Installation & Operation Manual
10 Operating information (continued)
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, the boost temperature is not 0, a space heating demand has been active continuously for a set period of time (time adjustable by installer) and there has been no HWG 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 and/or Hot Water Generator set point for each demand during a certain time each day. A start and stop time for each demand can be programmed for each day of the week. The controller can be programmed to reduce the tank set point as well. A different set of start and stop times can be programmed 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.
ModBus
The Crest boiler can be connected to and controlled by a Building Automation System through the ModBus interface. Connect the A and B wires to the A and B terminals. If connecting another cable (in a daisy chain), connect the shield wire of the first cable to one of the shield terminals, and the shield wire of the second cable to the other shield terminal. If it is desired to ground the cable shield at the heater, connect the shield wire to one of the shield terminals, and install a jumper across the two (2) terminals in connector X5 on the ModBus interface board.
0-10V Rate output
A
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.
Protection features
Outlet temperature, flue temperature, and temperature rise limiting
The outlet water 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 the minimum off time has expired and the outlet drops 10°F (5.5°C).
The control module monitors the flue temperature by a sensor located in the flue exhaust. If the flue temperature exceeds 350°F (176°C) the control will reduce the maximum fan speed. If the flue temperature exceeds 400°F (204°C) the control will shut the unit down. The unit will restart automatically once the flue temperature drops 50°F (27°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 80°F (27°C) the control will reduce the fan speed. If the temperature difference exceeds 90°F (32°C) the control will shut the unit down. The unit will restart automatically once the temperature difference has dropped below 50°F (28°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 TOUCH control module provides some protection for the boiler only
•The SMART TOUCH control module provides
•Below 45°F (7°C), the boiler and system pumps (if enabled) operate constantly.
•Below 37°F (3°C), the boiler turns on.
•Boiler and pumps turn off if boiler water temperature rises above 43°F (6°C).
CAUTION | This feature of the SMART TOUCH control | ||||
module does not eliminate the possibility | |||||
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| of freezing. The installation must still | ||||
| use recognized design, installation and | ||||
| maintenance practice to prevent freeze | ||||
| potential for the boiler and system. | ||||
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