50A55-143
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 50A55-143 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.
CONTENTS
Do not short out terminals on gas valve or pri-
marycontroltotest. Shortorincorrectwiringwill
damage thermostat and could cause personal
injury and/or property damage.
Description ......................................................... 1
Precautions ........................................................ 1
Specifications..................................................... 2
Installation.......................................................... 3
Mounting & Wiring
Operation ........................................................... 6
WHITE-RODGERS DIVISION
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
PART NO. 37-6095A
Printed in U.S.A.
ST. LOUIS, MISSOURI 63123-5398
9919
Download from Www.Somanuals.com. All Manuals Search And Download.
INSTALLATION
MOUNTING AND WIRING
WARNING
NOTE
All wiring should be installed according to local and
national electrical codes and ordinances.
!
Do not use on circuits exceeding specified
voltage. Higher voltage will damage control
and could cause shock or fire hazard.
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
!
Whenmountingthecontrol, anyorientationisacceptable.
Choose a location that will not damage, obstruct or place
stress on the control’s terminations, system wiring har-
ness or system components. After finding a suitable
To prevent electrical shock and/or equipment
damage, disconnect electric power to system at
main fuse or circuit breaker box until installation
is complete. Failure to earth ground the appli-
ance or reversing the neutral and hot wire con-
nection to the line can cause shock hazard.
1
location, drill four (4) ⁄8” holes for mounting control. To
ensurepropermountingholelocations, thereisa mount-
ing 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 har-
ness or other system components are not damaged. Four
(4) #8 sheet metal screws are provided to complete the
installation.
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.
Refer to the wiring diagram and wiring table when con-
necting the 50A55 control to other components of the
system.
UL approved, 105°C rated 18 gauge, stranded, 2⁄64” thick
insulation wire is recommended for all low voltage safety
circuit connections. Refer to 50A55 specification sheet
for recommended terminals to mate with those on the
control.
To prevent damage to the transformer, system
components or wiring harness, take care when
drillingnewmountingholes.Failuretodosomay
result in electrical shock, fire hazard or equip-
ment damage.
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 rec-
ommended terminals to mate with those on the control.
After installation or replacement, follow appliance
manufacturer’s recommended installation or service in-
structions to ensure proper operation.
The 50A55 has only one serviceable part–an automotive
typefuse,whichprotectsthelowvoltagetransformerfrom
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.
3
Download from Www.Somanuals.com. All Manuals Search And Download.
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
INDUCER
IGNITOR
IND
IGN
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
50A55-143
IN OTHER
FURNACES
TWINNING
APPLICATIONS
ONLY
THERMOSTAT
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
Download from Www.Somanuals.com. All Manuals Search And Download.
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
TWIN
one wire twinning terminal
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)
rollout switch OUTPUT
MV (2 terminals)
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)
2-pin
connector
& harness
IND
IGN
inducer HOT side
ignitor HOT side
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
COOL
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)
* maximum recommended flame probe wire length is 36 inches.
5
Download from Www.Somanuals.com. All Manuals Search And Download.
OPERATION
OPTION SWITCHES
At the end of the ignitor warm-up time, both valves in the
36E manifold gas valve are opened. Flame must be
Theoptionswitchesonthe50A55-143controlareusedto detected within 4 seconds.
determine the length of the heat delay-to-fan-off periods.
If flame is detected, the delay-to-fan-on period begins.
The following table shows the time periods that will result
from the various switch positions.
After the delay-to-fan-on period ends, the optional elec-
tronic air cleaner is energized and the circulator fan is
energized at heat speed. When the thermostat is satis-
fied, the gas valve is de-energized. After proof of flame
loss, the heat delay-to-fan-off period begins and the
inducerblowerremainsenergizedtopurgethesystemfor
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.
OPTION SWITCH POSITIONS
HEAT delay-
to-fan-on:
Set switch
#1
#2
15 sec.
30 sec.
45 sec.
60 sec.
Off
Off
On
On
Off
On
Off
On
If flame is not detected, both valves are de-energized, the
ignitor is turned off, and the 50A55 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 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.
