Delta T Alerts - Honeywell Prestige 2.0 THX9421 Manual

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.
159). 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.
160).
Fig. 159.
2. Press the up or down arrows to set the Minimum and
Maximum Limits and the Run Time.
Fig. 160.
3. Set appropriate Minimum and Maximum Delta T
Limits based on the reading from the equipment test
and what you consider to be unacceptable perfor-
mance 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 equip-
ment test. In the example shown in Fig. 158 and 160,
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
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THX9321 PRESTIGE 2.0 AND THX9421 PRESTIGE
minimum limit or above the maximum limit multiple times
(see Table 7), 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)
• Display Delta T Alerts to User (ISU 13190; Default: Yes)
• Allow Delta T Diagnostics:
— during humidification (ISU 13020; Default: Yes)
— during dehumidification (ISU 13030; Default: Yes*)
— during ventilation (ISU 13040; Default: Yes)
— only when indoor temperature is within a certain
range (ISUs 13050, 13090, 13130; Default: Always)
— only when indoor humidity is within a certain range
(ISUs 13060,13100, 13140; Default: Always)
— only when outdoor temperature is within a certain
range (ISUs 13070, 13110, 13150; Default: Always)
— only when outdoor humidity is within a certain range
(ISUs 13080, 13120, 13160; Default: Always)
* Default is Yes for Dehumidifiers and A/C with High
Speed Fan. The thermostat does NOT allow Delta T diag-
nostics during dehumidification if it is setup for A/C with
Low Speed Fan, Hot Gas Bypass, or Reheat.
The Delta T Alert Sensitivity is set on a scale of 1–5 in ISU
13180 (1 is the least sensitive; 5 is the most sensitive):
Table 7. Delta T Alert Sensitivity (ISU 13180).
Setting
1 10 of the last 15 valid cycles have the same fault, or
25 of the last 30 valid cycles have the same fault.
2 10 of the last 15 valid cycles have the same fault, or
20 of the last 30 valid cycles have the same fault.
3 5 of the last 5 valid cycles have the same fault, or
(Default) 10 of the last 15 valid cycles have the same fault, or
15 of the last 30 valid cycles have the same fault.
4 5 of the last 5 valid cycles have the same fault, or
8 of the last 15 valid cycles have the same fault, or
15 of the last 30 valid cycles have the same fault.
5 3 of the last 5 valid cycles have the same fault, or
8 of the last 15 valid cycles have the same fault, or
10 of the last 30 valid cycles have the same fault.
By default, Delta T alerts are displayed to the user, but can
be turned off and on in ISU 13190.

Delta T Alerts

The thermostat uses alerts and diagnostics to provide
greater comfort and efficiency. Alerts and diagnostics can
notify customers when maintenance or service is needed,
and display your contact information to make it easy for
them to reach you.
89
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Alert is logged and user is alerted if
IAQ WITH EIM
68-0311—07