Applications Guide Tracer Graphical Programming - Trane

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Chapter 3 Modifying the exhaust fan program
• Switch
• Or
Opening an existing program
Begin by opening your first program, Equip Rm Exhaust Fan. You can
have only one program open in the TGP editor at a time. If you try to open
another program, the first program is closed.
To open an existing program:
1. From the File menu, choose Open. The Open dialog box appears.
2. Select Exhaust Fan.tgp.
3. Click Open. The graphical program opens in the design space
(Figure 29).
Figure 29: Equipment room exhaust fan program
Reviewing the sequence of operation
In this scenario the equipment room remains as described in Chapter 2,
“Writing the exhaust fan program.” The room contains machinery that
generates a significant amount of heat. As a result, the temperature in
the room rises. The following criteria apply to control of the equipment
room exhaust fan.
• When the temperature exceeds 85°F, turn the exhaust fan on to draw
outside air through the equipment room.
• When the temperature falls below 80°F, turn the exhaust fan off.
• An operator must be able to adjust the limiting setpoint from the
operator display.
• If the temperature sensor fails, turn the fan on and indicate an alarm
condition.
There are three important differences from the original sequence of operation:
• The sequence incorporates a deadband into control of the fan.
• The temperature setpoint at which the fan turns on is adjustable by
the operator at the operator display.
• The sequence calls for an alarm indication when the temperature sensor
input fails.
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