61
APPENDIX A - CONTROL MODULE
1.4 Sequence of Operation
Operational State
User Interface Display
Explanation
Boiler operates in standby mode
until demand for Central Heat (CH) or
Domestic Hot Water (DHW) is detected.
CH or DHW pump is turned based on
type of heating demand.
(CH call is illustrated)
Control Module compares supply
temperature to set point. Boiler proceeds
to ignition if supply temperature is less
than set point.
Air Pressure Switch is checked for open
circuit before energizing Combustion Air
Blower
Closed Air Pressure Switch during this
stage will result in Lockout Error.
Combustion Air Blower is energized to
prove fl ow though Combustion and Vent
Systems.
Air Pressure Switch is checked for closed
circuit.
Open Air Pressure Switch during this
stage will result in Lockout Error after 3
trials.
Combustion Air Blower speed
modulates to prepurge setting for 15
seconds.
Sparking initiated sequence.
S t a n d b y : N o D e m a n d
Heat
Demand?
DHW CH
Pump on
Supply
Temperature
<Setpoint?
Air Pressure
Switch Open?
Combustion
Air Blower
On
15 Second
Prepurge
Ignition
Sparking
Air Pressure
Switch
Closed?
No
Yes
Lockout
Error
A15
No
Yes
No
Yes
Yes
After 2 seconds
No
After
3
Trials
Lockout
Error
A17
Summary of Contents for 075 97gb
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Page 57: ...57 14 WIRING DIAGRAM 14 2 Schematic Diagram of Ladder Form ...
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