Bryant 355CAV A Series Troubleshooting Manual
troubleshooting guide
Variable Speed, Step-Modulating
Electronic Condensing 355CAV
Four-Way Multipoise Gas Furnace Series A
INDEX
PAGE
Safety Considerations................................................................................. 1
Instructions.................................................................................................. 1
Example ...................................................................................................... 2
General........................................................................................................ 2
Sequence of Operation ............................................................................... 2
Single-Stage Thermostat and Step-Modulating Heating
(Adaptive Mode)................................................................................ 2
Two-Stage Thermostat and Two-Stage Low/High Heating.............4
Two-Stage Thermostat and Two-Stage Medium/High Heating...... 4
Cooling Mode ....................................................................................5
Single-Speed Cooling ........................................................................ 5
Single-Stage Thermostat and Two-Speed Cooling (Adaptive
Mode) ................................................................................................. 5
Two-Stage Thermostat and Two-Speed Cooling ............................. 5
Thermidistat Mode............................................................................. 6
Super-Dehumidify Mode................................................................... 6
Continuous-Blower Mode ................................................................. 6
Heat Pump Defrost............................................................................. 7
Component Test.................................................................................7
Service/Status Code Instructions ............................................................... 8
Start Here .................................................................................................. 10
Rapid Flashing AMBER LED.................................................................11
Improper Cooling Air Flow .....................................................................12
Medium And/Or High Heat Temperature Rise Too Low....................... 13
Status Code 11 - No Previous Code......................................................... 15
Status Code 12 - Blower On After Power Up ......................................... 15
Status Code 13 - Limit Circuit Lockout .................................................. 16
Status Code 14 - Ignition Lockout ........................................................... 17
Status Code 15 - Blower Motor Lockout................................................. 17
Status Code 21 - Gas Heating Lockout.................................................... 17
Status Code 22 - Abnormal Flame-Proving Signal.................................18
Status Code 23 - Pressure Switch Did Not Open....................................18
Status Code 24 - Secondary Voltage Fuse Is Open................................. 19
Status Code 25 - Model Selection or Setup Error ...................................21
Status Code 31 - Medium-Heat Switch or HPSR Relay did not
Close or Reopen...............................................................................22
Status Code 32 - Low-Heat Pressure Switch Did Not Close or
Reopened.......................................................................................... 24
Status Code 33 - Limit Circuit Fault........................................................ 26
Status Code 34 - Ignition-Proving Fault..................................................28
Status Code 41 - Blower Motor Fault...................................................... 30
Status Code 42 - Inducer Motor Fault .....................................................32
Status Code 43 - Low-Heat Pressure Switch Open While Medium-
Heat Pressure Switch Is Closed....................................................... 34
Status Code 45 – Control Circuitry Lockout...........................................34
Cleanup and Start-Up Instructions........................................................... 35
APPENDIX A - Board Layout & Wiring Schematic ............................. 36
APPENDIX B - ECM Blower Motor Description & Operation............38
APPENDIX C - Pressure Check Diagram ..............................................40
APPENDIX D - Static Pressure Reading Location Diagrams................41
APPENDIX E - Quick Reference Information ....................................... 43
Cancels: NEW SM355CAV-01
APPENDIX F - Furnace Staging Algorithm...........................................44
SAFETY CONSIDERATIONS
Installing and servicing heating equipment can be hazardous due to
gas and electrical components. Only trained and qualified personnel
should install, repair, or service heating equipment.
Untrained personnel can perform basic maintenance functions such as
cleaning coils, or cleaning and replacing filters. All other operations
should be performed by trained service personnel. When working on
heating equipment, observe precautions in literature, on tags, and on
labels attached to or shipped with the unit, and other safety
precautions that may apply.
Follow all safety codes. In the United States, follow all safety codes
including the National Fuel Gas Code (NFGC) NFPA 54-2006/ANSI
Z223.1-2006. In Canada, refer to the National Standard of Canada
Natural Gas and Propane Installation Codes (NSCNGPIC), CSA
B149.1-05.
Wear safety glasses and work gloves. Have a fire extinguisher
available during start-up, adjustment procedures, and service calls.
Recognize safety information. This is the safety-alert symbol .
When you see this symbol on the furnace and in instructions or
manuals, be alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, and CAUTION,
and NOTE. The words DANGER, WARNING, and CAUTION are
used with the safety-alert symbol. DANGER identifies the most
serious hazards which will result in severe personal injury or death.
WARNING signifies hazards which could result in personal injury or
death. CAUTION is used to identify unsafe practices which may
result in minor personal injury, or product and property damage.
NOTE is used to highlight suggestions which will result in enhanced
installation, reliability, or operation.
INSTRUCTIONS
This guide uses your expertise and observations to lead you to the
trouble spot as efficiently as possible. This is only intended as a guide
and should not be used blindly. Your experience and expertise are of
high value when troubleshooting this unit. Do not disregard all of
your instincts.
The variable speed furnace control was designed with diagnostic
capabilities built in. A AMBER LED is used to flash a status code
which will lead you to one of the sections as listed in the Index.
You should ALWAYS begin in the START HERE section (see Index
for page number) which will guide you to the appropriate section
where a minimal number of steps will be used to correct the problem.
10-08
!
- 1 -
Once in a section, read the ACTION. An ACTION may have a
number in the GO TO column. Do whatever the ACTION says, then
proceed to the step indicated in the GO TO column.
If the ACTION is a question (a question will have a number in the
YES or NO column), answer it YES or NO. If the answer is YES, go
to the step indicated in the YES column. If the answer is NO, go to
the step indicated in the NO column.
Let’s try our guide out using the EXAMPLE section below, and see
how it works. Suppose that the problem is a defective low heat
pressure switch (for example the contacts will not open). This is an
internal problem and cannot simply be seen. We go to the START
HERE section to Step 1.
EXAMPLE
Start Here Section
STEP ACTION YES NO GO TO
1. Step 1 tells us to remove main furnace door first and NOT TO REMOVE THE BLOWER
2 19
ACCESS PANEL. It then asks the question, “Is AMBER LED status light on?”. If the low
heat pressure switch was defective, a pressure switch did not open status code would be
flashing, so the answer is YES. We go to Step 2.
2. Step 2 asks the question, “Is the AMBER LED status light blinking rapidly without a pause?”.
3 4
If the low heat pressure switch was defective, a pressure switch did not open status code would
be flashing, so the answer is NO. We go to Step 4.
4. Step 4 asks the question, “Is the AMBER LED status light blinking ON/OFF slowly with a
5 7
combination of short and long flashes?”. If the low heat pressure switch was defective, a
pressure switch did not open status code would be flashing, so the answer is YES. We go to
Step 5.
5. Step 5 tells us to determine the status code. The status code is a 2 digit number with the first
6
digit determined by the number of short flashes and the second digit by the number of long
flashes. So we count the short and long flashes and see that status code 23 is flashing and go to
Step 6.
6. Step 6 tells us to go to status code 23 section INDEX
GENERAL
The furnace must have a 115-vac power supply properly connected
and grounded. Correct polarity must be maintained to enable gas
heating operation.
The gas service pressure must not exceed 0.5 psig (14-in.wc), and no
less than 0.16 psig (4.5-in.wc).
Thermostat wire connections to the furnace at R and W/W1 are the
minimum required for gas heating operation. W2 must be connected
for 2-stage heating thermostats. Y/Y2 and G are required to be
connected to the furnace for single-stage cooling and heat pumps. Y1,
Y/Y2, and G are required for two-stage cooling and heat pumps. G is
required for continuous-fan. C
OM-24V is required for some clock
thermostats. These connections must be made at the 24-vac terminal
block on the furnace control. (See Appendix A)
This furnace can be installed with either a single-stage heat/cool or a
two-stage heat/cool thermostat.
