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Setpoint Temp — This is the lowest boiler operating temperature that
the boiler will maintain when the outside air temperature is at the O.A.
Max. This setting is a Changeable Point from the Command Display.
Calculated Set Point — The water tem per a ture as adjusted by the
optional outdoor air reset function used on a heat ing boiler only. If no
outdoor reset function is used, this displays the same temperature as the
set point. The Outdoor Air Reset function is not available on a water
heater application.
These functions are shown in the screens of the Command Display.
Where noted, these settings are changeable from the Command
Display to configure boiler operation to the building heat load and
weather conditions in a spe cif ic geographic area.
MULTIPLE APPLIANCE
INSTALLATIONS
SEQUENCING BOX
(MULTI-BOILER)
REMOTE DISPLAY MOUNTING
CLOSED VIEW
COMPONENT
LOCATIONS
FIG. 58 Sequencer Control Panel
SEQUENCING OPTIONS
The sequencer is supplied as a separate control enclosure that is
connected to the multiple appliances via an E-bus connector on the
rear of the appliance. The sequencer comes mounted in an enclosure
that requires a field installed 24 VAC power source. An optional
enclosure with a sub base and 24 VAC power supply is available to
allow remote mounting of a Command Display adjacent to the
sequencer. Multiple sequencing options are available. The specific
software programming required to sequence multiple boilers must be
specified at the time the appliances are ordered. The sequencing
options are used to control how multiple boilers or water heaters are
cycled to meet system demand. The sequencing options are
programmed into an Excel 10 controller at the factory based on the
number of selectable sequencing algorithms or dered. The desired
method of se quenc ing multiple boilers or water heaters may be selected
from the screen of the Command Display. There are up to five
sequencing options that are selectable from the Command Display,
based on the sequencing package purchased.
NOTE:
Separate sequencers are required to control multiple boilers
and water heaters.
1. First On - First Off — This is a lead/lag control
functionality. The se quenc ing of the boilers or
water heat ers is based on the total loop load with
added units being brought on when the units
that are running are at 100% and the loop load is
not being met. Boilers or water heaters are turned
off when the loop load falls and the first boiler or
water heater on is at minimum load.
2. First On - Last Off — This is a simple first on/last
off without rotation of the lead boiler or water heater.
3. Efficiency Optimized — The lead/lag will be based
on first on/first off lead/lag. The overall efficiency
will be optimized to run the boilers or water heaters
at their highest ef fi cien cy. Highest efficiency
occurs at the minimum loading for each boiler or
water heater. Therefore, this option will add
boilers or water heaters when the load reaches a
point where the next boiler or water heater can
run at minimum load.
4. Efficiency Optimized with Time Equal iza tion —
This is the same as “Ef fi cien cy Optimized” but
the lead/lag is based on boiler or water heater run
times. The boilers or water heaters will be
sequenced to equalize run times to within
approximately a 24 hour time period. If no
opportunity is given to cycle, the control will not
interrupt action to equalize runtime.
5. None — This is the default for any boiler or water heater
control which has not purchased one of the
Sequencing Option Packages.