Greenheck DG/DGX Pilot Ignition (470651_IOM) - Manual (Page 24)

Direct Gas Burner Sequence
1. Supply Fan Contact Closed
• Power passes to the supply fan and heat switch
2. Heat Contact Closed
• Power passes to the heat relay then to the
Flame Safeguard
3. Flame Safeguard (FSG) Sequence
• Checks for proper airflow
• Verifies no flame present at burner
• Initiates 15 second prepurge
• Sends power to open pilot gas valve (V1) and
energizes the spark generator (SG)
• Tries for up to 10 seconds to light pilot and
confirm flame
• Powers the main gas valves (V2) open
• Shuts down spark generator (SG)
• Continuously monitors the flame and airflow
• Performs self-diagnostic check every five
seconds
Operation - Electrical
Electrical Sequence
1. Exhaust Fan Contact (S1) Closed
(optional)
• Power passes to N.C. exhaust overload contact
(ST2 OL) (optional)
• Power passes to exhaust starter(s) (ST2)
• N.O. exhaust starter switches are energized and
closed
• Power passes to exhaust fans
• Exhaust fan(s) (M2) start
2. Supply Fan Contact (S2) Closed
• Power passes through N.C. field-supplied fire
contact (FSC)
• Power passes through N.O. exhaust fan contact
(ST2) which is closed when the exhaust relay
(ST2) is activated (optional)
• Power passes to N.C. supply overload contact
(ST1OL)
• Power passes through N.C. contact on optional
freeze protection timer (RT4) which remains
closed if the temperature has remained above
the set point
• Power passes to optional inlet damper (D1)
which opens
• When damper is fully opened, damper relay
(D1) is energized and optional N.O. damper limit
switch (DL1) closes
• Power passes to and energizes supply starter
relay (RF)
• Power passes to N.O. fan contact (RF) which is
energized and closed
• Supply starter (ST1) is energized
• Supply starter contact (ST1) closes and power
reaches and energizes supply fan
• Supply fan (M1) starts
2. Heat Contact (S4) Closed
• Power passes to N.O. fan relay (RF) which is
energized and closed
• Power passes to optional inlet air sensor
contact (TS4) which is energized and closed if
the inlet air temperature is below the set point
• Power passes to and energizes the heat relay
(RH)
• N.O. heat relay contact (RH) closes
• Power passes to and energizes terminal 5 of the
Flame Safeguard (FSG). Power light on FSG is
on.
• Power passes to N.C. high limit control contact
(HLC1) which is closed if temperature has
remained below set point
• Power passes to optional N.O. and N.C. high
and low gas pressure contacts (PS4 and PS3),
which are both closed if gas pressure is within
the set range
• Power passes to terminal 6 of the Flame
Safeguard (FSG)
• Power begins direct gas burner sequence
(see Direct Gas Burner Sequence)
4. Optional Evaporative Cooling Contact
(S4) Closed*
• N.O. contact on fan relay (RF) is energized and
closed
• Power passes to optional inlet air sensor
contact (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 optional 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.
Model DG / DGX Pilot Ignition Make-Up Air 24
®