Crestron electronic 3 Benutzerhandbuch

        

Installation & Operation Manual

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.

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.

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.

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.

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.

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. 

A 0-10V signal which indicates the firing rate of the heater 
is available.  This output may be connected to a Building 
Management System (BMS) to allow it to monitor the actual 
firing rate.  Connect the - terminal to the COM or - terminal 
on the BMS, and connect the + terminal to the 0 - 10V or + 
terminal on the BMS.

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.

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.

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 -- not for 
the system.

 

•   The SMART TOUCH 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 (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).

This feature of the SMART TOUCH 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.

 CAUTION