Applications Guide Tracer Graphical Programming - Trane
Applications Guide Tracer Graphical Programming - Trane
Applications Guide Tracer Graphical Programming - Trane
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®<br />
<strong>Programming</strong> best practices<br />
Use comments to document your programs.<br />
Comments can provide helpful information, and although they may not<br />
seem important to the author of the program, they are especially useful<br />
for those who open an unfamiliar program. In Figure 188, comments provide<br />
more detail about the heat/cool decision.<br />
When possible, subdivide graphical programs according to<br />
the sequence of operation.<br />
Subdividing a program into logical modules makes the program easier to<br />
read and understand. For example, a program for a cooling tower that<br />
controls a fan, a sump heater, and a pump, would consist of three corresponding<br />
modules.<br />
Determine the number of programs required for an<br />
application by grouping control functions that require the<br />
same information and/or the same run frequency.<br />
In the PCM and the UPCM, process control language (PCL) programs<br />
often handled very discrete functions due to their limited size. <strong>Graphical</strong><br />
programscanbemuchlarger.Whileanair-handlingunitmayhave<br />
required 18 programs in a UPCM, the same air-handling unit functionality<br />
might be accomplished in four or five graphical programs. For example,<br />
a constant-volume air-handling unit requires the following control<br />
tasks:<br />
• Effective space setpoint calculation<br />
• Mode determination (heat/cool)<br />
• Supply fan control<br />
• Exhaust fan control<br />
• Mixed air/outdoor air damper control<br />
• Discharge air setpoint calculation<br />
• Cooling valve control, including dehumidification<br />
• Heating valve control, including dehumidification<br />
• Humidification<br />
• Alarm management<br />
Not every control function will fit into one program. Identify tasks that<br />
require the same information, and/or the same run frequency, and group<br />
those tasks together to form programs. Table 32 presents a recommended<br />
grouping for a constant-volume air handler.<br />
Table 32: Grouping programming tasks into programs<br />
Program name<br />
ModeAndSetpoints<br />
FanControl<br />
MixedAirControl<br />
Control functions<br />
Effective space setpoint calculation<br />
Mode determination<br />
Supply fan control<br />
Exhaust fan control<br />
Mixed air/outdoor air damper control<br />
232 CNT-APG001-EN
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