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10
Operation
A. Basic Operation
When a call for heat is provided, the boiler
attempts to maintain a target supply (outlet) water
temperature or header temperature (if header
sensor enabled). The boiler control varies fan
speed to modulate boiler output. As fan speed
changes, the gas valve regulates fuel gas flow to
match combustion air flow, resulting in a relatively
constant fuel: air ratio across the modulation
range. The control determines required output
by looking at both current and recent differences
between measured temperature and setpoint
temperature. As measured temperature
approaches setpoint temperature, the control
reduces boiler output by reducing fan speed.
The control also looks at return (inlet) water
temperature and flue gas temperature when
determining modulation rate.
B. Features
1. Boiler Control
The Concert Boiler Control contains features
and capabilities which help improve heating
system operation, and efficiency. By including
unique capabilities, the control can do more,
with less field wiring, and fewer aftermarket
controls and components – improving the
operation of both new and replacement boiler
installations.
2. Advanced Touch Screen Display
Boiler status and setup selections are available
from an easy to use, full color, Touch Screen
Display. In the event of a fault condition the
user is guided by blinking touch buttons to
help screens that explain the problem, cause,
and corrective action. Operation evaluation
and problem-solving is enhanced by historical
capability including graphic trends, lockout
history records, as well as boiler and circulator
cycle counts and run time hours.
3. Demand
Two demand inputs are provided on the
low voltage PCB: Enable/Disable for space
heating (Central Heat), and DHW Demand for
domestic hot water (DHW) or other heating
demand. Enable/Disable and DHW Demand
each have unique temperature and pump
settings. In a multiple boiler installation, the
sequencer control may also provide demand.
4. Outdoor Reset
When selected, outdoor reset automatically
adjusts supply water temperature based
106308-05 - 3/23
APEX
Installation, Operating, & Service Instructions
on outside air temperature, time of day, and
length of demand (boost) settings for energy
savings. Outdoor reset requires installation of
an outdoor sensor. Hard-wired and wireless
outdoor sensors are available.
5. Warm Weather Shutdown
Some boilers are used primarily for heating
buildings, and the boilers can be automatically
shut down when outdoor air temperature is
warm. When outside air temperature is above
the WWSD setpoint, this function will shut down
the boiler and system pump.
6. Pump Control
Three pump outputs are provided on the
120V PCB: Boiler Pump, System Pump, and
DHW Pump. Outputs are service rated relays.
Simple parameter selections allow all three
pumps to respond properly to various hydronic
piping arrangements. To help prevent rotor
seizing, pumps are automatically run for a 20
second exercise period after not being used
for longer than seven days.
7. Multiple Boiler Sequencer Boiler-to-Boiler
Network
The control includes state-of-the-art modulating
lead-lag sequencer for up to eight boilers
capable of automatic rotation, outdoor reset,
and boiler-to-boiler communication. Multiple
boiler sequencing requires plug-and-play
connections between boilers. Precise boiler
coordination is provided as boilers are
sequenced based on both header water
temperature and boiler modulation rate. For
example, the lead boiler (Sequencer Master)
can be configured to start a lag boiler after
operating at 50% modulation rate for longer
than an adjustable time. The boilers are
modulated in unison (parallel) modulation rate
to ensure even heat distribution.
8. Energy Management System (EMS) Interface
The control accepts a 4-20mA DC input from
an energy management system (EMS) for
either direct modulation rate or temperature
setpoint. A factory configured RS485 Modbus
interface is available for EMS monitoring, which
can be used in conjunction with the multiple
boiler sequencer.
9. Archives via USB Thumb Drive
Archives allow easy transfer of parameters
from one boiler to another using a USB thumb
drive. Additionally, Archives are a valuable
troubleshooting tool, providing alarm history
and operating history in spreadsheet (.csv)
format downloaded to a thumb drive.
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