Greenheck IG / IGX (464104 IOM) (Pre-2009) - Manual (Page 52)

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Operation - 2:1 Staged Sequence
Optional Exhaust fan switch (S1) manually closed
• Power passes through N.C. exhaust fan overload (ST2 O.L.) which is closed if exhaust fan (M2) has not
overloaded
• Power passes to exhaust fan starter (ST2)
• N.O. Exhaust fan starter contactor (ST2) is energized and closed
• Power passes to and energizes exhaust fan (M2)
Supply fan switch (S2) manually closed
• Power passes through N.C. field supplied fire contact (FSC)
• Power passes through the optional N.O. exhaust fan contact (ST2) which is energized and closed
• Power passes to the optional freeze protection (FZ1) and through N.C. freeze protection contact (FZ1) which is
closed if temperature has remained above set point
• Power passes to and energizes optional inlet damper (D1) which opens. Power also reaches optional return air
damper (D3) which will now modulate or open depending on control
• Power passes through damper limit switch (DL1) which is energized and closed if the 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 through N.C. supply starter overload (ST1 O.L.) which is closed if the supply fan has not
overloaded
• Power reaches supply fan starter (ST1)
• N.O. supply fan starter (ST1) is energized and closed
• Power reaches and energizes supply fan (M1)
Heat switch (S3) manually closed
• Power passes through N.O. supply fan starter (ST1) which is energized and closed
• Power passes through the optional N.O. inlet air sensor (TS1) which is closed if inlet air temperature has
remained below set point
• Power passes to the discharge air sensor (TS2)
• If the discharge air temperature is less than the discharge air sensor (TS2) set point, the furnace stage one N.O.
contact (SC1-1) will close, powering the ignition controller (IC1)
• If the discharge air temperature is also less than the discharge air sensor (TS2) set point, the furnace stage two
N.O. contact (SC1-2) will also close
• The ignition controller (IC1) will begin its sequence of operation
Ignition Controller (IC1) Sequence of Operation
• The N.O. low air proving switch (PS2) is open
• The ignition controller (IC1) energizes the combustion blower (CM1)
• The N.O. low air proving switch (PS2) closes
• The ignition controller completes a 15 second pre-purge
• The high fire relay (T2) is energized and the high fire contact (T2) closes
• The main gas valve (MV1) fully opens (100%)
• 10 second trial for ignition period begins
• Igniter begins sparking
• 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 10 seconds
• High fire contact (T2) will open
High Fire – Low Fire Sequence of Operation
• The furnace lights at high fire (100%), and remains at high fire for 10 seconds
• If the discharge temperature sensor (TS2) is above the discharge air sensor (TS2) set point, the furnace stage
two contact (SC1-2) will open and the furnace will go to low fire (50%)
• If the furnace is at low fire (50%) and the discharge temperature is above the discharge air sensor (TS2) set
point, the furnace stage one contact (SC1-1) will open and the furnace will shut down
• If the furnace is at low fire (50%), and the discharge temperature sensor (TS2) remains below the discharge air
sensor (TS2) set point, the furnace stage two contact (SC2-1) will close and the furnace will go to high fire
(100%)
Sequence of Operation
Operation