107
condenser when a cooling call has
been sent from the communicating
thermostat.
When this configuration is desired, use
the wiring diagram in Figure 64 to con-
nect the thermostat and condenser to
the furnace control.
NOTE: A heat pump condenser cannot
be installed with this configuration.
There is no control for the reversing
valve.
STARTUP FOR SYSTEMS CONFIG-
URED WITH COMMUNICATIONS
INSTALLATION OF LINE VOLTAGE
AND GAS MUST BE PERFORMED
ACCORDING TO INSTRUCTIONS
WRITTEN IN THIS MANUAL. FAIL-
URE TO DO SO COULD RESULT IN
INJURY OR DEATH.
When the furnace is configured for
communications, the components on
the network (i.e. furnace, thermostat
and condenser) must establish commu-
nications before engaging a heat (or
other) thermostat demand. The proce-
dure for establishing communications is
automatic and is described below.
Once communications is established,
the start-up procedure will be the same
as the general start-up instructions
SPECIAL CONFIGURATION
– COMMUNICATING THER-
MOSTAT AND FURNACE
WITH A NON-COMMUNI-
CATING CONDENSER
Y1 – This terminal may be used to con-
nect directly to a non-communicating
condenser when a communicating ther-
mostat is installed to the furnace but a
non-communicating condenser is
installed in the system. While the opti-
mum configuration is with a communi-
cating condenser connected to the net-
work, there may be installations where
this is not desired. In these cases, the
thermostat will be communicating with
the furnace control and the furnace
control will energize the condenser as
necessary (the additional relays have
been added to the furnace control to
allow this operation).
Two-stage cooling with a communicat-
ing thermostat and non-communicating
condenser is not possible as only Y1
has output capability to energize a con-
tactor.
The thermostat connections labeled
“Y1” on the I.F.C. is normally an input
to the furnace control to turn on the
blower when energized. However, in
this configuration, this (normally) input
becomes an output to energize the
described in the section of this man-
ual titled START-UP
PROCEDURES.
Once the communicating wiring is
properly installed and the furnace is
connected to line voltage, the sys-
tem can be turned on. The thermo-
stat will display the following text:
SEARCHING
is displayed several times for sever-
al seconds. Next, the text
FURNACE FOUND
and
AIR CONDITIONER FOUND
or
HEAT PUMP FOUND
(depending on which is installed in
the system) will be displayed. The
process can take several minutes
(up to a maximum of 30) to com-
plete. If these messages are not
displayed within 30 minutes after
energizing the system, communica-
tions can not be established. There
are many reasons why communica-
tions may not be established –
including improper settings of the
“TERM” and “BIAS” switches (see
BIAS / TERMINATION) and improp-
er wiring (see WIRING A FURNACE
FOR COMMUNICATIONS above).
FIGURE 64
WIRING DIAGRAM –
– SPECIAL CONFIGURATION: COMMUNICATING THERMOSTAT AND FURNACE WITH NON-COMMUNICATING CONDENSER
!
WARNING
ST-A1173-01
NOTE:
DEHUMIDIFICATION FUNCTION FROM A COMMUNICAT-
ING THERMOSTAT WILL NOT BE POSSIBLE WITH THIS
CONFIGURATION.
NOTE: Two-stage cooling with a communicating thermostat and non-com-
municating condenser is not possible as only Y1 has output capability to
energize a contactor.
