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8 Operating information
Temperature control
Modulation
The outdoor boiler is capable of modulating its firing rate
from a minimum of 20% 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 SYSTEM 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
With the outdoor air sensor 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. Any night setback event scheduled
within the next seven (7) days can be temporarily bypassed
if desired.
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 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 the control will reduce the maximum fan
speed. If the flue temperature exceeds 240°F the control will
shut the unit down. The unit will restart automatically once
the flue temperature drops 25°F 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 the control will reduce the maximum fan speed. If
the temperature difference exceeds 60°F the control will
shut the unit down. The unit will restart automatically once
the temperature difference has dropped below 55°F and the
minimum off time has expired.
Freeze protection
DO NOT install the boiler where it is likely to freeze.
The following integral feature of the SMART SYSTEM
control module provides some protection for the boiler only
-- not for the system.
• The SMART SYSTEM control module provides
freeze-up protection as follows when the boiler
water temperature drops below 45°F:
• Below 45°F, the boiler and system pumps operate
constantly.
• Below 37°F, the boiler turns on.
• Boiler and pumps turn off if boiler water
temperature rises above 45°F.
• Lower temperatures may be programmed for
systems with anti-freeze solutions.
This feature of the SMART SYSTEM
control module does not eliminate the
possibility of freezing. The installation
must still use recognized design,
installation and maintenance practice to
prevent freeze potential for the boiler and
system.
ƽ 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.
Outdoor Knight Boiler Installation & Operation Manual