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E. Boiler Sequence of Operation
1. Normal Operation
Table 13.3: Boiler Sequence of Operation
Status Screen Display
Boiler 1
119
DHW
F
<
Setpoint
120
F
Rate
50%
Priority: Domestic Hot Water
Status: Running
107774-01- 9/17
XIII. Operation
Priority:
(burner Off, circulator(s) Off)
Standby
Boiler is not firing and there is no call for heat, priority equals standby. The boiler
Status:
is ready to respond to a call for heat.
Standby
Priority:
(burner Off, circulator(s) On)
Central Heat
Boiler is not firing. There is a Central Heat call for heat and the Supply temperature
Status:
is greater than setpoint minus the "Diff Below".
Standby
When supply temperature drops burner demand continues with following Status
Priority:
shown:
Central Heat
Safe Startup:
Drive purge:
Status:
Prepurge:
Prepurge
After purge time is complete the following Status is shown:
Priority:
Drive light-off:
Central Heat
Pre-Ignition Test: After the blower reaches light-off rate a safety relay test is
Status:
Direct
Pre-ignition:
ignition
Direct Ignition:
(burner On, circulator(s) On)
Priority:
After flame is proven the sequence continues with run stabilization and low
Central Heat
fire hold time. Once the field adjustable low fire hold time is completed normal
Status:
boiler operation begins, modulation rate depending on temperature and setpoint
Running
selections.
Priority:
Domestic
If the Central Heat call for heat is active and a Domestic Hot Water (DHW) call for
>
Hot Water
heat received the DHW demand becomes the "priority" and the modulation rate,
and setpoint, are based on DHW setting.
Status:
Running
Priority:
(burner Off, circulator(s) Off)
Standby
If there is no call for heat the main fuel valve is closed and the blower is driven
Status:
to the fan post-purge speed. After the blower reaches the fan post-purge speed
Post-purge
setting, the combustion chamber purge is conducted.
Priority:
Standby
Standby delay status is entered when a delay is needed before allowing the burner
control to be available. Select "Help" button from the "Home Screen" to determine
Status:
the cause of the Standby Delay.
Standby
Delay
Priority:
A lockout status is entered to prevent the boiler from running due to a detected
Standby
problem. Select "Help" button from the "Home Screen" to determine the cause of
Status:
the Lockout. The last 5 Lockouts are recorded in the Lockout History.
Lockout
(continued)
Description
Flame circuit is tested.
The blower is driven to the fan purge speed.
After the blower reaches the fan purge speed setting the
combustion chamber purge is conducted.
The blower is driven to light-off rate.
conducted.
Spark is energized and it is confirmed that no flame is present
Spark and Main fuel valve are energized.
105
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