!
CAUTION: This furnace is equipped with a manual
reset switch in the gas control area. The switch will open
and shut off power to the gas valve, if a flame rollout or
overheating condition occurs in the gas control area. DO
NOT bypass the switch. Correct inadequate combustionair supply, component failure before resetting the switch.
Before operating the furnace, check each manual reset switch for
continuity. If necessary, press and release the button to reset the
switch.
SEQUENCE OF OPERATION
Using the schematic diagram in Appendix A, follow the sequence of
operation through the different modes. Read and follow the wiring
diagram very carefully.
Note: If a power interruption occurs during a call for heat (W/W1 or
W/W1-and-W2), the control will start a 90-second blower-only ON
period two seconds after power is restored, if the thermostat is still
calling for gas heating. The amber LED light will flash code 12
during the 90-second period, after which the LED will be ON
continuous, as long as no faults are detected. After the 90-second
period, the furnace will respond to the thermostat normally.
The blower access panel must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace control
CPU, transformer TRAN, inducer motor IDM, blower motor BLWM,
hot-surface igniter HSI, throttling valve TV, and gas valve GV.
1. SINGLE-STAGE THERMOSTAT AND STEPMODULATING HEATING (ADAPTIVE MODE)
Note: Low-heat only switch SW1-2 selects the low-heat only
operation mode when ON. Medium-heat only switch SW4-2
selects medium-heat only operation mode when ON. If both
switches are ON the furnace control will default to medium-heat.
If either or both switches are ON the furnace control will operate
at two-stages only as referenced in Section 2 below. If both
switches are OFF the furnace control will operate in the adaptive
heating mode in response to a call for heat. When the W2
thermostat terminal is energized it will always cause high-heat
operation as long as the R to W circuit is closed, regardless of the
setting of the low-heat or medium-heat only switches.
- 2 -
This furnace can operate as a step-modulating furnace with a
single-stage thermostat because the furnace control CPU
includes a programmed adaptive sequence of controlled
operation, which selects low-heat, medium-heat, or high-heat
operation. This selection is based upon the stored history of the
length of previous gas-heating periods of the single-stage
thermostat.
The furnace will start up in either medium-, or high-heat. The
furnace will operate in low-heat after starting and operating for 1
minute at medium-heat before transitioning to low-heat. The
furnace control CPU determines the combined low-heat and
medium-heat on-time (from 0 to 16 minutes) which is permitted
before switching to high-heat.
If the power is interrupted, the stored history is erased and the
furnace control CPU will select medium-heat for 1 minute, lowheat for 15 minutes and then switch to high-heat, as long as the
thermostat continues to call for heat. Subsequent selection is
based on stored history of the thermostat cycle times.
The wall thermostat "calls for heat", closing the R to W circuit.
The furnace control CPU performs a self-check, verifies the lowheat and medium-heat pressure switch contacts LPS and MPS
are open, then de-energizes the HPSR relay to close the NC
contact.
a. Inducer Prepurge Period - The furnace control CPU
turns on inducer motor IDM and slowly increases the
inducer motor speed. After the low-heat pressure switch
LPS closes the furnace control CPU continues to increase
the inducer motor speed until the medium-heat pressure
switch MPS closes. When the medium-heat pressure
switch MPS closes, throttling valve TV is energized,
inducer motor RPM is noted by the furnace control CPU,
and a 25-second prepurge period begins. The RPM is used
to evaluate vent system resistance. This evaluation is then
used to determine the required RPM necessary to operate
the inducer motor during medium-heat prepurge, the first
minute of medium-heat mode, and low-heat mode.
Note: The heat cycle can start in either high- or medium-
heat. If a high-heat cycle is initiated, the furnace control
CPU will continue to increase the inducer motor speed after
the medium-heat pressure switch MPS closes. When the
medium-heat pressure switch closes, throttling valve TV is
energized, inducer motor RPM is noted by the furnace
control CPU, and a 25-second prepurge period begins. The
RPM is used to evaluate vent system resistance. This
evaluation is then used to determine the required RPM
necessary to operate the inducer motor in high-heat prepurge, and high-heat mode.
b. Igniter Warm-Up - At the end of the prepurge period, the
Hot-Surface Igniter HSI is energized for a 17-second igniter
warm-up period.
c. Trial-For-Ignition Sequence - When the igniter warm-up
period is completed the main gas valve relay contact GVR
closes to energize the gas valve solenoid GV-M. The gas
valve solenoid GV-M permits gas flow to the burners where
it is ignited. Five seconds after the GVR closes, a 2-second
Flame-Proving period begins. The HSI igniter will remain
energized until flame is sensed or until the 2-second flame
proving period begins.
If the furnace control CPU selects high-heat operation, the
high-heat gas valve solenoid GV-HI is energized when the
high-heat pressure switch HPS closes.
d. Flame-Proving - When the burner flame is proved at the
flame-proving sensor electrode FSE, the furnace control
CPU begins the blower-ON delay period and continues to
hold the gas valve GV-M open. If the burner flame is not
proved within two seconds, the control CPU will close the
gas valve GV-M, and the control CPU will repeat the
ignition sequence for up to three more Trials-For-Ignition
before going to Ignition-Lockout. Lockout will be reset
automatically after three hours, by momentarily interrupting
115 vac power to the furnace, or by interrupting 24 vac
power at SEC1 or SEC2 to the furnace control CPU (not at
W/W1, G, R, etc.).
If flame is proved when flame should not be present, the
furnace control CPU will lock out of Gas-Heating mode
and operate the inducer motor IDM at full speed until
flame is no longer proved.
e. Inducer Speed Change – If the cycle starts in medium-
heat, the furnace control CPU reduces the inducer speed
slightly after flame sense. The reduction in speed in
medium-heat is to optimize combustion for maximum
efficiency. If the cycle starts in high-heat, the furnace
control CPU increases the inducer speed 15 seconds after
flame sense.
f. Blower-On delay – If the burner flame is proven the
blower-ON delay for low-heat and high-heat are as follows:
Medium-heat – 60 seconds after the gas valve GV-M is
opened the blower motor BLWM is turned ON at low- or
medium-heat airflow.
High-heat – 35 seconds after the gas valve GV-M is
opened the BLWM is turned ON at high-heat airflow.
Simultaneously, the humidifier terminal HUM and
electronic air cleaner terminal EAC-1 are energized and
remain energized throughout the heating cycle.
g. Switching from Medium- to Low-Heat – If the furnace
control switches from medium-heat to low-heat, the furnace
control will turn the blower ON at low-heat airflow,
energize the HPSR relay to open the NC contact, and
slowly decrease the inducer motor speed. When the HPSR
relay is energized and the NC contact opens the throttling
valve TV is de-energized and the gas flow reduces to lowheat rate.
Switching from Low- to Medium-Heat – If the furnace
control CPU switches from low-heat to medium-heat, the
furnace control CPU will de-energize the HPSR relay to
close the NC contact and slowly increase the inducer motor
speed until the medium-heat pressure switch MPS closes.
When the medium-heat pressure switch MPS closes, the
throttling valve solenoid TV is energized and the inducer
motor RPM is noted by the furnace control CPU. The
RPM is used to evaluate vent system resistance. This
evaluation is then used to determine the required RPM
necessary to operate the inducer motor in medium-heat and
high-heat mode. The blower motor BLWM will transition
- 3 -
to medium-heat airflow five seconds after the furnace
control CPU switches from low-heat to medium-heat.
