Smith Cast Iron Boilers GT Series - Manual (Page 31)

GT INSTALLATION AND OPERATION INSTRUCTIONS Page 31
Figure 43 - Operational Flow Chart
Displays version
t2.0 or t4.0
Awaiting
Input
Sentry 2100
Sentry 2100
Sentry 2100
Fan to SFS (75)
Sentry 2100
Error
ASO
Power to ignitor
120v from S1
Power to Gas valve
Flame Probe
Signal <1 microA
Sentry 2100
Modulates fan based
upon setpoint and
programming
Error
ASC
120v Power
Applied
Boiler in
standby Mode
Air
Switches Closed
Indirect thermostat or flow
switch closes A-C
(Call for Domestic)
Thermostat End switch
or relay closes T-C
(Call for Heat)
(Call for Ignition)
Igniter warm-up
5 seconds
Closed
Open
Greater than 1.0 microA
Three retries
for flame
Less than
1.0 microA
Prepurge
24 Volt signal
to blower
Call for flame ends
Energizes Indirect Pump
(Ap) turns off C1
Energizes Primary
Pump (C1)
IGNITION MODULE
S1 L1 L2 S2 W MV GND
Combi or
indirect
Closed
Open
Energizes 3 way
diverter valve
Energizes Primary
Pump (C1)
Indirect
Water
Heater
Combi model
Open
NO NC
Hi pressure
N. C. switch on
GT 400 only
Manifold & Stack Limit
(GT 150 & GT 200)
Manifold Limit & Flow
Switch
(GT 400)
24 V
24 V