50A62-820
Integrated Furnace Control
WHITE-RODGERS
INSTALLATION INSTRUCTIONS
Operator: Save these instructions for future use!
FAILURETOREADANDFOLLOWALLINSTRUCTIONSCAREFULLYBEFORE
INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL
INJURY AND/OR PROPERTY DAMAGE.
DESCRIPTION
The 50A62-820 is an automatic gas interrupted ignition
control that employs a microprocessor to continually
monitor, analyze, and control the proper operation of the
gas burner, inducer, and fan.
Signals interpreted during continual surveillance of the
thermostat and flame sensing element initiate automatic
ignition of the burner, sensing of the flame, and system
shut-off during normal operation.
Thesecontrolsincorporatesystemfaultanalysisforquick
gas flow shut-off, coupled with automatic ignition retry
upon sensing a fault correction.
PRECAUTIONS
CAUTION
GENERAL PRECAUTION
!
!
To prevent electrical shock and/or equipment
damage, disconnect electric power to system at
main fuse or circuit breaker box until installation
is complete.
Application of this type of control may cause
flame rollout on initial start-up and could cause
personal injury and/or property damage.
Replace only with exact model number, includ-
ing dash number. Failure to use exact replace-
ment control could cause personal injury and/or
property damage.
Label all wires prior to disconnection when ser-
vicing controls. Wiring errors can cause im-
proper and dangerous operation.
This control is not intended for use in locations
where it may come in contact with water. Suit-
able protection must be provided to shield the
control from exposure to water (dripping, spray-
ing, rain, etc.).
Ifindoubtaboutwhetheryourwiringismillivolt,line,orlow
voltage, have it inspected by a qualified heating and air
conditioning contractor, or licensed electrician.
Do not exceed the specification ratings.
All wiring must conform to local and national electrical
codes and ordinances.
WARNING
Do not use on circuits exceeding specified volt-
age. Higher voltage will damage control and
could cause shock or fire hazard.
!
This control is a precision instrument, and should be
handled carefully. Rough handling or distorting compo-
nents could cause the control to malfunction.
Do not short out terminals on gas valve or pri-
marycontroltotest. Shortorincorrectwiringwill
damage thermostat and could cause personal
injury and/or property damage.
CONTENTS
Description ......................................................... 1
Precautions ........................................................ 1
Specifications..................................................... 2
Installation.......................................................... 3
Mounting & Wiring
Operation ........................................................... 6
WHITE-RODGERS
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
ST. LOUIS, MISSOURI 63123-5398
PART NO. 37-6266A
Printed in U.S.A.
0119
INSTALLATION
MOUNTING AND WIRING
WARNING
NOTE
Replace 50A62 control as a unit - no user serviceable
!
parts.
Do not use on circuits exceeding specified volt-
age. Higher voltage will damage control and
could cause shock or fire hazard.
All wiring should be installed according to local and
national electrical codes and ordinances.
The 50A62 control may be mounted only in a control box
of a Lennox furnace.
The control must be secured to an area that will experi-
ence a minimum of vibration and remain below the maxi-
mum ambient temperature rating of 175°F. The control is
approved for minimum ambient temperatures of -40°F.
CAUTION
!
To prevent electrical shock and/or equipment
damage, disconnect electric power to system at
main fuse or circuit breaker box until installation
is complete.
Any orientation is acceptable.
Refer to the wiring diagram and wiring table when con-
necting the 50A62 control to other components of the
system.
Failure to earth ground the appliance or revers-
ingtheneutralandhotwireconnectiontotheline
can cause shock hazard.
UL approved, 105°C rated 18 gauge, stranded, 2⁄64” thick
insulation wire is recommended for all low voltage safety
circuit connections. Refer to 50A62 specification sheet
for recommended terminals to mate with those on the
control.
UL approved 105°C rated 16 gauge min., stranded, 4⁄64”
thick insulation wire is recommended for all line voltage
connections. Refer to 50A62 specification sheet for
recommended terminals to mate with those on the
control.
