50A65-843
Universal Integrated Furnace Control
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 50A65-843 is an automatic gas interrupted ignition control that employs a
microprocessor to continually monitor, analyze, and control the proper opera-
tion 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.
These controls incorporate system fault analysis for quick gas flow shut-off,
coupled with automatic ignition retry upon sensing a fault correction.
PRECAUTIONS
Installation should be done by a qualified heating and air
conditioning contractor or licensed electrician.
WARNING
If in doubt about whether your wiring is millivolt, line, or low
voltage, have it inspected by a qualified heating and air condi-
tioning contractor or licensed electrician.
Do not exceed the specification ratings.
Allwiringmustconformtolocalandnationalelectricalcodesand
ordinances.
Failure to comply with the following
warnings could result in personal injury
or property damage.
This control is a precision instrument, and should be handled
carefully. Rough handling or distorting components could cause
the control to malfunction.
FIRE HAZARD
Following installation or replacement, follow manufacturer’s
recommended installation/service instructions to ensure proper
operation.
• Do not exceed the specified voltage.
• Protect the control from direct contact with water
(dripping, spraying, rain, etc.).
• If the control has been in direct contact with water,
replace the control.
• Label all wires before disconnection when servic-
ing controls. Wiring errors can cause improper
and dangerous operation.
CAUTION
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
• Route and secure wiring away from flame.
SHOCK HAZARD
• Disconnect electric power before servicing .
• Ensure proper earth grounding of appliance.
• Ensure proper connection of line neutral and line
hot wires.
CONTENTS
EXPLOSION HAZARD
• Shut off main gas to appliance until installation is
Description ........................................................ 1
Precautions ....................................................... 1
Specifications .................................................... 2
Installation ......................................................... 3
Mounting & Wiring
complete.
Operation .......................................................... 6
Mounting Hole Template .................................... 8
PART NO. 37-6270E
Replaces 37-6270D
0701
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INSTALLATION
MOUNTING AND WIRING
All wiring should be installed according to local and national
electrical codes and ordinances.
WARNING
The control must be secured to an area that will experience a
minimum of vibration and remain below the maximum ambient
temperature rating of 175°F. The control is approved for mini-
mum ambient temperatures of -40°F.
FIRE HAZARD
When mounting the control, any orientation is acceptable.
Choose a location that will not damage, obstruct or place stress
on the control’s terminations, system wiring harness or system
• Do not exceed the specified voltage.
• Replace existing control with exact model and
dash number.
components. After finding a suitable location, drill four (4) 1¦8
”
holes for mounting control. To ensure proper mounting hole
locations, there is a mounting hole template on page 8 of this
instruction sheet. Detach the page with the template from the
instruction sheet and apply it to the mounting location. When
drilling the holes, take care so that the transformer, wiring
harnessorothersystemcomponentsarenotdamaged. Four(4)
#8 sheet metal screws are provided to complete the installation.
• Protect the control from direct contact with water
(dripping, spraying, rain, etc.).
• Label all wires before disconnection when servic-
ing controls. Wiring errors can cause improper
and dangerous operation.
• Route and secure wiring away from flame.
SHOCK HAZARD
Refer to the wiring diagram and wiring table when connecting
the 50A65 control to other components of the system.
UL approved, 105°C rated 18 gauge, stranded, 2¦64” thick insula-
tion wire is recommended for all low voltage safety circuit
connections. Refer to 50A65 specification sheet for recom-
mended terminals to mate with those on the control.
• Disconnect electric power before servicing .
• Ensure proper earth grounding of appliance.
• Ensure proper connection of line neutral and line
hot wires.
EXPLOSION HAZARD
• Shut off main gas to appliance until installation is
complete.
UL approved 105°C rated 16 gauge min., stranded, 4¦64” thick
insulation wire is recommended for all line voltage connections.
Refer to 50A65 specification sheet for recommended terminals
to mate with those on the control.
Afterinstallationorreplacement,followappliancemanufacturer’s
recommended installation or service instructions to ensure
proper operation.
CAUTION
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
The 50A65 has only one serviceable part–an automotive type
fuse, which protects the low voltage transformer from damage
if its output is short-circuited. If the fuse has opened up, remove
whatever caused the short circuit and replace the fuse with only
a 3 Amp automotive type fuse. If the fuse is not the cause of the
control’s problem, replace the entire 50A65 control. There are
no other user serviceable parts.
