Sequence of Operation
4:1 Electronic Modulation, continued
4. Ignition Controller (IC1) Sequence of Operation
•The N.O. contact on air proving switch (PS2) is open
•The ignition controller (IC1) energizes the induction relay (IR)
•N.O. contact on induction relay (IR) closes
•Power passes to and energizes the combustion blower (CM), sending it to high speed
•The N.O. contact on air proving switch (PS2) and high pressure switch (PS5) closes
•The ignition controller (IC1) begins a 15 second
•The main gas valve (MV) fully opens (100%) and the modulating gas valve (MOD) opens to high fire
•Igniter begins sparking
•10 second trial for ignition begins
•The furnace will light at high fire (100%)
•When the flame is detected, the igniter stops sparking
•The furnace will remain at high fire (100%) for 30 seconds
•The modulation controller (SC1) will adjust the modulating gas valve (MOD) and the combustion blower (CM) as needed between low and high fire
•The modulating controller (SC1) will monitor the high pressure switch (PS5) and run the furnace at low fire if the high pressure switch is not satisfied
5. High Fire – Low Fire Sequence of Operation
•The furnace lights at and remains at high fire
(100%) for 30 seconds
•If the discharge temperature sensor (TS2) reading is above the discharge temperature setting (dtS, FX Program Menu), and the furnace is not at low fire, the modulating controller (SC1) will adjust the modulating gas valve (MOD) down until the discharge temperature sensor (TS2) reading equals the discharge temperature setting (dtS, FX Program Menu)
•If the discharge temperature sensor (TS2) reading is below the discharge temperature setting (dtS, FX Program Menu), and the furnace is not at high fire, the modulating controller (SC1) will adjust the modulating gas valve (MOD) up until the discharge temperature sensor (TS2) reading equals the discharge temperature setting (dtS, FX Program Menu)
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 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)
•N.O. contact on cool relay (RC) is energized and closed
•Power passes to evaporative cooling pump (P1)
*If DX or chilled water coils are used rather than an evaporative cooler, the cooling sequence of operation will depend on the coil controls. Cooling coil controls are supplied by others.
42 Model IG / IGX
®
