Boiler Control Instruction & Operation Manual, Rev 1
Page
11
of 64
Product Features
Multiple Boiler Control Sequencer
Control Options
•
Modulating Sensors
1. Header
•
Modulation Setpoint
-
Outdoor Air Reset
-
Warm Weather Shutdown
-
Frost Protection
-
EMS interface
•
Device Control
-
Boiler, System & Domestic
pumps
-
Fresh Air Damper
Return
Water
System
Circulator
DHW
Circulator
Connects to
Up to Eight
Boilers
Header
Temperature
DHW
Temperature
Switch
ONLY
Sequencer Master
A single Control is parameter selected to be the
Sequencer Master. The Sequence Master does
not rotate. The call for heat, outdoor and header
sensors, and common pumps are wired to the
Sequencer Master
“enabled” Control.
Lead/Slave Sequencing
The Sequence Master is independent of the
“Lead” boiler. One boiler is a “Lead” boiler and the
remaining networked boilers are
“Slaves”. When
demand is increasing, the Lead boiler is the first to
start and the Slave boilers are started in
sequential order (1, 2, 3,
…) until the demand is
satisfied. 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.
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 first during
winter months and then selected to run last for the
remainder of the year.
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.
Figure 8: Multiple Boiler Hydronic Options
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
Pipe
d” is selected only the individual slave boiler,
with the wired DHW demand and pump, fires to
satisfy the DHW setpoint
.
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. However, the Sequence Master
always uses the Header sensor and does not use
the DHW Sensor.
Optimized Boiler Modulation
Boiler firing rate is managed to increase smoothly as
boilers are started. For example, when a
second boiler is started the initial firing rate is
100%/2 or 50%, when the third boiler is started the
firing rate starts at 200%/3 or 66%. After the initial
start, the Sequence Master develops a unison
firing rate demand based on its setpoint and
header temperature.
Selecting This Control Mode
Press Configure > Lead Lag Master Configuration;
Select Master enable = Enabled