Additional jumper wires are included in this package and
should be used if the original wiring does not reach the control
after mounting. Refer to the furnace wiring diagram for proper
connection of the wires.
Some applications may require connection to terminal E33
located in the middle of the contol cover. If the control being
replaced does not have this connection, it is not needed in the
application and connection to terminal E33 is not required.
Trane application - Jumper wire 151-2906 (provided with
control) must be installed on the furnace from R01 to R02 of the
12-pin connector.
3
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TYPICAL SYSTEM WIRING DIAGRAM
HOT
(LINE)
NEUTRAL
(LINE)
120 VAC
24 VAC CLASS II
TRANSFORMER
TH
24 VAC
TR
50A65-843
COOL
HEAT
PARK
PARK
LINE
CIRCU-
LATOR
BLOWER
XFMR
EAC
HUM
IND
IGN
IND N
IGN N
INDUCER
IGNITOR
HUMIDIFIER
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
E33
PRESSURE SWITCH (N. O.)
PS
HLI
HLO
FP
FLAME
SENSOR
PROBE
HIGH LIMIT
(N. C.)
AUX. HIGH
LIMIT (N. C.)
RO1
GND
RO2
MV
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
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TYPICAL SYSTEM WIRING TABLE
50A65
TERMINAL
TERMINAL
SYSTEM COMPONENT
TYPE
CONNECTION
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)
W
G
R
Y
Terminal
block with
captive
screws
C
24 VAC COMMON side of compressor contactor coil
gas valve (both gas solenoids are connected in parallel)
24 VAC transformer (low voltage COMMON side)
24 VAC transformer (low voltage HIGH side)
flame sensor probe*
MV (2 terminals)
TR
TH
FP
12-pin
PS
connector
& harness
pressure switch INPUT
HLI
high limit INPUT
HLO
high limit OUTPUT
GND
MUST BE RELIABLY GROUNDED TO CHASSIS
rollout switch OUTPUT
RO1
RO2
rollout switch INPUT
(1 unused terminal)
IND
inducer HOT side
4-pin
IGN
ignitor HOT side
connector
& harness
IND N
IGN N
inducer NEUTRAL side
ignitor NEUTRAL side
COOL
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
circulator blower COOL SPEED terminal
circulator blower HEAT SPEED terminal
unused circulator blower terminals
input voltage (120 VAC) HOT side
24 VAC transformer line voltage HOT side
electronic air cleaner HOT side
HEAT
PARK (2 terminals)
LINE
XFMR
EAC (optional)
HUM (optional)
CIR N
humidifier HOT side
circulator blower NEUTRAL terminal
input voltage (120 VAC) NEUTRAL side
24 VAC transformer line voltage NEUTRAL side
electronic air cleaner NEUTRAL side
humidifier NEUTRAL side
LINE N
XFMR N
EAC N (optional)
HUM N (optional)
E33
3/16" spade terminal Auxiliary flame sense
* maximum recommended flame probe wire length is 36 inches.
5
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OPERATION
OPTION SWITCHES
The option switches on the 50A65-843 control are used to
determine the length of the cool delay-to-fan-off, heat delay-to-
fan-on and heat delay-to-fan-off periods. The following table
shows the time periods that will result from the various switch
positions.
begins and the inducer blower remains energized to purge the
system for 5 seconds. When the purge is complete, the inducer
blower and humidifier are de-energized. After the delay-to-fan-
off period ends, the circulator fan and electronic air cleaner are
de-energized. If flame is not detected, both valves are de-
energized, the ignitor is turned off, and the 50A65 control goes
into the “retry” sequence.
The “retry” sequence provides a 60-second wait following an
unsuccessful ignition attempt (flame not detected). After this
wait, the ignition sequence is restarted again. If this ignition
attempt is unsuccessful, one more retry will be made before the
control goes into system lockout.
OPTION SWITCH POSITIONS
COOL delay-
to-fan-off:
Set switch
#1
45 sec.*
90 sec.
On
Off
If flame is detected, then lost, the 50A65 control will repeat the
initial ignition sequence for a total of four “recycles”. After four
unsuccessful “recycle” attempts, the control will go into system
lockout.
HEAT delay-
to-fan-on:
Set switch
#2
30 sec.*
45 sec.
