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Communicating Furnace
INTEGRATED FURNACE CONTROL
MODEL DATA CARD & DUAL SEVEN-SEGMENT DISPLAY
13. MODEL DATA CARD CONNECTOR (P6)
There is a factory-installed model data card which is
wire-tied to the furnace. At no time should this card be
removed from the furnace except during replacement
of the control.
MODEL DATA CARD
A model data card is defined as an electronic card that
carries a copy of the furnace model data.
The furnace control receives model-specific data from
the model data card.
Replacement model data cards with the appropriate fur-
nace model data for any given model can be ordered from
the Replacement Parts Division. In the event that the origi-
nal model data card is lost, the original furnace control has
been replaced and there is no furnace model data, the re-
placement model data card must be ordered and installed
into the connector at P6 to give the furnace valid furnace
model data. The furnace will not operate properly without
the correct furnace model data. When no furnace model
data is present either at the memory or on the furnace mi-
croprocessor a “d1” (NO MODEL DATA) fault code will be
displayed at both the thermostat active fault screen and at
the furnace control (I.F.C.) seven-segment displays.
If the original model data card is lost, it should be replaced
even if there is valid furnace model data on the IFC micro-
processor. The valid furnace model data on the IFC mi-
croprocessor should only be considered as a backup to
the model data card.
14. DUAL SEVEN-SEGMENT DISPLAY AND FAULT
CODES (U38)
NOTE:
Verify display orientation is correct before in-
terpreting fault codes. Otherwise the fault codes may
be upside down.
A dual seven segment display shall be provided to dis-
play status and diagnostic code information. A fault
level 1 is a low-level fault. In general, a level 2 fault is
a fault that is severe enough that it prevents furnace
or other critical (e.g. cooling) operation. Level 1 faults
generally permit operation to continue but operation
may not be at optimum performance (e.g. blower op-
erating at power maximum). Standard operating
codes (e.g. C for high-stage cooling) are considered
fault level “0” as they are not faults at all but only indi-
cations of current modes of operation which are con-
sidered normal (some operational codes are displayed
simultaneously with low level faults which do not inter-
rupt operation - see paragraphs below for details).
Since usually only one fault can be displayed at the
seven-segment display at any given time (see excep-
tions below), the fault displayed when two or more
faults are present at the same time shall be resolved
by the fault code list below which calls out the fault
code priority. Lower numbers are considered higher
priority than larger numbers. Therefore, fault code pri-
ority 0 has the highest priority and shall be displayed
when present regardless of any other fault that might
also be present at the same time. This mechanism
does not prevent simultaneous faults from being
logged into the fault code buffer.
The mode displays for heat mode (“h” “H”) shall reflect
the demand from the thermostat. This includes when
only a first stage heat call; “W1” is present (“W2” not
present), the mode displayed should reflect the first
stage demand by displaying the lower-case “h” and
not the actual output of the furnace during ignition
(since this configuration ignites at high stage).
Three exceptions to this rule exist as follows:
1. When the thermostat demand is for high stage and
only low heat can be provided because the high
pressure switch will not close or has opened and
will not re-close. In this case, the mode “h” (low
heat) shall be displayed alternately along with the
fault
“57”
(open high pressure switch) (See item 5
below in this section).
2. When autostaging has been activated and a re-
sponse to “W1” heat has been increased to high
heat by the furnace control after the user-specified
time even though a call for high heat (“W2”) is not
present. In this case a capital “H” shall be dis-
played and not a lower-case “h”.
!
WARNING
DO NOT REPLACE THE FURNACE CONTROL OR
MODEL DATA CARD OF THE FURNACE WITH A FUR-
NACE CONTROL OR MODEL DATA CARD OF AN-
OTHER FURNACE OR ANOTHER COMPONENT
(E.G.: A MODEL DATA CARD FROM A CONDENSER
OR AIR HANDLER). THE WRONG FURNACE CON-
TROL OR MODEL DATA CARD MAY SPECIFY PA-
RAMETERS WHICH WILL MAKE THE FURNACE RUN
AT UNDESIRED CONDITIONS INCLUDING (BUT NOT
NECESSARILY LIMITED TO) REDUCED AIRFLOW
DURING HEATING CAUSING EXCESSIVE UNDE-
SIRED OPERATION OF THE MAIN LIMIT CONTROL.
FURTHER, THE MODEL DATA CARD IS SPECIFIC TO
THE MODEL NUMBER AND BTU INPUT RATING FOR
A SPECIFIC FURNACE AND THIS INFORMATION
SHOULD NOT BE TRANSPORTED FROM ONE FUR-
NACE (OR COMPONENT) TO ANOTHER.
