50A55-843
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 50A55-843 is an automatic gas interrupted ignition control These controls incorporate system fault analysis for quick gas
that employs a microprocessor to continually monitor, analyze, flow shut-off, coupled with automatic ignition retry upon sensing
and control the proper operation of the gas burner, inducer, and a fault correction.
fan.
Signals interpreted during continual surveillance of the thermo-
stat and flame sensing element initiate automatic ignition of the
burner, sensing of the flame, and system shut-off during normal
operation.
TRANE APPLICATION - Installer MUST read page 3 “Mounting and Wiring”
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
Failure to comply with the following
warnings could result in personal injury
or property damage.
ordinances.
This control is a precision instrument, and should be handled
carefully. Rough handling ordistortingcomponents 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
Description ........................................................ 1
Precautions ....................................................... 1
Specifications .................................................... 2
Installation ......................................................... 3
Mounting & Wiring
EXPLOSION HAZARD
• Shut off main gas to appliance until installation is
complete.
Operation .......................................................... 6
Mounting Hole Template .................................... 8
White-Rodgers is a division
of Emerson Electric Co.
PART NO. 37-6265G
Replaces 37-6265F
0526
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
• Do not exceed the specified voltage.
• Replace existing control with exact model and
dash number.
on the control’s terminations, system wiring harness or system
1
components. After finding a suitable location, drill four (4) ¦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 50A55 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 50A55 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 50A55 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 50A55 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 50A55 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.
Amana/Goodman application - An additional wiring harness
(WR 115-0223) is included in this package. If the control being
replaced has a 2-pin (inducer/ignitor) connector, this wiring
harness will adapt the furnace wiring to the 4-pin connector of
the replacement control.
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
TYPICAL SYSTEM WIRING DIAGRAM
HOT
(LINE)
NEUTRAL
(LINE)
120 VAC
24 VAC CLASS II
TRANSFORMER
TH
24 VAC
50A55
TR
COOL
HEAT
PARK
PARK
LINE
CIRCULATOR
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
Y
W
G
R
COMPRESSOR
CONTACTOR
50A55-843
in other
furnace(s)
—
TWINNING
APPLICATIONS
ONLY
THERMOSTAT
C
TWIN*
TWIN*
PRESSURE SWITCH (N. O.)
PS
HLI
HLO
FP
RO1
GND
RO2
MV
FLAME
SENSOR
PROBE
HIGH LIMIT
(N. C.)
AUX. HIGH
LIMIT (N. C.)
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
50A55
TERMINAL
TERMINAL
SYSTEM COMPONENT
CONNECTION
TYPE
W
G
R
Y
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)
Terminal
block with
captive
screws
C
24 VAC COMMON side of compressor contactor coil
one wire twinning terminal
TWIN*
MV (2 terminals)
gas valve (both gas solenoids are connected in parallel)
24 VAC transformer (low voltage COMMON side)
24 VAC transformer (low voltage HIGH side)
rollout switch OUTPUT
TR
TH
RO1
RO2
12-pin
rollout switch INPUT
FP
connector
& harness
flame sensor probe*
PS
pressure switch INPUT
HLI
high limit INPUT
HLO
high limit OUTPUT
GND
MUST BE RELIABLY GROUNDED TO CHASSIS
(unused terminal)
IND
inducer HOT side
4-pin
connector
& harness
IGN
ignitor HOT side
IND N
IGN N
inducer NEUTRAL side
ignitor NEUTRAL side
COOL
HEAT
spade terminal circulator blower COOL SPEED terminal
spade terminal circulator blower HEAT SPEED terminal
PARK (2 terminals) spade terminal unused circulator blower terminals
LINE
spade terminal input voltage (120 VAC) HOT side
spade terminal 24 VAC transformer line voltage HOT side
spade terminal electronic air cleaner HOT side
XFMR
EAC (optional)
HUM (optional)
CIR N
spade terminal humidifier 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 electronic air cleaner NEUTRAL side
LINE N
XFMR N
EAC N (optional)
HUM N (optional) spade terminal humidifier NEUTRAL side
* The twinning feature is available only on models with six screw terminals; one of these terminals
will be designated “TWIN”. All 50A55-843 controls used in twinning applications must have the
“TWIN” terminal.
† Maximum recommended flame probe wire length is 36 inches.
5
OPERATION
OPTION SWITCHES
The option switches on the 50A55-843 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.
