Operation - electrical, Electrical sequence – Greenheck DG / DGX with Direct Spark (470652) User Manual

Page 24

Direct Spark Ignition Make-Up Air

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 gas valve (V2) and energizes

the spark generator

• Tries for up to 10 seconds to light and conﬁrm

ﬂame

• Shuts down spark generator

• Continuously monitors the ﬂame and airﬂow

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

(ST1 OL)

• 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 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

3. 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 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 N.O. and N.C. airﬂow switches

(PS2) which are closed if there is proper airﬂow
across the burner

• Power passes to terminal TH on the Flame

Safeguard (FSG) which begins it’s 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.

Operation - Electrical