Burnham ALPINE Installation, Operation And Service Instructions page 78

X. Modular installation (continued)
k. Advanced Boiler Sequencing
After there is a Call For Heat input, both header
water temperature and boiler firing rate percent
are used to start and stop the networked boilers.
The control starts and stops boilers when the water
temperature is outside the user selected "Diff
Above" and "Diff Below" settings. Also, in order
to minimize temperature deviations, the control
adjusts the number of boilers running based on the
firing rate. This combination allows the boilers to
anticipate slow load changes before they disrupt
water temperature yet still respond quickly to
sudden load changes. These special sequencer
features help reduce energy wasting system
temperature swings and the resulting unnecessary
boiler cycling. Refer to Figure 45A and 45B for a
graph of the following sequencer details:
i. Start Lead Boiler
When water temperature is below the setpoint
by more than the "Diff Below" setting, the
Lead Boiler is started and modulates to satisfy
the heat load.
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ii. Start 1 Lag Boiler (fast load change example)
When water temperature is below the setpoint
by more than the "Diff Below" setting for
longer than 2 minutes and firing rate is at the
"High Fire Limit", the second boiler is started
and both modulate in unison to satisfy the heat
load.
iii. Start Last Lag Boiler (slow load change
example)
When boiler firing rate has been next to the
"High Fire Limit" for longer than 20 minutes
the last boiler is started. After the last boiler is
started the High Fire Limit is released and the
boilers are free to modulate above the "High
Fire Limit" as required to satisfy the home
load.
iv. Stop Lag Boiler
When boiler firing rate has been next to low
fire limit for longer than 20 minutes or water
temperature is above the setpoint by more than
the "Diff Above" setting for 30 seconds the lag
boiler is stopped.
v. Stop Lead Boiler
When water temperature is above the setpoint
by more than the "Diff Above" the lead boiler
stops without delay.
vi. Stop All Boilers
All boilers are stopped without delay if the
Call for Heat input is removed or if the header
temperature is higher than 195 F.
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Figure 45A: Start Sequence Detail
Figure 45B: Stop Sequence Detail