11 Operating information
Temperature control
Modulation
The Knight wall mount 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.
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.
Installation & Operation Manual
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 in a room likely to freeze.
The following integral feature of the SMART SYSTEM control module provides some protection for the boiler only
•The SMART SYSTEM control module provides
•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
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. | |
| This feature of the SMART SYSTEM control | |
CAUTION | ||
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. |
64 