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THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ 2.0 WITH EIM
53 68-0311—01
Fig. 60.
5. Proceed to “Run a Test for Each Stage”.
Run a Test for Each Stage
Follow these steps to run a test for each stage in the HVAC
system.
1. Turn on stage 1.
Fig. 61.
2. For each stage you test, wait until Delta T begins to sta-
bilize, then turn on the next stage (if present). See Fig.
62 for an example.
Fig. 62.
3. Press Next Step after Delta T stabilizes for the last stage.
The thermostat saves the Delta T and Run Time Data for
each stage you test and is displayed on the next screen.
NOTE: The thermostat only saves test data for stages
that run 1 minute or longer.
Set Delta T Limits
1. Press Stage 1 to set the limits and run time (see Fig. 63).
Use the saved test data located in the upper right corner
of the screen to set the Delta T Minimum and Maximum
Limits and the Run Time (see Fig. 64).
Fig. 63.
2. Press the up or down arrows to set the Minimum and
Maximum Limits and the Run Time.
Fig. 64.
3. Set appropriate Minimum and Maximum Delta T Limits
based on the reading from the equipment test and what
you consider to be unacceptable performance from the
heating and cooling equipment.
4. When setting the run time, select a setting based on
when Delta T began to stabilize during the equipment
test. In the example shown in Fig. 62 and 64, Delta T
began to stabilize around 10-11 minutes.
5. Set the limits and run time for all stages of cooling using
steps 1–4 above.
6. Repeat steps 1–5 above for Heating.
After Delta T Diagnostics Setup is Complete
The thermostat will measure Delta T after the specified run
time, and compare Delta T to the minimum and maximum limits
for each valid cycle. If the system operates below the minimum
limit or above the maximum limit multiple times (see Table 3),
an alert is recorded in the Alerts Log. If configured to do so, an
alert is displayed to the user (Display Delta T Alerts to User,
ISU 13190). The user is alerted by default. For example, if 10
of the last 15 cycles have the same fault, an alert is logged and
the user is alerted.
Advanced Options for Delta T Diagnostics
To set Advanced Options for Delta T Diagnostics, select Yes for
ISU 13015.Then the following advanced options are displayed:
• Delta T Alert Sensitivity (ISU 13180; Default: 3)