Staged - Greenheck IG Installation, Operation And Maintenance Manual

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. field-supplied fire
contact (FSC)
• 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
pre-purge
• 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 Make-Up Air
43