Switching from Low- to High-Heat – If the furnace
control CPU switches from low-heat to high-heat, the
furnace control CPU will de-energize the HPSR relay to
close the NC contact and slowly increase the inducer motor
speed until the medium-heat pressure switch MPS closes.
When the medium-heat pressure switch MPS closes, the
throttling valve solenoid TV is energized and the inducer
motor RPM is noted by the furnace control CPU. The
RPM is used to evaluate vent system resistance. This
evaluation is then used to determine the required RPM
necessary to operate the inducer motor in medium- and
high-heat mode. The blower motor BLWM will transition
to high-heat airflow five seconds after the furnace control
CPU switches from low-heat to high-heat. As the inducer
RPM gradually increases the high-heat pressure switch HPS
closes and the gas valve solenoid GV-HI is energized.
Switching from Medium- to High-Heat – If the furnace
control CPU switches from medium-heat to high-heat, the
furnace control CPU will gradually increase the inducer
motor speed to the required high-heat RPM. The blower
motor BLWM will transition to high-heat airflow five
seconds after the furnace control CPU switches from
medium-heat to high-heat. As the inducer RPM gradually
increases the high-heat pressure switch HPS closes and the
gas valve solenoid GV-HI is energized.
Switching from High- to Medium- or Low-Heat – The
furnace control CPU will not switch from high-heat to
medium- or low-heat while the thermostat R to W circuit is
closed when using a single-stage thermostat.
h. Blower-Off Delay - When the thermostat is satisfied, the
R to W circuit is opened, de-energizing the gas valve GVM, stopping gas flow to the burners, and de-energizing the
throttling valve TV, and humidifier terminal HUM. The
inducer motor IDM will remain energized for a 15-second
post-purge period. The blower motor BLWM and air
cleaner terminal EAC-1 will remain energized at low-heat
airflow or transition to low-heat airflow for 90, 120, 150, or
180 seconds (depending on selection at blower-OFF delay
switches). The furnace control CPU is factory-set for a 120second blower-OFF delay.
2. TWO-STAGE THERMOSTAT AND TWO-STAGE
LOW/HIGH HEATING
Note: In this mode the low-heat only switch SW1-2 must be
ON to select the low-heat only operation mode in response to
closing the thermostat R to W1 circuit. Closing the thermostat
R to W1-and-W2 circuits always causes high-heat operation,
regardless of the setting of the low-heat only switch.
The furnace will start up in either medium-, or high-heat. The
furnace will operate in low-heat after starting and operating for 1
minute at medium-heat before transitioning to low-heat.
The wall thermostat "calls for heat", closing the R to W1 circuit
for low-heat or closing the R to W1-and-W2 circuits for highheat. The furnace control performs a self-check, and verifies the
low-heat and medium-heat pressure switch contacts LPS and
MPS are open, then de-energizes the HPSR relay to close the NC
contact.
The start up and shut down functions and delays described above
apply to the 2-stage low/high heating mode as well, except for
switching from high- to low-heat.
a. Switching from High- to Low-Heat - If the thermostat
R to W2 circuit opens, and the R to W1 circuit remains
closed, the furnace control CPU will gradually decrease the
inducer motor speed to the required medium-heat RPM.
When the inducer motor IDM reduces pressure sufficiently,
the high-heat pressure switch HPS will open and the highheat gas valve solenoid GV-HI will be de-energized. The
gas valve solenoid GV-M will remain energized as long as
the low-heat pressure switch LPS remains closed. When
the inducer motor speed gets within 15% of the required
medium-heat RPM the furnace control CPU will start a 5
second blower airflow change delay. After the 5 second
blower airflow change delay is completed the blower
airflow will transition to low-heat airflow. At this point the
furnace control CPU will energize the HPSR relay to open
the NC contact and slowly decrease the inducer motor
speed to the required low-heat RPM. When the HPSR
relay is energized and the NC contact opens the throttling
valve TV is de-energized and the gas flow reduces to lowheat rate. When the inducer motor IDM reduces pressure
sufficiently, the medium-heat pressure switch MPS will
open.
3. TWO-STAGE THERMOSTAT AND TWO-STAGE
MEDIUM/HIGH HEATING
Note: In this mode the medium-heat only switch SW4-2 must
be ON to select the medium-heat only operation mode in
response to closing the thermostat R to W1 circuit. Closing the
thermostat R to W1-and-W2 circuits always causes high-heat
operation, regardless of the setting of the medium-heat only
switch.
The wall thermostat "calls for heat", closing the R to W1 circuit
for medium-heat or closing the R to W1-and-W2 circuits for
high-heat. The furnace control performs a self-check, and
verifies the low-heat and medium-heat pressure switch contacts
LPS and MPS are open, then de-energizes the HPSR relay to
close the NC contact.
The start up and shut down functions and delays described above
apply to the 2-stage medium/high heating mode as well, except
for switching from high- to medium-heat.
a. Switching from High- to Medium-Heat – If the
thermostat R to W2 circuit opens, and the R to W1 circuit
remains closed, the furnace control CPU will gradually
decrease the inducer motor speed to the required mediumheat RPM. When the inducer motor IDM reduces pressure
sufficiently, the high-heat pressure switch HPS will open
and the high-heat gas valve solenoid GV-HI will be deenergized. The gas valve solenoid GV-M will remain
energized as long as the low-heat pressure switch LPS
remains closed. When the inducer motor speed gets within
15% of the required medium-heat RPM the furnace control
CPU will start a 5 second blower airflow change delay.
After the 5 second blower airflow change delay is
completed the blower airflow will transition to mediumheat airflow.
- 4 -
4. COOLING MODE
The thermostat "calls for cooling".
a. Single-Speed Cooling
The thermostat closes the R to G-and-Y circuits. The R to
Y circuit starts the outdoor unit, and the R to G-and-Y/Y2
circuits start the furnace blower motor BLWM on cooling
airflow. Cooling airflow is based on the A/C selection
shown in Table 1.
The electronic air cleaner terminal EAC-1 is energized
with 115 vac when the blower motor BLWM is operating.
When the thermostat is satisfied, the R to G-and-Y circuits
are opened. The outdoor unit will stop, and the furnace
blower motor BLWM will continue operating at cooling
airflow for an additional 90 seconds. Jumper Y/Y2 to
DHUM to reduce the cooling off-delay to 5 seconds. (See
Fig. 1.)
b. Single-Stage Thermostat and Two-Speed Cooling
(Adaptive Mode)
This furnace can operate a two-speed cooling unit with a
single-stage thermostat because the furnace control CPU
includes a programmed adaptive sequence of controlled
operation, which selects low-cooling or high-cooling
operation. This selection is based upon the stored history
of the length of previous cooling period of the single-stage
thermostat.
Table 1
AIR CONDITIONING (A/C) OR CONTINUOUS-FAN (CF)
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
MODEL
SIZE
060, 3T-080
5T-080, 100
120
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON)
MODEL
SIZE
060, 3T-080
5T-080, 100
120
1. DEFAULT A/C AIRFLOW WHEN A/C SWITCHES ARE IN OFF POSITION
2. DEFAULT CONT. FAN AIRFLOW WHEN CF SWITCHES ARE IN OFF POSITION
3. SWITCH POSITIONS ARE ALSO SHOWN ON FURNACE WIRING DIAGRAM
Note: The air conditioning relay disable jumper ACRDJ
must be connected to enable the adaptive cooling mode in
response to a call for cooling. (See Fig. 1.) When in place
the furnace control CPU can turn on the air conditioning
relay ACR to energize the Y/Y2 terminal and switch the
outdoor unit to high-cooling.
