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10
Operation
(continued)
L. Multiple Boiler Control Sequencer
1. Setup
NOTICE: Enable only one Sequencer Master boiler within a group of networked boilers. Erratic behavior
will result if more than one Sequencer Master is enabled. Assign all boilers a unique address. Undesirable
simultaneous operation occurs when two boilers' addresses are the same.
Complete steps shown in Table 10-23 to set up a multiple boiler system. Refer to J. Parameter Adjustment, parts
11 and 12.
Table 10-23: Multiple Boiler Setup Procedure
Step
Description
1
Wire the header
sensor
2
Install Ethernet
cables between
boilers
3
Set unique boiler
addresses
4
Enable one
Sequencer
Master boiler
5
Confirm
communication
2. Features
Sequencer Master
A single boiler is selected to be the permanent Sequencer Master (i.e. does not rotate). The call for heat,
outdoor and header sensors, and common pumps are wired to the Sequencer Master boiler.
Lead/Slave Sequencing
The Sequencer 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.
Sequence of Operation
Multiple boiler sequence of operation is illustrated in Figure 10-24. After there is a demand, both header water
temperature and boiler firing rate percent are used to start and stop networked boilers. The control starts and
stops boilers when water temperature is outside Difference Above and Difference Below settings. 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.
Lead Boiler Start - Temperature below setpoint by more than Difference Below
1
Temperature Based Lag Boiler Start - Temperature below setpoint by more than Difference Below for
2
longer than Boiler Start Delay (adjustable parameter)
Modulation % Based Lag Boiler Start – Firing rate has been at maximum for longer than 20 min.
3
Lag Boiler Stop – Firing rate has been at minimum for longer than 20 min. Additionally, lag boilers are
4
stopped when water temperature is above setpoint by more than Difference Above for longer than Boiler
Stop Delay.
Lead Boiler Stop – Lead boiler fires until water temperature is above setpoint more than Difference Above
5
for longer than Boiler Stop Delay.
106308-05 - 3/23
Wire a header sensor to Header Sensor terminals of the boiler to be used as the Sequencer
Master. See Figures 6-14 and 6-15 for header sensor installation detail.
NOTE: This step cannot be skipped. The Sequencer Master cannot be enabled unless a Header
Sensor is installed.
See Figure 8-9. Use standard Ethernet type cables to make connection between boilers.
Alternatively, terminal screws A, B, and C labeled Boiler-to-Boiler may be used.
Assign all boilers a unique Boiler Address using any number from 1 through 8. Select Main Menu
>> Adjust >> Sequencer Slave >> Boiler Address.
Enable the Sequencer Master on the boiler with header sensor installed. Enable only one boiler as
the Sequencer Master. Select Main Menu >> Adjust >> Sequencer Master >> Enable.
Power down all boilers. Power up Sequencer Master boiler first. On the Sequencer Master boiler,
select Status. The Sequencer display should show boiler addresses of communicating boilers.
If a boiler is not shown, check Ethernet cable connections and confirm all boilers have unique
addresses.
APEX
Installation, Operating, & Service Instructions
Comments
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