Shut off main gas to heating system until instal-
lation is complete.
Route and secure all wiring as far from flame
as practical to prevent fire and/or equipment
damage.
After installation or replacement, follow appliance
manufacturer’s recommended installation or service
instructions to ensure proper operation.
3
TYPICAL SYSTEM WIRING DIAGRAM
HOT
(LINE)
NEUTRAL
(LINE)
120 VAC
24 VAC CLASS II
TRANSFORMER
TH
24 VAC
50A62
TR
COOL
HEAT
FAN
M1
CIRCULATOR
BLOWER
M2
LINE
XFMR
EAC
HUM
INDUCER
IND
IGN
IGNITOR
HUMIDIFIER
GND
GND
CIR N
LINE N
XFMR N
HUM N
EAC N
ELECTRONIC
AIR CLEANER
Y
W
G
R
C
Y
W
G
R
COMPRESSOR
CONTACTOR
THERMOSTAT
FLAME
SENSOR
PROBE
FP
PRESSURE SWITCH
(N. O.)
PS
PS
HL
HIGH LIMIT
(N. C.)
RO1
GND
RO2
MV
ROLLOUT
(N. C.)
GAS
VALVE
MV
TR
TH
LEGEND
Low Voltage (24 VAC)
Line Voltage (120 VAC)
N. C. = Normally closed switch
N. O. = Normally open switch
4
TYPICAL SYSTEM WIRING TABLE
50A62
TERMINAL
TERMINAL
SYSTEM COMPONENT
CONNECTION
TYPE
W
G
R
Y
captive screw
captive screw
captive screw
low voltage thermostat W terminal (or equivalent)
low voltage thermostat G terminal (or equivalent)
low voltage thermostat R terminal (or equivalent)
low voltage thermostat Y terminal (or equivalent)
2nd wire from Y terminal goes to 24 VAC HOT side of
compressor contactor coil
captive screw
captive screw
C
24 VAC COMMON side of compressor contactor coil
gas valve (both gas solenoids are connected in parallel)
rollout switch OUTPUT
MV (2 terminals)
RO1
RO2
rollout switch INPUT
PS
pressure switch INPUT
9-pin
connector
& harness
PS
pressure switch OUTPUT
GND
MUST BE RELIABLY GROUNDED TO CHASSIS
high limit switch input
HL
(unused terminal)
IND
inducer HOT side
IGN
ignitor HOT side
6-pin
GND
connector
& harness
inducer NEUTRAL side
ignitor NEUTRAL side
GND
(unused 2 terminals)
COOL
HEAT
M1
spade terminal circulator blower COOL SPEED terminal
spade terminal circulator blower HEAT SPEED terminal
spade terminal unused circulator blower terminal
spade terminal unused circulator blower terminal
spade terminal circulator blower FAN SPEED terminal
spade terminal input voltage (120 VAC) HOT side
spade terminal 24 VAC transformer line voltage HOT side
spade terminal circulator blower NEUTRAL terminal
spade terminal input voltage (120 VAC) NEUTRAL side
spade terminal 24 VAC transformer line voltage NEUTRAL side
spade terminal humidifier HOT side
M2
FAN
LINE
XFMR
CIR N
LINE N
XFMR N
HUM
EAC (optional)
HUM N
EAC N (optional)
TR
spade terminal electronic air cleaner HOT side
spade terminal humidifier NEUTRAL side
spade terminal electronic air cleaner NEUTRAL side
spade terminal 24 VAC transformer (low voltage COMMON side)
spade terminal 24 VAC transformer (low voltage HIGH side)
spade terminal flame sensor port*
TH
FP
* maximum recommended flame probe wire length is 36 inches.
