7
1 2 3 4 5 6 7 8 9 10 11 12
YEL
CAPS
LGPS
PLUG P1
FURNACE CONTROL BOARD
LEGEND
ORN = ORANGE
YEL = YELLOW
LGPS = LOW GAS PRESSURE SWITCH
CAPS = COMBUSTION AIR PRESSURE SWITCH
ORN
ORN
= QUICK CONNECTION
A06487
Fig. 8 -- Pressure Switch Wiring for Two--Stage Units
Table 2 – Two--Stage Sequence of Operations
Inducer Pre--Purge Period: When the inducer motor comes up on high speed, the pressure switch closes, and the Infinity
t
ignition control
on the furnace board begins a 15 sec pre--purge period. If the pressure switch fails to remain closed, the inducer will remain running. After
the pressure switch recloses, the Infinity ignition control will begin a 15 sec pre--purge period.
Trial--for--Ignition Sequence: The spark igniter will spark for 3 sec, the main gas valve relay contact closes to energize the gas valve on low
stage. After 5 sec, the igniter is de--energized and a 2--sec flame--proving period begins.
NOTE:
The unit always lights on high speed inducer and low stage gas valve operation.
Flame--Proving: When the burner flame is proved at the flame--proving sensor, the furnace control determines what heating stage to run
based on feedback from the User Interface (UI). If the UI is asking for low stage gas heat, the ignition control will change the inducer speed
to low speed and keep the gas valve energized on low stage. If the UI is asking for high stage gas heat, the ignition control will maintain
running the inducer on high speed and energize the gas valve’s high stage relay to increase gas flow.
Table 3 – Two--Stage Rated Heating Input, Propane Gas (0--2000 ft [0--610 m] Altitude)
NAMEPLATE INPUT, HIGH STAGE (BTU/HR)
RATED HEATING INPUT PROPANE (BTU/HR)
HIGH STAGE
LOW STAGE
40,000
38,000
26,000
60,000
57,000
39,000
90,000
79,000
58,500
115,000
103,000
75,000
130,000
116,000
84,500
MANIFOLD
BURNER
BURNER FLAME
(Blue in appearance)
C99021
Fig. 9 -- Monoport Burner
CPL
P
CONV