Lennox iComfort SL280UH070V36A User manual

Page 1 ©2016 Lennox Industries Inc.
Corp. 1116-L4
SL280UHV(X)
Service Literature Revised 04/2020
iComfort®ENABLED SL280UHV(X) SERIES UNITS
SL280UHV(X) series units are 80% efficiency gas furnaces
used for upflow or horizontal applications only, manufac
tured with Lennox Duralokheat exchangers formed of
aluminized steel. SL280UHV(X) units are available in heat
ing capacities of 66,000 to 132,000 Btuh and cooling ap
plications 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. SL280UHV(X)
model units are equipped with the iComfort®enabled Sur
eLight®two-stage variable speed integrated control.
SL280UHV(X) unit meets the California Nitrogen Oxides
(NOx) Standards and California Seasonal Efficiency re
quirements. 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. Pro
cedures outlined in this manual are presented as a recom
mendation 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 consti
tute code.
TABLE OF CONTENTS
Specifications Page 2.............................
I Unit Components Page 5........................
II Installation Page 43.............................
III Start Up Page 43..............................
IV Heating System Service Checks Page 44.........
V Typical Operating Characteristics Page 47.........
VI Maintenance Page 48..........................
VII Wiring and Sequence of Operation Page 51......
VIII Field Wiring and Jumper Settings Page 55.......
IX Program Unit Capacity Size Mode Page 59.......
X Troubleshooting Page 60........................
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.

Page 2
SPECIFICATIONS
Gas
Heating
Performance
Model No. SL280UH070V36A SL280UH090V36B SL280UH090V48B
Model No. - Low Nox SL280UH070XV36A - - - SL280UH090XV48B
1AFUE 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 / 4.9 1.7 / 4.9 1.7 / 4.9
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 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.
SPECIFICATIONS
Gas
Heating
Performance
Model No. SL280UH090V60C SL280UH110V60C SL280UH135V60D
Model No. - Low Nox - - - SL280UH110XV60C - - -
1AFUE 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 71,500 85,800
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 / 4.9 1.7 / 4.9 1.7 / 4.9
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 24
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 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.

Page 3
OPTIONAL ACCESSORIES - MUST BE ORDERED EXTRA
“A” Width
Models
“B” Width
Models
“C” Width
Models
“D” Width
Models
CABINET ACCESSORIES
Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10 51W10
Return Air Base - Upow only 65W75 50W98 50W99 51W00
CONTROLS
ComfortSense® 7000 Thermostat Y0349 Y0349 Y0349 Y0349
Remote Outdoor Sensor (for dual fuel and Humiidtrol®) X2658 X2658 X2658 X2658
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
NIGHT SERVICE KITS
Night Service Kit 14C98 14C98 14C98 14C98
Safety Service Kit 89W19 89W19 89W19 89W19
1 Cleanable polyurethane, frame-type lter.
GAS HEAT ACCESSORIES
Input Natural Gas to
LPG/Propane Kit
LPG/Propane
to Natural Gas Kit
All models 11K51 11K46

Page 4
FIGURE 1
HEAT EXCHANGER
CABINET
COMBUSTION AIR INDUCER
BLOWER
ASSEMBLY
BURNER BOX
INNER BLOWER
ACCESS PANEL
ACCESS PAN
EL
SIGHT GLASS
COMBUSTION AIR INDUCER
PRESSURE SWITCH
GAS VALVE
CONTROL BOX
(Includes two-stage integrated control,
transformer and circuit breaker)
SECONDARY LIMITS
(2 switches)
PRIMARY LIMIT
SL280UHV Parts Arrangement