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
Ifflameisdetected,thenlost,the50A55controlwillrepeat
the initial ignition sequence for a total of four “recycles”.
After four unsuccessful “recycle” attempts, the control will
go into system lockout.
HEAT MODE
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A55 control’s heat-
ing sequence. The inducer blower and optional humidifier
are energized, and after the 30-second prepurge the
ignitor is powered within one second.
If flame is established for more than 10 seconds after
ignition, the50A55controllerwillcleartheignitionattempt
(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.
This controller has an adaptive algorithm that adjusts the
durationoftheignitorwarm-up,toextendignitorlife.Upon
initial application of power, the warm-up time is 17 sec-
onds. The ignitor on-time will then be increased or de-
creased depending on whether or not flame is achieved.
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.
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.
A momentary loss of gas supply, flame blowout, or a
shorted or open condition in the flame probe circuit will be
sensed within 2.0 seconds. The gas valve will de-ener-
gize and the control will restart the ignition sequence.
Recycles will begin and the burner will operate normally
ifthegassupplyreturns,orthefaultconditioniscorrected,
before the last ignition attempt. Otherwise, the control will
go into system lockout.
Upon a call for heat, if the warm-up time has not been
locked, it will be decreased by one second. This reduction
of the ignitor on-time will continue until flame fails to be
achieved (resulting in a retry).
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.
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.
In the event of two successive retry attempts, the warm-
up time will be unlocked and set to 21 seconds. If flame is
then achieved, 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.
6
Download from Www.Somanuals.com. All Manuals Search And Download.
COOL MODE
SYSTEM LOCKOUT AND
DIAGNOSTIC FEATURES
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 elec-
tronic air cleaner is energized, and the circulator fan is
energized at cool speed. After the thermostat is satisfied,
thecompressorisde-energizedandthecoolmodedelay-
to-fan-off period begins. After the delay-to-fan-off period
ends, the circulator fan and electronic air cleaner (op-
tional) are de-energized.
SYSTEM LOCKOUT FEATURES
When system lockout occurs, the gas valve is de-ener-
gized, the circulator blower is energized at heat speed,
and, if flame is sensed, the inducer blower is energized.
The diagnostic indicator light will flash or glow continu-
ously to indicate system status. (System lockout will
never override the precautionary features.)
Toresetthecontrolaftersystemlockout, dooneofthe
following:
MANUAL FAN ON MODE
1. Interrupt the call for heat or cool at the thermostat for
at least one second but less than 20 seconds (if flame
is sensed with the gas valve de-energized, interrupt-
ing the call for heat at the thermostat will not reset the
control).
If the thermostat fan switch is moved to the ON position,
the circulator fan (cool 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.
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.
TWINNING INTERFACE
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
willprocessacallforheat, coolorfanasdescribedabove.
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 circula-
torblowersatthesametime.Thisallowsforproperairflow
to be obtained. To assure proper control operation, both
controls must share a common transformer ground (TR).
3. Afteronehourinlockout,thecontrolwillautomatically
reset itself.
DIAGNOSTIC FEATURES
The 50A55 control continuously monitors its own opera-
tionandtheoperationofthesystem.Ifafailureoccurs,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.
To enable twinning, do the following.
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. Power supplied to both furnaces must be from the
same phase of the incoming 120 VAC power.
2. ConnecttheTWINscrewterminalsonthe50A55-143
of the furnaces to be twinned to each other using a
single wire (14-22 AWG.).
1 flash, then pause
System lockout
2 flashes, then pause Pressure switch stuck closed
3 flashes, then pause Pressure switch stuck open
4 flashes, then pause Open limit switch
5 flashes, then pause Open rollout switch
6 flashes, then pause 115 Volt AC power reversed/
improper ground
7 flashes, then pause Low flame sense signal
Continuous flashing
(no pause)
Flame has been sensed when
no flame should be present (no
call for heat)
The LED will also flash once at power-up.
7
Download from Www.Somanuals.com. All Manuals Search And Download.
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.
Download from Www.Somanuals.com. All Manuals Search And Download.
|