5
OPERATION
OPTION SWITCHES
flameloss,theinducerblowerremainsenergizedtopurge
the system for 5 seconds. When the purge is complete,
Theoptionswitchesonthe50A62-820controlareusedto the inducer blower and humidifier are de-energized and
determine the length of the heat delay-to-fan-off period. the delay-to-fan-off period begins. After the delay-to-fan-
The following table shows the time periods that will result off period ends, the circulator fan and electronic air
from the various switch positions.
cleaner are de-energized.
If flame is not detected, both valves are de-energized, the
ignitor is turned off, and the 50A62 control goes into the
“retry” sequence. The “retry” sequence provides a 15-
second wait following an unsuccessful ignition attempt
(flame not detected). After this wait, the ignition sequence
is restarted. If this ignition attempt is unsuccessful, one
more retry will be made before the control goes into
system lockout.
OPTION SWITCH POSITIONS
HEAT delay-
to-fan-off:
Set switch
#1
#2
180 sec.
120 sec.
90 sec.
On
On
Off
Off
On
Off
On
Off
60 sec.*
* Factory setting
Ifflameisdetected,thenlost,the50A62controlwillrepeat
the initial ignition sequence for a total of three “recycles”.
After three unsuccessful “recycle” attempts, the control
HEAT MODE
In a typical system, a call for heat is initiated by closing the will go into system lockout.
thermostat contacts. This starts the 50A62 control’s heat-
If flame is established for more than 10 seconds after
ing sequence. The inducer blower and humidifier are
energized (if there is an optional electronic air cleaner on
the system, the humidifier is not energized until the
electronic air cleaner is energized). The 768A Silicon
Nitride ignitor is powered within one second.
ignition, the50A62controllerwillcleartheignitionattempt
(or retry) counter. If flame is lost after 10 seconds, it will
restart the ignition sequence. This can occur a maximum
of five times before system lockout.
Duringburneroperation, amomentarylossofpowerof50
milliseconds or longer will de-energize the main gas
valve. When power is restored, the gas valve will remain
de-energized and a restart of the ignition sequence will
begin immediately.
This controller has an adaptive algorithm that reduces the
ignitor temperature to slightly greater than the minimum
temperature required to ignite gas in each particular
application. The control measures the line voltage and
determines an initial ignitor temperature setting based on
the measurement. After each successful ignition, the
control lowers the ignitor temperature slightly for the next
ignition attempt. The control continues to lower the ignitor
temperature until ignition does not occur, and the control
goes into retry mode. For the second attempt to ignite gas
within the same call for heat, the control increases the
ignitor temperature to the value it was on the third previ-
ous successful ignition. After ignition is successful, the
control sets the ignition temperature at this value for the
next 255 calls for heat, after which the control repeats the
adaptive algorithm. The control is constantly making
adjustments to the ignitor temperature to compensate for
changes in the line voltage.
A momentary loss of gas supply, flame blowout, or a
shorted or open condition in the flame probe circuit will be
sensed within 2 seconds. The gas valve will de-energize
and the control will restart the ignition sequence. Re-
cycleswillbeginandtheburnerwilloperatenormallyifthe
gas supply returns, or the fault condition is corrected,
before the last ignition attempt. Otherwise, the control will
go into system lockout.
If the control has gone into system lockout, it may be
possible to reset the control by a momentary power
interruption of one second or longer. Refer to PRECAU-
TIONARY, SYSTEM LOCKOUT, AND DIAGNOSTIC
FEATURES.
The 80 VAC Silicon Nitride ignitor manufactured by
White-Rodgers must be used. These ignitors are spe-
cially designed to operate with the 50A62’s adaptive
ignition routine to ensure the most efficient ignitor tem-
perature.
COOL MODE
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This starts the 50A62 control’s cool-
ing sequence. The compressor is energized and the cool
mode delay-to-fan-on period begins. After the delay-to-
fan-on period ends, the circulator fan is energized at cool
speed. The electronic air cleaner (optional) is also ener-
gized. After the thermostat is satisfied, the compressor is
de-energized and the cool mode delay-to-fan-off period
begins. After the delay-to-fan-off period ends, the circula-
tor fan and electronic air cleaner (optional) are de-ener-
gized.
