8105337-03 - 5/15
I. Operation
D. Multiple Boiler Control Sequencer
1. “Plug &Play”Multiple BoilerControlSequencer
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
Asingle 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/Slave Sequencing & Equalized Run Time
One boileris a“Lead” boilerand theremaining networked
boilers are “Slaves”. When demand is increasing, the
Lead boiler is the rst to start and the Slave boilers are
started in sequential order (1,2,3,…) until the demand
is satised. 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. Slave Boiler Rate Adjustment: Each slave boiler
continues to monitor supply, return and ue gas
temperatures and modies the Sequence Master’s
ring rate demand to help avoid individual boiler
faults, minimize boiler cycling and provide heat to
the building efciently.
d. Slave Boiler Status Monitoring: The Sequence
Master monitors slave boiler lockout status and
automatically skip over disabled boilers when
starting a new slave 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,Auxiliary
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 (82.2°C). When “Boiler Piped” is selected only
the individual slave 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 DHWTwo 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 modulating
condensing boiler peak operating efciency. Lower ring
rates boost efciency 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 (90.6°C) (eld adjustable).