AIRFLOW SELECTION CHART
SETUP SWITCH SW3 POSITIONS
525
DEF.
DEF.
DEF.
DEF.
DEF.
DEF.
700
2
700
875 1050
2
700 8752 1050
SETUP SWITCH SW3 POSITIONS
600
800
2
800
2
800 10002 1200
1000
1000 1200
875
1050
1225
1225
1200
1400
1400
1225
1225
1750
1750
1400
2000
2000
1
1
1
1
1225
1750
2100
1400
2000
2100
1
1400
1400
1400
1
1600
1600
The furnace control CPU can start up the cooling unit in
either low- or high-cooling. If starting up in low-cooling,
the furnace control CPU determines the low-cooling ontime (from 0 to 20 minutes) which is permitted before
switching to high-cooling.
If the power is interrupted, the stored history is erased and
the furnace control CPU will select low-cooling for up to
20 minutes and then energize the air conditioning relay
ACR to energize the Y/Y2 terminal and switch the
outdoor unit to high-cooling, as long as the thermostat
continues to call for cooling. Subsequent selection is
based on stored history of the thermostat cycle times.
The wall thermostat “calls for cooling”, closing the
R to G-and-Y circuits. The R to Y1 circuit starts the
outdoor unit on low-cooling speed, and the R to G-and-Y1
circuits starts the furnace blower motor BLWM at lowcooling airflow which is the true on-board CF selection as
shown in Table 1.
If the furnace control CPU switches from low-cooling to
high-cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay
ACR is energized the R to Y1-and-Y2 circuits switch the
outdoor unit to high-cooling speed, and the R to G-andY1-and-Y/Y2 circuits transition the furnace blower motor
BLWM to high-cooling airflow. High-cooling airflow is
based on the A/C selection shown in Table 1.
Note: When transitioning from low-cooling to highcooling the outdoor unit compressor will shut down for 1
minute while the furnace blower motor BLWM transitions
to run at high-cooling airflow.
The electronic air cleaner terminal EAC-1 is energized
with 115 vac whenever the blower motor BLWM is
operating.
When the thermostat is satisfied, the R to G-and-Y circuit
are opened. The outdoor unit stops, and the furnace
blower BLWM and electronic air cleaner terminal EAC-1
will remain energized for an additional 90 seconds.
Jumper Y1 to DHUM to reduce the cooling off-delay to 5
seconds. (See Fig. 1.)
c. Two-Stage Thermostat and Two-Speed Cooling
Note: The air conditioning relay disable jumper ACRDJ
must be disconnected to allow thermostat control of the
outdoor unit staging. (See Fig. 1.)
The thermostat closes the R to G-and-Y1 circuits for lowcooling or closes the R to G-and-Y1-and-Y2 circuits for
high-cooling. The R to Y1 circuit starts the outdoor unit
on low-cooling speed, and the R to G-and-Y1 circuit starts
the furnace blower motor BLWM at low-cooling airflow
which is the true on-board CF selection as shown in Table
1. The R to Y1-and-Y2 circuits start the outdoor unit on
high-cooling speed, and the R to G-and-Y/Y2 circuits start
the furnace blower motor BLWM at high-cooling airflow.
High-cooling airflow is based on the A/C selection shown
in Table 1.
- 5 -
The electronic air cleaner terminal EAC-1 is energized
with 115 vac whenever the blower motor BLWM is
operating.
When the thermostat is satisfied, the R to G-and-Y1 or
R to G-and-Y1-and-Y2 circuits are opened. The outdoor
unit stops, and the furnace blower BLWM and electronic
air cleaner terminal EAC-1 will remain energized for an
additional 90 seconds. Jumper Y1 to DHUM to reduce the
cooling off-delay to 5 seconds. (See Fig. 1.)
5. THERMIDISTAT MODE
The dehumidification output, DHUM on the Thermidistat
should be connected to the furnace control thermostat terminal
DHUM. When there is a dehumidify demand, the DHUM input
is activated, which means 24 vac signal is removed from the
DHUM input terminal. In other words, the DHUM input logic
is reversed. The DHUM input is turned ON when no
dehumidify demand exists. Once 24 vac is detected by the
furnace control on the DHUM input, the furnace control
operates in Thermidistat mode. If the DHUM input is low for
more than 48 hours, the furnace control reverts back to nonThermidistat mode.
The cooling operation described in item 3. above also applies to
operation with a Thermidistat. The exceptions are listed below:
a. When the R to G-and-Y1 circuit is closed and there is a
demand for dehumidification, the furnace blower motor
BLWM will drop the blower airflow to 86% of low-cooling
airflow which is the true on-board CF selection as shown in
Table 1.
b. When the R to G-and Y/Y2 circuit is closed and there is a
demand for dehumidification, the furnace blower motor
BLWM will drop the blower airflow to 86% of highcooling airflow. High-cooling airflow is based on the A/C
selection shown in Table 1.
c. When the “call for cooling” is satisfied and there is a
demand for dehumidification, the cooling blower-off delay
is decreased from 90 seconds to 5 seconds.
6. SUPER-DEHUMIDIFY MODE
Super-Dehumidify mode can only be entered if the furnace
control is in the Thermidistat mode and there is a demand for
dehumidification. The cooling operation described in item 3.
above also applies to operation with a Thermidistat. The
exceptions are listed below:
a. Low Cooling – When the R to Y1 circuit is closed, R to G
circuit is open, and there is a demand for dehumidification,
the furnace blower motor BLWM will drop the blower
airflow to 65% of low-cooling airflow for a maximum of 10
minutes each cooling cycle or until the R to G circuit closes
or the demand for dehumidification is satisfied. Lowcooling airflow is the true on-board CF selection as shown
in Table 1.
b. High Cooling – When the R to Y/Y2 circuit is closed, R to
G circuit is open, and there is a demand for
dehumidification, the furnace blower motor BLWM will
drop the blower airflow to 65% of high-cooling airflow for
a maximum of 10 minutes each cooling cycle or until the R
to G circuit closes or the demand for dehumidification is
satisfied. High-cooling airflow is based on the A/C
selection shown in Table 1.
c. Cooling Off-Delay – When the “call for cooling” is
satisfied and there is a demand for dehumidification, the
cooling blower-off delay is decreased from 90 seconds to 5
seconds.
7. Continuous Blower Mode
When the R to G circuit is closed by the thermostat, the blower
motor BLWM will operate at continuous blower airflow.
Continuous blower airflow selection is initially based on the CF
selection shown in Table 1. Factory default is shown in Table
1. Terminal EAC-1 is energized as long as the blower motor
BLWM is energized.
During a call for heat, the furnace control CPU will transition
the blower motor BLWM to continuous blower airflow, lowheat airflow, or the midrange airflow, whichever is lowest. The
blower motor BLWM will remain ON until the main burners
ignite then shut OFF and remain OFF for the blower-ON delay
(60 seconds in medium-heat, and 35 seconds in high-heat),
allowing the furnace heat exchangers to heat up more quickly,
then restarts at the end of the blower-ON delay period at lowheat, medium-heat, or high-heat airflow respectively.
The blower motor BLWM will revert to continuous-blower
airflow after the heating cycle is completed. In medium- or
high-heat, the furnace control CPU will drop the blower motor
BLWM to low-heat airflow during the selected blower-OFF
delay period before transitioning to continuous-blower airflow.
