Sequence of Operation
8:1 Staged Control
1.Exhaust Fan Contact (S1) Manually Closed (optional)
•Power passes through N.C. contact on exhaust fan overload (ST2 OL), which is closed if exhaust fan (M2) has not overloaded
•Power passes to exhaust fan starter (ST2)
•N.O. contact on exhaust fan starter (ST2) is energized and closed
•Power passes to and energizes exhaust fan (M2)
2. Supply Fan Contact (S2) Manually Closed
•Power passes through N.C.
•Power passes through optional N.O. contact on exhaust fan starter (ST2), which is closed when the optional exhaust starter (ST2) is activated
•Power passes through N.C. contact on supply starter overload (ST1 OL), which is closed if the supply fan has not overloaded
•Power passes through N.C. contact on optional freeze protection timer (RT4), which is closed if the temperature has remained above the set point
•Power passes to and energizes optional inlet damper (D1), which opens
•Power passes through optional damper limit switch
(DL1), which is energized and closed if the optional inlet damper is open. It may take several minutes for the damper to fully open and for the damper limit switch to close
•Power passes to and energizes fan relay (RF)
•Power passes through N.O. contact on fan relay
(RF), which is closed once the fan relay (RF) is activated
•Power passes to and energizes starter relay (ST1)
•N.O. contact on supply fan starter (ST1) is energized and closed
•Supply fan (M1) starts
3. Heat Contact (S4) Manually Closed
•Power passes through N.O. contact on fan relay
(RF), which is energized and closed if the supply fan (M1) is on
•Power passes to and energizes the heat relay (RH)
•N.O. contact on heat relay (RH) closes
•The stage controller (SC1) compares the inlet air temperature to the inlet air set point (iAS, FX Program Menu). If the inlet air temperature is below the discharge air setting (dtS, FX Program Menu), the stage controller sends a call for heat to the ignition controller (IC1)
4. Ignition Controller (IC1) Sequence of Operation
•The N.O. contact on air proving switch (PS2) is open
•The stage controller (SC1) energizes the combustion blower relay (CR)
•N.O. contact on combustion blower relay (CR) closes
•Power passes to and energizes the combustion blower (CM)
•The N.O. contact on air proving switch (PS2) closes
•Power passes to and energizes air proving switch relay (R9)
•N.O. contacts on air proving switch (R9) closes
•The ignition controller (IC) completes a 30 second
•The main gas valve (MV) fully opens (100%)
•Igniter begins sparking
•10 second trial for ignition begins
•The furnace will light
•The stage controller (SC1) will choose which stage to light the furnace at based on the discharge air temperature setting (dtS, FX Program Menu) and the outside air temperature (TS1)
•When the flame is detected, the igniter stops sparking
•The furnace will remain at high fire (100%) for 20 seconds
•The stage controller (SC1) will stage the main gas valves (MV#) as needed between low fire, high fire and off
•If the furnace is at low fire and the discharge temperature sensor (TS2) reading remains above the discharge air temperature setting (dtS, FX Program Menu) for more than six minutes, the furnace will shut down
5. Staging Control Sequence of Operation
•If the discharge temperature (TS2) is below the discharge air temperature set point (dtS, FX Program Menu), the furnace will stage up
•If the discharge temperature (TS2) is above the discharge air temperature set point (dtS, FX Program Menu), the furnace will stage down
•If the discharge temperature (TS2) is above the discharge air temperature set point (dtS, FX Program Menu) and the furnace is at low fire, the furnace will shut off
•If the furnace is at high fire and the discharge air temperature setting (dtS, FX Program Menu) is not satisfied, the furnace will remain at high fire
•If the furnace is at low fire and the discharge air temperature setting (dtS, FX Program Menu) is satisfied, the furnace will shut off
6.Optional Evaporative Cooling Contact (S4) Closed*
•N.O. contact on fan relay (RF) is energized and closed
•Power passes through N.O. contact on optional inlet air sensor (TS4), which is energized and closed if the inlet air temperature is above the set point
•Power passes to and energizes cool relay (RC)
®
Model IG / IGX
