FIVE (5)

MINUTE WAIT PERIOD IS INITIATED BEFORE

RETRY. WERE 5 ATTEMPTS MADE FOR

SECOND−STAGE HEAT?

YES

NO

SEE BOX C

FIRST−STAGE HEAT DEMAND SATISFIED?

HEAT DEMAND SATISFIED?

STATUS LED −− HEARTBEAT.

YES

TWO STAGE THERMOSTAT MODE?

(DIP SWITCH SET AT TWO")

SINGLE−STAGE THERMOSTAT MODE

(DIP SWITCH SET AT SINGLE")

YES

YES

FIRST AND SECOND STAGE HEAT

DEMAND SATISFIED SIMULTANEOUSLY.

STATUS LED −− HEARTBEAT.

YES

GAS VALVE OFF, COMBUSTION AIR

INDUCER OFF AFTER 5−SECOND

LOW SPEED POST PURGE PERIOD,

INDOOR BLOWER OFF DELAY

INITIATED ON LOW HEAT SPEED.

STATUS LED −− HEARTBEAT.

DEMAND FOR HEAT SATISFIED.

POWER ON STAND BY.

STATUS LED −− PULSE.

YES

SECOND STAGE HEAT

DEMAND SATISFIED?

STATUS LED −− HEARTBEAT.

NO

GAS VALVE, COMBUSTION AIR INDUCER

AND INDOOR BLOWER RETURN TO FIRST−

STAGE OPERATION.

STATUS LED −− HEARTBEAT.

YES

FIRST STAGE HEAT DEMAND SATISFIED?

YES

GAS VALVE OFF. COMBUSTION AIR INDUCER

OFF AFTER 5−SECOND LOW SPEED POST−

PURGE PERIOD. INDOOR BLOWER OFF.
DELAY INITIATED ON LOW HEAT SPEED.

STATUS LED −− PULSE.

CONTINUED

SECOND−STAGE (HIGH FIRE) HEAT

PRESSURE SWITCH CLOSED?

Page 34

Troubleshooting: Cooling Sequence of Operation

COOLING SEQUENCE OF OPERATION

SIGNAL POLARITY REVERSED.

CONTROL WILL CONTINUE TO CALL FOR COOLING

IN THIS CONDITION.

STATUS ERROR CODE 5 + 4.

POWER ON

YES

IS POLARITY REVERSED?

THERMOSTAT CALLS FOR FIRST−STAGE COOL.

COMPRESSOR AND CONDENSER FAN

ENERGIZED.

NO

IS THERE

PROPER GROUND?

YES

NO

INDOOR BLOWER ENERGIZED ON FIRST STAGE

COOL SPEED AFTER 2 SECOND DELAY.

FIRST−STAGE DEMAND FOR COOL SATISFIED?

NO

THERMOSTAT CALLS FOR SECOND−STAGE COOL.

COMPRESSOR AND CONDENSER FAN DE−ENERGIZED.

INDOOR BLOWER DE−ENEGIZED.

YES

INDOOR BLOWER RAMPS UP TO SECOND−STAGE COOL SPEED.

SECOND−STAGE DEMAND FOR COOL SATISFIED?

YES

UNIT RETURNS TO FIRST STAGE COOL

SIGNAL IMPROPER GROUND AT LED.

CONTROL WILL CONTINUE TO CALL FOR COOLING

IN THIS CONDITION.

STATUS ERROR CODE 5 + 3.

Page 35

Troubleshooting: Continuous Fan Sequence of Operation

CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION

MANUAL FAN SELECTION MADE AT THERMOSTAT.

AFTER 2 SECOND DELAY, INDOOR BLOWER IS

ENERGIZED ON CONTINUOUS FAN SPEED.

THERMOSTAT CALLS FOR FIRST−STAGE HEAT.THERMOSTAT CALLS FOR FIRST STAGE COOL.

YES

YES

AFTER 45−SECOND DELAY, INDOOR BLOWER

SWITCHES TO LOW HEAT SPEED.

FIRST−STAGE HEAT DEMAND SATISFIED.

YES

NO

THERMOSTAT CALLS FOR SECOND−STAGE HEAT.

YES

INDOOR BLOWER SWITCHES TO HIGH HEAT SPEED

AFTER 30−SECOND RECOGNITION PERIOD.

SECOND−STAGE HEAT DEMAND SATISFIED.

YES

YES

INDOOR BLOWER RAMPS DOWN TO LOW

HEAT SPEED.

INDOOR BLOWER RAMPS TO FIRST STAGE

COOLING SPEED AFTER A 2−SECOND DELAY.

FIRST−STAGE COOL DEMAND SATISFIED?

YES

NO

SECOND STAGE COOL DEMAND SATISFIED?

INDOOR BLOWER RAMPS TO SECOND

STAGE COOL SPEED

YES

SECOND STAGE COOL DEMAND

INDOOR BLOWER RAMPS DOWN TO FIRST STAGE

COOL SPEED.

YES YES