At the end of the ignitor warm-up time, both valves in the
36E manifold gas valve are opened. Flame must be
detected within 4 seconds.
If flame is detected, the delay-to-fan-on period begins.
After the delay-to-fan-on period ends, the circulator fan is
energized at heat speed. If there is an optional electronic
air cleaner on the system, the electronic air cleaner and
the humidifier are energized. When the thermostat is
satisfied, the gas valve is de-energized. After proof of
6
SYSTEM LOCKOUT FEATURES
MANUAL FAN ON MODE
When system lockout occurs, the gas valve is de-ener-
gized, the circulator blower is energized at heat speed,
and, ifflameissensed, theinducerblowerisenergizedfor
5 seconds. The diagnostic indicator light will flash or glow
continuously to indicate system status. (System lockout
will never override the precautionary features de-
scribed above.)
If the thermostat fan switch is moved to the ON position,
the circulator fan (fan speed) and optional electronic air
cleaner are energized. When the fan switch is returned to
the AUTO position, the circulator fan and electronic air
cleaner (optional) are de-energized.
PRECAUTIONARY, SYSTEM
LOCKOUT, AND DIAGNOSTIC
FEATURES
Toresetthecontrolaftersystemlockout, dooneofthe
following:
1. Interrupt the call for heat at the thermostat for at least
one second (if flame is sensed with the gas valve de-
energized, interrupting the call for heat at the thermo-
stat will not reset the control).
PRECAUTIONARY FEATURES
The following precautionary features are built into the
50A62 control.
2. Interrupt the 24 VAC power at the control for at least
one second. You may also need to reset the flame
rollout sensor switch.
1. If, at any time, the flame rollout sensor opens, the gas
valve and ignitor are de-energized.
3. Afteronehourinlockout,thecontrolwillautomatically
reset itself.
2. If, at any time, flame is sensed when the gas valve is
de-energized, the heat circulator blower and inducer
fan are energized and the ignition sequence will go
into system lock out. The heat circulator and inducer
will remain on as long as flame is detected. If flame
is no longer detected, the inducer will turn off in 5
seconds and the circulator will turn off using the
maximum heat off delay.
DIAGNOSTIC FEATURES
The 50A62-820 control continuously monitors its own
operation and the operation of the system. If a failure
occurs, theDIAG1andDIAG2LEDswillindicateafailure
code as shown below.
3. If, at any time, the flame rollout switch opens, the heat
circulator blower and inducer fan are energized and
theignitionsequencewillgointosystemlockout. The
inducer will remain energized for 5 seconds. The
circulator will remain on as long as the flame rollout
switch is detected open, then use the maximum heat
off delay.
SAFETY CIRCUIT
Limit Control
DIAG 1
Slow Flash
Off
DIAG 2
On
Pressure Switch
Slow Flash
Watch Guard - Burners
Failed to Ignite
Alternate
Slow Flash
Alternate
Slow Flash
4. If at any time the main valve sense input does not
correspond to the program’s requested gas valve
state, the inducer is de-energized and the ignition
sequence will go into system lock out. The heat
circulator blower will be energized using the maxi-
mum heat off delay, provided a heat off delay is
already in progress.
Flame Sensed Without
Valve Energized
Slow Flash
Off
Roll Out Open or 9-Pin
Connector Disconnected
On
On
Slow Flash
On
Bad Board
Power On
Simultaneous Simultaneous
Slow Flash
Slow Flash
Fast Flash
Slow Flash
Slow Flash
Slow Flash
Low Flame
Reverse Polarity
Low Voltage or
Ignitor Disconnected
Alternate
Fast Flash
Alternate
Fast Flash
Simultaneous Simultaneous
Fast Flash Fast Flash
Heat Demand
7
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