O137 17
HEATING MODE
• The furnace control checks for an open main limit (this limit is normally closed). If the main limit
is open, the furnace will remain inoperable until the limit is closed. During an open limit the cir-
culating air blower and vent blower will be energized. The status light will blink four (4) times.
• The room thermostat reacts to a demand for heat.
• The control will then check to insure that the vent pressure switch is open. If, at this point, the
vent pressure switch is closed the control will blink two (2) times and will remain inoperable un-
til this situation is corrected.
• The venter blower is energized.
• The vent pressure (vacuum) switch will close when it detects a pressure in excess of it’s set-
ting. If the pressure switch fails to close the status light will flash three (3) times. The sequence
cannot continue until the pressure switch closes.
• After a pre-purge period, the electronic ignition device will be energized.
• After a slight delay, the gas valve will open if the flame roll-out switchs are closed.
• The burners will ignite and the flame sensor will detect the presence of flame. The igniter will
then deenergize. If the sensor does not detect the burner flame, the gas valve will close and
the ignition cycle will be repeated for a total of three attempts. If, after the third attempt, the
presence of flame is not detected, the furnace will go into a lockout condition for one (1) hour.
It will then repeat the ignition cycle. This one (1) hour lockout and retry will occur indefinitely.
• Thirty (30) seconds after the main valve is energized the circulating air blower will be activated.
• The furnace will remain in operation until the demand for heat is satisfied.
• Once the demand is satisfied the venter will shut off, and the circulating air blower will shut off
after field adjustable time is attained.
• The furnace will remain dormant until the next demand for heat.
COOLING MODE
The control checks for an open limit. If an open limit is detected the furnace will remain inoperable
until the condition is corrected. During an open limit condition the circulating air blower will be en-
ergized. The status light will blink four (4) times.
• A demand for cooling is initiated.
• The condenser contactor will close.
• After a short delay, the circulating air blower will start on the cooling speed.
• After the room thermostat is satisfied the condenser contractor will open.
• The circulating air blower will remain in operation for approximately sixty (60) seconds.
REMOVING AN EXISTING APPLIANCE
When replacing an existing appliance, the resulting installation must comply with all local codes, or
in the absence of local codes, to the National Fuel Gas Code ANSI Z223.1 and/or CAN/CGA B149
Installation Codes as well as these installation instructions.
If the installation of this furnace requires that an existing appliance be removed from a venting
system that still serves another gas fired appliance it may require that the existing vent be re-
sized. The following steps shall be performed with each appliance connected to the venting sys-
tem placed in operation while any other appliance connected to the venting system are not in op-
eration;
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