Applications Guide Tracer Graphical Programming - Trane

®
Chapter 4 Cooling tower with two-speed fan example
4. Connect the 2.0 constant block to the Deadband port of the Deadband
block (Figure 74).
Figure 74: Deadband incorporated in sump heater module
Comparing the outdoor air temperature with the
freezing point
Use a Less Than or Equal block to maintain the sump heater on continuously
when the outdoor air temperature is less than or equal to the freezing
point.
To compare the outdoor air temperature with the freezing point:
1. Place a Less Than or Equal block in the design space.
2. Connect the OutdoorAirTemp wireless read block and the 32.0 constant
block to the Less Than or Equal block (Figure 75).
Figure 75: Less Than or Equal comparison in sump heater module
Controlling the sump heater on or off
Add an Or block to combine the two paths so that if the sump temperature
falls below 40°F or the outdoor air temperature is less than or equal
to the freezing point, the sump heater is controlled on.
To control the sump heater on or off:
1. Place an Or block in the design space and connect the Deadband block
and the Less Than or Equal block to the Or block.
2. Connect the Or block to the Sump Heater On/Off output block
(Figure 76 on page 71).
3. Compile and save your program to check for errors and to preserve
your work.
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