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Operating information
Temperature control
Modulation
The Knight XL is capable of modulating its firing rate
from a minimum of 10% to a maximum of 100%. The
firing rate is dictated by the call for heat (i.e., space heating
or domestic hot water), the heating load, ramp delay (if
enabled), and various other temperature limitations.
Ramp delay
For systems with lower flow, the SMART TOUCH can
limit the firing rate (when enabled) when a space heating
call for heat starts, or when switching from a DHW call for
heat to a space heating call for heat. There are six (6) limits
that can be programmed, as well as six (6) time intervals
corresponding to each limit. The sixth limit will also limit
the firing rate for the rest of the call for heat.
Gradient limiting
If during operation of the boiler the outlet water temperature
is rising too quickly, the control will reduce the firing rate
to its lowest setting.
Outdoor air reset
If an outdoor air sensor is connected, the control module
will calculate the set points of the three (3) space heating
demands based on the programmed reset curves. The
installer can change the slope of the reset curves by several
adjustable parameters. The user can limit the maximum
set point for the system using the space heating set points.
Boost function
If outdoor air reset is active, and any space heating
demand has been active continuously for a set period of
time (time adjustable by installer) and there has been no
DHW demands, the control will increase the set point of
that demand by a fixed number of degrees (adjustable by
installer). This process will continue until the space heating
demand ends, the set point reaches the programmed set
point or a maximum of 20 increases has occurred. Once the
system heat demand is satisfied, the set point will revert to
the value determined by the reset curve.
Night setback
The controller may be programmed to reduce the space
heating and DHW set points during certain times
each week. Seven different start and stop times may be
programmed for the space heating setback and seven start
and stop times for the DHW setback.
Flame current support
To prevent nuisance shutdowns when the boiler is firing
at minimum rates, the control will increase the firing rate
when the flame signal drops too low.
Protection features
Outlet temperature, flue temperature, and temperature
rise limiting
The outlet temperature is monitored by the boiler outlet
temperature sensor. When the outlet temperature exceeds
185°F, the unit will reduce the fan speed. If the outlet water
temperature exceeds 195°F (90°C) the control will shut the unit
down until it cools off.
The control module monitors the flue temperature by a sensor
located in the flue exhaust. If the flue temperature exceeds
215°F (102°C) the control will reduce the maximum fan speed.
If the flue temperature exceeds 225°F (107°C) the control will
shut the unit down. The unit will restart automatically once the
flue temperature drops 10°F (6°C) and the minimum off time
has expired.
The control monitors the temperature difference between
the inlet and the outlet sensor. If this difference exceeds 55°F
(13°C) the control will reduce the maximum fan speed. If the
temperature difference exceeds 60°F (15°C) the control will
shut the unit down. The unit will restart automatically once the
temperature difference has dropped below 55°F (13°C) and the
minimum off time has expired.
Freeze protection
DO NOT install the boiler in a room likely to freeze.
Installation & Operation Manual
⚠
DANGER
Freezing Conditions: If this boiler may
have been exposed to freezing conditions,
prevent from firing. Shut off power and
gas to the appliance immediately and
contact the factory for further instructions.
Allowing the boiler to fire when the heat
exchanger or near boiler piping is frozen
will result in death or serious injury and
significant property damage.
The following integral feature of the boiler control module
provides some protection for the boiler only -- not for the
system.
The boiler control module provides a freeze protection
feature with the following attributes:
• Below an inlet temperature of 45°F (7°C), the boiler
pump operates constantly.
• Below an inlet temperature of 37°F (3°C), the burner
fires.
• Boiler and pumps turn off if boiler water inlet
temperature rises above 45°F (7°C).
