63
11
Operating information
(continued)
Temperature control
Modulation
Th
e Knight XL is capable of modulating its fi ring rate
from a minimum of 20% to a maximum of 100%. Th
e
fi ring 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 fl ow, the SMART SYSTEM can
limit the fi ring 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. Th
ere are six (6) limits
that can be programmed, as well as six (6) time intervals
corresponding to each limit. Th
e sixth limit will also limit
the fi ring 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 fi ring 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. Th
e
installer can change the slope of the reset curves by several
adjustable parameters. Th
e 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 fi xed number of degrees (adjustable by
installer). Th
is 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 satisfi ed, the set point will revert to
the value determined by the reset curve.
Night setback
Th
e controller may be programmed to reduce the space
heating and DHW set points during certain times
each week. Seven diff erent 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 fi ring
at minimum rates, the control will increase the fi ring rate
when the fl ame signal drops too low.
Protection features
Outlet temperature, fl ue temperature, and temperature
rise limiting
Th
e 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 .
Th
e control module monitors the fl ue temperature by a sensor
located in the fl ue exhaust. If the fl ue temperature exceeds
215°F (102°C) the control will reduce the maximum fan speed.
If the fl ue temperature exceeds 240°F (115°C) the control will
shut the unit down. Th
e unit will restart automatically once the
fl ue temperature drops 25°F (-4°C) and the minimum off time
has expired.
Th
e control monitors the temperature diff erence between
the inlet and the outlet sensor. If this diff erence exceeds 55°F
(13°C) the control will reduce the maximum fan speed. If the
temperature diff erence exceeds 60°F (15°C) the control will
shut the unit down. Th
e unit will restart automatically once the
temperature diff erence 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.
Th
e following integral feature of the SMART SYSTEM control
module provides some protection for the boiler only -- not for
the system.
•
Th
e SMART SYSTEM control module provides
freeze-up protection as follows when the boiler
water temperature drops below 45°F (7°C):
• Below 45°F (7°C), the boiler and system pumps
operate constantly.
•
Below 37°F (3°C), the boiler turns on.
• Boiler and pumps turn off if boiler water
temperature rises above 45°F (7°C).
•
Lower temperatures may be programmed for systems
with anti-freeze solutions.
Th
is feature of the SMART SYSTEM
control module does not eliminate the
possibility of freezing. Th
e installation must
still use recognized design, installation and
maintenance practice to prevent freeze
potential for the boiler and system.
CAUTION
NOTICE
When system return temperatures
are maintained below the dew point,
condensation will form on the inside of the
boiler jacket causing some internal sheet
metal components to rust.
Installation & Operation Manual