When the thermostat "calls for low-cooling", the blower motor
BLWM will switch to low-cooling airflow. When the
thermostat is satisfied, the blower motor BLWM will operate an
additional 90 seconds at low-cooling airflow before
transitioning back to continuous-blower airflow.
When the thermostat "calls for high-cooling", the blower motor
BLWM will switch to high cooling airflow. When the
thermostat is satisfied, the blower motor BLWM will operate an
additional 90 seconds at high-cooling airflow before
transitioning back to continuous-blower airflow.
When the R to G circuit is opened, the blower motor BLWM
will continue operating for an additional 5 seconds, if no other
function requires blower motor BLWM operation.
a. Continuous Blower Speed Selection from Thermostat
To select different continuous-blower airflows from the
room thermostat, momentarily turn off the FAN switch or
push-button on the room thermostat for 1-3 seconds after
the blower motor BLWM is operating. The furnace
control CPU will shift the continuous-blower airflow from
the factory setting to the next highest CF selection airflow
as shown in Table 1. Momentarily turning off the FAN
switch again at the thermostat will shift the continuousblower airflow up one more increment. If you repeat this
procedure enough you will eventually shift the continuousblower airflow to the lowest CF selection as shown in
Table 1. The selection can be changed as many times as
- 6 -
desired and is stored in the memory to be automatically
used following a power interruption.
8. HEAT PUMP DEFROST
When installed with a heat pump, the furnace control
automatically changes the timing sequence to avoid long blower
off times during demand defrost cycles. Whenever W/W1 is
energized along with Y1 or Y/Y2, the furnace control CPU will
transition to or bring on the blower motor BLWM at cooling
airflow, low-heat airflow, or the midrange airflow, whichever is
lowest. The blower motor BLWM will remain on until the
main burners ignite then shut OFF and remain OFF for 25
seconds before coming back on at heating airflow. When the
W/W1 input signal disappears, the furnace control begins a
normal inducer post-purge period while changing the blower
airflow. If Y/Y2 input is still energized the furnace control
CPU will transition the blower motor BLWM airflow to cooling
airflow. If Y/Y2 input signal disappears and the Y1 input is still
energized the furnace control CPU will transition the blower
motor BLWM to low-cooling airflow. If both the Y1 and Y/Y2
signals disappear at the same time, the blower motor BLWM
will remain on at low-heat airflow for the selected blower-OFF
delay period. At the end of the blower-OFF delay, the blower
motor BLWM will shut OFF unless G is still energized, in
which case the blower motor BLWM will operate at continuous
blower airflow.
9. COMPONENT TEST
The furnace features a component test system to help diagnose
a system problem in the case of a component failure. To initiate
the component test procedure, ensure that there are no
thermostat inputs to the control and all time delays have
expired. Turn on setup switch SW1-6. (See Appendix A)
Note: The component test feature will not operate if the control
is receiving any thermostat signals or until all time delays have
expired.
The component test sequence is as follows:
a. The furnace control CPU turns the inducer motor IDM ON
at medium speed and keeps it ON through step c.
b. After waiting 10 seconds the furnace control CPU turns
the hot surface igniter ON for 15 seconds, then OFF.
c. The furnace control CPU then turns the blower motor
BLWM on at midrange airflow for 15 seconds, then OFF.
d. After shutting the blower motor OFF the furnace control
CPU shuts the inducer motor IDM OFF.
Note: The EAC terminals are energized when the blower is
operating.
After the component test is completed, 1 or more status codes
(11, 25, 41, or 42) will flash. See Service Label on blower
access panel or Service/Status Code Instructions for explanation
of status codes.
Note: To repeat component test, turn setup switch SW1-6 to
OFF and then back ON.
- 7 -
SERVICE/STATUS CODE INSTRUCTIONS
If status code recall is needed disconnect the “R” thermostat lead, reset power, and put setup switch “SW1-1” in the ON position. To clear the status
code history put setup switch “SW1-1” in the ON position and jumper thermostat terminals “R”, “W/W1”, and “Y/Y2” simultaneously until status code
#11 is flashed.
LED CODE STATUS
CONTINUOUS OFF - Check for 115 VAC at L1 and L2, and 24 VAC at SEC-1 and SEC-2.
CONTINUOUS ON - Control has 24 VAC power.
RAPID FLASHING - Line voltage (115 VAC) polarity
reversed.
EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE
NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.
11 NO PREVIOUS CODE – Stored status codes are erased automatically after 72 hours or as specified above.
12 BLOWER ON AFTER POWER UP – (115 VAC or 24 VAC) – Blower runs for 90 seconds, if unit is powered up during a call for heat (R-
W/W1 closed) or (R-W/W1 opens) during the blower on-delay period.
13 LIMIT CIRCUIT LOCKOUT – Lockout occurs if the limit, or flame rollout switch is open longer than 3 minutes or 10 successive limit trips
occurred during high-heat. Control will auto reset after 3 hours. Refer to status code #33.
14 IGNITION LOCKOUT – Control will auto reset after 3 hours. Refer to status code #34.
15 BLOWER MOTOR LOCKOUT – Indicates the blower failed to reach 250 RPM or the blower failed to communicate within 30 seconds after
being turned ON in two successive heating cycles. Control will auto reset after 3 hours. Refer to status code #41.
21 GAS HEATING LOCKOUT – Control will NOT auto reset. Check for:
- Mis-wired gas valve.
- Defective control (valve relay).
22 ABNORMAL FLAME-PROVING SIGNAL – Flame is proved while gas valve is de-energized. Inducer will run until fault is cleared. Check
for:
- Leaky gas valve.
- Stuck-open gas valve.
23 PRESSURE SWITCH DID NOT OPEN – Check for:
- Obstructed pressure tubing.
- Pressure switch stuck closed.
24 SECONDARY VOLTAGE FUSE IS OPEN – Check for :
- Short circuit in secondary voltage (24 VAC) wiring.
25 MODEL SELECTION OR SETUP ERROR – Either Indicates the model plug (PL4) is missing or incorrect or setup switch “SW1-1” or
“SW1-6” is positioned improperly. If code flashes only 4 times on power-up control is defaulting to model selection stored in memory. Check
the following:
- Thermostat call with “SW1-1” ON.
- Thermostat call with “SW1-6” ON.
- “SW1-1” and “SW1-6” both ON together.
- Two different furnace models twinned.
- Wiring diagram for model plug number and resistance values if code flashes continuously.
- Board does not recognize new model plugs HK70EZ017 – 021. New board software version V12 or later required.
31 MEDIUM-HEAT PRESSURE SWITCH OR HPSR RELAY DID NOT CLOSE OR REOPENED – Indicates the medium-heat pressure
switch input failed to close on a call for medium- or high-heat, or opened during medium- or high-heat. Control relay may be defective or gas
valve is mis-wired. Refer to status code #32.
32 LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED – Indicates the low-heat pressure switch input failed to close on a
call for low-heat, or opened during low-heat. If opens during blower on-delay period , blower will come on for the selected blower off-delay. If
opens during low heat within 5 minutes after ignition the next heating cycle will be restricted to high-heat. Check for:
- Proper vent sizing.
- Plugged condensate drain.
- Low inlet gas pressure (if LGPS used).
- Excessive wind.
- Restricted combustion air supply.
- Improper pressure switch wiring.
- Failed or “Out-of-Calibration” pressure switches.
- Water in vent piping, possible sagging pipe.
- Disconnected or obstructed pressure tubing.
