Greenheck DG / DGX Industrial Space Heating (464044 IOM) (Pre-2009) - Manual (Page 18)

Operation - Electrical with 7 Day Timer
1. Switch (S2) in Summer Mode
• Power passes to terminal G
• 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 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
2. Switch (S2) in Winter Mode
• If space temperature is less than the daytime temperature setting, the the N.O. temperature sensor
contact (TS1) closes and power passes to the timer (TC1). If the timer is on, power passes to terminal
(W1). If timer (TC1) is off, but the space temperature is less than the nighttime temperature setting, the
N.O. temperature sensor contact (TC2) closes and power passes to terminal (W1).
• Power passes to fan relay (R4)
• Fan relay (R4) is energized and N.O. contact (R4) closes
• Power passes to terminal G
• 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 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 and heat relay (R2)
• N.O. heat relay contact (R2) closes
• Power passes to and energizes terminal 5 of the Flame Safe Guard (FSG)
• Power passes to N.C. high limit control contact (HLC1) which is closed if the temperature has remained
below the HLC1 set point
• Power passes to N.O. and N.C. gas pressure contact(s) (PS1, PS3) 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)
3. Flame Safe Guard (FSG) Sequence
• Verifies proper airflow with airflow switch PS2
• Verifies no flame present at burner
• Initiates 10 second prepurge
• Sends power to open pilot valve (V1) and energizes the spark generator (SG1) (clicking of the spark
generator may be heard).
• Energizes spark generator for up to 10 seconds to light pilot and confirm flame.
• Powers the main gas valves (V2 and V3) open
• Shuts down spark generator
• Continuously monitors the flame and airflow
• Performs self diagnostic check every five seconds
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