Greenheck DG / DGX with Pilot Ignition (463555 IOM) (Pre-2008) - Manual (Page 32)

32
Operation - Electrical
1. Exhaust Fan Contact (S1) Closed -
Optional
• Power passes to exhaust starter(s) ST2(3)
• N.O. exhaust starter switches are energized
and closed
• Power passes to exhaust fans
• Exhaust fans start
2. Supply Fan Contact (S2) Closed
• N.O. contact(s) ST2(3) are closed
• Power passes to optional freeze protection
relay (FZ1) and if temperature is acceptable
N.C. contact (FZ1) remains closed
• Power passes to damper 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 (ST1)
• Supply starter contact (ST1) closes and power
reaches and energizes supply fan
• Supply fan starts
4. Evaporative Cooling Contact (S4)
Closed*
• N.O. contact on fan relay is energized and closed
• Power passes to optional inlet air sensor
contact (TS2) which is energized and closed if
the inlet air temperature is above the set point
• Power passes to and energizes cool relay (R1)
• N.O. contact R1 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.
3. Heat Contact (S4) Closed
• Power passes to N.O. fan relay which is
energized and closed
• Power passes to optional inlet air sensor
contact (TS) which is energized and closed if
the inlet air temperature is below the set point
• Power passes to and energizes heat relay (RH)
• N.O. heat relay contact (RH) closes
• Power passes to and energizes terminal 5 of
the Flame Safe Guard (FSG)
• Power passes to optional N.C. high limit control
contact (HLC) which is closed if the
temperature has remained below the high limit
set point
• Power passes to optional N.O. and N.C. gas
pressure contacts (PS) which are both closed if
gas pressure is within the set range
• Power passes to terminal 6 of the FSG
• FSG begins direct gas burner sequence (see
direct gas 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 Safe Guard
3. Flame Safe Guard (FSG) Sequence
• Checks for proper air flow
• Verifies no flame present at burner
• Initiates 10 second prepurge
• Sends power to open pilot valve (V1) and
energizes the spark generator (SG) (clicking of
the spark generator may be heard).
• Tries for up to 10 seconds to light pilot and
confirm flame.
• Powers the main gas valves open
• Shuts down spark generator
• Continuously monitors the flame and airflow
• Performs self diagnostic check every five
seconds
Electrical Sequence Direct Gas Burner Sequence
Operation