- 8 -
33 LIMIT CIRCUIT FAULT – Indicates the limit, or flame rollout is open or the furnace is operating in high-heat only mode due to 2 successive
low or medium heat limit trips. Blower will run at medium heat airflow for 4 minutes or until open switch remakes whichever is longer. If open
longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33 continues to flash until blower shuts off. Flame
rollout switch requires manual reset. Check for:
- Proper rear air baffle.
- Loose blower wheel.
- Defective switch or connections.
- Improper low- or medium- heat gas input adjustment.
- Stuck high-heat solenoid in gas valve
- Improper or misaligned limit and/or limit shield.
34 IGNITION PROVING FAILURE – Control will try three more times before lockout #14 occurs. If flame signal is lost during blower on-delay
period, blower will come on for the selected blower off-delay. Check for:
- Low inlet gas pressure.
- Control ground continuity.
- Gas valve defective or turned off.
- Defective Hot Surface Igniter.
- Manual valve shut off.
- Oxide buildup on flame sensor (clean with fine steel wool).
- Proper flame sense micro amps (.5 micro amps DC min., 4.0 – 6.0 nominal).
- Green/Yellow wire MUST be connected to furnace sheet metal.
- Inadequate flame carryover or rough ignition.
- Flame sensor must not be grounded.
41 BLOWER MOTOR FAULT – Indicates the blower failed to reach 250 RPM or the blower failed to communicate within the prescribed time
limits. Thirty seconds after being turned ON or ten seconds during steady-state operation.
42 INDUCER MOTOR FAULT – Indicates the inducer has not started within 20 seconds after a call for heat, the inducer motor RPM is outside its
valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation. Check for:
- Proper vent sizing.
- Restricted combustion air supply.
- Failed inducer motor.
- Improper motor wiring.
43 LOW-HEAT PRESSURE SWITCH OPEN WHILE MEDIUM-HEAT PRESSURE SWITCH IS CLOSED – Check for:
- Low inlet gas pressure (if LGPS used).
- Plugged condensate drain.
- Improper pressure switch wiring.
- Water in vent piping, possible sagging pipe.
- Stuck open low-heat pressure switch.
- Disconnected or obstructed pressure tubing.
45 CONTROL CIRCUITRY LOCKOUT – Auto-reset after 1 hour lockout due to:
- Flame sense circuit failure.
- Gas valve relay stuck open.
- Software check error.
Reset power to clear lockout. Replace control if status code repeats.
COMPONENT TEST
To initiate the component test sequence, shut “OFF” the room thermostat or disconnect the “R” thermostat lead. Reset power and then put setup switch
“SW1-6” in the ON position to start the component test sequence. Once initiated the furnace control will turn the inducer ON at high-heat speed. The
inducer motor will run for the entire test. The hot surface igniter and blower motor will be turned ON for 15 seconds each. When the blower is turned
OFF the inducer will be turned OFF. When the component test is completed one or more of the following codes will flash.
LED CODE DESCRIPTION
11 Indicates the blower motor tested OK. Visual check of inducer motor and hot surface igniter required.
25 SETUP ERROR – Same as code 25 above.
41 BLOWER MOTOR FAULT – Indicates blower motor failed test. Check blower, wiring, and furnace control.
42 INDUCER MOTOR FAULT – Indicates inducer motor failed test. Check inducer, wiring, and furnace control.
To repeat component test turn setup switch “SW1-6” OFF and then back ON. After component test is completed put setup switch “SW1-6” in the OFF
position and reconnect the “R” thermostat lead.
- 9 -
START HERE - If a problem exists, the service technician should always begin
troubleshooting here.
SPECIAL NOTE: ALL VOLTMETERS ARE NOT THE SAME - YOUR VOLTAGE READINGS WILL VARY. THIS APPLIES TO THE
ENTIRE CONTENT OF THIS TROUBLESHOOTING MANUAL. THEY ARE NOT ABSOLUTE VALUES. CORRECT 115-VAC VOLTAGE,
CURRENT, AND POWER MEASUREMENTS CANNOT BE TAKEN ON VARIABLE SPEED FURNACES UNLESS USING A TRUE RMS
METER.
STEP ACTION YES NO GO TO
1. Remove main furnace door first. DO NOT REMOVE BLOWER ACCESS PANEL! Record
status of AMBER LED. See Service/Status Code Instructions.
Is AMBER LED status light on?
2. Is the AMBER LED status light blinking rapidly without a pause? 3 4
3. Go to the page number indicated in the Index for RAPID FLASHING LED. INDEX
4. Is the AMBER LED status light blinking ON/OFF slowly with a combination of short and
long flashes?
5. Determine status code. The status code is a 2 digit number with the first digit determined by
the number of short flashes and the second digit by the number of long flashes.
6. Go to page number indicated in the Index for the section covering the status code. INDEX
7. To retrieve previous codes, disconnect the User Interface ABCD connector (if used) or the R
thermostat lead (if used) from the furnace control board and wait for the blower to turn off if it
is running. Put setup switch SW1-1 in the ON position and record the status codes listed in the
status code history. The status codes will flash in the order of occurrence. Read status codes
until an 11 code flashes. After the 11 code flashes the status codes will repeat.
8. Was there a previous status code other than code 11?
Note: Status codes are erased after 72 hours or can be manually erased by putting setup switch
SW1-1 in the ON position and jumpering R, W/W1, and Y/Y2 simultaneously until status
code 11 is flashed.
9. Go to page number indicated in the Index for the section covering the first previous status
code.
10. Does the problem appear to be low cooling airflow? 11 12
11. Go to page number indicated in Index for the section covering IMPROPER COOLING
AIRFLOW.
12. Set thermostat to call for heat and set the thermostat fan control to AUTO position if equipped. 13
13. Does the furnace respond to the call for heat? 14 28
14. Observe operation of furnace for 20 minutes or until AMBER LED status light starts blinking. 15
15. Does the AMBER LED status light blink ON/OFF slowly with a combination of short and
long flashes?
16. Is the temperature rise below the range specified on the rating plate when the unit is operating
in medium and/or high heat?
Note: If the temperature rise is above the range specified on the rating plate refer to the StartUp and Adjustment section in the Installation, Start-Up, and Operating Instructions.
17. Go to page number indicated in Index for the section covering MEDIUM AND/OR HIGH
HEAT TEMPERATURE RISE TOO LOW (COLD BLOW).
18. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. INDEX
19. Make sure power is being supplied to the furnace. 20
20. Check fuses, breakers, or manual disconnects to be sure they are correctly set. If not, reset
them and go back to step 1.
21. Remove blower access panel and depress door switch. Use a piece of tape to hold switch
closed.
22. Is 115-vac across L1 and L2? 24 23
23. Turn power off. Check continuity of power leads and door switch. If necessary repair power
leads and/or replace door switch.
24. Is 24-vac across SEC-1 and SEC-2? 25 26
25. Replace the variable speed furnace control. 18
2 19
5 7
6
8
9 10
INDEX
INDEX
5 16
17 18
INDEX
21
22
18
- 10 -
STEP ACTION YES NO GO TO
26. Is 115-vac across the transformer leads? 27 25
27. Replace the transformer. 18
28. Is 24-vac across W/W1 and on the variable speed furnace control?
You will not be able to check for voltage across W/W1 and C
connected to a User Interface at the ABCD connector. Go to step 29.
29. You have a defective thermostat, or a break in wiring between thermostat and furnace. Fix
problem.
30. Disconnect all thermostat leads from the thermostat terminal block and jumper R to W/W1.
Does the furnace respond to the call for heat?
31. You have an incompatible thermostat. Do any of the following:
1. Wire the thermostat C terminal to C
2. Isolate the W/W1 input with a relay.
3. Install ballast resistor across W/W1 and C
4. Replace the thermostat with a compatible model.
OM-24V.
