Applications Guide Tracer Graphical Programming - Trane

®
Chapter 8, “Constant-volume AHU with warm-up, pre-cool, and communica-
Figure 200: Valve override interpretation
Selected enumerations for the state, or override mode, are shown in
Table 36. Remember, you are checking for values of 0, 4, or 5.
Table 36: SNVT_hvac_overrid (hvac_overrid_t) enumerations
Value Identifier Notes
0 HVO_OFF Not overridden
1 HVO_POSITION Override position—use percent field
2 HVO_FLOW_VALUE Override flow in liters/second—use
flow field
3 HVO_FLOW_PERCENT Override flow percentage—uses
percent field
4 HVO_OPEN Override to position = 100%
5 HVO_CLOSE Override to position = 0%
6 HVO_MINIMUM Override to configured minimum
7 HVO_MAXIMUM Override to configured maximum
–1 HVO_NUL Invalid value
Note:This table was adapted from the LonMark Standard Enumeration Master List.
Figure 200 shows the logic used to interpret the valve override. The
De-Enumerator block interprets the override mode. The Switch blocks
select the appropriate desired valve position based on the override
mode. The resulting wireless connections are used to communicate
the override values to both the cooling and heating valves as shown in
Figure 201 on page 246 and Figure 202 on page 246.
Next,startwiththecoolingvalvemodulepicturedinFigure172on
page 208. Substitute a wireless connection, CoolValve, for the cooling
valve analog output. Then add another Switch block to select the
source of the cooling valve control. In normal operation, the calculated
cooling valve position is passed to the analog output. When an override
exists, the override value is passed to the analog output
(Figure 201 on page 246).
CNT-APG001-EN 245