Page 5
I-UNIT COMPONENTS
SL280UHV(X) unit components are shown in figure 1. The
gas valve, combustion air inducer and burners can be ac
cessed by removing the access panel. Electrical compo
nents are in the control box (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 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 elec
tronic 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 sec
ondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in se
ries with line voltage. When the inner blower access panel
is removed the unit will shut down.
FIGURE 2
CONTROL BOX SL280UHV
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 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.
FIGURE 3
CIRCUIT BREAKER CB8
PRESS TO RESET
WARNING
Shock hazard.
Disconnect power before servicing. Integrated
control is not field repairable. If control is inoper
able, simply replace entire control.
Can cause injury or death. Unsafe operation will re
sult if repair is attempted.
4. Integrated Control (A92)
Units are equipped with the icomfortenabled Sur
eLight®two-stage, variable speed integrated control. This
control is used with the icomfort Wi-Fi®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 (figures 4 and 5) with control pin designa
tions in tables 1, 2 and 3 and ignitor (figure 13). 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
heating. The furnace combustion air inducer, gas valve and
indoor blower are controlled in response to various system
inputs such as thermostat signal, pressure and limit switch
signal and flame signal. The control features a seven-seg
ment LED display, indicating furnace status (including in
door blower) and error codes. The LED flashes in single
digits. For example using table 5 under LIMIT CODE, an
“E” followed by “2” followed by “5” followed by “0”, the limit
switch circuit is open. The control also has two unpowered
(dry) 1/4” contacts for a humidifier and a 120 volt accessory
terminal. Both rated at (1) one amp each.
Electronic Ignition
At the beginning of the heat cycle the integrated control
monitors the first stage and second stage combustion air
inducer prove switch. The control will not begin the heating
cycle if the first 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 first stage heat. However, if the
second stage prove switch closes during the first stage
heat pre-purge, the control will allow second stage heat.
Once the first stage prove switch is determined to be open,

Page 6
the combustion air inducer is energized on low (first stage)
heat speed. When the differential 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 fire pres
sure 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.
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 sec
onds. After a total of five trials for ignition (including the ini
tial 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 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
after a "recognition period". DIP switch 2, labeled SECOND
STAGE DELAY, is factory set in the OFF position for a 7
minute recognition period. The switch can be moved to the
ON position for a 12 minute recognition period, after which
time the unit will switch to secondstage heat.
While in the two-stage thermostat mode (two DIP switch
setting) the burners will fire on first-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 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.
TABLE 1
SureLight®Control 5 Pin Terminal Designation
PIN # Function
1 Ignitor
2Combustion Air Inducer High Speed
3Combustion Air Inducer Low Speed
4Combustion Air Inducer Neutral
5Ignitor Neutral
TABLE 2
SureLight®Control 12 Pin Terminal Designation
PIN # Function
1Gas Valve High Fire
2Second Stage Prove Switch
3Rollout In
4 Ground
524V Hot
6Primary Limit In
7Gas Valve Low Stage
8Gas Valve Common
924V 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
2 Common
3Not Used
4Data Output To Motor
55 Volt Bias Supply
6Not Used

Page 7
FIGURE 4
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 = 24VAC COMMON
RS-BUS INDOOR (TB84)
R = 24VAC
I + = DATA HIGH CONNECTION
I - = DATA LOW CONNECTION
C = 24VAC 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 CCRDHLODS
RI + I - CRI + I - C
7 SEGMENT LED
ACC
LINE 1
HUM
12 PIN LOW
VOLTAGE
CONNECTOR
NON-COMMUNICATINGNG
24V TERMINALS
HS/ CAI
INTEGRATED CONTROL