OM-24V.
OM-24V if the furnace is
30 29
18
31 25
18
RAPID FLASHING AMBER LED - Indicates line voltage polarity is reversed, furnace is not
grounded, or the transformers are out of phase in twinned units.
STEP ACTION YES NO GO TO
1. Is this furnace twinned with another furnace? 7 2
2. Remove blower access panel and depress door switch. Use a piece of tape to hold switch
closed.
3. Is 115-vac across L2 and chassis ground? 4 20
4. Line voltage polarity is reversed. Fix problem. 5
5. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. INDEX
6. Replace the variable speed furnace control. 5
7. Remove blower access panels and depress door switch in each unit. Use tape to hold switches
closed.
8. Is the AMBER LED status light blinking rapidly in only one of the twinned units? 9 16
9. Are the fuses, breakers, or manual disconnects to the problem unit correctly set? 11 10
10. Fix problem. 5
11. Are the Auxiliary Limit switches properly set? 12 10
12. Do you have 115-vac across L1 and L2 in the problem unit? 13 15
13. Do you have 24-vac across SEC-1 and SEC-2 in the problem unit? 6 14
14. Replace the transformer. 5
15. Turn power off to both units. Check continuity of power leads and door switch in the problem
unit. If necessary repair power leads and/or replace door switch in the problem unit.
16. Check the furnace circuit breaker location in the service panel.
On single-phase (residential) systems, each furnace circuit breaker should be located directly
across from each other in service panel, or each furnace circuit breaker should be located on
the same side of service panel, but must skip 1 space to be connected to the same leg of the 1phase power supply.
On 3-phase (commercial) systems, each furnace circuit breaker should be located directly
across from each other in service panel, or each furnace circuit breaker should be located on
the same side of service panel, but must skip 2 spaces to be connected to the same leg of the 3phase power supply.
17. Check the 115-vac power lead connections at the variable speed furnace control of each
furnace. The BLACK lead goes to L1 and the WHITE lead goes to L2.
18. Check the 115-vac transformer lead connections at the variable speed furnace control of each
furnace. The BLACK lead goes to L1 and the WHITE lead goes to L2.
19. If the circuit breaker location and the 115-vac wiring is correct reverse the transformer
secondary lead connections SEC-1 and SEC-2 in the MAIN furnace.
20. Is the furnace properly grounded back to the service panel? 6 10
3
8
5
17
18
19
5
- 11 -
IMPROPER COOLING AIR FLOW - Generally, this indicates the Y/Y2 thermostat lead is not
properly connected. If User Interface is connected to ABCD connector then the wrong size
outdoor unit could be configured in the User Interface.
STEP ACTION YES NO GO TO
1. Remove blower access panel and depress door switch. Use a piece of tape to hold switch
closed.
2. Set thermostat to call for cooling. If thermostat does not have G connection jumper across
thermostat terminals R and G.
3. Make sure thermostat fan control is in the AUTO position if equipped. 4
4. Do you have 24-vac across Y/Y2 and COM-24V on the variable speed furnace control? 8 5
5. You have a defective thermostat, or a break in the wiring between the thermostat and the
furnace, or the Y/Y2 thermostat terminal is not wired to the thermostat.
6. Fix the problem. 7
7. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. INDEX
8. Are the air conditioning airflow select switches A/C set to the proper airflow as required by the
condensing unit? Typical airflow is based on 350 CFM/TON (See Table 2.)
9. Set the air conditioning airflow select switches A/C to the proper airflow as required by the
condensing unit. (See Table 2.)
10. Disconnect the G thermostat lead or jumper if used. 11
11. Does the blower motor turn off in 5 seconds when the G thermostat lead is disconnected?
Note: When using a Thermidistat the blower may change airflow when the G thermostat lead
is disconnected and a call to dehumidify is active.
12. Replace the variable speed furnace control. 7
13. Reconnect the G thermostat lead or jumper and observe operation of furnace in cooling mode
for 10 minutes.
14. Does the furnace operate properly in cooling mode? 15 16
15. - Check outdoor unit for correct suction pressure and verify charge.
- Check filter(s) and ductwork for restrictions.
- Check furnace coil.
16. Does the AMBER LED abruptly shut off as the blower comes up to speed? 17 24
17. Do you have less than 17-vac between R and COM-24V on the variable speed furnace control? 18 24
18. Do you have less than 90-vac between L1 and L2 on the variable speed furnace control? 19 20
19. Make sure the wire gage between main fuse box and furnace complies with wire size
specification in Installation, Start-Up, and Operating Instructions.
20. Disconnect the R thermostat lead. 21
21. Do you have less than 17-vac between R and COM-24V on the variable speed furnace control? 22 23
22. Replace transformer. 7
23. Check the thermostat wire gage between furnace and thermostat, and furnace and outdoor unit.
It is recommended that AWG No. 18 color-coded copper thermostat wire be used for lengths
up to 100 ft. For wire lengths over 100 ft, use AWG No. 16 wire.
24. Is Status Code 41 flashing? 25 26
25. Go to the page number indicated in the Index for Status Code 41. INDEX
26. - Check outdoor unit for correct suction pressure and verify charge.
- Check furnace coil.
27. Is a User Interface connected to the ABCD connector? 28 2
28. The wrong size outdoor unit may have been selected in the User Interface. You will need to
set the proper size of the outdoor unit in the User Interface. If set properly then the User
Interface may be reducing the airflow for dehumidification.
27
3
6
10 9
7
12 13
14
INDEX
6
6
7
7
- 12 -
Table 2 – Cooling Tonnage vs. Airflow (CFM)
AIR CONDITIONING TONS
(12,000 BTU/HR)
1-1/2
2
2-1/2
3
3-1/2
4
5
6
AIR CONDITIONING (A/C) OR CONTINUOUS-FAN (CF)
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
MODEL
SIZE
060, 3T-080
5T-080, 100
120
DEF.
DEF.
DEF.
AIRFLOW
(CFM)
060, & 3T-080
MODEL
5T-080 & 100
MODEL
120 MODEL
525 X
700 X X X
875 X X X
1050 X X X
1225 X X X
1400 X X
1750 X X
2100 X
AIRFLOW SELECTION CHART
SETUP SWITCH SW3 POSITIONS
525
700
875
1050
1225
1225
1750
1750
1
1
1225
1750
2100
2
700
875 1050
2
700 8752 1050
1225
1225
1
1400
1400
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON)
MODEL
SIZE
060, 3T-080
5T-080, 100
120
1. DEFAULT A/C AIRFLOW WHEN A/C SWITCHES ARE IN OFF POSITION
2. DEFAULT CONT. FAN AIRFLOW WHEN CF SWITCHES ARE IN OFF POSITION
3. SWITCH POSITIONS ARE ALSO SHOWN ON FURNACE WIRING DIAGRAM
DEF.
DEF.
DEF.
SETUP SWITCH SW3 POSITIONS
600
800
2
800
2
800 10002 1200
1000
1000 1200
1200
1400
1400
1
1400
1600
1600
1400
2000
2000
1
1
1400
2000
2100
MEDIUM AND/OR HIGH HEAT TEMPERATURE RISE TOO LOW - Generally, this indicates the
HI solenoid in gas valve GV has failed, the throttling valve TV has failed, the furnace is
extremely underfired, or the gas valve GV is miswired.
STEP ACTION YES NO GO TO
1. Remove the blower access panel. Disconnect User Interface ABCD connector (if used) or the
R thermostat lead (if used) from the furnace control board. If setup switches SW1-2 or SW4-2
are ON then set them to OFF.
