Alpine Installation, Operating, and Service Instructions

94 103448-02 - 6/13
X. Operation D. Multiple Boiler Control Sequencer (continued)
D. Multiple Boiler Control Sequencer
1. “Plug & Play” Multiple Boiler Control Sequencer
When multiple boilers are installed, the Control’s
Sequencer may be used to coordinate and optimize the
operation of up to eight (8) boilers. Boilers are connected
into a “network” by simply “plugging in” standard
ethernet cables into each boiler’s “Boiler-To-Boiler
Communication” RJ45 connection.
2. Sequencer Master
A single Control is parameter selected to be the Sequencer
Master. The call for heat, outdoor and header sensors,
and common pumps are wired to the Sequencer Master
“enabled” Control.
3. Lead/Lag Sequencing & Equalized Run Time
One boiler is a “Lead” boiler . When demand is increasing,
the Lead boiler is the rst to start and the remaining
boilers are started in sequential order (1,2,3,…) until
the demand is satised. When demand is decreasing,
the boilers are stopped in reverse order with the Lead
boiler stopped last (…,3,2,1). To equalize the run time
the sequencer automatically rotates the Lead boiler after
24 hours of run time.
4. Improved Availability
The following features help improve the heat availability:
a. Backup Header Sensor: In the event of a header sensor
failure the lead boiler’s supply sensor is used by the
Sequence Master to control ring rate. This feature
allows continued coordinated sequencer control even
after a header sensor failure.
b. “Stand Alone” Operation Upon Sequence Master
Failure: If the Sequence Master Control is powered
down or disabled or if communication is lost
between boilers, individual boilers may be setup to
automatically resume control as a “stand alone” boiler.
c. Boiler Rate Adjustment: Each boiler continues to
monitor supply, return and ue gas temperatures and
modies the Sequence Master’s ring rate demand to
help avoid individual boiler faults, minimize boiler
cycling and provide heat to the building efciently.
d. Boiler Status Monitoring: The Sequence Master
monitors boiler lockout status and automatically skip
over disabled boilers when starting a new boiler.
5. Customized Sequences
Normally, boilers are started and stopped in numerical
order. However, custom sequences may be established
to optimize the heat delivery. For example, in order to
minimize boiler cycling, a large boiler may be selected
to run rst during winter months and then selected to
run last for the remainder of the year.
6. Multiple Demands
The Sequence Master responds to Central Heat, DHW
and frost protection demands similar to the stand alone
boiler. For example, when selected and DHW priority
is active, the sequence master uses DHW setpoint, “Diff
Above”, “Diff Below” and pump settings.
7. Shared or Isolated DHW Demand
When the Indirect Water Heater (IWH) parameter is set
to “Primary Piped” the Sequence Master sequences all
required boilers to satisfy the DHW setpoint (default 180
F). When “Boiler Piped” is selected only the individual
boiler, with the wired DHW demand and pump, res to
satisfy the DHW setpoint.
8. DHW Two boiler Start
When the Indirect Water Heater (IWH) parameter is set
to “Primary Piped” and the “DHW Two Boiler Start”
parameter is set to “Enabled” two boilers are started
without delay in response to a DHW call for heat. This
feature allows rapid recovery of large IWH’s and multiple
IWH’s.
9. Optimized Boiler Modulation
Boiler ring rate is managed to increase smoothly as
boilers are started. For example, when a second boiler is
started the initial ring rate is 100%/2 or 50%, when the
third boiler is started the ring rate starts at 200%/3 or
66%. After the initial start, the Sequence Master develops
a unison ring rate demand based on it’s setpoint and
sensed header temperature.
10. Innovative Condensing Boiler Control
During low loads, the Sequence Master limits ring rates
to a ‘Base Load Common Rate” to ensure peak operating
efciency. Lower ring rates boost efciency by helping
increase the amount of ue gas water vapor condensation.
The Control maintains a “Base Load Common Rate” until
the last lag boiler is started. At this point, the “Base Load
Common Rate” is released to allow boilers to modulated
as required to meet heat load.
11. Advanced Boiler Sequencing
After there is a Call For Heat input, both header water
temperature and boiler ring 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 ring 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.
12. 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 (eld adjustable).