Page 8
FIGURE 5
HEATING BLOWER−OFF DELAY
60 SECOND
HTG BLOWER
OFF DELAY
120 SECOND
HTG BLOWER
OFF DELAY
180 SECOND
HTG BLOWER
OFF DELAY
FLAME
15
HSI/CAI
2ND STAGE HEAT ON DELAY
7 MIN
UPSTAGE
DELAY
12 MIN
UPSTAGE
DELAY
*CONTINUOUS FAN MODE BLOWER SPEED
COOLING MODE BLOWER RAMPING
CLG BLOWER SPEED ADJUSTMENT
COOLING MODE BLOWER SPEED
W915
2 STAGE
COMPR
1−STG COMPRESSOR
2−STAGE
COMPRESSOR LINK
(JUMPERS Y1 to Y2)
W915
DO NOT CUT
2−STG COMPRESSOR
HEAT PUMP LINK
(JUMPERS R to O)
W951
DEHUMIDIFICATION−
HARMONY LINK
(JUMPERS R to DS)
W914
W915
2 STAGE
COMPR
CUT LINK
A/C UNIT
DO NOT CUT
HEAT PUMP UNIT
CUT LINK
W951
HEAT
PUMP
W951
HEAT
PUMP
W914
DEHUM
or
NO HARMONY ZONING
OR
NO SIGNATURESTAT
W/ DS CONNECTION
DO NOT CUT
HARMONY ZONING
OR
SIGNATURESTAT W/
DS CONNECTION
CUT LINK
HARMONY
W914
DEHUM
or
HARMONY
1
1
1
ON−BOARD LINK
OPTION SELECTION
1234567
1234567
123567
4
123567
4
NEUTRALS
L1
ACC
HUM
14
36
P79
110
312
J2
4 7
W915
2 STAGE
COMPR
W951
HEAT
PUMP
W914
DEHUM
HARMONY
CUT FOR
OPTION
SELECTION
OUTDOOR SENSOR
DISCHARGE AIR SENSOR
123456
10 12
911
13
ON
ON
SureLight®
W1W2 GY2 Y1 C C DHL O DSR
W1 W2
G
Y2 Y1
C C
R
L
DH
HIGH
SPEED
(100%)
MEDIUM−HIGH
SPEED
(70%)
MEDIUM−LOW
SPEED
(38%)
LOW
SPEED
(28%)
*
OPTION A
OFF−50%−82%−
100%−50%−OFF
OPTION B
OFF−82%−100%−OFF
OPTION C
OFF−100%−100%−OFF
OPTION D
OFF−100%−OFF
*
DEFAULT
+ 10%
− 10%
*
HIGH
SPEED
MEDIUM−HIGH
SPEED
MEDIUM−LOW
SPEED
LOW
SPEED
*
7
−PROTECTIVE PLASTIC FILM ON DIP SWITCHES MAY BE
REMOVED FOR EASE IN SETTING OF DIP SW.
−CUT ON−BOARD LINK (SOLDER TRACE) COMPLETELY THROUGH
BOTH LAYERS ON THE CONTROL BOARD
−LINKS CUT IN ERROR −INSTALL A JUMPER ON THE APPROPRIATE
TERMINALS ON THE TERMINAL STRIP
1
910 11 12 13 14
ON
ON
ON
ON
ON
ON
ON
ON
90 SECOND
HTG BLOWER
OFF DELAY
*1234567
ON
1234567
ON
THERMOSTAT SELECTION
1−STAGE
THERMOSTAT
(TIMED STAGING)
−SEE SW #2
TWO STAGE
THERMOSTAT
*1234567
1234567
ON
ON
−BLOWER ON DELAY − 30 SEC. FIXED
15
910 11 12 14 15
910 11 12 14 15
910 11 12 14 15
8
8
8
8
8
8
8
81234567
1234567
ON
ON
1234567
ON
1234567
ON
8
8
8
8
910 11 12 13 14
ON
ON
ON
ON
15
910 11 12 14 15
910 11 12 14 15
910 11 12 14 15
910 11 12 13 14
ON
ON
ON
ON
15
910 11 12 14 15
910 11 12 14 15
910 11 12 14 15
HEATING MODE BLOWER SPEED
1234567
ON
1234567
ON
1234567
ON
8
8
8
910 11 12 13 14
ON
ON
ON
ON
15
910 11 12 14 15
910 11 12 14 15
910 11 12 14 15
FACTORY
DEFAULT
+ 24%
+ 18%
+ 12%
+ 6%
− 6%
− 12%
− 18%
8
14 15
INCREASE AIR HTG CFM
DECREASE AIR HTG CFM
SENSE
RI+ I− CRI+ I− C
OUTDOOR EQUIPMENT
I+ I−
INDOOR EQUIPMENT
IGN
CAI2
CAI1
N N
J3
S1
S4S3
13
13
13
13
13
13
13
* FACTORY DEFAULT
13
13
*
DIAGNOSTIC
LED
DIAGNOSTIC
PUSH BUTTON
INTEGRATED CONTROL CONFIGURATION GUIDE

