107
106308-05 - 3/23
APEX Installation, Operating, & Service Instructions APEX Installation, Operating, & Service Instructions
Backup Header Sensor
If the header sensor fails, the Sequencer
Master uses the lead boiler’s supply sensor to
control firing rate. This feature allows continued
coordinated sequencer control even after a
header sensor failure.
Improved Availability
The following features help improve the heat
availability:
• Slave Boiler Rate Adjustment – Each slave
boiler continues to monitor supply, return
and flue gas temperatures and modifies the
Sequencer Master firing rate demand to
help avoid individual boiler faults, minimize
boiler cycling and efficiently provide heat to
the building.
• Slave Boiler Status Monitoring – Sequencer
Master monitors slave boiler lockout status
and automatically skips over disabled
boilers when starting a new slave boiler.
• Stand Alone Operation Upon Master
Failure – Individual boilers are configured
to continue to operate in the event the
Sequencer Master control is powered down,
disabled or boiler-to-boiler communication
is lost. The following are design
considerations for backup “Stand Alone”
operation. Once the Sequence Master is
restored to operation the individual boilers
automatically resume their position as
sequencer slaves.
o Enable/Disable – Upon loss of
Sequencer Master, each boiler will
automatically begin local control.
This means it will operate only if it
has a call for heat. For this reason
slave boilers should have their
Enable/Disable terminals jumpered
so each boiler has demand if
Sequencer Master is lost.
o Modulation – Once running, each
slave boiler will use its selected
central heat modulation sensor
and setpoint to produce heat for
the building. To allow continued
header water temperature control,
slave boilers may have separate
header sensors wired with the
CH Modulation Sensor parameter
selected as Header Sensor.
o Pumping – Consideration must be
given to how the system pump is
powered. If the Sequencer Master
enabled boiler is powered down,
how will the system pump be
operated? It may be required to wire
the system pump to multiple boilers.
10 Operation (continued)
To Next Page
Loading...
Need help?
General
