Burnham K2WT Residential, Installation, Operating And Service Instructions

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107672-03 - 5/18
XII. Operation
(continued)
indication is provided. Additionally, the control
monitors an air proving switch. During the boiler
start sequence the control requires the air proving
switch to be in the “open” position before the
blower starts and in the “closed” position after
the blower starts. If the air proving switch is not
in the required position the start sequence is
halted or the boiler is shut down and the open
limit indication is provided. The air proving switch
is only required to be closed during pre-purge.
It is normal for the air proving switch to be open
during run mode.
6. Stack High Limit
The Control monitors the flue gas temperature
sensor located in the vent connector. If the
flue temperature exceeds 194°F (90°C), the
control begins to reduce the maximum blower
speed. If the flue temperature exceeds 204°F
(96°C), a forced boiler recycle results. If the flue
temperature exceeds 214°F (101°C), the control
activates a manual reset Hard Lockout.
7. Flame Current Modulation Boost
To help prevent nuisance shutdowns when the
boiler is firing at minimum firing rates, the control
will increase the firing rate when the flame current
is too low.
8. Ignition Failure
The Control monitors ignition using a burner
mounted flame sensor. In the event of an ignition
failure, the control retries 5 times and then goes
into soft lockout for one hour.
9. Central Heating System Frost Protection
When enabled, Frost Protection starts the boiler
and system pump and fires the boiler when low
outside air and low supply water temperatures
are sensed. The Control provides the following
control action when frost protection is enabled:
Table 12.2: Frost Protection
Device
Started
Start
Temperatures
Stop
Temperatures
Boiler Pump
Outside Air < 0°F (-18°C)
Supply Water < 45°F (7.2°C)
Outside Air > 4°F (-16°C)
Supply Water > 50°F (10°C)
Boiler Supply Water < 38°F (3.3°C) Supply Water > 50°F (10°C)
FROST PROTECTION NOTE
The Control helps provide freeze protection for the boiler
water. Boiler flue gas condensate drain is not protected
from freezing. Since the Control only controls the system
and boiler circulators individual zones are not protected.
It is recommended that the boiler be installed in a location
that is not exposed to freezing temperatures.
D. Multiple Boiler Control Sequencer
1. “Plug & Play” Multiple Boiler Control
Sequencer
When multiple boilers are installed, the Control’s
Sequencer may be used to coordinate and
optimize the operation of up to eight (8) boilers.
Boilers are connected into a “network” by simply
“plugging in” standard ethernet cables into each
boiler’s “Boiler-To-Boiler Communication” RJ45
connection.
2. Sequencer Master
A single Control is parameter selected to be the
Sequencer Master. The call for heat, outdoor and
header sensors, and common pumps are wired
to the Sequencer Master “enabled” Control.
3. Lead/Slave Sequencing & Equalized Run Time
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.
4. Improved Availability
The following features help improve the heat
availability:
a. Backup Header Sensor: In the event of a
header sensor failure the lead boiler’s supply
sensor is used by the Sequence Master to
control firing rate. This feature allows continued
coordinated sequencer control even after a
header sensor failure.
b. “Stand Alone” Operation Upon Sequence
Master Failure: If the Sequence Master
Control is powered down or disabled or
if communication is lost between boilers,
individual boilers may be setup to automatically
resume control as a “stand alone” boiler.
c. Slave Boiler Rate Adjustment: Each slave boiler
continues to monitor supply, return and flue
gas temperatures and modifies the Sequence
Master’s firing rate demand to help avoid
individual boiler faults, minimize boiler cycling
and provide heat to the building efficiently.
d. Slave Boiler Status Monitoring: The Sequence
Master monitors slave boiler lockout status
and automatically skip over disabled boilers
when starting a new slave boiler.