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installed. These L.E.D.'s will not ener-
gize if a traditional 24V thermostat
only is used to control the furnace.
"RX" (Green) L.E.D. – This L.E.D. indi-
cates that communications is being
sensed to or from (i.e.: something on
the network is trying to communicate)
other components (e.g. a condenser) on
the network. This L.E.D. will blink ran-
domly any time a message is received
by the furnace control. If no blinking is
seen within five minutes, it can be
assumed that there is not valid commu-
nications established. Check wiring to
make sure that all points are connected
properly.
Further, if this L.E.D. is on continuously,
it is an indication that mis-wiring has
occurred. Most probably, connections
"1" and "2" are reversed. Double-check
the wiring and make sure that the wire
connected to pin "1" on the condenser is
the same wire connected to pin "1" on
the thermostat and the furnace control.
The same follows for the wires to pins
"2", "R" and "C".
"STAT" (STAT US ) (Red) L.E.D. – This
L.E.D. blinks twice slowly (¼ second
ON, ¾ second OFF) upon power-up.
LEARN BUTTON
Pressing the learn button for two sec-
onds will cause the green "RX" L.E.D. to
blink rapidly (for a short period) to indi-
cate an attempt at communications. If
the L.E.D. does not blink, communica-
tions can not be established. The prob-
lem may be that the wires at the J9 con-
nector "1" and "2" on the I.F.C. may be
reversed. Check to make sure that
wiring is from "1" on the IFC leads to "1"
on the thermostat and condenser (if pre-
sent) and the same follows for connec-
tions "2", "R" and "C".
MEMORY CARD CONNEC-
TOR (J15)
This connector is used to insert a mem-
ory card.
MEMORY CARD
A memory card is defined as an elec-
tronic card that carries a copy of the
furnace shared data.
RULES FOR WRITING, DISTRIBUTION
AND ARBITRATION OF MULTIPLE
COPIES OF FURNACE SHARED DATA
FOR COMMUNICATING-CAPABLE
FURNACES
60
Furnace shared data is defined as
data specific to a given furnace that
is critical for proper furnace opera-
tion. More specifically, it is data
which defines the operation of the
furnace and is unique to a given fur-
nace platform and model. The most
critical of these data are the coeffi-
cients that control the blower opera-
tion (i.e. define the blower speed-
torque operation). Because of this,
each furnace control is programmed
with furnace shared data for that
model furnace only. The furnace
shared data from any given furnace
can NOT be transferred to another
furnace for any reason. Doing so
can adversely affect operation of the
furnace. Further, if no furnace
shared data is present, the furnace
will not operate in any mode and a
fault will be displayed.
Valid Furnace Shared Data is defined
as furnace shared data for the fur-
nace series in question with the cor-
rect motor horsepower. However, it
is impossible for the furnace control
to determine if the furnace shared
data is matched to the furnace input
BTU's if the motor horsepower is cor-
rect. This means, for example, fur-
nace shared data for a 120KBTU
upflow furnace could be installed and
recognized as valid furnace shared
data in a 90KBTU downflow furnace.
VALID FURNACE SHARED DATA
simply means that there is no motor
horsepower conflict and that the fur-
nace shared data is for the series of
furnace in question. VALID FUR-
NACE SHARED DATA is data that
will be used by the furnace control
with no fault reported. VALID FUR-
NACE SHARED DATA may not nec-
essarily mean that the furnace
shared data is correct for the furnace
in question. The input BTU's could
still be incorrect and this is why it is
important to never exchange memory
cards from one furnace to another.
Furnace shared data is programmed
into the furnace control microproces-
sor and attached memory card at the
factory. The attached memory card
cannot be programmed in the field
but furnace shared data inside the
furnace IFC microprocessor may be
written or rewritten in the field
through the network depending on
the circumstances.
WARNING
DO NOT REPLACE THE FURNACE
CONTROL OR MEMORY CARD OF
THE FURNACE WITH A FURNACE
CONTROL OR MEMORY CARD OF
ANOTHER FURNACE OR ANOTH-
ER COMPONENT (E.G.: A MEMO-
RY CARD FROM A CONDENSER
OR AIR HANDLER). THE WRONG
FURNACE CONTROL OR MEMO-
RY CARD MAY SPECIFY PARA-
METERS WHICH WILL MAKE THE
FURNACE RUN AT UNDESIRED
CONDITIONS INCLUDING (BUT
NOT NECESSARILY LIMITED TO)
REDUCED AIRFLOW DURING
HEATING CAUSING EXCESSIVE
UNDESIRED OPERATION OF THE
MAIN LIMIT CONTROL. FUR-
THER, THE MEMORY CARD IS
SPECIFIC TO THE MODEL NUM-
BER AND BTU INPUT RATING
FOR A SPECIFIC FURNACE AND
THIS INFORMATION SHOULD
NOT BE TRANSPORTED FROM
ONE FURNACE (OR COMPO-
NENT) TO ANOTHER.
The memory card is the default
memory location to be used first
when there is any conflict. If the
memory card has been replaced
with a card that has data for another
furnace, the furnace will assume the
identity of the "other" furnace. In all
cases, the memory card has the
final say about the data to use. It is
only when the memory card is not
present, is corrupt or specifies a
motor larger or smaller than what is
found in the furnace that the furnace
control will use the data stored in
the microprocessor (a mirror of the
most recent memory card with blow-
er size matching that found in the
furnace). The hierarchy of data to
be used in the event of a lost card
or conflict is listed in order of impor-
tance below.
1. An ATTACHED memory card is
physically connected to the fur-
nace control and almost appears
to be part of the furnace control
itself. A photo is shown in Figure
62 below and is this is how the
furnace control with memory card
is shipped from the factory.
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Table of Contents
Troubleshooting