Page 9
TABLE 4
Integrated Control Diagnostic Modes
Display Action (when button released)
No change (idle)* Remain in idle mode
Solid “E” Enter diagnostic recall mode
Solid “D” Discharge Air Installed
Solid “F” Enter flame signal mode
Solid “P” (variable speed only) Program unit capacity/size (Unit Code)
* No change implies the display will continue to show whatever is currently being displayed for normal operation (blinking
decimal, active error code, heat state, etc..)
Diagnostic LED (Figure 4)
The seven-segment diagnostic LED displays operating
status, target airflow, error codes and other information.
The table beginning on Page 10 lists diagnostic LED
codes.
Diagnostic Push Button (Figure 4)
The diagnostic push button is located adjacent to the
seven-segment diagnostic LED. This button is used to en
able the Error Code Recall “E” mode and the Flame Signal
“F” mode. Press the button and hold it to cycle through a
menu of options. Every five seconds a new menu item will
be displayed. When the button is released, the displayed
item will be selected. Once all items in the menu have been
displayed, the menu resumes from the beginning until the
button is released.
Error Code Recall Mode
Select ”E” from the menu to access the most recent 10 error
codes. Select “c” from the Error Code Recall menu to clear
all error codes. Button must be pressed a second time
while “c” is flashing to confirm command to delete codes.
Press the button until a solid “≡” is displayed to exit the Error
Code Recall mode.
Flame Signal Mode
Select ”F” from the menu to access the flame signal mode.
The integrated control will display the flame current on 7
segment LED in in micro amps (uA).
Flame signal mode is exited after any of the following:
Power is reset
Pressing and holding push button until 3 horizontal
lines “≡” are displayed
10 minutes after entering the flame sense mode.
Program Unit Capacity/Size Mode
After the “P” is selected (by releasing the push button) the
integrated control will start flashing the “P” on display for 90
seconds. If push button is pressed again and held during
that time, the control will start to display characters corre
sponding to different variable speed furnace models for 3
seconds each. While the wanted character-model is dis
played push button has to be released. Selected option will
flash display for 10 seconds and during that time push but
ton has to be pressed and held for 5 seconds. Once control
accepts new setting it will store data in non-volatile memory
and reset itself. If 10 seconds expires or push button is held
less than 5 seconds, control will exit field test mode and go
into idle without changing programming the unit size.

Page 10
TABLE 5
Integrated Diagnostic Codes/Status of Equipment I.
Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover
.Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF).
ACubic feet per minute (cfm) setting for indoor blower (1 second ON, 0.5
second OFF) / cfm setting for current mode displayed.
CCooling stage (1 second ON, 0.5 second OFF) / 1 or 2 displayed / Pause
/ cfm setting displayed / Pause / Repeat codes).
dDehumidification mode (1 second ON) / 1 second OFF) / cfm setting dis
played / Pause / Repeat Codes).
hHeat pump stage (1 second ON, 0.5 second OFF) / % of input rate dis
played / Pause / cfm setting / Pause / Repeat codes.
HGas Heat Stage (1 second ON, 0.5 second OFF) / 1 or 2 displayed /
Pause / cfm
setting displayed / Pause / Repeat codes. Blinking during ignition.
dF Defrost mode.
UDischarge Air Temperature
E 105 Device communication problem - No other devices on RS BUS (Commu
nication
system).
Equipment is unable to communicate. Indicates
numerous message errors. In most cases errors are
related to electrical noise. Make sure high voltage
power is separated from RSBus. Check for mis-
wired and/or loose connections between the stat,
indoor unit and outdoor unit. Check for a high volt
age source of noise close to the system. Fault
clears after communication is restored.
E 110 Low line voltage. Line Voltage Low (Voltage lower than nameplate
rating). Check power line voltage and correct. Alarm
clears 5 seconds after fault recovered.
E 111 Line voltage polarity reversed. Reverse line power voltage wiring. System resumes
normal operation 5 seconds after fault recovered.
E 112 Ground not detected System shuts down. Provide proper earth ground.
System resumes normal operation 5 seconds after
fault recovered.
E 113 High line voltage. Line Voltage High (Voltage higher than nameplate
rating). Provide power voltage within proper range.
System resumes normal operation 5 seconds after
fault recovered.
E 114 Line voltage frequency out-of-range. No 60 Hertz Power. Check voltage and line power
frequency. Correct voltage and frequency problems.
System resumes normal operation 5 seconds after
fault recovered.
E 115 Low 24V - Control will restart if the error recovers. 24-Volt Power Low (Range is 18 to 30 volts). Check
and correct voltage. Check for additional power-rob
bing equipment connected to system. May require
installation of larger VA transformer to be installed
in furnace / air handler. Clears after fault recovered.
E 116 High 24V. 24 Volt Power High (Range is 18 to 30 volts). Check
and correct voltage. Check for proper line voltage
(120V, 240V, etc.) to equipment. Clears when con
trol senses proper voltage.
E 117 Poor ground detected (Warning only) Provide proper grounding for unit. Check for proper
earth ground to the system. Warning only will clear
30 seconds after fault recovered.
E 120 Unresponsive device. Communication only. Usually caused by delay in outdoor unit responding
to indoor unit poling. Recycle power. Check all wir
ing connections. Cleared after unresponsive device
responds to any inquiry.