On
Off
If flame is established for more than 10 seconds after ignition,
the 50A65 controller will clear the ignition attempt (or retry)
counter. If flame is lost after 10 seconds, it will restart the ignition
sequence. Thiscanoccuramaximumof11timesbeforesystem
lockout.
HEAT delay-
to-fan-off:
Set switch
#3
#4
60 sec.
90 sec.
120 sec.
180 sec.*
On
Off
On
Off
On
On
Off
Off
A momentary loss of gas supply, flame blowout, or a shorted or
openconditionintheflameprobecircuitwillbesensedwithin2.0
seconds. The gas valve will de-energize and the control will
restart the ignition sequence. A recycle will begin and the burner
will operate normally if the gas supply returns, or the fault
condition is corrected, before the last ignition attempt. Other-
wise, the control will go into system lockout.
* Factory setting
HEAT MODE
If the control has gone into system lockout, it may be possible to
reset the control by a momentary power interruption of ten
seconds or longer. Refer to SYSTEM LOCKOUT FEATURES.
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A65 control’s heating
sequence. The inducer blower and optional humidifier are
energized and the 768A silicon nitride ignitor is powered within
one second.
COOL MODE
This control 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
thecontrolgoesintoretrymode. Forthesecondattempttoignite
gaswithinthesamecallforheat,thecontrolincreasestheignitor
temperature to the value it was on the third previous 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.
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This energizes the 50A65 control and the
compressor. The cool delay-to-fan-on period begins. After the
delay period ends, the optional electronic air cleaner is ener-
gized, and the circulator fan is energized at cool speed. 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 circulator fan and electronic air cleaner
(optional) are de-energized.
MANUAL FAN ON MODE
If the thermostat fan switch is moved to the ON position, the
circulatorfan(coolspeed)andoptionalelectronicaircleanerare
energized. When the fan switch is returned to the AUTO posi-
tion, the circulator fan and electronic air cleaner (optional) are
de-energized.
The 80 VAC Silicon Nitride ignitor manufactured by White-
Rodgers must be used. These ignitors are specially designed
to operate with the 50A65’s adaptive ignition routine to ensure
the most efficient ignitor temperature.
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 is also ener-
gized. When the thermostat is satisfied, the gas valve is de-
energized. After proof of flame loss, the delay-to-fan-off period
6
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DIAGNOSTIC FEATURES
SYSTEM LOCKOUT AND
DIAGNOSTIC FEATURES
The 50A65-843 control continuously monitors its own operation
and the operation of the system. If a failure occurs, the LED will
indicate a failure code as shown below. If the failure is internal
to the control, the light will stay on continuously. In this
case, the entire control should be replaced, as the control
is not field-repairable.
SYSTEM LOCKOUT FEATURES
When system lockout occurs, the gas valve is de-energized, the
circulator blower is energized at heat speed, and, if flame is
sensed, the inducer blower is energized. The diagnostic indica-
tor light will flash or glow continuously to indicate system status.
(System lockout will never override the precautionary fea-
tures.)
If the sensed failure is in the system (external to the control), the
LED will flash in the following flash-pause sequences to indicate
failure status (each flash will last approximately 0.25 seconds,
and each pause will last approximately 2 seconds).
To reset the control after system lockout, do one of the
following:
1 flash, then pause
System lockout
2 flashes, then pause
3 flashes, then pause
4 flashes, then pause
5 flashes, then pause
6 flashes, then pause
Pressure switch stuck closed
Pressure switch stuck open
Open limit switch
Open rollout switch
115 Volt AC power reversed/Im-
proper ground
Low flame sense signal
Check ignitor
Flame has been sensed when
no flame should be present (no
call for heat)
1. Interruptthecallforheatorcoolatthethermostatforatleast
one second but less than 20 seconds (if flame is sensed
with the gas valve de-energized, interrupting the call for
heat at the thermostat will not reset the control).
2. Interrupt the 24 VAC power at the control for at least one
second.Youmayalsoneedtoresettheflamerolloutsensor
switch.
7 flashes, then pause
8 flashes, then pause
Continuous flashing
(no pause)
3. After one hour in lockout, the control will automatically reset
itself.
The LED will also flash once at power-up.
7
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MOUNTING HOLE TEMPLATE
MOUNTING HOLE TEMPLATE
FOR MOUNTING HOLE LOCATIONS
4.172 ± .007
(2 plcs.)
6.402 ± .010
(2 plcs.)
Refer to page 3 of the installation instructions for proper installation.
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