INDEX
PAGE
Instructions .....................................................................................1
General ........................................................................................1-3
Furnace Model Nomenclature........................................................2
Example ..........................................................................................3
Sequence of Operation................................................................3-6
Adaptive Heating Mode—Single-Stage Thermostat
with 2-Stage Heating........................................................3-4
Non-Adaptive Heating Mode—Two-Stage Thermostat
with 2-Stage Heating...........................................................4
Cooling Mode ........................................................................4-5
Continuous Blower Mode.........................................................5
Heat Pump Mode...................................................................5-6
Defrost.......................................................................................6
Component Test ........................................................................6
Service Information Label .............................................................7
Start Here........................................................................................8
Rapid Flashing LED ......................................................................9
Improper Cooling Airflow........................................................9-11
High-Heat Temperature Rise Too Low.......................................11
Status Code 11—No Previous Code ...........................................12
Status Code 12—Blower On After Power Up............................12
Status Code 13—Limit (LS) or Flame Rollout (FRS) Switch
Lockout.......................................................13-14
Status Code 14—Ignition Lockout ..............................................14
Status Code 21—Gas Heating Lockout .................................14-15
Status Code 22—Abnormal Flame-Proving Signal ....................15
Status Code 23—Low-Heat Pressure Switch Did Not Open .....15
Status Code 24—Secondary Voltage Fuse Is Open ..............16-17
Status Code 31—High-Heat Pressure Switch or Relay Did
Not Close or Reopened..............................18-19
Status Code 32—Low-Heat Pressure, Draft Safeguard, or
Auxiliary Limit (Downflow Only) Switch
Did Not Close or Reopened ......................20-22
Status Code 33—Limit (LS) or Flame Rollout (FRS) Switch
Is Open .......................................................22-24
Status Code 34—Ignition-Proving Fault................................24-25
Status Code 43—Low-Heat Pressure, Draft Safeguard, or
Auxiliary Limit Switch Open While
High-Heat Pressure Switch Is Closed .......26-27
Status Code 45—Replace Control...............................................27
Cleanup and Start-Up Instructions ..............................................28
APPENDIX A—Board Layout and Wiring Schematics .......29-31
APPENDIX B—ICM Blower Motor Description and
Operation .....................................................32-35
APPENDIX C—Pressure Check Diagram ..................................36
APPENDIX D—Quick Reference Troubleshooting Guide ........37
APPENDIX E—Static Pressure Reading Location
Diagrams......................................................38-39
APPENDIX F—Thermostat Staging Algorithm....................40-41
APPENDIX G—Quick Reference Information ..........................42
APPENDIX H—Twinning .....................................................43-45
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 2-stage furnace control was designed with diagnostic capa-
bilities built in. A RED LED is used to flash a status code which
will lead you to 1 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. If you are very experienced at how this furnace
operates, you can use the Quick Reference Troubleshooting Guide
in Appendix D to isolate the problem. 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 table on page 3, 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.
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
be no less than 0.16 psig (4.5-in.wc).
Thermostat wire connections to furnace at R and W/W1 are the
minimum required for gas heating operation. W2 must be con-
nected for 2-stage heating thermostats. Y/Y2 and G are required to
be connected to furnace for cooling and heat pumps. G is required
for continuous fan. C
OM
-24V is required for some clock thermo-
stats. These connections must be made at 24-vac terminal block on
furnace control. (See Appendix A.) O is required for heat pumps
for ICM blower motors only. Y1 is required for 2-stage cooling
and 2-stage heat pumps for ICM blower motors only. The O and
Y1 connections must be made to ICM furnaces’ orange and blue
leads flagged "O" and "Y1", respectively.
These furnaces can be installed with either a single-stage heating
or a 2-stage heating thermostat.
For single-stage thermostats, connect thermostat R to W/W1 at
furnace control terminal block. For single-stage thermostats, the
control determines (based on lengths of previous heating on and
off cycles) when to operate in low- and high-gas heat for optimum
comfort. (See Appendix F.) Setup switch-2 (SW-2) must be in
factory-shipped OFF position.
troubleshooting guide
DELUXE 2-STAGE GAS-FIRED
INDUCED-COMBUSTION FURNACES
WITH PSC OR ICM BLOWER MOTORS
Cancels:
New
SM04-3
8-95
—1—
