Lochinvar KNIGHT 399 - 800 - Manual (Page 57)

Installation & Operation Manual
57
11
Operating information
(continued)
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
If an outdoor air sensor is connected, the control module
will calculate the set point based on the programmed reset
curve. The installer can change the slope of the reset curve
by several adjustable parameters. The user can limit the
maximum set point for the system using the space heating
set point.
Boost function
If outdoor air reset is active, and a 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 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 set point during a certain time each day. A start
and stop time can be programmed for each day of the week.
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 240°F (115°C) the control will
shut the unit down. The unit will restart automatically once the
flue temperature drops 25°F (-4°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 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.
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 (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).
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