If flame is detected, the delay-to-fan-on period begins. After the
delay-to-fan-on period ends, the optional electronic air cleaner
is energized and the circulator fan is energized at heat speed.
When the thermostat is satisfied, the gas valve is de-energized.
After proof of flame loss, the heat delay-to-fan-off period begins
and the inducer blower remains energized to purge the system
for 15 seconds. When the purge is complete, the inducer blower
and humidifier are de-energized. After the delay-to-fan-off pe-
riod ends, the circulator fan and electronic air cleaner are de-
energized.
OPTION SWITCH POSITIONS
COOL delay-
to-fan-off:
Set switch
#1
Ifflame is not detected, both valvesare de-energized, theignitor
is turned off, and the 50A55 control goes into the “retry” se-
quence. The “retry” sequence provides a 60-second wait follow-
ing an unsuccessful ignition attempt (flame not detected). After
this wait, the ignition sequence is restarted with an additional 2
seconds of ignitor warm-up time. If this ignition attempt is
unsuccessful, one more retry will be made before the control
goes into system lockout.
45 sec.*
90 sec.
On
Off
HEAT delay-
to-fan-on:
Set switch
#2
30 sec.*
45 sec.
On
Off
If flame is detected, then lost, the 50A55 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-off:
Set switch
#3
#4
60 sec.
90 sec.
120 sec.
180 sec.*
On
Off
On
Off
On
On
Off
Off
If flame is established for more than 10 seconds after ignition,
the 50A55 controller will clear the ignition attempt (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.
* Factory setting
During burner operation, a momentary loss of power of 50
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.
HEAT MODE
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A55 control’s heating
sequence. The inducer blower and optional humidifier are
energized and the ignitor is powered within one second.
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. Recycleswill beginand 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.
This controller has an adaptive algorithm that adjusts the dura-
tion of the ignitor warm-up, to extend ignitor life. Upon initial
application of power, the warm-up time is 17 seconds. The
ignitor on-time will then be increased or decreased depending
on whether or not flame isachieved. The warm-up time is limited
to a maximum of 21 seconds. During the first 64 warm-up
periods following power-up, the warm-up time may not be less
than 17 seconds.
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 SYSTEM LOCKOUT FEATURES.
Upon a call for heat, if the warm-up time has not been locked, it
willbedecreasedbyonesecond.Thisreductionoftheignitoron-
time will continue until flame fails to be achieved (resulting in a
retry).
COOL MODE
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This energizes the 50A55 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.
In the event of a retry, the warm-up time will be increased by two
seconds and locked in at that duration. Once the warm-up time
is locked, it remains fixed until another call for heat results in a
retry, in which case the warm-up time is again increased by two
seconds and remains locked.
In the event of two successive retry attempts, the warm-up time
willbeunlockedandsetto21seconds. Ifflameisthenachieved,
the warm-up time will begin adapting again with the next call for
heat. If, however, this third attempt fails to achieve flame, the
control will go into system lockout.
MANUAL FAN ON MODE
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 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.
6
DIAGNOSTIC FEATURES
TWINNING INTERFACE
The 50A55-843 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.
If the control has six screw terminals, one of which is
designated TWIN, the control is equipped with a single wire
twinning interface. If twinning is used, either control will
process a call for heat, cool or fan as described above.
However, after the heat-, cool-, or fan-on delay time expires,
both units will energize the circulator blowers at the same
time. Likewise, after the heat-, cool-, or fan-off delay time
expires, both units will de-energize the circulator blowers at
the same time. This allows for proper air flow to be obtained.
To assure proper control operation, both controls must share
a common transformer ground (TR).
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).
1 flash, then pause
System lockout
To enable twinning, do the following.
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
1. Power supplied to both furnaces must be from the same
phase of the incoming 120 VAC power.
2. Connect the TWIN screw terminals on the 50A55-843 of
the furnaces to be twinned to each other using a single
wire (14-22 AWG.).
7 flashes, then pause
Continuous flashing
(no pause)
Low flame sense signal
Flame has been sensed when
no flame should be present (no
call for heat)
SYSTEM LOCKOUT AND
DIAGNOSTIC FEATURES
The LED will also flash once at power-up.
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.)
To reset the control after system lockout, do one of the
following:
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.
3. After one hour in lockout, the controlwill automatically reset
itself.
The Emerson logo is a
trademark and a service mark
of Emerson Electric Co.
7
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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