2. Depress the door switch. Use piece of tape to hold it closed. 19
3. Jumper R and W/W1 thermostat terminals. 4
4. When the furnace is running in medium heat, clock the medium heat gas rate. On propane
installations check the manifold pressure.
5. Jumper R and W2 thermostat terminals. When the furnace is running in high heat, clock the
high heat gas rate. On propane installations check the manifold pressure.
6. Is the high heat rate approximately the same as the medium heat rate? 7 13
7. Do you have 24-vac across terminals HI and C on gas valve GV during high heat? 12 8
8. Are the BLUE and GREEN/YELLOW wires on the gas valve GV reversed? The BLUE wire
should be connected to the M terminal and the GREEN/YELLOW wire should be connected
to the C terminal.
9. Is 24-vac across BROWN wire on the high heat pressure switch HPS and COM-24V on
variable speed furnace control?
10. You have an open wire or bad terminal on the BROWN wire from the high heat pressure
switch HPS to the gas valve GV. Repair it or replace the harness.
2
5
6
18 9
10 35
11
- 13 -
STEP ACTION YES NO GO TO
11. Go to the page number indicated in Index for the CLEANUP AND STARTUP
INSTRUCTIONS.
12. Replace the gas valve GV. 11
13. Is the high heat rate within 2% of that specified on the rating plate? 15 14
14. Ensure the gas inlet pressure and burner orifice are correct. Then adjust the gas valve to the
proper rate. If it cannot be adjusted to the proper rate, replace the gas valve GV.
15. Is outdoor condensing unit operating during heating cycle? 18 16
16. Check temperature rise and external static pressure with blower access panel in place.
Temperature rise should be mid range or higher than midpoint of range stated on furnace rating
plate. External static pressure must not exceed .7 in.w.c. If return temperature is below 60
deg. F condensation may form on heat exchangers. If left uncorrected failure will result.
17. Check return air ducts in unheated spaces for leaks. 11
18. Fix problem. 11
19. Is the temperature rise problem in high heat only?
If the temperature rise problem occurs in medium and high heat go to step 20.
20. Put setup switch SW4-2 into the ON position. 3
21. Jumper R and W/W1 thermostat terminals. 22
22. Once the blower motor turns ON and the furnace is running in low heat, clock the low heat gas
rate. You have 15 minutes on this first call for heat before the units switches to high heat. On
propane installations check the manifold pressure.
23. Remove jumper across R and W/W1 thermostat terminals and wait for blower motor to turn
OFF.
24. Put setup switch SW4-2 into the ON position. 25
25. Jumper R and W/W1 thermostat terminals. 26
26. When the furnace is running in medium heat, clock the medium heat gas rate. On propane
installations check the manifold pressure.
27. Is the medium heat rate approximately the same as the low heat rate? 28 31
28. Do you have 24-vac across both terminals on throttling valve TV during medium heat? 30 29
29. You have an open wire or bad terminal on the VIOLET wire from the medium heat pressure
switch MPS to the throttling valve TV or the GREEN/YELLOW from gas valve GV to
throttling valve TV. Repair it or replace the harness.
30. Replace the valve train assembly. The valve train assembly includes the gas valve GV and the
throttling valve TV. The throttling valve TV is not a serviceable part by itself.
31. Is the medium heat rate within 2% of that specified on the rating plate? 33 32
32. Ensure the gas inlet pressure and burner orifice are correct. Then adjust medium heat on the
gas valve to the proper rate. If medium heat cannot be adjusted to the proper rate, replace the
gas valve GV.
33. Is outdoor condensing unit operating during heating cycle? 18 34
34. Check medium heat temperature rise and external static pressure with blower access panel in
place. Temperature rise should be mid range or higher than midpoint of range stated on
furnace rating plate. External static pressure in medium heat should be less then .25 in.w.c. If
return temperature is below 60 deg. F condensation may form on heat exchangers. If left
uncorrected failure will result.
35. Replace the pressure switch assembly. 11
INDEX
11
17
20 21
23
24
27
11
11
11
- 14 -
Status Code 11
NO PREVIOUS CODE - Stored status codes are erased after 72 hours or can be cleared by jumpering R, W/W1, and Y/Y2
thermostat leads while setup switch SW1-1 is ON. Run system through a heating or cooling cycle to check system.
This usually indicates one of the following:
- The status history has been cleared and setup switch SW1-1 is in the ON position.
- Component test was successfully completed and setup switch SW1-6 is in the ON position.
STEP ACTION YES NO GO TO
1. Remove the blower access panel, depress the door switch. Use piece of tape to hold it closed. 2
2. Is setup switch SW1-1 in the ON position. 3 5
3. Put setup switch SW1-1 in the OFF position. 4
4. Go to the page number indicated in Index for the CLEANUP AND STARTUP
INSTRUCTIONS.
5. Is setup switch SW1-6 in the ON position. 6 7
6. Put setup switch SW1-6 in the OFF position. 4
7. Jiggle setup switches SW1-1 and SW1-6 back and forth. If status code 11 continues to flash
replace the variable speed furnace control
INDEX
4
Status Code 12
BLOWER ON AFTER POWER UP - Blower will run for 90 seconds when furnace power is interrupted and later restored during
a call for heat (R-W/W1 closed) or if the call for heat is interrupted (R-W/W1 opens) during the blower on-delay period. If this
status code repeats every couple of minutes it is probably caused by a direct short in the pressure switch circuits, gas valve
GV, throttling valve TV, wiring to gas valve GV, wiring to throttling valve TV, or humidifier coil.
STEP ACTION YES NO GO TO
1. Remove the blower access panel and disconnect User Interface ABCD connector (if used) or
the R thermostat lead (if used) from the furnace control board.
2. Depress the door switch. Use piece of tape to hold it closed. 3
3. Jumper R and W/W1 thermostat terminals. 4
4. Does the furnace keep repeating the following cycle?
Induced draft motor IDM runs, induced draft motor IDM stops, blower motor BLWM runs for
90 seconds while AMBER LED status light flashes status code 12.
5. Do you have less than 17-vac across R and COM-24V on the variable speed furnace control? 6 14
6. Do you have less than 90-vac across L1 and L2 on the variable speed furnace control? 7 10
7. Make sure wire gage between main fuse box and furnace complies with wire size specification
in Installation, Start-Up, and Operating Instructions.
8. Fix problem. 9
9. Go to the page number indicated in Index for the CLEANUP AND STARTUP
INSTRUCTIONS.
10. Disconnect the R thermostat lead. 11
11. Do you have less than 19-vac across R and COM-24V on the variable speed furnace control? 12 13
12. Replace transformer. 9
13. The thermostat and/or thermostat wires are loading down the transformer. Replace the
thermostat or repair thermostat wires.
14. Does the hot surface igniter HSI come on during the cycle? 15 27
15. Disconnect the humidifier lead from HUM terminal on variable speed furnace control. 16
16. Does the furnace still alternately cycle induced draft motor IDM and blower motor BLWM as
described in Step 4.
17. The humidifier may not be wired into the system properly or there is a direct short in wiring to
humidifier solenoid coil, diode bridge(if used), or humidifier solenoid coil.
18. There is a short in the gas valve GV or wiring to gas valve GV. Refer to Appendix E to check
gas valve GV.
19. There is a direct short in the ORANGE wire from the low heat pressure switch LPS. 8
20. While the unit is operating in low heat jumper R and W2 thermostat terminals. 21
2
5 20
8
INDEX
9
18 17
8
8
- 15 -
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