Installation guide

1BHFt%3*45&&.7BQPSMPHJD 3 Installation and Operation Manual
RH/dew point/demand graph
The RH (or dew point or demand) graph provides a graphical
depiction of RH change over time. Examples of this are shown in
Figures 80: 1–3.
The vertical axis either displays RH in 1% increments, dew point in
1 degree increments, or demand in 2.5% increments depending on
system configuration. On the RH graph, the RH set point is denoted
by SP in the middle of the vertical axis.
Data is graphed over three different time intervals: the last 10
minutes, the last 1 hour, or the last 24 hours. Scroll through each
interval by pressing the Scale soft key.
Use the Back soft key to return to the Reports menu. Use the Main
soft key to return to the Main menu. The left and right arrows move
the blinking cursor across each data point on the curve. The value
of the blinking cursor’s data point appears in the upper right corner
of the screen. The time (how long ago) when that data point was
taken appears directly below its value.
The graph is useful when tuning the PID loop (adjusting the
proportional, integral, and derivative gain values). Consider the
following examples: Figure 80-1 depicts a system where the RH
is oscillating and may not maintain the RH set point. This is an
example where Ki (integral gain) is too high. Figure 80-2 depicts
a system where the RH either takes too long to reach set point or
never reaches set point. This system would benefit from increased
Ki. Figure 80-3 depicts a perfectly tuned system.
Main menu: Reports screen,
continued
Figure 80-1:
Oscillating RH demand graph
2
Figure 80-2:
RH demand graph, set point not reached
Figure 80-3:
RH demand graph, operating properly
VL3_IOM.pdf 84 11/19/2009 9:11:16 AM