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CIRCULATOR BLOWER FAN TIMING ADJUSTMENT
NOTE: Items in this section refer to the air circulator blower fan
NOT to the induced draft blower. The induced draft blower timing
sequence is not adjustable. The circulator blower fan timing is
adjustable
only on models with optional “heating fan OFF delay”
adjustment pins or switches. It is NOT adjustable in any other
circumstances.
As shipped, the circulator blower fan will remain on for 150 seconds
after the gas valve closes. When a call for cooling occurs, the circu-
lator fan comes on and remains on for 45 seconds after the call for
cooling ends. During normal heating operation, the circulator fan will
come on approximately 34 seconds after the gas valve opens.
SECOND
DELAY
SECOND
DELAY
Switch viewed in an upflow installation.
Adjustment Switch
SETTING FURNACE OPERATING MODE
This furnace is designed to operate with either a single gas input rate
or with two distinct gas input rates. The Mode DIP switch is used to
select the single gas input rate or two distinct input rates.
Setting the Mode switch to “1 STG” forces the furnace to operate at
the furnace’s highest input rate only. Operation is as described
under Sequence of Operation (Integrated Ignition Control) – Mode
DIP Switch is set to “1 STG” position.
Setting the Mode switch to “2 STG” allows the furnace to operate at
the furnace’s highest input AND at an input rate that is 75% of the
highest input rate. For this mode of operation, the furnace oper-
ates at the low input rate for a pre-determined time period then
steps to the high input rate. Operation is as described under Se-
quence of Operation (Integrated Ignition Control) – Mode DIP Switch
is set to “2 STG” position.
The time period is determined by the 2
nd
Stg Dly DIP switch. Setting
the 2
nd
Stg Dly DIP switch to 5 minutes fixes the delay period at 5
minutes. Setting the 2
nd
Stg Dly DIP switch to Auto enables an
algorithm that calculates a delay period based on the heating cycle
time and the total cycle time. The delay period can range from 1
minute to 12 minutes.
NOTE: The ACSH, AMH, AMEH, GCH, GDH, GMH and GME hybrid
furnaces require a single stage thermostat. These furnaces utilize a
control board with single stage or two stage capability. The second
stage feature is established by setting dip switch #2 on the board,
either one stage or two stage. All of the second stage timing is then
controlled by dipswitch 3 on the circuit board.
O
N
O
F
F
2
O
N
O
F
F
3
SECOND
STAGE
ONLY
5
MINUTES
O
N
O
F
F
1
150
SECOND
DELAY
100
SECOND
DELAY
1-STAGE
2-STAGE
HEAT OFF
DELAY
MODE
AUTO
XV. NORMAL SEQUENCE OF OPERATION
POWER UP
The normal power up sequence is as follows:
• 115 VAC power applied to furnace.
• Integrated control module performs internal checks.
• Integrated control module LED will light.
• Integrated control module monitors safety circuits
continuously.
• Furnace awaits call from thermostat.
HEATING MODE
(MODE DIP SWITCH IS SET TO “1 STG” POSITION)
The normal operational sequence in heating mode is as follows:
• R and W thermostat contacts close, initiating a call for heat.
• Integrated control module performs safety circuit checks.
• Induced draft blower is energized for 15 second pre-purge
period causing pressure switch contacts to close.
• Igniter warm up begins after 15 second prepurge expires.
• Low and high stage gas valves open at end of igniter warm
up period, delivering gas to burners and establishing flame.
• Integrated control module monitors flame presence. Gas
valve will remain open only if flame is detected.
• Circulator blower is energized on high heat speed following
a fixed thirty second blower on delay. Electronic air cleaner
terminals are energized with circulator blower.
• Furnace operates; integrated control module monitors
safety circuits continuously.
• R and W thermostat contacts open, completing the call for
heat.
• Gas valve closes, extinguishing flame.
• Induced draft blower is de-energized following a fifteen
second post purge.
• The circulator blower remains at high heat speed for thirty
seconds. The circulator blower then switches to low heat
speed for the remainder of the selected heat off delay period.
For example, the selected heat off delay period is 150 seconds.
The circulator blower operates at high heat for 30 seconds
and at low speed for 150 - 30 = 120 seconds.